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.