Dementia and capsular genu ischemia in patients with severe bacterial meningitis.

Infarction in the genu of the internal capsule causes dementia that is characterized by abulia, lethargy and memory loss without obvious motor palsy (capsular genu syndrome). We found infarction or decreased cerebral blood flow in the genu of the internal capsule in 6 of 13 patients with severe bacterial meningitis. Four of these six patients developed post-meningitis dementia, characterized by abulia, lethargy, and memory loss. Of 24 patients with viral meningitis, none developed capsular genu ischemia or post-meningitis dementia. In patients with severe bacterial meningitis, capsular genu ischemia may play some role in the development of post-meningitis dementia. In patients with viral meningitis, absence of such ischemia may explain, at least in a part, the rarity of post-meningitis dementia.