Cerebral arteritis with unusual distribution.

Giant cell arteritis (GCA), especially its cerebral manifestation, is probably underdiagnosed. Very few lesions affecting the carotid siphon have been reported but no reference can be found to the disease involving the anterior or posterior cerebral arteries. In the case presented here, anterior and posterior cerebral arteries were involved, as well as both carotid siphons; and angiography was an important ingredient of the diagnosis. The differential diagnosis is discussed, and a review of the literature is presented which uncovered several misconceptions regarding the diagnosis of GCA. The importance is stressed of recognising this life-threatening condition, which can be effectively controlled with steroids. The radiologist can be the first person to raise the alarm.