Presenting as Manic Symptoms To the Editor: Differentiating a manic

episode of bipolar disorder from mania secondary to a medical condition in older adults is challeng-ing. The diagnostic dilemma appears when the patient has an established diagnosis of bipolar disorder from a young age. The neuropsychiatric manifestations are similar, and there have been numerous conditions to which secondary mania can be attributed. A thorough differential diagnosis should be considered to help guide appropriate management. Evidence suggests that neurological conditions are the most common causes of secondary mania. In a retrospective study examining 50 manic patients older than age 65, neurological disorders were reported in 74 % of the patients.1 We summarize a case of mania that emerged in the context of acute demyelinating encephalitis in an elderly patient with a diagnosis of bipolar disorder since adolescence. Case Report A 60-year-old woman was first di-agnosed with bipolar disorder at age 16 and was treated with divalproex sodium. She had neither medical nor family history of psychiatric illness. She was admitted for manic symp-toms attributed to medication non-adherence. She was treated with lithium 900 mg daily (serum level on discharge was 0.83 mEq/L) and risperidone 4 mg daily. Two months later, she was readmitted because of mood lability and disorganized thoughts for 1 week. She was found to be lethargic and had delirium. Her lithium level was 0.41 mEq/L. Lab-oratory tests including urine toxicol-ogy were negative. Head CT was negative. Neuropsychological as-sessment revealed impairment in areas of visuospatial and visuomotor functioning, attention, and executive functioning. The neurology consul-tation found no focal deficits, and brain MRI suggested a demyelinat-ing disease. Lithium and risperidone were stopped, and the patient was transferred to a neurological floor for further evaluation. Video-EEG showed diffuse slowing but no epi-leptiform activity. Lumbar puncture and paraneoplastic panel were nega-tive. A serial of brain MRI suggested acute demyelinating encephalitis, most pronounced within the frontal and temporal lobes, right greater than left. She was treated with in-travenous immunoglobulin and cor-ticosteroid. Her delirium resolved, but she continued to have residual mood symptoms that took several weeks to subside