Acute disseminated encephalomyelitis (ADEM) is a rare acute widespread demyelinating condition affecting brain and spinal cord.¹ It is characterized by multiple white matter lesions present on neuroimaging studies.¹ The clinical manifestations vary widely and usually include a combination of neurological and psychiatric symptoms, however a predominantly psychiatric presentation is possible.^{2, 3}

Bipolar disorder is an affective disorder (BPAD) characterized by distinctive episodes of depression and mania with or without psychotic symptoms and full interepisode recovery.⁴

We report a case of a woman with history of bipolar disorder who developed ADEM which presented clinically very similarly to a manic episode initially indistinguishable from her pre-existing psychiatric condition.

A 31 year old woman with bipolar disorder was admitted with a relapse of manic symptoms. On admission, her physical examination, baseline blood tests and urine drug screen were unremarkable. She was recommenced on lithium and quetiapine but continued to present as elevated, highly labile and irritable despite restarting her usual treatment. After five weeks she achieved only partial resolution of symptoms, in contrast to her previous manic episodes that had resolved within a few weeks. Her medication was gradually changed to sodium valproate and risperidone, to which she developed severe extrapyramidal side effects. Risperidone was thus changed to olanzapine. Her mental state continued to fluctuate with evidence of disorientation, confusion and fluctuating attentiveness. A full neurological exam found no specific abnormalities other than parkinsonian signs. Neuroleptic malignant syndrome was considered but excluded due to normal serum creatine kinase, absence of pyrexia and autonomic instability. Her white cell count was mildly elevated with neutrophilia, but no infective focus was detected. Electroencephalogram was normal. Upon further questioning of family members history of an observed seizure prior to initial admission was obtained. An urgent magnetic resonance image (MRI) of her brain was arranged showing multiple areas of increased signal intensity on T2/FLAIR images in periventricular, subcortical, and brainstem regions bilaterally with no enhancement post-gadolinium.

The patient was transferred urgently to the neurology ward. A lumbar puncture was conducted which found no abnormalities. Oligoclonal bands were positive in cerebrospinal fluid only. Serology testing and autoimmune markers were negative. A diagnosis of ADEM was made. The patient was commenced on IV Ceftriaxone and Methylprednisolone. Her delirium resolved but she continued to have residual mood and psychotic symptoms that took several weeks to improve. Her follow up brain MRI scan performed two months after the symptoms onset was unchanged. She was discharged home with a scheduled follow up appointment in the neurology outpatient clinic.

Our patient developed ADEM that was initially diagnosed and treated as a relapse of bipolar disorder. ADEM can mimic various psychiatric disorders³ making its diagnosis in psychiatric patients extremely difficult. This case highlights the importance of taking a detailed neurological and medical history in every patient presenting with psychiatric symptoms. It additionally emphasizes the significance of recognizing atypical clinical features, such as poor response to usual treatment, increased sensitivity to medication side effects, changeable presentation and onset of delirium indicating organic rather than purely psychiatric aetiology.