Are You Crazy or is it Just Your Antibodies? Autoimmune Encephalitis

Autoimmune encephalitis is a rare but can’t-miss cause of acute psychosis, especially in previously healthy children and young adults. Anti-NMDA receptor disease dominates the syndrome, and normal CT or even normal MRI does not exclude it. The bedside clues are psychiatric change plus abnormal movements, seizures, or autonomic instability.

Autoimmune Encephalitis in Acute Psychosis

• High-risk clinical pattern: Previously healthy children and young adults with acute or subacute personality change, language disintegration, and new psychosis deserve consideration of autoimmune encephalitis rather than a primary psychiatric disorder.
• Movement disorder clues: Abnormal orofacial movements and subtle limb movements are classic early clues, with ataxia, chorea, dystonia, myoclonus, or tremor broadening the motor phenotype.
• Late neurologic red flags: Seizures, prolonged status epilepticus, and autonomic instability signal advancing disease and help separate autoimmune encephalitis from routine psychiatric presentations.
• Imaging can mislead: CT is almost always normal, and MRI is normal in about 50% of cases, so a reassuring scan should not lower suspicion too quickly. We get into the imaging nuance in the episode.
• Lumbar puncture priority: All patients with suspected autoimmune encephalitis should undergo lumbar puncture, with CSF typically showing lymphocytic pleocytosis, normal glucose, and only slight protein elevation.
• EEG and antibody testing: EEG is abnormal in roughly 90% of cases with diffuse slowing, while extreme delta brush is the pathognomonic but uncommon pattern; CSF antibody testing targets anti-NMDA and related panels.

Treatment and Disposition Priorities

• First-line immunotherapy: Initial treatment centers on corticosteroids, IVIG, and plasmapheresis, with escalation to rituximab or cyclophosphamide in refractory cases.
• Tumor association search: Reproductive-system tumors can drive disease, especially ovarian teratoma, so targeted ultrasound matters because resection can accelerate recovery.
• Need for higher-level care: Many patients need prolonged ICU-level management for seizures and dysautonomia, and transfer is a strong move if immunotherapy or neurocritical support is not available locally.
• Anti-NMDA predominance: Anti-NMDA receptor encephalitis accounts for about 90% of autoimmune encephalitis cases, while anti-GABA-B and anti-GAD syndromes are much less common.

References:

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