Isolated Hypoglossal Nerve Palsy Due to an Osteophyte with Atlantoaxial Dislocation.

Isolated hypoglossal nerve palsy (IHP), or hypoglossal nerve palsy without any other neurological signs, is rare. We report a woman with atlantoaxial dislocation (AAD) who presented with IHP due to hypoglossal nerve compression by an osteophyte at the hypoglossal canal. A 77-year-old woman presented with speech difficulties and the feeling of a swollen tongue on the left side for 3 days. Her only neurological feature was left hypoglossal nerve palsy. She had been diagnosed with AAD 2 years before. Computed tomography (CT) and high-resolution magnetic resonance imaging (MRI) revealed the compression of the basicranial hypoglossal nerve at the external orifice of the hypoglossal canal by an AAD osteophyte which was causing IHP. IHP can develop due to hypoglossal nerve compression by an osteophyte from AAD. CT and high-resolution MRI revealed this rare mechanism of IHP.