Post-infectious Cytomegalovirus Rhombencephalitis in an Immunocompetent Adult: A Case Report.

Cytomegalovirus (CMV) is a ubiquitous virus that typically causes subclinical infection in immunocompetent hosts. Neurological complications, particularly encephalitis, are exceedingly rare in this population. We present a case of a previously healthy young man who developed an acute brainstem syndrome characterised by dysarthria, ataxia, and altered consciousness. Early investigations were inconclusive, with bland cerebrospinal fluid (CSF) findings despite raised opening pressure and normal initial MRI. Repeat imaging revealed a subtle medullary lesion, while serology demonstrated primary CMV infection with detectable viraemia and negative CSF CMV polymerase chain reaction (PCR), consistent with a post-infectious mechanism. The patient made a steady, spontaneous recovery without antiviral therapy. This case highlights the diagnostic challenges posed by atypical presentations of CMV-associated rhombencephalitis in immunocompetent individuals, the value of repeat neuroimaging and serological testing, and the importance of multidisciplinary decision-making to avoid unnecessary treatment in selected cases.