Motor Unit Number Estimation in the Quantitative Assessment of Severity and Progression of Motor Unit Loss in Hirayama Disease

Publication date: Available online 16 March 2017
Source:Clinical Neurophysiology
Author(s): Chaojun Zheng, Yu Zhu, Dongqing Zhu, Feizhou Lu, Xinlei Xia, Jianyuan Jiang, Xiaosheng Ma
ObjectiveTo investigate motor unit number estimation (MUNE) as a method to quantitatively evaluate severity and progression of motor unit loss in Hirayama Disease (HD).MethodsMultipoint Incremental MUNE was performed bilaterally on both abductor digiti minimi and abductor pollicis brevis muscles in 46 HD patients and 32 controls, along with handgrip strength examination. MUNE was reevaluated approximately 1 year after initial examination in 17 HD patients.ResultsThe MUNE values were significantly lower in all tested muscles in the HD group (P<0.05). Despite abnormally low MUNE values, 54.3% (25/46) HD patients had normal ipsilateral grip power. There was a significant inverse correlation between MUNE values and disease duration (P<0.05). A longitudinal follow-up MUNE analysis demonstrated slow progression of motor unit loss in HD patients within approximately 1 year (P<0.05), even in patients with an illness duration greater than four years.ConclusionsA reduction in the functioning motor units was found in HD patients compared with controls, even in the early asymptomatic stages. Moreover, the motor unit loss in HD progresses gradually as the disease advances.SignificanceThese results have providedevidenceforapplication of MUNE in estimating the reduction of motor unit in HD and confirm the validity of MUNE for tracking the progression of HD in a clinical setting.



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