prevalent in infants due to the smaller surface area for fluid resorption.

•\ Ventriculoureteral Shunts: The terminus of the shunt is located in the ureter through a Roux-­ en-­Y anastomosis. Diversion of cerebrospinal fluid can result in electrolyte abnormalities and cystitis.

•\ Ventriculocholecystic Shunts: Shunt tip terminations in the gallbladder have a satisfactory long-term success rate of over 60%. The most common complications include obstruction and cholecystitis, with an incidence of about 10% each.

6.1.4\ Ventriculosubgaleal Shunts

6.1.4.1\ Discussion

Ventriculosubgaleal shunting is diversion of intraventricular cerebrospinal fluid into the subgaleal space for temporary absorption by the subcutaneous tissues of the scalp. These shunts are a relatively straightforward, effective, and safe option for temporary treatment of hydrocephalus. Ventriculosubgaleal shunting can avoid the need for external drainage or frequent cerebrospinal fluid aspiration in unstable neonates until the cerebrospinal fluid characteristics and abdomen are suitable for ventriculoperitoneal shunting. On CT and MRI, the ventriculosubgaleal shunt catheter can be traced from the ventricular system to the subgaleal space, where there is often a variable amount of cerebrospinal fluid accumulation (Fig. 6.12).

6.1.5\ Ventriculo-cisternal

(Torkildsen) Shunts

6.1.5.1\ Discussion

The Torkildsen shunt was initially conceived to bypass aqueductal stenosis and allow cerebrospinal fluid to drain directly through an extracranial pathway from the lateral ventricle to the cervical subarachnoid space. While this technique has been replaced by endoscopic third ventriculocisternostomy, the Torkildsen shunt approach is occasionally necessary in cases of complex hydrocephalus. The Torkildsen shunt typically courses from a

a

c

lateral­ ventricle to the cisterna magna at the level of the foramen magnum (Fig. 6.13). These shunts are introduced into the lateral ventricle via a pari- eto-occipital burr hole and then exit to the extracranial space via that burr hole to course into the foramen magnum where the shunting tube is introduced into the cervical subarachnoid space. Occasionally, a C1 laminectomy is required for this procedure. The proximity of the distal end of the shunt to the cervicomedullary junction can predispose to upper spinal cord compression, rarely resulting in cervical myelopathy. Imaging can be used to evaluate such symptoms.

b

d

Fig. 6.13  Ventriculo-cisternal shunt. The patient has a history of chronic headaches and multiple shunts, including a Torkildsen shunt that was placed many years before. Lateral radiograph (a) and axial CT images (b–d) demonstrate the course of the internal shunt catheter (arrows)

from the right lateral ventricle, inferiorly behind the cerebral hemisphere and cerebellum, and terminating at the level of the foramen magnum. There is a right occipital burr hole, through which the catheter was introduced

6.1.6\ Percutaneously Accessed

Cerebrospinal Fluid

Reservoirs

6.1.6.1\ Discussion

The subcutaneous cerebrospinal fluid devices consist of reservoirs positioned over the calvarium in the subgaleal space and catheters inserted into the intracranial compartment. The catheters can be inserted into the ventricular system or tumor cyst

a

for decompression and connected to the reservoirs (Fig. 6.14). The reservoir can be accessed percutaneously using a needle. Ventricular reservoirs can also be converted into ventriculosubgaleal shunts or ventriculoperitoneal shunts, as many of these also have side ports. Complications of ventricular reservoirs include skin erosion and intracranial migration, which may require endoscopic retrieval, as well as generic complications encountered with all shunting systems.

b