FV 9. How Degenerative Cervical Myelopathy Affects the Functional Imaging Correlates of the Somatosensory Cortex

Abstract

Question. Degenerative Cervical Myelopathy (DCM) shows growing prevalence in industrial nations due to the demographic development. Nevertheless, the surgical decision-making is still challenging due to the lack of sufficiently reliable predictors of disease progression and surgical outcome. Neither the interplay of involved pathomechanisms, nor the definite effect on neural networks within the central nervous system has been investigated sufficiently, yet. Recently, the compensatory potential of reorganization processes within the cerebrospinal motor network has been discussed. Somatosensory impairment as an early but often overlooked symptom of DCM, however, was not in the main focus of research so far. We, therefore, investigated how the primary and secondary somatosensory cortex (S1 & S2) adapt in DCM. Methods. A cohort of 18 right-handed participants, consisting of 9 DCM patients (age 56 ± 12 years, 7 male, mean JOA score 13.3 ± 2.3) and 9 age- and gender-matched healthy control subjects (age 57 ± 12 years, 7 male) underwent an fMRI (3T) session using a block design. The fMRI procedure consisted of alternating, passive somatosensory stimulation of the subjects' hands and feet by means of a felt stick. Using MATLAB® 2019a and the SPM12 software package, a ROI-wise analysis of BOLD-response was performed at the group level using a three-way ANOVA, including the factors “group” (patients/controls), “limb” (hand/foot) and “side” (left/right). Results. In both, patients and controls, we found a strongly left-lateralized cortical response in S1 and S2 (p ≤ 0.05, FWE-corrected) regarding the somatosensory stimulation of the right (dominant) hand. However, activation in patients was lower than in healthy control subjects (p≤0.001, uncorrected). Regarding the other task conditions, controls showed significant responses within the somatosensory cortex (p ≤ 0.05, FWE-corrected), including a consistent activation within the ipsilateral S2. In contrast, patients showed only weak activation in S1 (p ≤ 0.001, uncorrected) and a much scarcer involvement of ipsilateral areas. Conclusions. Our results imply that DCM patients show reduced cortical responsiveness to peripheral stimuli. The cortical somatosensory representation of the right (preferred) hand seems to be more robust to deviations due to DCM than the representations of the other tested limbs. It remains to be investigated whether clinical impairment is correlated with cortical somatosensory responsiveness and if the alterations outlined above are reversible after surgical decompression.