Other causes (2 to 27%), including (from most to least common): vasculitis, cocaine use, non-atherosclerotic vasculopathy, multiple etiologies, arterial dissection, medication use, sickle cell crisis, carcinomatous meningitis, carotid stump syndrome
Cryptogenic (10 to 32%)
Investigations
Assess for rash, manifestations of neurosyphilis, signs of infection
Laboratory investigations
If indicated, lumbar puncture for cell count, protein, glucose, and other infectious workup