Relative vulnerability of various spinal tracts in C3-4 cervical spondylotic myelopathy: multi-modal spinal cord evoked potentials.

ABSTRACT

STUDY DESIGN: Retrospective study. OBJECTIVE: To investigate the progression of spinal tract lesions in cervical spondylotic myelopathy (CSM) at C3-4 intervertebral level using spinal cord-evoked potensials (SCEPs). SETTING: This study was conducted at the Department of Orthopaedic Surgery, Yamaguchi University Graduate School of Medicine, Japan. METHODS: A total of 30 patients with CSM were investigated in this study. In all patients, only the C3-4 intervertebral level was symptomatic, as shown by examination of SCEPs. SCEPs were recorded following median nerve stimulation (MN-SCEPs), transcranial electric stimulation (TES-SCEPs) and spinal cord stimulation (spinal-SCEPs). RESULTS: The incidence of abnormalities varied in the order of MN-SCEPs (100%), TES-SCEPs (90%) and spinal-SCEPs (67%). Patients were grouped into three types according to SCEPs transverse (all SCEPs abnormal), post-erolateral (abnormalities in the MN-SCEPs and TES-SCEPs) and upper limbs sensory (abnormal only for MN-SCEPs). In all, 20 of the 30 patients (67%) were the transverse type, 7 (23%) the post-erolateral type and 3 (10%) the upper limbs sensory type. CONCLUSION: The present study showed the lateral part of the posterior funiculus mediating upper limb sensory function was more vulnerable than the lateral corticospinal tract, which is consistent with numbness tending to appear at an early stage of mild CSM.