Anatomic Variations of the Floor of the Third Ventricle: An Endoscopic Study.

Objective: Anatomical variations of the floor of the third ventricle are common in hydrocephalic patients and can significantly affect outcomes of endoscopic third ventriculostomy (ETV). We sought to categorize variations in third ventricle anatomy and to discuss the implications of these variations for ETV.

Methods: Intraoperative videos and pictures of 50 patients who underwent ETV between April 2001 and August 2010 were reviewed. Twenty-seven patients with clearly demonstrable third ventricular floors that satisfied our criteria were selected for the study.

Results: Images of variations were organized into the following categories: 1) thinned floor, 2) thickened floor, 3) partially effaced floor, 4) ballooning/herniating floor, 5) small prepontine interval, 6) narrowed third ventricle, and 7) other significant anomalies.

Conclusions: The third ventricle is a common site for anatomical variations in hydrocephalic patients. A good knowledge of these variations is essential before performing ETV, because they have the potential to increase operative risk.