Cisternal enhancement after subarachnoid hemorrhage.

Abnormal computed tomographic enhancement in the basal cisterns and cortical sulci was observed in 21 of 42 patients after subarachnoid hemorrhage. The appearance is similar to that described in granulomatous infection and metastatic disease. The enhancement was associated with an increased incidence of hydrocephalus, but it did not correlate with clinical grade, arterial spasm, location of bleed, or temporal relation to bleed. Presumably, abnormal cisternal enhancement is due initially to increased vascular permeability and later to increased vascularity associated with arachnoiditis.