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Third Ventriculostomy

A third ventriculostomy refers to the surgical creation of a communicating channel between one of the brain's interior fluid chambers, the third ventricle, and an external fluid cistern on the underside of the brain.

This is done to bypass any obstruction to the free flow of fluid within the interior of the brain that results in hydrocephalus. The creation of the channel reestablishes normal circulation of the cerebrospinal fluid effectively treating the hydrocephalus by allowing the cerebrospinal fluid to circulate up to pores (villi) where it is absorbed back into the bloodstream.

Prior to the availability of shunts, third ventriculostomy was the most favored treatment of hydrocephalus. In 1920 a surgeon reported on doing an operation to make an outlet at the base of the brain to treat hydrocephalus. He later altered the surgery, making the outlet in the region we currently use. He reported a 39 percent success rate in the 92 patients he performed this later procedure on. On further analysis, he found that those over the age of 1 (n = 29) had an 83 percent success rate, but those under 1 (n = 63 with 10 loss to follow-up) had only a 23 percent success rate. A New York physician reported a 54 percent success rate, with a 15 percent mortality rate in 44 patients upon whom he performed such a surgery. The mortality rates with these procedures was too high to sustain interest in them, however, once shunting materials became available. These were "open" procedures where the sites for the openings were directly visualized (i.e., major brain operations). 

As experience was gained with shunting of hydrocephalus, and physicians grew to appreciate the incidence of morbidity and mortality of shunted patients with long-term follow-up, interest was rekindled in third ventriculostomy for the treatment of obstructive hydrocephalus. In 1968 a surgeon reported on 15 patients who had a catheter placed via a small hole in the skull through the third ventricle, penetrating its floor to rest straddling the floor with inlets in both the third ventricle and interpeduncular cistern. In 1973 a physician described 20 patients in whom he guided a cutting instrument to the floor of the third ventricle using a camera sitting in the lateral ventricle to make an outlet. He reported a 75 percent success rate in control of the hydrocephalus. Ten patients had the floor of their third ventricle opened using a stereotactically guided cannula with a 100 percent success rate by two surgeons.

Currently, there is a consensus that obstructive hydrocephalus due to late-onset aqueductal stenosis (see Hydrocephalus and Its Treatment (Shunts)) is an indication for a third ventriculostomy. This includes acquired aqueductal stenosis secondary to tumors in the upper brain stem. The efficacy of a third ventriculostomy for other types of obstructive hydrocephalus is less clear. With regard to "congenital" hydrocephalus (occurring at or close to birth) due to aqueductal stenosis, several authors have reported poor outcomes when treating the condition with third ventriculostomies, postulating that there had been a congenital failure of the normal fluid pathways outside of the brain to develop. An Australian physician, on the other hand, favors an attempt to treat the condition with a third ventriculostomy, reporting a 60 percent success rate, a rate of success identical to that of his late-onset obstructive hydrocephalic treated with third ventriculostomies.

There have also been reports of successfully treating other type of flow-blockage problems with a third ventriculostomy. Of the 28 cases treated of late-onset aqueductal stenosis and 14 cases of obstructive hydrocephalus due to a tectal plate tumor, there has been a 90 percent success rate. One of the failures was in an individual who had been shunted for late-onset aqueductal stenosis, developed a subdural hematoma after the shunting, and then had the shunt removed and a third ventriculostomy performed. Although a follow-up MRI scan showed flow through the third ventriculostomy, there was a progressive enlargement in the ventricles. The patient was subsequently shunted.

At least two other patients treated at other institutions had similar experiences, so it appears that a history of subdural hematoma is a relative contraindication to performing a third ventriculostomy. We have had a 75 percent success rate in treating congenital aqueductal stenosis (four cases). Only 40 percent of the third ventriculostomies done to treat hydrocephalus in children with brain stem gliomas have been successful (five cases), and we have seen a 100 percent failure rate for third ventriculostomies in five infants with myelomeningoceles and associated hydrocephalus. Older children with a history of myelomeningocele, shunt dependency and a need for a shunt revision are better candidates for a third ventriculostomy.