Spinal Cord Morphology and Dynamics During Cervical Laminoplasty

STUDY DESIGN: An intraoperative sonographic study for evaluating spinal cord decompression status was conducted. OBJECTIVES: To analyze the spinal cord decompression status using intraoperative sonography and to evaluate the relation to postoperative neurologic recovery following cervical laminoplasty. SUMMARY OF BACKGROUND DATA: Since the 1980s, several papers have introduced that the intraoperative ultrasound allowed assessment of the adequacy of decompression and configuration of the spinal cord in compressive myelopathy. However, there have been no reports systematically evaluating the decompression status. METHODS: Spinal cord decompression status of 80 consecutive patients with cervical compressive myelopathy was evaluated by intraoperative sonography during cervical laminoplasty. The decompression status was classified into 4 grades according to the restoration pattern of the space ventral to the cord. In addition, amplitude of the cord pulsation and compression type in axial view were also assessed. This study analyzed whether those findings from intraoperative sonography had relevance to preoperative spinal cord conditions evaluated by magnetic resonance images (MRI) and postoperative neurologic recovery. RESULTS: The mean neurologic recovery rate was 48.3% at the final follow-up. According to intraoperative sonographic evaluation, 50 cases who acquired the space ventral to the cord showed significantly higher recovery rate (59.2%) than 30 cases who failed to acquire the space (recovery rate, 31.0%) in total. Twenty-seven of 60 cases with intramedullary T2 high lesion on preoperative MRI more frequently failed to restore the ventral space, and their neurologic recovery rate indicated 30.2%. The amplitude of spinal cord pulsation or compression type did not correlate with the neurologic recovery. CONCLUSION: Intraoperative sonography during laminoplasty appears to be very useful for evaluating spinal cord decompression status. Our original classification system based on restoration patterns of the space ventral to the spinal cord is considered to be practical for predicting neurologic improvement in cervical compressive myelopathy.