ventriculostomy

[vĕn-trĭk′yə-lŏstə-mē]
n.
  1. A surgical procedure used in the treatment of hydrocephalus in which an opening is established in a ventricle, usually from the third ventricle to the subarachnoid space.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.