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ALTERNATIVE OPERATIVE APPROACHES TO HYDROCEPHALUS

 

Endoscopic Third Ventriculostomy

Percutaneous endoscopic third ventriculostomy (ETV) has been repopularized as a technique for bypassing an obstruction at the aqueduct of Sylvius or fourth ventricle in non-communicating hydrocephalus. It has gained appeal as the result of advances in stereotactic and endoscopic technology, and in some cases may eliminate the need for ventricular shunting and its associated risks.

 

ETV is performed through a standard coronal burr hole approach. A small endoscope is guided into the lateral ventricle, then through the foramen of Monro into the third ventricle. A probe is used to puncture the floor of the third ventricle anterior to the mammillary bodies. The fenestration is enlarged using a small balloon catheter. All instruments are introduced through working channels in the thin endoscope sheath, so the procedure is “minimally invasive”. It works by allowing CSF to exit the ventricular system and then circulate normally in the subarachnoid space. ETV is thus an effective treatment for non-communicating hydrocephalus e.g. aqueductal stenosis. It is not effective for communicating hydrocephalus, because the obstruction in this condition is further downstream.

ETV works best in patients with acquired or late-onset presentation of aqueductal stenosis. Presumably, this is because these patients have already developed adequate absorptive pathways distal to the acquired aqueductal obstruction. In such patients, third ventriculsotomy is simply a means of bypassing an obstruction at the aqueduct of Sylvius. Careful patient selection is essential for successful third ventriculostomy.


Choroid Plexus Coagulation

Coagulation of choroid plexus has been utilized as a treatment for hydrocephalus with generally unsatisfactory results. The aim of treatment is to decrease CSF pressure by reduction CSF production. Since not all CSF is produced by the choroid plexus, there is a theoretical limit to the efficacy of this procedure.

The idea of removing or coagulating choroid plexus as a treatment for hydrocephalus dates back to the turn of the century. Early procedures met with limited success, but subsequent investigators reported improved results and lower morbidity and mortality rates. The efficacy of choroid plexus coagulation is difficult to assess because there are no controlled comparisons with ventricular shunting procedures, and authors use variable criteria to judge success of the procedure. In general, although it is now technically feasible, choroid plexus coagulation has been largely abandoned as ineffective as a means of controlling hydrocephalus.