Case Presentation:
29-year-old female with a history of Bipolar I Disorder, in remission off medication, presented to the Psychiatric Emergency Department with hyperactivity, insomnia, impulsive purchasing and audiovisual hallucinations for two weeks. The patient was admitted to psychiatry for treatment of mania with psychotic features.
The patient’s mania was treated with lithium, aripiprazole and clonazepam, but she continued to decompensate, becoming hypersexual and aggressive towards patients and staff. She required numerous doses of intramuscular haloperidol to control her behavior. Her mental status deteriorated into catatonia and she was transferred to the Internal Medicine service for workup of her persistently altered mental status.
The patient’s initial exam was notable for tachycardia, dysarthria, facial flushing, and pupillary dilatation. Anticholenergic poisoning and primary catatonia were both considered, but neither a physostigmine challenge nor lorazepam challenge improved her symptoms. A non-contrast head CT and Brain MRI were unremarkable. An electroencephalogram revealed a non-specific pattern consistent with diffuse cerebral dysfunction. A lumbar puncture was notable for a lymphocytic pleocytosis and the cerebrospinal fluid was sent for a viral and autoimmune workup. The patient was empirically started on acyclovir and intravenous immunoglobulin (IVIG) to treat herpes simplex virus and autoimmune encephalitis respectively.
The patient responded well to this treatment, with resolution of her symptoms and physical examination findings. Her CSF anti-NMDA receptor antibody was found to be elevated 1:10, establishing a diagnosis of anti-NMDA receptor encephalitis. Chest and abdominal imaging did not reveal any malignancy. The patient completed a five-day course of IVIG and was discharged home on oral prednisone, with plans to taper as an outpatient.
Discussion:
This case illustrates the difficulty in assessing altered mental status in a patient with a history of mental illness and what an appropriate workup should be for this presentation. Although this patient did have a medical etiology of her delirium, her previous history of mental illness served as a cognitive anchor for her triage and treatment. It was not until her encephalitis produced significant delirium and autonomic findings that any other diagnoses were considered. In addition to anti-NMDA receptor encephalitis, the patient’s workup included other potential causes of encephalopathy in a psychiatric patient such as infection, iatrogenic toxidrome or medication refractory psychosis.
Conclusions:
Altered mental status and psychosis in the setting of autonomic dysfunction must be worked up appropriately in all patients regardless of underlying mental illness. Anti-NMDA receptor encephalitis should be included in the differential diagnosis in this context.