Anthrax meningoencephalitis

Abstract

Objective: To review reported cases of anthrax meningoencephalitis and describe the clinical findings, diagnostic test results, treatment, and outcome over the past 50 years.

Methods: Retrospective review of English language articles published since Haight's (1952) review.

Results: Thirty-four core articles were identified, describing 70 patients with cutaneous (29%), gastrointestinal (17%), inhalational (39%), and unknown (16%) sources of infection. Clinical signs on presentation included fever, malaise, meningeal signs, hyperreflexia, and delirium, stupor, or coma. CSF analyses demonstrated hemorrhagic meningitis, with positive Gram's stains and CSF cultures. Many patients presented in extremis following a prodromal period of 1 to 6 days, and 75% died within 24 hours of presentation. Despite aggressive treatment in many cases, only 6% (4 of 70) survived, none of whom had pulmonary anthrax. Surviving patients generally had a cutaneous portal of entry, were younger, and had less severely abnormal initial CSF results than patients who died. Most of the survivors recovered fully. Pathologic findings included hemorrhagic meningitis, multifocal subarachnoid and intraparenchymal hemorrhages, vasculitis, and cerebral edema.

Conclusions: Anthrax meningoencephalitis has a high case-fatality rate, even with aggressive antibiotic treatment and supportive therapy. Hemorrhagic meningitis should raise suspicion of anthrax infection, particularly if gram-positive rods are demonstrated on Gram's stain. Anthrax meningoencephalitis can develop from any primary focus, but survival appears to be most likely if meningoencephalitis develops from cutaneous anthrax. Treatment of surviving patients was generally begun before signs and symptoms of meningoencephalitis were present.