Delayed C5 palsy following thoracolumbar deformity surgery: a case report.

Background: C5 palsy is a known complication following decompressive cervical spine surgery, most often attributed to factors such as foraminal stenosis, cord drift, or traction. While its incidence after cervical procedures is well-documented, C5 palsy occurring after thoracolumbar deformity surgery has not been previously described. Case: A 70-year-old woman with a prior C2-T4 posterior cervical spinal fusion underwent thoracolumbar deformity correction with T4-pelvis fusion. Two months postoperatively, she developed sudden right deltoid and biceps weakness. Laboratory and imaging workups ruled out other pathological causes, and electromyography confirmed a new C5 palsy. She was treated with physical therapy and electrical stimulation and achieved complete recovery by 6 months post-thoracolumbar surgery. Conclusion: This case describes isolated delayed C5 palsy following thoracolumbar deformity surgery in a patient with prior cervical spine fusion 2 years earlier. Potential contributing factors include global alignment changes, altered neural tension, and intrinsic anatomic fragility of the C5 nerve root. This presentation expands the clinical context of postoperative C5 palsy and highlights the importance of monitoring for cervical neurologic deficits, even in the absence of cervical intervention. Level of Evidence: 5 - Case Report.