BACKGROUND: Fibrous dysplasia (FD) affecting the upper cervical spine is exceptionally rare and results in severe cervico-occipital pain and limited neck mobility due to altered biomechanics and irritation of the third occipital nerve (TON). Surgical management is challenging because of the proximity to critical neurovascular structures. In the absence of neurological deficits, targeted TON blocks have shown promise as part of conservative management.

CASE REPORT: A 33-year-old woman presented with a 7-year history of neck and suboccipital pain. Imaging revealed expansile FD at C1-C2 with partial fusion and no neurovascular compromise. An ultrasound-guided right-sided TON therapeutic block was administered, which resulted in immediate and substantial pain relief (Numeric Rating Scale 8/10 reduced to 3/10) and sustained functional improvement for 3 months.

CONCLUSIONS: Ultrasound-guided TON block provided meaningful long-term pain relief and avoided high-risk surgical intervention in this rare case of C1-C2 FD.

KEYWORDS: Fibrous dysplasia, case report, cervical vertebrae, third occipital nerve block, ultrasound-guided intervention