(126) Rapid Progression to Brain Death in Primary Amebic Meningoencephalitis

Introduction: Primary amebic meningoencephalitis (PAM) caused by Naegleria fowleri is rare, rapidly progressive, and often fatal. The Centers for Disease Control has documented 154 US cases with only 4 survivors; thus timely diagnosis and treatment remain a challenge.

Description: A previously healthy 17-year-old female, who often swam at a lake, was admitted to PICU with 5 days of fever, headache, and 24 hours of progressive altered mental status. In the pediatric emergency department, the patient was profoundly encephalopathic with Glasgow Coma Score of 6 and decorticate posturing. She was emergently intubated and given hypertonic saline. Head CT demonstrated early hydrocephalus without herniation or bleed. Brain MRI showed severe leptomeningitis, encephalitis with evolving cortical infarcts, and mild hydrocephalus. Acyclovir, ceftriaxone, doxycycline, metronidazole, and vancomycin were administered. In the ICU, osmotherapy was continued, and an external ventricular drain was placed with initial ICP 50-70mmHg. Hyperventilation, sedation, neuromuscular blockade, and pentobarbital infusion led to ICP less than 20mmHg. That evening her pupils became fixed and dilated with absence of brain activity on continuous electroencephalogram which continued despite discontinuation of all sedation and paralytics. A repeat head CT at 48 hours demonstrated diffuse cerebral edema, severe effacement of basilar cisterns with loss of gray-white differentiation, and tonsillar herniation. CSF analysis was negative for bacteria and common viruses. Amebae trophozoites were visualized in the CSF and sent to a reference lab for further testing. Brain death exams were performed more than 50 hours after discontinuation of pentobarbital. Patient’s cause of death was PAM with tonsillar herniation. Confirmatory CSF polymerase chain reaction revealed Naegleria fowleri.

Discussion: Primary source of PAM is freshwater exposure, particularly in warm climates. While the presentation is similar to bacterial meningitis, a clinician should consider PAM in a patient with recent freshwater exposure. If there is a high clinical suspicion for PAM, early therapy with the combination of amphotericin B, azithromycin, fluconazole, miltefosine, and rifampin should be considered.