Primary Amebic Meningoencephalitis Mimicking Acute Bacterial Meningitis: Survival Following Early Empirical Therapy

Primary amebic meningoencephalitis (PAM) is a rare but rapidly fatal infection of the central nervous system caused by the thermophilic free-living amoeba Naegleria fowleri. The disease often presents with clinical and cerebrospinal fluid (CSF) findings that closely mimic acute bacterial meningitis, making early diagnosis particularly challenging. We report the case of a 29-year-old woman with poorly controlled type 1 diabetes who presented with acute fever, severe headache, vomiting, and meningeal signs. Within 24 hours, her condition progressed to visual and auditory hallucinations, generalized tonic-clonic seizures, and decreased consciousness. CSF analysis revealed neutrophilic pleocytosis, elevated protein levels, and low glucose concentration, initially suggesting bacterial meningitis. Brain MRI demonstrated bilateral cortical-subcortical hyperintense lesions involving the frontal, insular, and temporal regions, with associated microhemorrhages, consistent with necrotizing meningoencephalitis. Further history revealed a recent nasal ablution using warm lake water. Microscopic examination of CSF showed findings suggestive of an amoeboid trophozoite, raising suspicion for N. fowleri infection, although definitive parasitological confirmation could not be obtained. Empirical therapy with liposomal amphotericin B, fluconazole, and rifampicin was initiated promptly. The patient showed progressive clinical improvement, with complete recovery of consciousness and marked radiological resolution of lesions on follow-up imaging. This case highlights the diagnostic challenges posed by PAM and underscores the importance of early clinical suspicion and prompt empirical therapy in suspected cases, even in the absence of definitive laboratory confirmation.