Localisation of cervical spinal cord compression by TMS and MRI

The authors set out to study the role of transcranial magnetic stimulation (TMS) in the pre-surgical assessment of patients with cervical spondylotic myelopathy. Central motor conduction time (CMCT) was calculated in 50 patients and 50 controls by recording muscle evoked potentials from upper limb muscles. The level of spinal cord compression was determined according to the pattern of CMCT prolongation and compared with the level disclosed by MRI. Direct comparison of the TMS and MRI results was possible in 42 cases and agreement was noted in 25 (59.5%). In the 23 patients in whom the two methods did not give convergent findings, post-operative data were used in order to determine the actual level of compression. This level was correctly indicated by TMS in 87.5% of cases and by MRI in 12.5%. TMS is a neurophysiological tool that can complement existing methods for determining the level of cervical spinal cord compression.