Assessment of upper motor neuron dysfunction by triple stimulation technique in patients with Charcot-Marie-Tooth disease

Abstract

To investigate the presence of upper motor neuron dysfunction in patients with Charcot-Marie-Tooth disease (CMT) by triple stimulation technique (TST) to provide evidence for gene diagnosis. A total of 65 CMT patients confirmed by genetic testing from Peking University Third Hospital between August 2013 and August 2015, underwent physical examination and routine electrophysiological tests and triple stimulation technique. The TST combined transcranial magnetic stimulation (TMS) of the motor cortex with peripheral collision studies. The results were expressed by the TST amplitude ratio (TST test/ TST control). Based on the result of physical examination and the ratio of TST, the function of upper motor neuron was assessed. All of the CMT patients had typical presentations and were confirmed genetically. Hyperreflexia, Babinski sign and muscular hypertonia were discovered in lower limbs in 7 CMT patients, while 2 patients complicated with hyperreflexia and Hoffmann sign in upper limbs. TST amplitude ratio was significantly altered in 10 patients, including 5 patients with pyramid sign: hyperreflexia, Babinski sign and muscular hypertonia was discovered in lower limbs while 2 patients complicated with hyperreflexia and Hoffmann sign in upper limbs. The disease-causing mutations were: MFN2 mutations in 5 patients, 1 patient with BSCL2 mutation, 3 patients with GJB1 mutations and 1 patient with GDAP mutation. In summary, 18.5% (12 patients) of the 65 CMT patients had upper motor neuron dysfunction based on the result of physical examination and the ratio of TST. Upper motor neuron dysfunction may be found in CMT patients, which may provide clues for the testing of disease-causing mutations.