Abstract Introduction Autoimmune encephalitis associated with anti-N-methyl-D-aspartate receptor (NMDAR) antibodies is an uncommon but serious cause of encephalopathy and neurobehavioral deterioration in young adults. Classic cases show both serum and cerebrospinal fluid (CSF) antibody positivity with prominent behavioral or seizure activity. However, atypical forms lacking CSF confirmation or clear neuroimaging abnormalities may present primarily as psychiatric or catatonic states. We present a challenging case of isolated serum NMDAR antibody positivity with unremarkable neuroimaging and a prolonged, refractory catatonia requiring multidisciplinary neurocritical management. Case Description A 21-year-old previously healthy male presented with a 3-week history of headache, viral prodrome, and progressive confusion. Neurological evaluation revealed psychomotor slowing, mutism, and minimal interaction without focal deficits. The hospital course was complicated by recurrent seizure-like activities and worsening catatonia (rigidity and posturing) unresponsive to multiple doses of lorazepam, prompting transfer to the intensive care unit for frequent neurological examination, EEG monitoring, and hemodynamic surveillance. Brain MRI did not reveal any focal abnormalities. EEG showed diffuse slowing without epileptiform activity. CSF was acellular with normal protein and glucose, but oligoclonal bands were present. Serum anti-NMDAR IgG was positive at high titer (1:80), while CSF was negative. No underlying tumor was identified. Extensive infectious and other autoimmune workup was negative. Given the high clinical suspicion for NMDA encephalitis, high-dose corticosteroids, intravenous immunoglobulin (IVIG) followed by plasmapheresis were initiated with minimal early response. Over the following weeks, structured supportive care, physical and speech therapy, and a carefully titrated combination of clonazepam and low-dose antipsychotics facilitated gradual cognitive and functional recovery. Discussion and Clinical Implications Anti-NMDAR encephalitis usually affects young women and is often linked to an underlying neoplasm. In contrast, our patient was a young male who had only oligoclonal bands as evidence of central inflammation, illustrating how autoimmune encephalitis can present with minimal laboratory or radiologic evidence despite profound neuropsychiatric dysfunction. Early critical care involvement is essential in ruling out life-threatening causes, monitoring for seizure activity, respiratory and autonomic stability, and coordinating immunotherapy while addressing neurobehavioral complications. In our case, treatment was further complicated by limited response to standard immunotherapy and refractory catatonia, which ultimately improved with clonazepam and antipsychotic therapy. This case underscores the importance of maintaining high clinical suspicion, pursuing early immunotherapy when criteria are met, and employing individualized, multidisciplinary management that integrates neurologic, psychiatric, and critical care expertise. Recognition of such atypical cases is essential to prevent delays in treatment and optimize neurologic recovery. This abstract is funded by: None
Hayee et al. (Fri,) studied this question.
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