Low Sensitivity of Neurological Examination, Curve Laterality, and Thoracic Kyphosis for Detecting Chiari I Malformation and Syrinx in Operative Pediatric Scoliosis.

BACKGROUND

For pediatric patients with presumed adolescent idiopathic scoliosis, surgeons rely on abnormal neurological exam, left-sided thoracic curve, or thoracic hyperkyphosis to initiate preoperative magnetic resonance imaging; however, the sensitivity of these screening criteria for detecting neural axis anomalies of Chiari malformation type I (CM1) and syrinx is not well understood. We aim to determine the frequency of abnormal neurological exam, left-sided thoracic curve, and hyperkyphosis of thoracic curves in patients with operative scoliosis and CM1 and/or syrinx.

METHODS

A retrospective analysis was conducted with patients who underwent surgical management for pediatric scoliosis and were diagnosed with either CM1 (n=4), syrinx (n=23), or both conditions (n=20). Neurological exams before surgery were reviewed and screened for abnormal deep tendon reflexes, abnormal abdominal reflexes, motor disturbance, sensory disturbance, muscle mass asymmetry, spasticity/contracture, abnormal gait, abnormal balance, and ankle clonus. Thoracic curvature direction, T2-T5 kyphosis, and T5-T12 kyphosis were also obtained.

RESULTS

Across all patients with CM1 and/or syrinx that underwent surgery for scoliosis, 9 of 47 (19%) had an abnormal preoperative neurological exam, 11 of 43 (26%) had a left-sided thoracic curve, 5 of 41 (12%) had a T2-T5 hyperkyphosis, and 9 of 41 (22%) had a T5-T12 hyperkyphosis. The T1-T12 kyphosis across the whole cohort averaged 38 degrees. In patients with known CM1 and/or syrinx, the sensitivity of neurological exam abnormality, left-sided curve, or hyperkyphosis was 27 of 41 (66%). Patients with both CM1 and syrinx were not more likely to have an abnormality on imaging or physical exam compared to patients with isolated CM1 or syrinx conditions.

CONCLUSIONS

These results indicate that neurological exam abnormalities, left-sided thoracic curve, and thoracic hyperkyphosis have a relatively low sensitivity when used as a screening metric for detecting CM1 and/or syrinx in patients with scoliosis. Thirty-four percent of patients with CM1/syrinx and operative scoliosis had a normal neurological exam, right-sided curve, and a normal amount of kyphosis. Surgeons should consider the sensitivity of these screening metrics when determining which patients should obtain a preoperative MRI before scoliosis surgery.

LEVELS OF EVIDENCE: Diagnostic studies-investigating a diagnostic test level III with a retrospective analysis.