Correlation Between Spinal Cord Function Assessed by Intraoperative SCEPs and Morphology of the Compressed Spinal Cord on MRI.

Study Design: Retrospective study.
Objectives: The objective of this study was to examine whether the morphology of the compressed spinal cord reflects spinal cord dysfunction in cervical spondylotic myelopathy (CSM).
Summary of Background: Segmental levels responsible for clinical symptoms in CSM are usually diagnosed by neurological examination and imaging studies such as magnetic resonance imaging (MRI). Electrophysiological examination makes it possible to assess the spinal cord function quantitatively. There are few detailed studies about correlation between intraoperative spinal cord-evoked potentials (following SCEPs) and preoperative MRI.
Materials and Methods: A total of 25 CSM cases diagnosed with single intervertebral dysfunction based on preoperative neurological findings and intraoperative SCEPs were included. We recorded 3 different SCEPs and divided the cases into 2 groups: the transverse type (T-type) (n=18) that had abnormalities in all SCEPs; and the upper limbs sensory (abnormal only for MN-SCEPs) and posterolateral (abnormalities in the MN-SCEPs and Tc-SCEPs) type (US-PL-type) (n=7) that had abnormalities other than SCEPs following thoracic spinal cord stimulation. Morphometry was performed on MRI T1-weighed axial images. Clinical preoperative impairment was evaluated using the Japanese Orthopedic Association score.
Results: The average Japanese Orthopedic Association score of T-type cases was 8.1 points and that of US-PL-type cases was 10.5. There were no severe cases with <7 points in the US-PL-type group, but there were 9 cases in the T-type group. By morphometric comparison, both the central and the 1/4-lateral compression ratio were significantly lower in the T-type cases.
Conclusions: Spinal cord morphology, as observed on MRI in patients with CSM reflected spinal cord dysfunction to some extent and could become the index for functional diagnosis, but it is necessary to consider a dynamic factor.