Acute limbic encephalitis is seen in patients with herpes simplex virus infection. These patients have an acute onset, with fever, behavioral changes, and meningismus. MRI reveals swelling, often with hemorrhage, bilaterally but asymmetrically in the temporal lobes, cingulate gyri, insula, or subfrontal areas.
The virus usually cannot be cultured from the cerebrospinal fluid, but polymerase-chain-reaction analysis for viral DNA is reliably positive after the first 2 to 3 days.
Human herpesvirus 6 may cause more indolent limbic encephalitis, but HHV6 encephalitis is usually limited to patients with immunosuppression.
New England Journal of Medicine - Vol. 359, No. 8, August 21, 2008