RECURRENT IONM SIGNAL LOSS WITH PROFOUND HAEMODYNAMIC INSTABILITY DURING AIS CORRECTION: AN INTRAOPERATIVE AUTONOMIC CRISIS

A 15-year-old girl with severe, rapidly progressive adolescent idiopathic scoliosis underwent posterior spinal deformity correction. Preoperative full-spine radiographs and MRI demonstrated no abnormalities. Pedicle screws were inserted under navigation guidance and intraoperative neuromonitoring (IONM), followed by nine-level Ponte osteotomies and resection of five right ribs. Deformity correction was initiated using simultaneous translation. After insertion of the right cobalt-chromium rod, excellent correction was achieved but right-sided IONM signals were abruptly lost. Rod removal resulted in prompt recovery. Repeated attempts at reduced correction caused recurrent unilateral and subsequently bilateral signal loss. Insertion of the left rod with gentle derotation produced complete bilateral IONM loss accompanied by profound hypotension, with systolic blood pressure approximately 50 mmHg, and bradycardia. The rod was immediately removed. Intraoperative CT confirmed correct pedicle screw placement. Although IONM partially recovered, minimal manipulation or chest-wall contact repeatedly triggered hypotension and bradycardia, raising concern for an autonomic or thoracic sympathetic chain-related mechanism rather than direct spinal cord injury. After a 45-minute pause and supportive anesthetic management, two titanium rods with reduced curvature were inserted using gentle translation. IONM stabilized, although intermittent hemodynamic instability persisted, and signals returned to baseline by the end of surgery. No postoperative neurological deficit occurred. At six months, the patient had excellent functional recovery but developed mild autonomic disturbances, including asymmetric axillary sweating and persistent lower-limb temperature asymmetry. This case highlights the importance of immediate response to IONM changes, rapid de-escalation of correction maneuvers and multidisciplinary decision-making when neurological and profound hemodynamic abnormalities occur during deformity correction.