Paraneoplastic cerebellar degeneration (PCD) is a rare disorder, presenting with severe cerebellar dysfunction. In addition to motor deficits, cognitive and behavioural changes can be associated with cerebellar damage. The cerebellar cognitive affective syndrome (CCAS) describes affective disturbances and impairments in executive function, spatial cognition and language.

We describe, using a timeline, a patient who developed a psychiatric disorder following PCD.

A 19-year-old female presented with subacute ataxia, dysarthria and nystagmus. She was diagnosed with Hodgkin's lymphoma and achieved complete remission following chemotherapy. Over the next seven years she experienced recurrent episodes of altered mood. Her depressive symptoms included low mood, crying spells, irritability, apathy, lack of energy and early waking. There were periods when she felt “high”, harboured unrealistic optimism, had reduced attention, increased her alcohol intake and was described as being “reckless” by her family. She was diagnosed with bipolar affective disorder and eventually stabilised on imipramine and lithium.

This presentation appears to describe a case of CCAS, in which the affective component is bipolar affective disorder, type II. The psychiatric findings are a direct result of the neuropathology, emphasizing the role of the cerebellum in affective illness. While depression, mood instability and psychosis are the possible psychiatric consequences of CCAS, bipolar disorder appears to be a more unusual variant.

This presentation adds to the existing literature suggesting a cerebellar role in the modulation of emotion, and emphasizes the importance of addressing psychiatric sequelae in the treatment and rehabilitation of patients with paraneoplastic cerebellar degeneration.