Callosal angle

The callosal angle has been proposed as a useful marker of patients with idiopathic normal pressure hydrocephalus (iNPH), helpful in distinguishing these patients from those with ex-vacuo ventriculomegaly (see hydrocephalus versus atrophy). 

Method

Ideally the angle should be measured on a coronal image perpendicular to the anterior commissure - posterior commissure (AC-PC) plane at the level of  the posterior commissure ^1,2.

Values

In general patients with iNPH have smaller angles than those with ventriculomegaly from atrophy or normal controls. 

A normal value is typically between 100-120°. In patients with iNPH that value is lower, between 50-80° ².  

In one study, symptomatic iNPH patients who responded to shunting had a significantly smaller mean preoperative callosal angle (59° (95% CI 56°-63°)) compared with those who did not respond (68° (95% CI 61°-75°)) ¹.