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).
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.
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.
- 1. Virhammar J, Laurell K, Cesarini KG et-al. The callosal angle measured on MRI as a predictor of outcome in idiopathic normal-pressure hydrocephalus. J. Neurosurg. 2014;120 (1): 178-84. doi:10.3171/2013.8.JNS13575 - Pubmed citation
- 2. Ishii K, Kanda T, Harada A et-al. Clinical impact of the callosal angle in the diagnosis of idiopathic normal pressure hydrocephalus. Eur Radiol. 2008;18 (11): 2678-83. doi:10.1007/s00330-008-1044-4 - Pubmed citation