Classification of cervical spondylosis or disc protrusion by preoperative evoked spinal electrogram. Follow-up study.

The evoked spinal electrogram (SEG) was studied in 11 patients with cervical spondylotic myelopathy or disc protrusion. All the patients were severely handicapped before surgery. The evoked SEG was classified in three grades before and during surgery. Periodic follow-up studies were done at 18 to 35 months, with an average of 24 months. Four of six patients were normal or slightly abnormal SEG recordings showed satisfactory improvement of the disability; however, only one patient showed any improvement when the recording was moderately or severely abnormal. Location of the cord lesion and type of surgery were similar in all patients examined, and the difference was likely ascribed to the physiological change of the intramedullary structures. The evoked SEG provides some information relative to the surgical treatment of spondylotic myelopathy or disc protrusion with cord lesion.