Report a case of primary amebic meningoencephalitis (PAM)

Primary amebic meningoencephalitis (PAM) is an often fatal meningoencephalitis caused by Naegleria fowleri. It is usually due to exposure to amoeba in contaminated water. N. Fowleri is associated with a 98% percent mortality within two weeks of exposure. 

Patient is a 55 year-old-male who presented to the hospital with 2-month history of generalized weakness, and falls. MRI brain showed multiple cortical restricted diffusion involving multiple vascular territories concerning for acute embolic infarcts. One of the lesions demonstrated susceptibility artifact with some subtle peripheral enhancement which could represent developing abscess or septic emboli. Initial exam was remarkable for mild confusion and bilateral upper extremity ataxia. Later, patient developed new onset bilateral tonic clonic seizure requiring intubation and ICU admission. Continuous EEG revealed cyclic seizures originating from both hemispheres requiring 3 antiseizure medications and medically-induced burst suppression for seizure control. Cerebrospinal fluid was significant for total nucleated cell count of 36 (71% lymphocytes), protein of 1414, glucose of 70, and lactate of 6.9. During this time, he was maintained on IV Vancomycin, Ceftriaxone, Acyclovir, and Metronidazole.

Patient was sedated for seizure control so exam was unreliable. After 5 days, the patient developed diabetes insipidus. Repeat MRI brain showed dramatic progression with new lesions, enlargement of prior lesions, leptomeningeal enhancement, and hydrocephalus. MRI of the spine showed extensive leptomeningeal enhancement and intense enhancement of cauda equina nerve roots. IVIG and IV Methylprednisolone were initiated due to concern for autoimmune encephalitis. 3 days later, the EEG became completely suppressed and repeat CT head was consistent with catastrophic brain injury. Autopsy results were consistent with PAM. 

PAM is a rapidly progressive disease with high mortality due to low morbidity and limited awareness of pathogenesis and drug availability. Preventative strategies are the optimal way to avoid PAM.