The Operation for Slit Ventricle Syndrome in Children

General Principles

• Goal of surgical intervention: The goal of surgical intervention for this syndrome is the resolution of symptoms. Secondary benefit is obtained if shunt independence is achieved.
• Prevention of slit ventricle syndrome: Prevention with initial placement of a programmable valve or a valve with an antisiphon chamber has been advocated (11).
• Shunt removal without replacement: After externalization, the shunt may be removed without replacement if the ICP is normal after an EVD has been clamped.

Indicated surgery as function of ICP

• Elevated ICP and shunt malfunction: Revision can be very difficult in the setting of small ventricles.  Sometimes the use of an endoscope to assist in the proximal catheter revision can be helpful. The valve can be changed to a programmable valve, or an antisiphon device can be added to an existing shunt to prevent further failures.  An option remains to externalize the shunt as a ventriculostomy and monitor ICP (patient monitored closely in ICU), allowing for an increase in ventricular size so an ETV can be performed safely, possibly making the patient shunt independent; this option depends on ventricular compliance (see Management algorithm below) (12-14).
• Elevated ICP and shunt failure but normal ventricular volume:  Shunt revision, open or endoscopically, can be attempted. Shunting the subarachnoid space, i.e., a lumboperitoneal shunt, may be required if the shunt revision fails, or a cranial expansion can be considered.
• Elevated ICP and shunt functional: Shunt revision is not indicated. This situation occurs in cephalocranial disproportion and often requires a cranial enlargement procedure, especially if there is cranial deformity. A lumbar shunt can be added to the existing ventriculoperitoneal shunt. Patients with spina bifida, previous lumbar surgery, severe deformity, or stenosis may be excluded as candidates. In those cases, there are reports of decompressive surgery for the enlargement of the posterior fossa to create a larger cisterna magna. The enlarged cistern is then shunted. There are only two case reports available, and the revision rates and technical limitations are significant (23, 24).   
• Low ICP or overdrainage:  Nonsurgical management can be attempted with monitoring of symptoms.  Otherwise, a valve upgrade or the addition of an antisiphon device will be needed.

Intervention

Shunt revision

• Endoscopic-assisted revision: Preparation must be made to cannulate the ventricular catheter with an endoscope that fits down the barrel of the shunt catheter. If the tip is near the choroid plexus or in a suboptimal location, replacing the catheter with a longer or shorter one can be helpful.
• Computer-assisted image-guided placement: Neuronavigation can also be used for placement of a new catheter into a ventricle.

ETV

• Adequate ventricular volume required: An ETV is performed through a frontal bur hole (new or previous shunt bur hole). The ventricles, namely the lateral and third, need to be expanded before an ETV is undertaken (usually by shunt externalization).
• Adequate pre-pontine cisternal space: There should also be adequate pre-pontine cisternal space for ventriculostomy.

Cranial expansion

• Several techniques available: Various techniques have been endorsed for cranial expansion, from occipital craniotomy with decompression of venous sinuses (coronal suture posteriorly) to simple subtemporal decompression with or without dural opening, to morsellation procedures (19, 20, 26).