Transient reactive lymphocytosis associated with acute middle cerebral artery aneurysmal rupture

A 78-year-old female with a prior history of migraine and mild hypertension presented to the emergency room with severe headache and mild meningism. The patient had transient significant reactive lymphocytosis, and a computed tomography scan of the head followed by a cerebral angiogram revealed an acute right-sided middle cerebral artery aneurysm rupture. This case illustrates that acute changes in the peripheral blood smear may suggest a more sinister cause for the presentation such as that of a ruptured middle cerebral artery aneurysm, particularly when multiple etiology for the presentation is possible.