A Complex Case of Febrile Illness in an Elderly Male withNeurological Symptoms and Negative Csf Cytopathology: ADiagnostic and Management Challenge

Abstract

An elderly male in his eighties presented with persistent high-grade fever, altered mental status, and features suggesting central nervous system (CNS) involvement. The clinical picture was concerning for infectious or inflammatory encephalopathy. The diagnostic workup included cerebrospinal fluid (CSF) analysis, cartridge-based nucleic acid amplification test (CBNAAT), line probe assay (LPA), cytopathology, fungal microscopy, and aerobic culture. Despite significant systemic symptoms, CSF analyses returned negative for tuberculosis, fungal infection, and malignant cytology. MRI and MR spectroscopy findings revealed pontine hyperintensities and metabolic abnormalities suggestive of neuronal dysfunction. The imaging also showed decreased N-acetylaspartate
(NAA) and elevated choline, with a lactate peak—findings supportive of encephalopathy or inflammatory pathology. Treatment was initiated empirically with broad-spectrum antibiotics, antifungals, and supportive neurological and systemic care. Electrolyte imbalance and hypertension were addressed promptly. Despite extensive diagnostics, no specific pathogen was identified, and the patient’s clinical course required close multidisciplinary monitoring. The case exemplifies the diagnostic and therapeutic challenges posed by febrile encephalopathy in the elderly, where overlapping features of metabolic, infectious, and vascular etiologies complicate definitive diagnosis. This report highlights the role of advanced imaging and CSF analysis in guiding management when primary infectious markers are inconclusive. Further follow-up, especially with culture data and clinical evolution, remains essential for ongoing care.