Post-Chemoradiation Infectious Atlanto-Axial Instability

Grisel syndrome is a rare, nontraumatic atlantoaxial subluxation, predominantly described in children following upper respiratory infections or otolaryngologic procedures. Adult presentations are uncommon and typically associated with predisposing factors such as malignancy, immunosuppression, or prior radiotherapy. We report a rare case of adult Grisel syndrome caused by mixed bacterial and fungal infection in a patient with nasopharyngeal carcinoma previously treated with chemoradiation. A 28-year-old man presented with fever, neck pain, torticollis, and progressive neurological deficits 3 weeks after endoscopic nasopharyngectomy. Imaging revealed atlantoaxial instability with prevertebral and epidural inflammatory changes, along with posterior circulation infarcts. Despite negative blood cultures, intraoperative cultures from the C1–C2 joint grew methicillin-resistant Staphylococcus aureus and Candida albicans . The patient was managed with antimicrobial therapy, skeletal traction, and definitive C1–C2 fixation, resulting in significant neurological recovery. This case highlights the importance of early recognition, targeted antimicrobial therapy, and timely surgical stabilization in adult Grisel syndrome, particularly in postradiation patients, where aggressive infection and instability are more likely.