Cerebral Reorganization in Cervical Myelopathy Measured by Navigated Transcranial Magnetic Stimulation

Overview

In degenerative cervical myelopathy (DCM) the dynamics of disease progression and the outcome after surgical decompression vary inter individually and do not necessarily correlate with radiological findings. By better characterization of the underlying pathophysiology this study aims to improve diagnostic power in DCM using Navigated transcranial magnetic stimulation (nTMS).

120 patients with DCM due to cervical spinal canal stenosis will be examined preoperatively and postoperatively with nTMS. On the basis of the initial Japanese Orthopedic Association (JOA) Score two patient groups will be established (JOA≤12/\>12). The resting motor threshold, recruitment curve, cortical silent period and motor area will be determined. Accordingly, 40 healthy subjects will be examined. To the investigators knowledge, this study is the first to analyze changes of corticospinal excitability and reorganization in patients with cervical spondylotic myelopathy with navigated TMS. In the present study, there was a significant difference in parameters of excitability and motor area activation between the severely symptomatic and clinically stable patient group. The investigators analysis showed that chronic CSM induces a recruitment of the non-primary motor area and corticospinal disinhibition, so that axonal damage can be compensated through recruitment of new cortical and supplementary motor connections, to a certain degree. Upon exhaustion of these mechanisms further axonal damage translates directly into new neurological deficits. These results lay the ground for a novel concept in CSM, the "corticospinal reserve capacity". This study lays the foundation for future research to examine the pathomechanisms in CSM. Functional reorganization occurs on a spinal as well as on a cortical level. The concept of the corticospinal reseve capacity describes a compensatory, increased recruitment of non primary motor areas and corticospinal disinhibition in order to preserve motor function. By detecting the degree of reorganization, a stratification for an unfavourable as well as stable clinical course could be made. This innovative approach to describe the pathomechanisms in CSM might revise current concepts of clinical diagnostics and might have an impact on future treatment strategies.

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