Para-infectious cerebellitis – a life-threatening case in a young adult

<h3></h3> A 19-year-old female presented with a 2-day history of new frontal headache, nausea, and fever. During evaluation in the emergency department, she developed a progressive decline in consciousness. A non-contrast CT head revealed right tonsillar descent and hydrocephalus. An emergency external ventricular drain was placed, demonstrating significantly raised intracranial pressure. We screened for several infectious agents in serum and CSF. IgM and IgG to mumps was identified, suggesting recent exposure to the virus. CSF testing for Mumps PCR later returned negative. The patient was treated with intravenous ceftriaxone, acyclovir and dexamethasone with gradual neurological improvement following normalisation of intracranial pressure. MRI revealed bilateral T2 signal change within the cerebellar hemispheres and vermis with evidence of early tonsillar herniation. Post-contrast enhancement was observed in the posterior cerebellar folia. Following step down to the Neurology ward, examination confirmed left-sided appendicular dysmetria and an ataxic gait. Interval neurological examination and brain imaging 8 weeks later showed continuing clinical and radiological improvement. We diagnosed a parainfectious cerebellitis, potentially triggered by exposure to the mumps virus. Para-infectious cerebellitis in adults is a rare entity, with the disorder more commonly reported in young children with a benign course. Viral infections are the most identified pathogens in this disorder. This case highlights the disease spectrum can also include life- threatening complications including cerebellar oedema, hydrocephalus and raised intracranial pressure.