Idiopathic scoliosis: a transcranial magnetic stimulation study

Various neurophysiological parameters of the motor system were investigated in 43 female patients with Idiopathic Scoliosis (IS) and 31 sex and age matched controls using transcranial magnetic stimulation (TMS).

To investigate whether asymmetries in excitatory and inhibitory brain processes, as studied by TMS, are a causative factor in IS.

Previous studies associated IS with pathological asymmetries of the cerebral cortex and the brain stem at the level of the corticospinal tracts.

Forty-three female patients with right IS and 31 normal female subjects entered the study. Various TMS parameters, including the study of ipsilateral pyramidal tract, were studied. Electrophysiological data were correlated with clinical data, the degrees of the scoliotic curve and the Perdriolle and Nash & Moe indexes.

In upper limbs, detailed testing failed to reveal any statistically significant differences between the patient and the control group. In lower limbs, side-to-side differences of central motor conduction time (CMCT) and facilitated cortical-to-muscle latencies were increased in the scoliotic patients (p<0.05). This finding correlated significantly with Nash & Moe and Perdriolle indexes (Spearman's r=0.406 and 0.575, respectively, p<0.05). Following the Bonferroni adjustment, however, differences in CMCT SSDs were not statistically significant (p>0.05).

The present TMS data do not support the concept of a generalized brain asymmetry in IS. In lower limbs, a trend towards increased asymmetries in side-to-side differences of CMCT and cortical latencies was detected probably representing subclinical involvement of the corticospinal tracts secondary to mechanical compression. Finally, it is concluded that non-decussation of the pyramidal tracts is not involved in the pathogenesis of IS.