Early somatosensory evoked potential monitoring warnings during positioning for cervical laminoplasty in ossification of the posterior longitudinal ligament patients.

BACKGROUND

Neurological deterioration during cervical laminoplasty for ossification of the posterior longitudinal ligament (OPLL) remains a significant clinical concern. This study evaluated the utility of somatosensory evoked potential (SEP) monitoring initiated immediately after anesthetic induction as an early warning system during surgical positioning.

METHODS

We retrospectively reviewed 63 consecutive patients with cervical OPLL who underwent laminoplasty (2023-2026). SEP monitoring of all four limbs was initiated in the supine position after induction to establish the intraoperative baseline. Alarm thresholds were 70% (caution) and 50% or below (critical) of baseline amplitudes in any monitored limb. Neurological status was assessed using the modified Japanese Orthopaedic Association (mJOA) scale.

RESULTS

Positioning-related SEP deterioration occurred in 8 patients (12.7%); all were detected before skin incision, and resolved following positional correction (i.e., typically in the opposite direction). No patient developed a permanent neurological deficit. Transient C5 palsy occurred in two patients in the no-SEP-change group that resolved within 3 weeks. All patients demonstrated mJOA improvement at 3 months.

CONCLUSION

SEP monitoring detected significant changes during positioning for laminoplasty in 12.7% of OPLL patients, all of which resolved in a timely fashion.