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136 Section II: Intracranial Procedures

middle of the spinous process of C2. The muscles are sharply diverticulum location, a 25G needle can be used to puncture the
incised on the midline, elevated off the occiput, and retracted later- dura and a small amount of fluid aspirated. Do not remove so
ally to expose the caudal portion of the occiput and the arch of C1. much fluid that the diverticulum collapses. A small hole is drilled
Hemorrhage is controlled with bipolar electrocautery. in the bone adjacent to the site of catheter insertion and nonab-
A high‐speed air drill and Lempert and Kerrison rongeurs are sorbable monofilament suture is preplaced to secure the catheter.
used to remove a portion of the occiput. Borders of the craniec- Alternatively, the suture can be tied to a small titanium screw
tomy are the atlanto-occipital joints laterally, the foramen mag- inserted into the skull.
num ventrally, and a point approximately halfway between the The dura is coagulated with bipolar cautery and incised just large
external occipital protuberance and the dorsal aspect of the fora- enough to accommodate the ventricular catheter without resistance
men magnum dorsally. The diverticulum is located dorsal and and avoid CSF leakage around the catheter. The ventricular catheter
rostral to the cerebellum. Larger diverticula are evident at the is placed into the diverticulum in a transverse orientation and
dorsal portion of the craniectomy whereas smaller diverticula secured to the edge of the craniectomy with the preplaced suture
may require gentle retraction of the cerebellum ventrally for tied in a finger‐trap pattern around the catheter or anchored to the
exposure. The dura over the diverticulum usually has a blueish titanium screw. The distal portion of the shunt is tunneled subcuta-
tint. The dura is incised on the midline, extending from the dor- neously and inserted into the abdomen as described for ventriculo-
sal to the ventral aspect of the craniectomy. Any dural vessels are peritoneal shunt placement. The cranial and abdominal incisions
coagulated with bipolar cautery and the dura is sharply incised. are closed routinely.
The outer wall of the diverticulum is often adherent to the dura.
Most of the outer wall of the diverticulum is excised to provide a
wide communication with the subarachnoid space. There is little Postoperative Management
if any benefit in attempting to strip the inner wall of the diver- Adequate analgesics are provided and any antiseizure medications
ticulum from the adjacent neural tissue. A collagen‐based dural continued. For patients with a diverticuloperitoneal shunt, two‐
graft implant (Duraform; Codman & Shurtleff, Raynham, MA) is view radiographs of the entire shunt from skull to abdomen are
trimmed to fit the craniectomy and laid in place. Closure is obtained. Any preoperative medications such as prednisone and
routine. diuretics are tapered as the neurological deficits resolve. If neuro-
If the majority of the diverticulum is located rostral to the tento- logical deficits persist or recur later, CT or MRI is performed to
rium, exposure involves a rostrotentorial craniectomy or if neces- assess diverticulum size.
sary a combined rostrotentorial/suboccipital craniectomy with
sacrifice of the transverse sinus. The combined approach provides
greater exposure but carries a risk of hemorrhage from the trans- Prognosis
verse sinus. Rostrotentorial craniectomy is described in Chapter 11. The prognosis with both fenestration/marsupialization and
For a combined lateral rostrotentorial/suboccipital craniectomy, a shunting is generally good [18,20,23,24]. Neurological deficits
horseshoe‐shaped incision is made starting on the dorsal midline at usually resolve soon after surgery, although seizures may persist.
the bregma, extending caudally to the occipital protuberance, and Complications associated with diverticuloperitoneal shunting are
curving ventrally to a point just caudal to the ear. The temporalis similar to those for ventriculoperitoneal shunting, including shunt
fascia is incised lateral to the sagittal crest, leaving enough fascia obstruction, migration, disconnection, and infection. The main
medially to suture for closure. The temporalis muscle is reflected off complications associated with diverticulum fenestration are incom-
the lateral surface of the skull down to the level of the zygomatic plete resolution or recurrence of the diverticulum.
arch and retracted rostrally. The muscles overlying the occiput are
incised along the nuchal crest on the operated side and reflected
caudally. A rostrotentorial craniectomy is created in the parietal Editors’ Note
and temporal bones using an air drill as described. An occipital cra-
niotomy is performed as described for diverticulum fenestration. Fenestration and Marsupialization
The drill is then used to remove the bone overlying the lateral of the Lateral Ventricles
aspect of the transverse sinus, being careful not to penetrate the In human pediatric neurosurgery, neuroendoscopic fenestration
sinus. After the majority of bone is removed to expose the sinus, of the third ventricle into the basal cistern (endoscopic third
bone wax is placed in the dorsal and ventral aspect of the boney ventriculostomy or ETV) has often replaced the use of ventricu-
canal to occlude the transverse sinus. The collapsed sinus and any loperitoneal shunts in the treatment of hydrocephalus. The tech-
remaining bone are removed with a Lempert and Kerrison ron- nique restores physiological CSF circulation, and implantation of
geurs. This allows the rostrotentorial craniectomy to be connected external shunt valve systems can be avoided [25]. A technique
with the occipital craniectomy. using the same principle in young dogs and cats has been used
successfully by one of the editors (A.S.). This technique involves
a small opening into the lateral ventricle through an overlying
Diverticuloperitoneal Shunt cerebral gyrus, insertion of a small uninflated Foley catheter,
Shunting can be performed with an occipital, rostrotentorial, or a inflation of the catheter, removal of the inflated catheter to
combined rostrotentorial/suboccipital craniectomy, depending enhance the size of the fenestration and to pull the ventricular
on the location of the majority of the diverticula. A shunt system lining into the opening, and finally performing a duraplasty over
designed to treat hydrocephalus is used. Once the bone is the fenestration to allow flow of CSF into the subarachnoid space
removed the diverticulum is located. The site of catheter inser- (Figure 14.13). Short‐term results have been very good in a vast
tion is located at the ventrolateral aspect of the diverticulum majority of patients [26].
adjacent to the lateral edge of the craniectomy. To confirm the