Title : A mind under attack: A rare case of autoimmune anti-NMDA receptor encephalitis in a 19-year-old male
Abstract:
A 19-year-old Filipino male presented with a one-week history of intermittent headache, followed by focal neurologic symptoms including right-sided lip twitching, right-sided weakness, and vomiting. This progressed to a one-minute episode of generalized tremors, musculoskeletal spasms, and upward eye deviation lasting 3–5 minutes, followed by transient loss of consciousness and disorientation. He was initially managed in the emergency department with antiepileptics, antiplatelet therapy, and supportive medications. Initial laboratory workup revealed hypokalemia and hyperuricemia, which were corrected. Empiric antimicrobial therapy with ceftriaxone and acyclovir was initiated for possible infectious etiologies. Electroencephalography and neuroimaging, including computed tomography and magnetic resonance imaging, were unremarkable. The patient improved clinically and was discharged after five days on levetiracetam.
Four days after discharge, the patient developed recurrent vomiting, followed by new-onset left-sided weakness and involuntary movements without loss of consciousness. Two days later, he experienced another seizure episode, prompting readmission. On arrival, he had active musculoskeletal spasms, nuchal rigidity, and hypoxemia (oxygen saturation 77%), necessitating oxygen support. He was treated with benzodiazepines, antiepileptics, and broad-spectrum antimicrobials. Episodes of agitation characterized by restlessness and verbal hostility required sedation with midazolam and dexmedetomidine. Chest radiography revealed lung opacities consistent with aspiration pneumonia, leading to escalation of antibiotic therapy.
A lumbar puncture demonstrated elevated opening pressure (>200 mmH?O) with otherwise normal cerebrospinal fluid (CSF) cell count. Extensive infectious workup, including testing for tuberculosis and cryptococcosis, returned negative. Cardiac monitoring showed sinus rhythm with transient premature atrial contractions, while arterial blood gas analysis revealed uncompensated respiratory acidosis attributed to prior sedation. The patient was admitted to the intensive care unit, where he stabilized without recurrence of seizures. Corticosteroids and valproate were added to his treatment regimen.
Following transfer to the wards, the patient’s condition continued to improve. Gastrointestinal symptoms, including acute watery diarrhea, resolved with supportive therapy. On hospital day five, CSF testing returned positive for anti–N-methyl-D-aspartate (NMDA) receptor antibodies, confirming a diagnosis of autoimmune encephalitis. A positron emission tomography–computed tomography scan revealed no hypermetabolic brain lesions or infectious foci, allowing discontinuation of antimicrobial therapy.
The patient was treated with intravenous immunoglobulin (IVIG) for five days, which was well tolerated without adverse effects. He demonstrated progressive clinical improvement, with resolution of seizures and agitation, improved appetite, and near-complete neurologic recovery, except for a persistent left-sided Babinski sign. Antiepileptic therapy was gradually tapered.
He was discharged in stable condition on a steroid taper and maintenance levetiracetam, with plans for outpatient neurology follow-up. This case highlights the diagnostic challenges of autoimmune encephalitis in the absence of early radiologic and electroencephalographic abnormalities and underscores the importance of maintaining a high index of suspicion. Early recognition and timely initiation of immunotherapy are critical in achieving favorable clinical outcomes.
