Brainstem encephalitis: an unusual presentation of herpes simplex virus infection

Herpes simplex virus (HSV) encephalitis has a predilection for the temporal and frontal lobes but occasionally affects the brainstem. We describe a patient who developed HSV brainstem encephalitis that progressed to quadriplegia. Using MEDLINE, we conducted a comprehensive review of other published cases of HSV brainstem encephalitis. Twenty-four published cases of HSV brainstem encephalitis met our inclusion criteria. The mean age was 41.4 years (range 18-71). HSV-1 was the etiologic agent in 79% of reported HSV brainstem encephalitis cases, and HSV-2 accounted for 21% of cases. Infection was limited to the brainstem in 29% of cases and multi-focal, including the brainstem, in 71%. Common manifestations of HSV brainstem encephalitis included neuro-ophthalmologic findings (81%), cranial nerve deficits (69%), and fever (69%). Quadriplegia, as occurred in our patient, was an unusual finding (19%). The mortality rate of HSV brainstem encephalitis was 41%. Intravenous acyclovir showed a beneficial effect on mortality (75% vs. 22%, p = 0.06). HSV brainstem encephalitis is a distinct type of HSV encephalitis. With the increasing use of HSV-PCR, more cases of HSV brainstem encephalitis may be identified. A greater recognition of this syndrome will help better define its optimal treatment and prognosis.