[Application value of motor unit number index in patients with amyotrophic lateral sclerosis]

Objective: To investigate the application value of motor unit number index (MUNIX) for diagnosis and assessment progress in patients with amyotrophic lateral sclerosis (ALS). Method: Sixty healthy controls and 60 ALS patients in the clinic were enrolled from May 2017 to December 2018. The bilateral deltoid, abductor digiti minimi, quadriceps femoris and tibialis anterior muscles of the subjects were detected by MUNIX method, and the negative peak amplitude of compound muscle action potential (CMAP) of ulnar nerve, femoral nerve, peroneal nerve, axillary nerve in bilateral was collected. MUNIX and motor unit size index (MUSIX) of muscles were compared between ALS group and control group. The difference between the MUNIX abnormal rate of muscles and abnormal rate of the corresponding CMAP negative peak amplitude in ALS patients was further compared. Meanwhile, the correlation between the disease course of ALS patients and MUNIX and MUSIX was analyzed. Results: Compared with the control group, the MUNIX values of the deltoid, abductor digiti minimi, quadriceps femoris and tibialis anterior decreased significantly (97±24 vs 183±38, 48±17 vs 191±39, 54±15 vs 159±22, 49±16 vs 147±25, all P<0.05). MUSIX values increased ((175±32) μV vs (47±15) μV, (189±34) μV vs (54±16) μV, (170±30) μV vs (49±13) μV, (190± 36) μV vs (48± 14) μV, all P<0.05)). In ALS patients, the abnormal rate of MUNIX was respectively 81%, 87%, 75% and 89%. The negative peak amplitude abnormal rate of corresponding neuralCMAP was 35%, 40%, 31% and 36%, respectively, with a significant difference (P<0.05). There was a negative correlation between MUNIX value and the course of disease in ALS patients (P<0.05), and a positive correlation between MUSIX value and the course of disease (P<0.05). Conclusion: The MUNIX technique exhibits the features of quantifying the proximal upper and lower limb muscles and assessing the loss of motor units in motor neuron degeneration.