Correlation between muscle atrophy on MRI and manual strength testing in hereditary neuropathies.

MRI shows areas where muscle has been replaced by fat, a process which occurs in neuropathies. The purpose of this study was to investigate the usefulness of MRI in assessing disease severity in Charcot-Marie-Tooth (CMT) and hereditary motor neuropathy (HMN) compared to manual muscle testing (MMT). MRI and MMT correlated well (Spearman's rank correlation coefficient 0.910, 0.789-1.0). MRI was useful to document the extent and pattern of muscle atrophy and fat replacement and to determine the level of denervation. In addition, nerve length dependent denervation was confirmed in both CMT and HMN. MRI will be useful to confirm MMT findings and may be helpful for diagnosis of early or subclinical disease, as well as to further investigate the mechanisms of hereditary neuropathies.