Ophthalmoplegia with a focal lesion in the interpeduncular fossa as the initial symptoms of multiple sclerosis: 3-year follow-up.

The differential diagnosis of isolated ophthalmoplegia includes a range of pathologies. In this case, a 26-year-old man of Han nationality presented with ophthalmoplegia. Neuroimaging revealed an atypical focal lesion in the interpeduncular fossa. Initial systemic workup indicated intracranial infection, but there was no evidence to support a diagnosis of other autoimmune diseases (e.g., myasthenia gravis or multiple sclerosis). Neuroimaging follow-up over the next 3 years revealed progression from atypical solitary lesions to multifocal lesions in the white matter of the brain. Key immunological markers were observed in cerebrospinal fluid during follow-up, suggesting the evolution of multiple sclerosis. Ophthalmoplegia with a focal lesion in the interpeduncular fossa was an unusual set of symptoms indicating multiple sclerosis onset. The findings in this case suggest that infection is an important but overlooked factor involved in the pathogenesis of multiple sclerosis. Upon initial detection, atypical lesions should receive sufficient attention and patients should undergo systematic screening to identify infection and its associated immunological abnormalities.