Primary Amoebic Meningoencephalitis

Abstract

Case Presentation A 9-year-old female with an unremarkable past medical history presented to a Tyler, Texas emergency department with a 7-day history of worsening frontal headache and bilateral lower extremity “aches.” During the previous 4 days she had also experienced a cough, nasal congestion, and rhinorrhea. Her condition rapidly progressed to include an increasingly severe headache, photophobia, nonbloody emesis, neck pain, fever (103.6°F), irritability, and disorientation along with episodes of verbal outbursts, purposeless movements, and eye rolling. The patient underwent a lumbar puncture, and cerebral spinal fluid was analyzed with the following results: glucose 71 mg/dL (Normal 40-70 mg/dL), protein 148 mg/dL (Normal 15-45 mg/dL), nucleated cells 1080 cell/μL consisting of 69% neutrophils, 25% lymphocytes, and 6% monocytes (Normal up to 20 lymphocytes/μL in children), red blood cells 126 cells/μL (Normal no RBCs). A presumed diagnosis of bacterial meningitis was made and ceftriaxone was started. The patient was transferred to Children’s Medical Center of Dallas where her medical condition continued to deteriorate. A head-computed tomography was performed and revealed no abnormalities. Upon further questioning it was discovered that the patient had been swimming in an eastern Texas lake shortly before the onset of symptoms. This increased the suspicion for primary amoebic meningoencephalitis (PAM). Empiric intrathecal amphotericin B and systemic rifampin was initiated. Subsequent wet mount analysis of the CSF revealed Naegleria fowleri trophozoites, the etiologic agent of PAM. The patient’s condition continued to worsen and she died several days later. Clinical Background Etiology of PAM Primary amoebic meningoencephalitis is a rapidly progressive disease that generally results in death within 7 to 10 days of symptom onset. The etiologic agent is the freeliving amoeba Naegleria fowleri. Infection occurs most commonly in young, healthy individuals following exposure to contaminated water sources. Inoculation occurs when contaminated water is forced into the nasal cavity. Access to the CNS is achieved by invasion into the olfactory neuroepithelium with subsequent penetration of the cribriform plate. Once in the CNS, the organisms colonize cerebral gray matter leading to a rapidly fatal meningoencephalitis. The genus Naegleria contains several species of which N fowleri is the only known human pathogen. These protozoa are found ubiquitously in the environment and are distributed worldwide. They can be found in warm, stagnant bodies of water, and even chlorinated swimming pools, making contact with humans inevitable. Etiology of Primary Amoebic Meningoencephalitis (PAM) Laboratory diagnosis of PAM The need for early detection of PAM Differentiating Naegleria fowleri from Acanthamoeba species Treatment and Prognosis