6.2.6\ Slit Ventricle Syndrome

6.2.6.1\ Discussion

Slit ventricle syndrome can be defined as a hydrocephalus patient that presents with headache and narrow ventricles on imaging, with a functioning cerebrospinal fluid shunting device, but an elevated cerebrospinal fluid pressure when tested by lumbar puncture. This relatively rare condition may result from reduced brain compliance, often due to the use of a siphoning-valve shunting device at an early age. On imaging, the ventricles appear to be very small and do not increase in proportion to the increased intraventricular pressure (Fig. 6.36). The condition can be very serious and should not be misinterpreted as small ventricles simply due to overshunting.

Fig. 6.36  Slit ventricle syndrome. The patient had clinical evidence of intracranial hypertension. Coronal CT image shows small size of the ventricular system with right transparietal shunt catheter in position

6.2.7\ Chronic Overshunting

and Associated Findings

6.2.7.1\ Discussion

Chronically shunted patients occasionally can develop intracranial hypotension secondary to long-term overdraining of cerebrospinal fluid that manifests as diffuse meningeal thickening and enhancement (Fig. 6.37). This process may extend into the cervical spine and rarely results in cervical myelopathy. Otherwise, headache is a common symptom. However, elderly patients are usually asymptomatic due to brain atrophy.

Chronic low-pressure ventricular shunting in children may also lead to hyperostosis cranii ex vacuo. This process is usually diffuse and involves predominantly the inner table of both the skull base and calvarium (Fig. 6.38). On CT, the new bone formation can display a layered appearance. In infants, there may be associated premature closure of the sutures (Fig.6.39), which in turn can result in a cranial stenosis syndrome of elevated intracranial pressure.

Fig. 6.37  Intracranial hypotension. There is diffuse thickening and avid enhancement of the meninges. A right parietal ventriculostomy catheter (arrow) is present

Fig. 6.39  Post-shunt craniosynostosis. Axial CT image (a) after recent ventriculoperitoneal shunt insertion shows patent cranial sutures. Follow-up axial CT image

(b) obtained several months later shows interval closure of the cranial sutures