Case Presentation: This is a 64 year old male with a past medical history of bipolar disorder without previous psychiatric admissions, type 2 diabetes mellitus, stroke and autoimmune encephalitis that presented to the emergency room from a subacute rehabilitation facility (month long stay since an L3-L4 discectomy) with altered mental status. While at the rehabilitation facility, the patient began experiencing memory loss and delusions of bowel dysfunction. With the progressive deterioration of his mental status including confusion, agitation and aphasia, he was admitted to an outside hospital. A lumbar puncture was performed showing elevated cerebrospinal fluid protein and ganglionic acetylcholine receptor antibodies. He was treated with 5 days of IVIG and high dose steroids with no improvement of mental status. Patient continued to have worsening mental status and transferred to tertiary care center. Upon arrival, the patient was altered, combative and catatonic with muscle rigidity. Multiple bruises were noted over body including an expanding left thigh femoral hematoma with leukocytosis and anemia. Initial concern was for neuroleptic malignant syndrome superimposed delirium from infected leg hematoma, or sequelae of autoimmune encephalitis. Given the patient’s progressive deterioration, the decision was made to treat for autoimmune encephalitis with plasma exchange. The patient’s mental status and catatonia improved with 7 sessions of plasma exchange and a course of Rituximab. Serum neuroimmunology panel showed Neuronal AChR, Ganglionic Alpha-3 antibody supporting the diagnosis of autoimmune encephalitis. Patient was discharged to SAR with intact mental status and resolution of catatonia.
Discussion: Autoimmune encephalitis is a term for immune mediated inflammatory conditions of the brain with antibodies that act against neuronal cell surfaces and synaptic proteins. Many neuropsychiatric manifestations arise with acute deficits in cognition, movement, psychosis, catatonia, seizures, and coma. As a result, the differential diagnosis for encephalitis is extensive including toxic-metabolic, infectious, vascular, neurodegenerative, psychiatric, neoplastic and inflammatory disorders. Detection of specific autoantibodies can establish a definitive diagnosis of autoimmune encephalitis. However, the absence of antibodies does not rule out autoimmune encephalitis. Patients with suspected autoimmune encephalitis should have neuroimaging (MRI), lumbar puncture, and serologic antibody testing to exclude alternative etiologies and confirm the diagnosis. Prompt diagnosis is especially important as early initiation of immunotherapy of high dose steroids, IVIG, or plasmapheresis has shown to quicken recovery, reduce relapses and improve outcomes. In this case, management was difficult as the patient had multiple potential etiologies for encephalitis. The knowledge of previous history of autoimmune encephalitis was essential towards guiding the appropriate management of this patient.
Conclusions: The diagnosis of autoimmune encephalitis is often difficult due to multiple potential etiologies and confounding factors that can attribute to the wide spectrum of neuropsychiatric symptoms. Hospitalists should consider autoimmune encephalitis, especially for patients with a known history of autoimmune encephalitis, as a potential etiology for altered mental status.