Treatment of Hydrocephalus: Shunts
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Childhood Hydrocephalus: Clinical Features, Treatment, and the Slit-Ventricle Syndrome

 

Arno H. Fried, M.D., Mel H. Epstein, M.D.

 

Abstract

 

The use of shunting for hydrocephalus has a long history of improvements made through basic science, as well as clinical innovations and biomedical products. Shunting has dramatically changed the outlook of children with hydrocephalus, with many of them having normal life expectancies and attaining normal intelligence. The use of shunts, however, has created many unique problems of shunt dependence with frequent shunt revisions being the rule for most hydrocephalic children. Shunt problems assume a major amount of all neurosurgeon’s efforts. In addition, the slit ventricle syndrome has posed many new questions regarding what the post-shunting ventricular size should be, and what problems are created by having a slit-like ventricular system.

 

This article reviews current concepts of childhood hydrocephalus with respect to the various hydrocephalic syndromes, and provides detailed descriptions of problems unique to various shunting systems. In addition, the slit ventricle syndrome is distinguished from asymptomatic post shunted slit-ventricles. The various forms of the slit-ventricle syndrome are described , and proposed guidelines for classifying, working up, and treating the slit ventricle syndromes are provided.

Key Words: hydrocephalus, shunting, cerebrospinal fluid, slit ventricle syndrome, shunt infection.


Childhood Hydrocephalus: Clinical Features, Treatment and the Slit-Ventricle Syndrome

Arno H. Fried, M.D, F.A.C.S.

 

The prognosis of childhood hydrocephalus is now very predictable, with most children developing with relatively normal intelligence. This, however, has come at the price of permanent shunt dependency in most children(14, 22, 56). These children, despite the improvement in mortality and intellectual deficits, are prone to multiple problems related to shunt dependency and malfunction. Just as our present level of knowledge was due to a combination of basic science and clinical observations, future progress in treating hydrocephalus will also come through continued research into mechanisms of fluid movement in the brain, as well as innovative biomedical technical advances.

 

This review will discuss the clinical aspects of childhood hydrocephalus. Special emphasis is given to the technical aspects of shunting for hydrocephalus. The review will end with a discussion of shunt dependency and the "slit-ventricle syndrome."

 

Historical Aspects

 

Observations by Key and Retzius in 1875 demonstrated the CSF pathways and ventricles, providing the groundwork for future physiological advances(31). Dandy and Blackfan demonstrated the CSF production within the ventricles by choroid plexus and divided hydrocephalus into communicating and non communicating types(5). This classification was made based upon the appearance of Phenolsulfonphthein (PSP) in the lumbar CSF space after introducing it in the ventricle. Choroid plexectomy, first open (Dandy), then endoscopically (Scarff) was tried with marginal success(6, 52). Stookey and Scarff tried third ventriculostomy to bypass a blockage in the CSF pathways until extracranial shunts became feasible and more successful(57). More recently, however, Hoffman and others have advocated third ventriculostomy as a good option in hydrocephalus that is acquired, in that the subarachnoid space distally is adequately developed(24, 30). This may apply to causes of hydrocephalus acquired post-natally such as tectal tumors.

 

There are numerous reviews of the history of shunting, describing the vast diversity in shunts and sites of distal placement(48). These have included ureter, peritoneum, pleura, heart, gall bladder and fallopian tube. Future improvements would be to improve techniques and shunt materials, but the outcome of hydrocephalic children was clearly changed by CSF shunting eliminating severely handicapping disorder.

 

The modern shunting era began with Nulson and Spitz, creating a one way pressure regulated valve which they placed in the atrium via the jugular vein. John Holter was the father of a hydrocephalic child who worked on the early development of the shunt valve. Becker and Nulson's landmark paper on the use of one way ventricular atrial shunts set a new standard in hydrocephalus treatment, due to improved biomaterials such as silicone, and led the way for ventricular peritoneal shunts as today's standard(2).

 

The natural history of untreated hydrocephalus was studied in the classic paper by Lawrence and Coates, demonstrating a 46% ten year survival with intellectual impairment in 62%(33). The impact of CSF shunting was shown by Foltz and Shurtleff to be significantly improved(14,56). Their 10 year survival of shunted children was nearly 95% with intellectual impairment in only 30% of children. Other studies have shown the improved intellectual development associated with a decrease in the ventricular size(58, 64). Continued problems, however, are related to shunt dependency, which is usually present for the life of the child. These shunt related problems include shunt malfunction, shunt infection, overdrainage and the "slit ventricle syndrome", and will be discussed later in this chapter.

 

Childhood Hydrocephalic Syndromes

 

There are unique clinical features of hydrocephalus due to specific etiologies. These are important in terms of knowing the natural history of the specific hydrocephalic syndrome, which children to shunt, and predicting problems and outcomes outcome to families. Most causes of childhood hydrocephalus are due to impaired CSF absorption. CSF absorption, however, is usually still possible in most cases of hydrocephalus through either normal CSF absorptive pathways or alternate CSF absorptive pathways(4,35,50). This is particularly evident in instances of arrested hydrocephalus, where ventricular enlargement stabilizes due to these alternate pathways. Laurence noted up to 45% of children with hydrocephalus will eventually have arrest of the progressive ventricular enlargement. This is at the cost, however, of a high morbidity and mortality(33). A better way to look at the phenomenon of arrested hydrocephalus is to consider it compensated hydrocephalus. Many factors can upset this balance, (fever, infections) leading to sudden decompensation of the hydrocephalus and elevated intracranial pressure (ICP). Close follow-up, therefore, is needed with suspected shunt independent "compensated" hydrocephalus.

 

Congenital Malformations.

 

Congenital malformations of various sorts account for a large percentage of childhood hydrocephalus. Aqueductal stenosis is the etiology in roughly 40% of cases. There is enlargement of the lateral and 3rd ventricles with a normal

4th ventricle. There are different pathologic forms of aqueductal stenosis, as described in the monograph by Russell(49). The aqueduct can be atretic and subdivided into several small forked channels. A web or membrane composed of ependymal cells can run across the aqueduct. A third variety consists of two blind-ended channels with no true lumen. Rarely aqueductal stenosis can be familial with an X-linked recessive form of inheritance(8). Experimentally mumps virus can be associated with aqueductal stenosis.

 

The cerebral aqueduct can become secondarily stenotic in shunted hydrocephalus due to other causes, usually with obstruction of the 4th ventricle outflow pathways as the etiology of the hydrocephalus(15). This produces a situation where the 4th ventricle becomes trapped due to blockage of its outflow and inability of fluid to flow upward into the shunt. If symptomatic, the encysted, trapped 4th ventricle needs a second ventricular catheter which is connected into the existing shunt above the valve to ensure equal flow in both compartments.

 

The MRI scan is an excellent study to visualize the cerebral aqueduct and diagnose the stenosis. It will also differentiate aqueductal stenosis from a periaqueductal glioma, an indolent midbrain tectal tumor which is usually not seen on CT scanning. Aqueductal stenosis is seen in association with Chiari malformations either due to stenosis or narrowing due to the angulation and distortion of the brainstem with the Chiari malformation. The posterior fossa is small in hydrocephalus due to aqueductal stenosis.

 

Hydrocephalus due to aqueductal stenosis usually becomes manifest in-utero or by the first three months of infancy with typical signs of elevated intracranial pressure, bulging anterior fontanelle, splitting of the sutures, Macewan's crackpot sound to head percussion and "setting-sun sign" due to tectal compression. Teenagers and young adults can present for the first time with aqueductal stenosis and hydrocephalus. This older group of patients usually presents with chronic headaches in the setting of having head which is large on the growth chart, and there may be history of school problems and learning disabilities throughout the learning years of childhood. Appropriate imaging studies diagnose the problem, and if symptomatic a VP shunt is recommended. Hydrocephalus in-utero is frequently noted by ultrasound studies during pregnancy.

 

The Chiari malformations are a cause of childhood hydrocephalus. Type I Chiari malformations, with cerebellar tonsillar ectopia is usually seen without spina bifida and myelomeningocele. Symptoms can be referable to the hindbrain malformation with neck pain, vertical nystagmus, swallowing difficulty and voice abnormalities. There may be an associated syrinx of the spinal cord, with arm and hand weakness and atrophy, long tract signs in the legs, scoliosis and cape-like pain and sensory loss of the shoulders. Enlarged ventricles can accompany Chiari I syndromes, and must be recognized since treating the Chiari I malformation with untreated hyrocephalus can lead to complications, including pseudomengocele and wound leakage. Similarly, with a symptomatic cord syrinx and hydrocephalus, the hydrocephalus should be treated with a VP shunt prior to posterior fossa decompression.

 

The Chiari II malformation is a cause of hydrocephalus, often seen in the setting of spina bifida and myelomeningocele. In children with myelomeningocele, 90% will have an associated Chiari II malformation and 70%-80% of the children will have hydrocephalus. The higher the level of the lesion, the greater the chance of developing hydrocephalus. The enlarged ventricles develop usually in the week or two following the closure of the back defect. Occasionally, there will be significant hydrocephalus seen at the time of birth or in-utero. This is a relatively poor prognostic sign in terms of intellectual outcome(38). The malformation consists of caudal displacement of the vermis of the cerebellum, along with the 4th ventricle into the cervical spinal canal, often down to C4 or C5. There is fusion of the displaced tissue to the underlying brainstem and cervical spinal cord. This blocks the foramen of Magendie, contributing to the hydrocephalus. There is kinking of the lower medulla due to the malformation, as well as aqueductal stenosis, polygyria, microgyria, abnormalities of brainstem nuclei and enlargement of the inferior commissure. The treatment of the hydrocephalus needs to be done early in children with myelomeningocele to prevent several complications. With symptoms referable to brain stem compression, a shunt is usually needed in addition to decompressing the Chiari. If there is cerebrospinal fluid (CSF) leakage after closing the back, a VP shunt should be performed.

 

Hydrocephalus can be caused by cysts, either porencephalic cysts within the brain adjacent to the ventricle, or arachnoid cysts in the subarachoid space or in the ventricle. Arachnoid cysts can enlarge due to a one way ball valve effect, and compress brain or block the CSF pathways. There is no evidence that the arachnoidal membrane is capable of secreting CSF on its own. Common sites include the middle fossa, the cerebellopontine angle angle, suprasellar cistern and quadrigeminal cistern. When there is an arachnoid cyst causing the hydrocephalus, if it is not appreciated pre-shunt, then it is seen on the CT or MRI scan after the ventricles are decompressed. Symptoms referable to direct compression by the cyst such as Parinaud's syndrome with quadrigeminal cysts will not improve after VP shunting. This leads to the need for further shunting of the arachnoid cyst. In infants and young children, it may be possible to use the ultrasound to direct a shunt catheter into both the arachnoid cyst and the ventricles. The use of a fiberoptic ventriculoscope can also be used to communicate the cyst with the ventricle and then shunt this combined space.

 

The Dandy-Walker cyst is a posterior fossa CSF cyst in communication with an enlarged 4th ventricle, associated with aplasia of the vermis of the cerebellum. The posterior fossa is large, and the Torcula Herophili and inion are elevated. There is absence or blockage of the foramen of Magendie resulting in the encysted 4th ventricle and progressive hydrocephalus in some children. When symptomatic with advancing ventricular enlargement, the treatment is to place a shunt. Both the ventricle and the posterior fossa cyst need to be shunted with a single distal shunt system. Shunting is the procedure of choice compared to craniotomy and fenestration of the cyst.

 

Platybasia is a deformity where the angle formed by the basisphenoid and the clivus, normally 130-140 degrees, is increased with flattening of the skull base. There is associated shortening of the basi-occipital bone and several malformations around the foramen magnum and cervical spine, such as Klippel-Feil syndrome. The shortening of the skull base can lead to compression at the foramen magnum and cervical spine. Deformity of the skull base in achondroplasia contributes to the development of hydrocephalus in these children(45).

 

An important distinction should be made between maximal hydrocephalus and hydranencephaly. Hydranencephaly is characterized by complete absence of cerebrum supplied by the anterior cerebral artery and middle cerebral artery bilaterally. The only intact brain tissue is the basal ganglia, brain stem, and a small amount of occipital lobe, supplied by the posterior cerebral artery. Hydranencephaly is presumably caused by an intrauterine stroke in the distribution of both internal carotid arteries. These newborns will cry, suck and feed. The MRI scan will confirm complete absence of all brain tissue except that mentioned above. Children with hydranencephaly may have progressive head enlargement and a severe crying and irritability syndrome. The progressive head enlargement and high pitched crying are indications for shunting, with the parents aware, of course, that it will not improve function. In maximal hydrocephalus there is a very thin rim of cortical mantle seen on the MRI scan. The EEG will show cortical activity. Shunting should be performed, and there is sometimes surprising cortical reconstitution on follow-up scans.

 

Acquired Hydrocephalus

 

Obstructive hydrocephalus is produced by many childhood tumors, since the midline posterior fossa, suprasellar region, 3rd ventricle and pineal region are common sites in children for tumors to occur. Although controversial, our practice will not perform a preoperative shunt unless the child is very symptomatic from hydrocephalus and cannot be taken right to surgery for tumor removal. In most childhood tumors, the hydrocephalus is treated by preoperative Decadron and Diamox, which improves signs of elevated intracranial pressure. The dosage of Diamox is 80-100 mg/kg/day in order to block 99% of carbonic anhydrase and decrease CSF production. The surgery to remove the tumor should have as a major goal to open the blocked CSF pathways, frequently avoiding a shunt. Only 20% of children will need a shunt postoperatively. A temporary ventriculostomy is usually needed to control ventricular size in the immediate postoperative period.

 

Postmeningitic and postinflammatory hydrocephalus are usually a communicating hydrocephalus due to obstruction at the basal cisterns. E. Coli meningitis and Hemophilus influenza meningitis are the usual infectious agents. Moderate ventricular enlargement is very common, which will either resolve, progress into hydrocephalus which requires a VP shunt, or a picture of atrophy may evolve with hydrocephalus-ex-vacuo. The finding of progressive ventricular enlargement and an enlarging head circumference confirms the need for a shunt.

 

In premature infants weighing less than 1500 gms, 50-60% will develop a germinal matrix and intraventricular hemorrhage(16, 29, 37). Shortly after the hemorrhage, nearly 3/4 of infants will develop ventricular enlargement. Signs which herald a bleed include; stupor, respiratory difficulty, seizures, falling Hct, unstable vital signs and a bulging fontanelle. Several pharmacological agents can be used to prevent intraventricular hemorrhage (IVH). These include Phenobarbital, Indomethacin and Ethamsylate (a capillary stabilizing drug). When given within 1 hour after birth, Phenobarbital can reduce the prevalence of IVH from 47% to 25% in infants less than 1800 gms(7). Indomethacin is a prostaglandin synthesis inhibitor with promising experimental data, but less convincing clinical data(43, 44).

 

When IVH occurs, and is accompanied by hydrocephalus, the initial treatment is to relieve the hydrocephalus without a shunt, since the blood would occlude the catheter, the infant is usually too small to support a shunt and the hydrocephalus may resolve over time. While the incidence of acute hydrocephalus is up to 60%, the long term incidence of progressive hydrocephalus requiring a shunt falls to 10 - 20%. To treat the acute hydrocephalus Diamox and daily lumbar punctures are initially tried. The head size, signs of elevated ICP, and cranial sonograms are followed to determine further treatment. If the lumbar puncture fails to adequately relieve the excess CSF, ventricular taps through the lateral aspect of the anterior fontanelle can be performed. Since repeated ventricular taps can cause a needle tract porencephaly, it is our practice to insert a ventricular tapping device, which is an implanted internal 2-3 cm. catheter attached to a small reservoir(37). This can be tapped as often as needed through the skin with a 23-gauge butterfly needle, withdrawing roughly 15cc of CSF. In time it will become clear if the hydrocephalus is resolving, or if a permanent VP shunt will be needed. When it becomes apparent that a shunt will be required, it is useful to wait until the infant weighs at least 1800 Gms., and the CSF protein falls to approximately 250 mg%. When shunting a premature infant, a very low pressure shunt should be selected. The system needs to be very low profile so that it doesn't erode through the skin. We will give prophylactic antibiotics to try and offset the 25-50% shunt infection rate in this population (29). It is especially important to have an experienced pediatric neurosurgeon perform this shunt, since the speed of the operation can help prevent complications which are unique and frequent in this group(3).

 

Vascular lesions can cause childhood hydrocephalus. In particular, vascular malformations of the vein of Galen can present with hydrocephalus in infancy. The pathophysiology involves blockage of the cerebral aqueduct by the enlarged Vein of Galen, as well as elevated venous pressure due to the arteio-venous shunting, which reduces CSF absorption by bulk flow. Hydrocephalus as a presenting sign of a vein of Galen AVM is usually not seen in the immediate newborn period, where high flow cardiac failure predominates the mode of presentation. Shunting should be performed in cases of progressive hydrocephalus, although some children show progressive thrombosis of the malformation and resolution of the ventricular enlargement. When a VP shunt is required, a catheter trajectory away from the AVM and dilated vessels should be designed, usually by placing a frontal ventricular catheter.

 

Thrombosis of the dural sinuses can lead to hydrocephalus. The condition "otitic hydrocephalus" described by Symonds, is seen in children with middle ear infection with thrombosis of the lateral sinus adjacent to the petrous bone(59). Sagittal sinus thrombosis can occur in children due to direct extension of an infection or in cases of severe hypernatremic dehydration. This can lead to a pseudotumor-like picture with a swollen brain. Enlarged ventricles, however, are also seen in this disorder. Thrombosis of the superior vena cava in cases of mediastinal tumor or long standing indwelling catheter can lead to a progressive communicating hydrocephalus. The use of Tissue Plasminogen Activator(TPA) has been used in a variety of cerebrovascular disorders to dissolve clotted blood. TPA may play a role in these thrombotic disorders and avoid progressive hydrocephalus.

 

When there is progressive ventricular enlargement with signs of elevated ICP, the decision to place a shunt is straightforward. A condition to recognize, however, is "benign external hydrocephalus" since a shunt is almost never required in this disorder. Benign external hydrocephalus is characterized by enlargement of subarachnoid spaces and mild to moderate ventricular enlargement ( figure 1 ). The fontanelle is not bulging with no "setting-sun sign." The "setting-sun" sign is a description of downward deviation of a child’s eyes due to compression of the tectal (or collicular) area of the dorsal midbrain. The compression is most often due to an enlarged third ventricle in hydrocephalus but can also be a sign of a causitive lesion causing hydrocephalus such as a pineal mass, collicular region cyst, or a vein of Galen vascular malformation. With " benign external hydrocephalus" the head circumference does enlarge progressively, and crosses percentile lines. This produces a child with an obviously large head. There is often a family history of large heads. These families need reassurance that the problem will resolve without a shunt. At roughly 18 months of age, the enlarging head circumference will plateau, allowing the child's body growth to catch up. A follow up CT scan should be done. A shunt would only be required to prevent a grotesque looking enlarging head.

 

Treatment of Childhood Hydrocephalus.

 

Cerebrospinal fluid shunting is the well-accepted standard treatment for childhood hydrocephalus. There is a vast array of shunting devices with different components, all having similar features. The currently used shunt systems have valve systems incorporated in the shunt with an opening and closing pressure so that currently used shunts are, for the most part, pressure regulated. Given the fact that shunt systems all drain CSF relatively quickly once the child assumes an upright posture due to the effect of siphoning, most flow characteristics in currently used shunts are relatively unimportant. There are other technical aspects of shunt insertion which are far more important to maintain adequate shunt function then the specific details of the shunt valve characteristics. An ideal shunt still needs to be the goal in the future of treating hydrocephalus. The ideal shunt would allow for a flow regulated control to drain a specific amount of fluid, which could be tailored to an individual child's needs. In addition, there would be the ability to monitor externally shunt function and potential shunt malfunction. This ideal valve would allow the drainage of only the amount of fluid that is really excess for a given child, and may avoid the problems of shunt dependency. The currently used valves, however, as mentioned above, are still pressure regulated.

 

Shunt valve systems can be located proximal, as well as distal. Distal slit valves are now to be avoided because of the high frequency of distal shunt malfunction, as well as unpredictable flow characteristics. Valve mechanisms include slit valves, spring-ball valves or diaphragm valves(47). The slit valve is somewhat unpredictable, and flow can vary markedly given the amount of previous irrigation or the stickiness of the valve. Spring-ball and diaphragm valves maintain a more constant flow rate. Siphoning is a factor which comes into play when a child assumes an upright position and a negative pressure is exerted, which is related to the vertical distance between the inlet and the outlet of the shunt. In rare cases in which siphoning appears to be detrimental to a child, an antisiphon device can be inserted to negate this negative effect only in the vertical position(39, 46). The characteristics to be aware of is that shunt valves are described by the pressure above which CSF will flow, as well as resistance to flow. A valve can be low pressure but have a high resistance so that the rate at which fluid flows down to the closing pressure of the shunt will be a gradual drop off . A low resistance valve will drop quickly and then stop abruptly when the fluid pressure reaches the closing pressure of the valve.

 

We believe the antisiphon device rarely has to be used in the placement of childhood shunts. Occasionally, however, there is a situation where a child is having low pressure symptoms or recurring proximal shunt occlusions due to collapse of the ventricles around the ventricular catheter, and an antisiphon device may be useful to help control this form of slit ventricle syndrome. One needs to be careful about the use of antisiphon devices, since it may slow down the function of the shunt too much and cause symptoms that are due to inadequate shunt function(39). This is particularly important in infants, if the antisiphon device is used with a medium pressure shunt. An antisiphon device works only when there is a negative pressure exerted due to the vertical position of a child, and the resultant siphoning. It consists of a diaphragm that covers the inlet to the device, and when there is a negative pressure exerted from below the diaphragm moves downward occluding the inlet so that the shunt is essentially closed. In this way, this closes the shunt only when there is negative pressure present in the distal part of the system.

 

Occasionally in borderline cases of progressive hydrocephalus, an attempt is made to treat the hydrocephalus nonoperatively. Diamox can occasionally be used to reduce CSF production and help lead to a situation of arrested hydrocephalus. The dose of Diamox can be as high as 100 mg/kg, since in order for it to be effective, more than 99% of carbonic anhydrase must be blocked by the Diamox before CSF production decreases significantly. One needs to watch for a metabolic acidosis produced with this treatment. In addition, Furosemide (Lasix) has been shown to decrease CSF production and may be useful for temporizing in the treatment of borderline hydrocephalus. These nonoperative methods would be most appropriate in cases of posthemorrhagic hydrocephalus, where temporizing measures may occasionally avoid the need for a permanent shunt.

 

Shunting For Hydrocephalus.

 

While it is certainly not the most glamorous neurosurgical operation, shunting is one of the basic neurosurgical procedures, and also has the highest failure rate. It has a relatively high complication rate and is probably the most common operation which has to be redone for either malfunction or infection. Shunt operations are often delegated to the most junior and inexperienced member of the neurosurgical team, resulting in suboptimal technique and judgment in the management of shunting. Clearly, one of the best ways of managing shunt problems is avoiding them in the first place. Pediatric shunting should be performed by a pediatric neurosurgeon who is well experienced in the various shunt hardware and techniques, and has experience in thinking through the technical problems of shunt dependency and shunt revisions. These children will require close follow-up to recognize at an early stage some of the complications of shunting, and to pick up on subtle signs of shunt dysfunction. A close working relationship needs to exist between the pediatric neurosurgeon and the families, as well as the child's pediatrician, to provide the best comprehensive evaluation of a shunt problem and recognize at an early stage.

 

Despite the large amount of different shunt systems, particularly valves with different pressures and flow characteristics, we really do not think they play a major role in the success of shunting operation. There are some unique features of the hardware construction that are important, however, in preventing shunt malfunctions, as well as dealing with them when they occur. From our perspective, a one piece shunt system is advantageous in that it is easier to insert, with a quicker operation, and it avoids the possibility of shunt disconnection or disintegration associated with a connector. A connector will also prevent the extra tubing from elongating, since the connector will become fixed in its position subcutaneously due to ingrowth of scar tissue. The should also have a right angle ventricular catheter valve just distal to the right angle. This enables the surgeon to easily have access to the shunt catheter. It avoids having to work underneath a reservoir with a catheter that becomes partially embedded in the brain. The valve system should have incorporated in it some sort of flushing or tapping chamber to have an access to tapping a shunt, as well as ability to pump and test a shunt in the neurosurgeon's office. This mechanism needs to have either a proximal and distal occluder system, so that the proximal and distal portions of the shunt can be tested separately, or a double bubble configuration which also allows separate testing of both proximal and distal limbs of the shunt.

 

A low pressure ventriculoperitoneal (VP) shunt is the initial shunt of choice in most hydrocephalic children. The usual anesthetic and room warming issues should be followed, since many shunts are performed in small children. Position is important to correctly implant the shunt. The head is turned sharply to the left, and the placement is a right occipital placement. The burr hole is placed approximately 4 cm up from the inion and 3-4 cm off the midline. This occipital placement allows a relatively straight shot into the body of the ventricle so that the shunt catheter is mostly within the ventricle. This trajectory avoids the risk of going to low, through the internal capsule, which can happen with shunt placement sites that are more lateral and inferior, such as at Kean's point. An adequate length of ventricular catheter needs to be selected to place the tip anterior to the foramen of Munroe, where there is less choroid plexus. Generally, a 6 cm catheter is used in a small newborn, an 8 cm catheter in an older infant and young child, and a 10 cm catheter in a child 18 months or older. We use perioperative antibiotics, although definitive data showing that this is mandatory is still lacking(21, 32, 63). A rolled towel is placed across the shoulderblades to elevate the chest and neck, and allow for a straight passage of the shunt passer with no secondary incisions between the head and the abdomen. The abdominal incision is a horizontal incision, either just below the ribcage or just lateral to the umbilicus. Once the shunt is laid in position, the dura is opened with a pinpoint cautery to have just a big enough opening to allow the passage of the catheter. A large dural opening can allow CSF to flow around the shunt and cause a subcutaneous fluid collection. The ventricle is tapped using a rigid brain cannula and once obtaining a good flow of CSF the ventricular catheter is fed into the ventricle through this tract without a stylette. Fluid should then be aspirated from the lower end of the shunt to insure that the valve system is opened and then it is placed into the peritoneal cavity. A large amount of tubing can be placed in the peritoneal cavity, and up to the full length has been used without any problems to allow for growth. We will typically place 15-20" of peritoneal catheter in at the time of the initial shunt placements.

 

The neurosurgeon should also be familiar with ventriculoatrial shunting and ventriculopleural shunting, as these are often useful secondary shunting sites. Our own preference is to utilize the ventricoatrial shunt for children 8 years or less as the second choice for a shunt, and a ventriculopleural shunt in children 8 years or more as the second choice once they are large enough to be able to handle the fluid that goes into the pleural space. For ventriculoatrial shunts, an incision is made across the anterior border of the sternomastoid muscle, and the jugular vein identified. Some surgeons will place the shunt into the common facial vein just as it enters the jugular vein as an alternative technique. Once the jugular vein is isolated both proximally and distally with ligatures, the vein is tied off distally and a small opening made into the jugular vein to pass the shunt down the jugular vein into the right atrium of the heart. On the right side, this is easily done using electrocardiographic (EKG) control, attaching an alligator clip to the stylette of the distal tubing and connecting it to lead 2 of the anesthesia EKG machine(42). The atrium is indicated by the P wave configuration becoming more and more upright, and when it becomes a biphasic P-wave the tip has just entered the atrium, which is the optimal placement. A chest x-ray done in the recovery room should confirm that the catheter is at the T6 level. On the left side where there is more turns of the venous anatomy to negotiate, fluoroscopic control using a flexible wire is useful for placing the distal shunt in the right atrium properly. If a ventriculoatrial shunt is used, lengthening should be considered when the shunt tip rises above the T4 level, since above that distal malfunction is significantly more common.

 

Shunt Lengthening Surgery

 

Once a VP shunt is working properly, a consideration that comes up with the growth of the child is whether the shunt needs to be lengthened, and if so what age this should be done. The obvious question that must be answered in these situations is whether the child is shunt dependent and continues to need the shunt, as it becomes short. Most children are shunt dependent after they are shunted, and the dictum "once a shunt, always a shunt" is probably true for most children(22, 26). Despite this, careful thought should be given as to whether an elective shunt lengthening should be done to allow for the growth of the child. It is our practice that routine shunt lengthening are not performed based solely on the presence of a short shunt on a shunt series x-ray examination. We will electively lengthen a shunt if the following conditions are present:

 

1. The child is shown to be shunt dependent from previous shunt malfunctions.

 

2. There is poor availability to a pediatric neurosurgeon due to travel distance or access to medical care.

 

3. A CT scan showing slit ventricles and/or a thick calvarium, since both of these features are shown to be associated with a shunt dependency.

 

If any of these criteria are met then an elective revision will be done as the shunt tubing comes close to coming out of the abdomen. It is very important to never place a connector down at the abdominal end of the incision, since this will limit the ability of a catheter to elongate with continued growth and will frequently result in separation of the connector. If a child has previously had no shunt problems and is completely asymptomatic with a short shunt, then continued observation is recommended, and the shunt is not electively lengthened. In those cases, however, very close follow-up is needed, since a child may develop subtle signs of decompensated hydrocephalus with change in behavior patterns, a falloff in school performance, so that careful CT, neurologic and neuropsychologic follow up is mandatory.

 

Shunt Malfunction and Shunt Revisions.

 

In most cases of shunt malfunction, the diagnosis is obvious because of the overt signs of elevated intracranial pressure, including headaches, vomiting and lethargy. This mode of presentation occurs in approximately 70% of shunted children(54, 55). The other 30%, however, may present with more subtle signs of deterioration, with neuropsychologic, cognitive and behavioral symptoms heralding their shunt dysfunction(17). When a shunt malfunction is suspected, the first step is to determine the site of the malfunction (figure 1). Workup should begin with a CT scan or MRI scan to compare the ventricular size and show the most definitive signs of a malfunction: interval enlargement of the ventricles. A shunt series should also be done to look for continuity of the shunt, optimal placement of the shunt catheter or a distal shunt problem such as a short distal shunt. Most cases of shunt malfunction are due to occlusion of the proximal ventricular catheter. In these instances palpation of the shunt will show a valve that is slow to refill, or does not refill at all coupled with an imaging scan which shows ventricles large enough so that if the shunt were working properly, the valve should have refilled promptly.

 

Infection is an important cause of shunt malfunction. In cases where a suspected distal malfunction is present, the majority of this type of malfunction is due to a shunt infection(32). A preoperative CSF specimen from a shunt tap should be obtained to exclude this possibility. During shunt revisions an important principle is that the entire shunt system should be prepared and draped at the time of surgery, since unknown factors may become apparent in the course of a revision. The more proximal system can be tested by insuring free flow of CSF, whereas the more distal system can be tested by runoff using a manometer.

 

Proximal Catheter Obstruction.

 

The most common type of shunt malfunction is that of the proximal portion of the shunt(1). Most often the ventricular catheter becomes occluded with choroid plexus. The first issue relative to proximal catheter obstruction is the initial placement. As mentioned previously, the catheter needs to lie anterior to the foramen of Monroe. This can be accomplished either through the occipital placement with a catheter long enough to reach the front of the ventricular system or a frontal catheter placement. In performing a frontal catheter placement, the burr hole is placed at the coronal suture, approximately 12 cm. up from the nasion and 3 cm. off the midline. The catheter is directed towards the ipsilateral inner aspect of the pupil and pointed back slightly towards the external auditory canal. A 5-6 cm. ventricular catheter should be used when done through the frontal route. It is important to design the incision so that no part of the shunt hardware or shunt system lays under the incision line. The use of the frontal catheter placement is sometimes useful when there is the symptomatic slit ventricle syndrome, as will be discussed later. The occipital placement needs to be far enough posteriorly so that one does not risk placing the catheter through the internal capsule. When an error in placement of the ventricular catheter has been made, and this is detected on the postoperative scan, an assessment as to how the patient is doing should be made before deciding on elective revision. Suboptimally placed ventricular cathethers do not have to be automatically revised. There are two situations, however, which have a high incidence of leading to shunt failure, and elective revision should be considered. The first is the situation where the catheter is barely in the ventricle, so that when ventricular decompression occurs the catheter would actually become intraparenchymal. The second situation is a catheter that is located in the anterior part of the temporal horn where subsequent shunt occlusion is very likely to occur. The use of intraventricular flexible endoscopes are available to aid in several shunt related techniques. Endoscopes can be used to accurately place ventricular catheters, and fenestrate cysts and comunicate loculated ventricles. Intra-operative ultrasound can also be used to assist catheter placement and locate cysts. Both of these techniques, however are not yet proven to improve shunt surgery and lessen shunt complications.

 

When occlusion of a ventricular catheter is found, the catheter is usually adherent to the choroid plexus. It can be difficult to remove. Proximal catheter malfunctions are usually associated with the precipitous development of elevated intracranial pressure so that a rapid shunt revision should be performed shortly after the patient arrives at the hospital. The revision is performed, replacing the occluded catheter with a right angle ventricular catheter of an appropriate chosen length. This is then connected to the rest of the shunt assembly with a single straight connector. In cases where the ventricular catheter is stuck, several maneuvers may help free the catheter and avoid intraventricular hemorrhage from overly aggressive pulling on a stuck ventricular catheter. First, the ventricular catheter can be grasped with a hemostat and rotated. This may free the catheter from the underlying choroid plexus, and there may be a sudden give in the resistance. If the twisting of the catheter does not free it, the next step is to place the stylette down the shunt catheter and touch the Bovie cautery to the stylette. This sometimes will coagulate the choroid plexus at the tip of the catheter and release it. If there is still firm resistance, the catheter should be left in place, a new burr hole placed next to the existing one, and a new ventricular catheter utilized. Intraventricular endoscopy may be particularly useful in this situation. The adherent choroid plexus can be coagulated and freed from the ventricular catheter Using the working channel of the endoscope.

 

If a proximal revision needs to be performed in the face of relatively small ventricles, there are special considerations that will ensure the safety of this operations. It usually occurs in the setting of shunt dependency where the ventricles were slit-like when the patient was well, but have dilated only slightly with the shunt malfunction. It is frequently wise to place a tube at a frontal site leaving the blocked occipital catheter in place. A second alternative is to attempt to slide a new ventricular catheter down the same tract following the removal of the old ventricular catheter. No attempt should be made at placing the catheter with a stylette or brain needle, since it may veer off the tract and be difficult to hit the small ventricle. If the catheter does not find its way into the ventricle, then a single attempt with a brain needle or stylette in the ventricular catheter can be made to try and cannnulate the small ventricle. If this is unsuccessful, however, repeated attempts should not be made, and the operation should be aborted. The patient should be watched closely for signs of elevated intracranial pressure, as well as serial CT scans, and a proximal shunt revision subsequently performed when the ventricle has dilated. In this setting it may then be useful to utilize the frontal shunt placement, where it can be easier to hit a small ventricular system.

 

If a proximal revision is performed, and on placing the new ventricular catheter, blood-tinged CSF is obtained, then an effort should be made to clear the ventricular system of this bleeding which is coming from the choroid plexus. The new catheter should be attached to a three way stopcock and irrigated with saline until it begins to clear. This often requires patience, as it may require up to 20 minutes of gentle irrigation with saline. Once the CSF does clear, a new ventricular catheter should be placed so that there is no risk of a catheter being left in place which is occluded with a blood clot. These patients obviously need to be watched closely for signs of shunt failure within the first few hours after a revision, in which case a temporary ventriculostomy may be needed until the blood clears.

 

Distal Shunt Malfunction.

 

With the advent of Silastic shunt tubing the current site of choice for the distal tubing is in the peritoneum. Advantages of this site are

 

1. If an infection develops, it is not as potentially

life threatening, as with shunts in the venous

system.

 

2. A large amount of tubing can be place intra-

peritoneal to minimize the need for elective lengthening.

 

3. The overall ease in placing peritoneal shunts

in a relatively short operation.

 

Most distal malfunctions that are not associated with a short catheter are due to shunt infections. In the face of a distal malfunction, one should look carefully at the CSF prior to shunt revision to make sure an infection is not present. The presence of an abdominal pseudocyst detected on abdominal ultrasound or CT scanning should be considered a shunt infection until proven otherwise ( figure 2 ). It is especially important to allow the fluid to be analyzed in the laboratory for a longer period of time than usual to look for diptheroids, which may not grow on the culture medium in the first two days. Distal shunts have been known to erode into various abdominal viscera. There are reports of shunts eroding into the intestine, the bladder, the vagina and even protruding from the anus(18). Most of these complications were seen with the spring loaded distal shunt tubing, which now should be avoided.

 

Shunt Infections

 

Shunt infections continue to plague the neurosurgeon with an incidence of 2-8% of each shunt operation being associated with a postoperative shunt infection(3, 32, 41, 63). Overall, between 5 and 15% of shunts can be expected to become infected over the life of the shunt. Of these infections, 70% are diagnosed within one month after surgery and close to 90% by six months. There are, however, late shunt infections which can occur after six months of a shunt procedure. Shunt infections can present with signs of meningitis and ventriculitis, as well as with external signs showing redness along the path of the shunt and subcutaneously. In addition, signs of septicemia or peritonitis can be seen, depending on the type of shunt. Distal shunt malfunctions frequently accompany shunt infections. The most common agents are Staphylococci, but gram positive bacilli and enterobacilli can also contaminate shunts.

The treatment of shunt infections is somewhat controversial(21, 28, 32, 36, 41, 53). The gold standard treatment is to remove all of the shunt hardware system, and treat with appropriate antibiotics. Approximately 10 days later, a new shunt system can be placed. While the child is on the systemic antibiotics, a temporary ventriculostomy may be necessary to control the hydrocephalus. Once the infection is cleared, we will place the new VP shunt in the same site, unless there are skin abnormalities which would necessitate placing the shunt on the opposite side. After a shunt has been externalized for approximately 7 days, and CSF cultures have cleared, then a completely new VP shunt is placed, and antibiotics are continued for an additional two days. The antibiotics can then be discontinued. Once a shunt infection is identified, and is going to be treated with shunt removal, this is usually done within 2 days of the diagnosis, with antibiotics having been started at the time of the diagnosis. If, however, there are signs of peritonitis, or distal shunt malfunction, then the shunt should be externalized emergently. A septic child may be too great an anesthetic risk until the vital signs have stabilized.

 

In cases where a nonfulminating shunt infection is diagnosed within the first month after a shunt insertion, an attempt can occasionally be made to treat the shunt infection with intravenous and intrathecal antibiotics without removing the shunt system(36, 53). The families need to understand that this method of treatment may fail, and that ultimately the shunt would have to be removed. This method, however, does provide a way of saving the shunt system and successfully treating many early shunt infections (see figure). In these cases, two weeks of intravenous antibiotics with daily injection of intrathecal Gentamicin or Vancomycin is done. This method of treatment, however, must be abandoned if cultures do not become sterile within several days, or if more aggressive signs of infection are noted.

 

Vascular Shunts.

 

Ventriculoatrial shunts are often done as a second or third choice if the peritoneal cavity cannot be used. There are special aspects of shunt problems associated with ventriculoatrial shunts. A short atrial shunt is indicated when the tip of the catheter rises above the level of T4 on the plain chest x-ray. If a short VA shunt is noted, the surgeon needs to be prepared to attempt and lengthen the atrial shunt by suspending open the hole in the vein with 4-0 sutures placed from inside-out to hold the vein open. A new longer catheter can then sometimes be fed down the tract into the atrium. The surgeon must be prepared, however, to convert this to a peritoneal shunt or pleural shunt if a lengthening cannot be done.

 

Shunt nephritis is a unique complication to vascular CSF shunts(60). It presents with proteinuria, hematuria and progressive decline in kidney function. Shunt nephritis should be thought of as diagnostic of a shunt infection. The entire shunt should be promptly removed with external ventricular drainage used for 10 days, then a new distal site chosen for the new shunt. Often the CSF fails to grow the responsible organism, but culture of the shunt hardware will yield positive cultures. Obviously, generalized systemic sepsis with positive blood cultures can also occur with infected VA shunts.

 

Complications of VA shunts also include pericardial effusion, cardiac tamponade and endocarditis. In cases where a distal catheter becomes disconnected and lost in the superior vena cava or atrium, the neurosurgeon should not hesitate in consulting a cardiothoracic surgeon or interventional vascular radiologist to remove the lost catheter.

 

Shunt Dependency and the Slit Ventricle Syndrome.

 

Most children who are shunted early in childhood are permanently dependent on their shunt to maintain control of intracranial pressure and fluid dynamics(26). As discussed previously, the concept of arrested hydrocephalus is somewhat of a misnomer in that some children will have their hydrocephalus compensated and be shunt independent. This, however, is a dynamic situation and children who have compensated shunt independent hydrocephalus can become symptomatic at other times in their life and need careful follow-up to detect signs of decompensation. Experimentally, cats who are made hydrocephalic can go from a compensated to a decompensated state by altering the container properties of the skull leading to decompensation of the hydrocephalus(23).

 

When children with shunted hydrocephalus are shunt dependent, their signs of shunt failure fall into two groups. In 70% of children, shunt failure is heralded by acute and overt signs of elevated intracranial pressure, including headaches, vomiting and lethargy, which will progress to stupor and coma if prompt revision is not done(54). These "acute deteriorators" are children who when they are healthy have a ventricular size that has been reduced to either normal size or slit-like ventricles. In the face of a shunt malfunction the ventricles increase a slight to moderate amount. Of note, however, is that in this group of acute deteriorators even though the changes in ventricular size may be small, there will be an increase in ventricular size and pressure with an occluded shunt (). In addition to a small ventricular system, these children will also have a thickened calvarium.

 

In the other 30% of shunted hydrocephalic children, a shunt malfunction will present with slow or subtle signs of deterioration(17). These "subtle deteriorators" show a slow increase in their ventricular size with ventricles often being moderate to large in size when the diagnosis is made. They present with a change in behavior, neuropsychologic changes and often daily headaches. A falloff in school performance, change in attention span or change in behavior such as temper tantrums may be a sign of a suboptimally working shunt in this group which would prompt a shunt evaluation. Subtle deteriorators should be looked at as equally shunt dependent, as the acute deteriorator group and properly functioning shunt should be re-established through a shunt revision. There are biomechanical and CSF dynamic testing that can be done to differentiate these two groups, and there are biomechanical profiles characteristic of each group of shunt dependent children. These biomechanical profiles can offer explanations, explaining pressure phenomenon in these two shunt dependent states(17, 54, 55).

 

The problem of chronic headaches in the shunted child is a problem the pediatric neurosurgeon often faces(11). Since there are many causes for headaches in children, and some may be shunt related while many are completely unrelated to the shunt, a careful workup needs to be performed. Obvious other causes for daily headaches should be looked for, such as features of childhood migraine or sinus related headaches. Neuropsychologic problems which could be causing stress/tension headaches should also be evaluated. In the child with continued daily headaches, in whom CT scans do not definitively show much of a change in ventricular size, one needs to consider the possibility of one of the symptomatic slit ventricle syndromes, as will be discussed shortly(11, 13, 34, 61). In this group, referred to as the "symptomatic slit ventricle syndrome," there may be signs of elevated intracranial pressure such as headaches, vomiting and lethargy despite an adequately functioning shunt. Intracranial pressure monitoring may be useful in this group to demonstrate waves of elevated intracranial pressure. The ICP monitoring may also demonstrate the occasional child with low CSF pressure due to true overdrainage. It may also identify the child who has perfectly normal intracranial pressure physiology in whom the headaches are unrelated to a shunt problem. Obviously, if there is enlargement of the ventricles, then an occluded shunt is diagnosed, and an appropriate revision planned.

 

The Slit Ventricle Syndrome.

 

One of the factors that has become obvious in children who have had shunts placed in childhood is the concept of the "slit ventricle syndrome." This has been a concept that has been difficult to define, as well as to treat. There has been confusion in the literature as to what to expect in terms of post shunted ventricular size, what constitutes the slit ventricle syndrome, and does it automatically mean an occluded shunt(9, 10, 19, 20, 40). Early papers on the outcome in shunted hydrocephalus reported that the presence of slit ventricles were in and of themselves pathologic, and that efforts should be made surgically to revise the shunt and lead to enlargement of ventricles that had previously been made slit-like by the original shunt(27, 51, 62).These papers advocated upgrading valve pressures, placement of antisiphon devices, or subtemporal craniectomies done purely on the basis of follow up neuroimaging studies. Recently, we have gained more experience of what is the normal ventricular outcome after the placement of a shunt(10, 61). The presence of a slit like ventricular system after the placement of a shunt is actually quite common, and most of these children are totally asymptomatic from their slit ventricles. Since all working shunts will overdrain, whether there is a high pressure valve or low pressure valve, it is understandable that the incidence of asymptomatic slit ventricles is so high. In one large study, the incidence of asymptomatic slit ventricles after shunting was just over 60%. If children with hydrocephalus due to aqueductal stenosis, myelomeningocele, or posthemorrhagic hydrocephalus were considered, and those with large porencephaly were excluded, the incidence of asymptomatic slit ventricles post shunting then increased to 80% of shunted children(61). Table 1

 

The asymptomatic slit ventricle syndrome, therefore, refers to the presence of a slit-like ventricular system occurring on routine follow up scans of children with shunts. The symptomatic slit ventricle syndrome refers to a group of disorders with different etiologies, all related to the presence of post shunted slit-like ventricles. While the incidence of asymptomatic slit ventricles is relatively common, several studies have shown that the symptomatic slit ventricle syndrome occurs infrequently in approximately 6-12% of shunted children(10, 61). Rather than being one discreet entity, the symptomatic slit ventricle syndrome refers to several different symptom complexes, each with a different cause and each should be treated differently. Additionally in one study where the incidence of symptomatic slit ventricle syndrome was 11.5%, only 6.5% of the total group of shunted children needed surgical intervention to correct the slit ventricles. All these groups of children have as a common factor chronic headaches, occasional vomiting and lethargy. The subgroups that comprise the symptomatic slit ventricle syndrome include(10, 61): Table 2

 

1. Postural headaches only on assuming an upright posture due to true overdrainage with negative intracranial pressure.

 

2. The on-off again symptom complex due to elevated intracranial pressure waves seen in the presence of a functioning shunt ( figure 3 ).

 

3. Recurring proximal ventricular catheter obstruction due to collapse of the ventricles around the catheter with true shunt occlusion ( figure 4 ).

 

4. Chronic subdural fluid collections due to shunt

overdrainage.

 

ICP monitoring is useful to differentiate whether one is dealing with high pressure headaches or low pressure headaches, and to diagnose a child with this syndrome into one of these four groups. This can then lead to tailoring the treatment to the specific type of slit ventricle syndrome(10, 11).

 

The most common subgroup of the slit ventricle syndrome is the on-off again symptom complex(61). These children have waves of elevated intracranial pressure, often up to 50-75 mmHg of mercury, associated with acute neurologic deterioration(13). Their shunts are functional, as demonstrated by shunt flow studies as well by serial CT scans showing absolutely no change in the ventricular size with persistence of the slit-like ventricular system. In this group shunt revision would be futile, as the shunts are actually open. Medical treatment with Diamox or Lasix is useful to lower intracranial pressure until the bouts of pressure waves subside. These children typically have flare-ups of this every several months, with the CT scans always showing complete slit-like ventricles. As a second line of medication, antimigraineous therapy such as Inderal or Periactin is sometimes useful in aborting these waves of elevated intracranial pressure. This is probably related to the effects of these drugs on the cerebral vasculature. If the symptoms become severe and do not respond to medical treatment, then this group may benefit from some sort of cranial expansion procedure such as subtemporal decompressions, although it rarely becomes so severe that the surgeon needs to resort to this(12, 25, 62).

 

The group with recurring proximal ventricular catheter obstructions are diagnosed because the symptom complex is associated with a definite enlargement of the ventricular system. This enlargement may be small, however, so that serial CT scan reviews may be very helpful. Once the diagnosis of an occluded shunt is made by enlargement of the ventricles, then appropriate revisions are performed. With recurring proximal catheter obstructions, it is useful to move the catheter to a frontal placement, and in this group upgrading the valve pressure and/or insertion of an antisiphon device may prevent the collapse of the ventricles around the catheter and break the cycle of recurring shunt obstructions.

 

In the group with postural symptoms, their ICP monitoring will show negative pressures on assuming the upright position. In this group, upgrading the valve pressure, adding a second valve at the lower end of the shunt before it enters the abdomen, or insertion of an antisiphon device are all useful measures to prevent the overdrainage and the negative ICP. Subdural fluid collections should be treated by both external drainage of the subdural fluid collections, coupled with changing the shunt and adding either a higher pressure valve or an antisiphon device.

 

The treatment of the various slit ventricle syndromes, therefore, involves diagnosing which subgroup one is dealing with. Proper treatment can vary from increasing shunt function to decreasing function, depending on the various syndrome one is dealing with. It is most important to differentiate the group of recurring proximal shunt obstructions from the on-off again symptom group, since upgrading the valve pressure in the case of the on-off symptom group where there is elevated intracranial pressure waves would make the situation even worse in that the shunt would be less able to decompress CSF and abort these pressure waves.

 

This article has reviewed the current concepts in treating childhood hydrocephalus. Some of the technical details are the preferences of the authors, however they are details that have seemed to improve shunt survival and outcome. Clearly, the best treatment of shunt complications is to perform the initial shunt in a way to avoid these problems. The "slit-ventricle syndrome" is now better understood and the significance of small ventricles as well as the thinking involved in slit-ventricle problems can be rationally approached. Further research into choroid plexus secretory properties and shunt biomechanics are on-going in our laboratories to tackle these problems caused by shunts.

 

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61. Walker, M.L., Fried, A., Petronio, J., Wright, L.C. Diagnosis and treatment of the slit-ventricle syndrome In: Butler A. and McClone, D.(editors). Neurosurgical Clinics of N. America, 1993, W. B. Saunders Co. Publ., in press

 

62. Walsh, J.W., James, H.E. Subtemporal craniectomy and evaluation of shunt valve opening pressure inthe management of small ventricles - induced CSF shunt dysfunction. Neurosurgery 1982;10:698-703.

 

63. Walters, B.C., Hoffman, H.J., Hendrick, E.B., et al. Cerebrospinal fluid shunt infection: Influences on initial management and subsequent outcome. Journal of Neurosurgery 1984;60: 1014-1021.

 

64. Young, H.F., Hulsen, F.E., Weiss, M.H., Thomas, P. The relationship of intelligence and cerebral mantle in treated infantile hydrocephalus. Pediatrics 1973;51:38-44.

 

Published in Neurosurgical Quarterly, Nov. 1993

 

 

 

 

 

 

 

 

 

 

 

Table 1. Incidence of symptomatic versus asymptomatic post shunted slit-ventricles in hydrocephalic children.

 

Post-shunt Group

 

Incidence (% of shunted children)

Asymptomatic slit ventricles

75.0

Symptomatic slit ventricle syndrome

11.5

Symptomatic slit ventricle syndrome needing surgical correction

 

6.5

 

 

Table 2. Incidence of the various sub-groups of the symptomatic slit-ventricle syndrome.

 

 

Type of Slit-ventricle syndrome

 

 

Incidence (% with slit-vents)

On again - Off again symptoms

8.0

Recurring proximal shunt malfunctions

5.0

Postural headaches - low ICP

4.0

Subdural hematomas

2.0

 

 

 

Legends

Figure 1

CT scan of an infant with a head circumferance well above the 98% and crossing percentile lines. There is slight ventricular enlargement and enlargement of the subarachnoid space, indicating "benign external hydrocephalus". A shunt was not done and the head size plateaued by 18 months.

Figure 2

Abdominal CT scan in a boy with several months of headache and low grade fever. The shunt was externalized based on this abdominal pseudocyst and a diptheroid organism was cultured from the distal shunt catheter.

Figure 3

Two sets of CT scans in a child with severe headaches and lethargy. Scans on the left are when he was asymptomatic. Scans on the right were when he had the current signs of elevated intracranial. There is no interval increase in ventricle size and his signs resolved in 36 hours. This is an example of the on-again, off-again symptom complex of the slit-ventricle syndrome, with a functioning shunt.

Figure 4

Serial CT scans in a child with slit-ventricle syndrome and recurring proximal shunt occlusions. Left - CT on admission showing minimal ventricular enlargement. Center - With worsening signs, followup CT shows significant enlargement indicating a shunt blockage requiring a revision. Right - After shunt revision, the ventricles become slit like which is optimal for this child.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 




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