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Although extremely rare, hypoglossal nerve palsy(HNP) can occur in isolation causing dysphagia, dysarthria, and tongue deviation. Documented cases of isolated hypoglossal nerve palsy(IHNP) were found to be caused by various etiologies, which include: tumor, trauma, surgery, (post)infection, sarcoidosis, atlanto-occipital dislocation, aberrant ectatic vessel in the hypoglossal canal, and stroke. We report 2 cases of IHNP, one of which had an etiology yet to be reported before.

Case 1, a 78-year-old male with history of arthritis who awoke to find he had slurred speech, difficulty swallowing, and tongue deviation to the right. No tongue tumors, edema, or tenderness on exam. No recent history of infection, cancer, neck surgeries, or COVID-19. MRI head and neck revealed erosive arthritis at the C1-C2 articulation, hypertrophic pannus surrounding the atlantoaxial articulation. Pannus seen extending into the spinal canal and foremen magnum, displacing the medulla and crowding the right hypoglossal nerve at the canal. No reported cases of infiltrative pannus causing IHNP was found in literature review. Surgery was scheduled to resect the infiltrating tissue.