Sphenoclival fibrous dysplasia with cyst formation causing abducens nerve palsy in an older patient: illustrative case.

Background: Fibrous dysplasia (FD) is typically asymptomatic but is known to occasionally cause neurological symptoms such as visual disturbances. However, FD-associated abducens nerve palsy is extremely rare.

Observations: A 76-year-old woman had a left abducens nerve palsy due to mass effect on the abducens nerve at Dorello's canal caused by FD and its associated cyst, which was resolved by resection of the cyst through an endoscopic transnasal route.

Lessons: Although FD is generally an asymptomatic lesion occurring in younger patients, it can occasionally cause abducens nerve palsy even in older patients. In particular, cystic degeneration within FD tends to trigger a mass effect and thus can require surgical decompression. https://thejns.org/doi/10.3171/CASE24424.