Title : Unmasking the great mimic: Diagnostic challenges and therapeutic efficacy in anti-NMDA receptor encephalitis
Abstract:
Introduction: Autoimmune encephalitis is a critical differential for acute neuropsychiatric syndromes, with an incidence now comparable to infectious encephalitis. Known as a "great mimic," anti-N-methyl-D-aspartate (NMDA) receptor encephalitis often presents with symptoms that overlap with viral or bacterial meningitis and paraneoplastic processes. Because initial diagnostic workups can be misleadingly normal, a high index of clinical suspicion is required for timely intervention
Case Presentation: A previously healthy 19-year-old Filipino male presented with a one-week history of intermittent headaches, followed by acute right-sided weakness and generalized seizures. Despite these severe symptoms, initial neuroimaging (CT and MRI) and EEG were unremarkable, leading to a brief discharge. He was readmitted four days later with newonset left-sided weakness and severe agitation, characterized by physical restlessness and verbal hostility. On readmission, he exhibited nuchal rigidity and a positive Babinski sign, eventually requiring intensive care for status epilepticus and hypoxemia
Diagnostic Evaluation: Lumbar puncture revealed an elevated opening pressure (>200 mmH2O). Definitive diagnosis was confirmed through cerebrospinal fluid (CSF) positivity for anti-NMDA receptor antibodies. To address potential triggers, a PET-CT scan was performed, which showed no evidence of underlying malignancy or hypermetabolic brain lesions, establishing a non-paraneoplastic etiology
Management and Outcome: The patient completed a 5-day course of intravenous immunoglobulin (IVIG) alongside a tapering corticosteroid regimen. This prompt initiation of first-line immunotherapy resulted in marked clinical improvement, with complete resolution of seizures and agitation. He was discharged with a favorable neurocognitive trajectory
Conclusion: This case solves a complex "neuropsychiatric puzzle," demonstrating that antiNMDA receptor encephalitis must be considered in young patients even when initial imaging is negative. It highlights the importance of unmasking this "mimic" through CSF antibody testing, as early recognition and prompt immunotherapy are essential for reducing longterm morbidity and achieving complete functional recovery.
