Indications
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Patients with late-onset (adolescent or adult) nontumoral obstructive hydrocephalus have the highest rate of success after endoscopic third ventriculostomy (close to 90%). The high success rate in this group is likely related to the presence of intact pathways for cerebrospinal fluid (CSF) absorption.
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Patients with obstructive hydrocephalus resulting from other etiologies also have high success rates after this procedure. These etiologies include CSF pathway obstruction from tumors, cysts, infectious or hemorrhagic processes, and congenital obstructive hydrocephalus.
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Attempts to treat other forms of hydrocephalus with endoscopic third ventriculostomy have lower rates of success and are controversial. Regardless, successful outcomes have been reported after this procedure in patients with spinal dysraphism–associated hydrocephalus, slit ventricle syndrome, shunt infection or malfunction, normal-pressure hydrocephalus, encephalocele-associated hydrocephalus, and idiopathic hydrocephalus.
Contraindications
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Patients who have anatomic features that prevent them from being able to undergo endoscopic third ventriculostomy safely are not candidates for the procedure. The patient must have sufficient space between the basilar artery and the clivus under the floor of the third ventricle and a sufficiently enlarged third ventricle to allow for movement of the endoscope without injury to the lateral walls of the ventricle or surrounding structures.
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Patients with a history of prior whole-brain radiation, meningitis, or subarachnoid hemorrhage with associated subarachnoid scarring have impaired CSF absorption pathways and are highly unlikely to benefit from endoscopic third ventriculostomy.
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Relative contraindications include the presence of communicating hydrocephalus, slitlike ventricles, thin cortical mantle, history of prior shunt placement or meningitis, and age younger than 2 years. Because successful reports have been described in patients who have all of these features, the decision to offer the procedure to patients with relative contraindications is at the discretion of the treating neurosurgeon.
Planning and positioning
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Before surgery, standard laboratory values should be obtained, including basic metabolic profile, complete blood count, and coagulation profile. The etiology of hydrocephalus should be assessed, and the likelihood of a successful outcome and possibility for future shunting procedures should be discussed with the patient and family.
Figure 51-1: Preoperative evaluation should include careful study of the patient’s ventricular anatomy. Sagittal magnetic resonance imaging (MRI) should be obtained to evaluate the relationship between the floor of the third ventricle and the underlying structures in the interpeduncular cistern.
Figure 51-2: After induction of anesthesia, the patient is placed in the supine position with a small roll under the shoulders. The head is placed in a doughnut-shaped head support or horseshoe headrest and elevated approximately 30 degrees to prevent excessive CSF loss. The endoscope monitor should be positioned directly opposite the surgeon for unobstructed viewing during the endoscopic portion of the procedure. A small area of the scalp is shaved, and after standard skin preparation and draping, a 2- to 3-cm vertical incision is made based at the coronal suture and in the mid-pupillary line.Related posts:
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