Suboccipital endoscopic management of the entrapped fourth ventricle: technical note

Entrapped fourth ventricle is the result of both inlet aqueduct and outlet fourth ventricular midline and lateral foraminae obstruction. It occurs as a sequalae of intracranial hemorrhagic or inflammatory disease condition. Usually it presents after previous shunting for communicating hydrocephalus with a period of improvement, after which manifestations of posterior fossa expanding process appear. The diagnosis of this rare condition is easy considering the patient past history and the recent clinical state, together with the midline CSF density of the dilated fourth ventricle in either the CT or MR images. The treatment options for this condition include open and endoscopic approaches together with the traditional ventricular to extracranial CSF diversionary procedures.

The aim of the study was to adopt a procedure for treatment of entrapped fourth ventricle that carries the advantage of the minimally invasive technique thus avoiding the complications of the traditional opened and shunt surgeries as well as decreasing multiple procedures due to aqueduct restenosis or stent fall.

Thirteen patients with symptomatic entrapped fourth ventricle underwent suboccipital endoscopic trans-fourth ventricular aqueductoplasty from May 2007 till November 2011. The Gabb endoscopic system was used and aqueductoplasty was performed using 3F Fogarty balloon followed by stent placement. Nine patients were females. The mean age was 3.6 years and the mean follow up period was 23 months. All cases had a previous one or two supratentorial VP shunt placement.

Short stent was used in eight patients. During the follow up, stent migration occurred in five of them. Three of these five patients developed posterior fossa compression manifestations due to aqueduct restenosis. Long stent from the aqueduct till the bur hole site for these three patients and the following five patients was used. All cases showed both clinical and radiologic improvement. Apart from the stent migration, no procedure-related complications were encountered.

Endoscopic suboccipital paramedian aqueductoplasty with the use of a stent is a safe and effective surgical option that-in our opinion-should stand as the first line treatment for the entrapped fourth ventricle. Long stent is better used after aqueductoplasty to avoid the restenosis if no stent is used or stent fall after short stents. However, good case selection, familiarity with this fairly common endoscopic approach and longer follow-up is needed for obtaining an optimal result.