When MRI and CSF are inconclusive: A case report of neurobrucellosis presenting with dysarthria in an adolescent.

Introduction: Neurobrucellosis is a serious complication of brucellosis, a common zoonotic infection. Its clinical diagnosis is often challenging due to the wide spectrum of clinical manifestations and the limited sensitivity of conventional diagnostic tools, including neuroimaging and cerebrospinal fluid (CSF) analysis, which may be normal or non-diagnostic. Case presentation: A 17-year-old male was recently diagnosed with brucellosis and was on standard triple antibiotic therapy. He presented with worsening systemic symptoms and new dysarthria. Contrast-enhanced brain magnetic resonance imaging was normal despite clear neurologic involvement. Lumbar puncture showed a mildly abnormal CSF with 10 white blood cells/mm3, normal protein and glucose levels. Blood and CSF cultures were negative, but Brucella serology was strongly positive. CSF Brucella PCR returned positive, confirming central nervous system involvement. Management and outcome: Due to the high clinical suspicion of neurobrucellosis in the setting of non-diagnostic routine investigations, therapy was escalated to intravenous ceftriaxone for improved central nervous system penetration, in addition to doxycycline and rifampicin. The patient showed rapid and marked clinical improvement following appropriate CNS-targeted therapy, with resolution of dysarthria and systemic symptoms, and was discharged to complete a prolonged antibiotic course. Conclusion: This case highlights the diagnostic challenge of neurobrucellosis when conventional investigations such as MRI and CSF analysis are non-specific or minimally abnormal. Clinicians should maintain a high index of suspicion in endemic areas, as early diagnosis often relies on clinical judgment supported by serology and molecular testing. Recognition of the limitations of routine investigations is essential to avoid delayed treatment and prevent neurological complications.