Hirayama disease simple presenting proximal upper extremity muscular atrophy

Objective To investigate the clinical features and magnetic resonance imaging (MRI) findings of patients with Hirayama disease simply presenting proximal upper extremity muscular atrophy. Methods Three patients with Hirayama disease simply

A clinical neurophysiology study of Hirayama disease

Background Hirayama disease is a rare disease characterized by juvenile-onset of asymmetric amyotrophy, of which etiology has not been clarified. The aim of our study was to investigate the clinical and neurophysiologic characteristics of Hirayama disease. Methods Neurophysiological tests, including nerve conduction studies （NCS）, F-wave and routine electromyography （EMG）, were performed in seventy-three patients with Hirayama disease. EMG was selectively performed on upper and lower extremities, sternocleidomast and thoracic paravertebral muscles according to the clinical features of the patients. Results Abnormal NCS parameters, including decreased compound muscle action potentials or delayed distal motor latency, were found in 34.2% （25/73） and 12.3% （9/73） of the patients, respectively. A total of 24.6% （18/73） of the patients showed decreased F-wave frequency. EMG demonstrated the presence of neurogenic lesions in all patients with spontaneous potentials, prolonged duration or augmentation of amplitude in motor unit potentials （MUPs）, or a single pattern of MUP recruitment. About 17.8% （13/73） of the patients showed neurogenic lesions, mostly in the C7-8 level of the cervical cord, only in the upper extremity of affected side, whereas 35.6% （26/73） of the patients possessed lesions in the upper extremities bilaterally. A total of 46.6% （34/73） of patients exhibited abnormalities in the lower extremities, sterno- cleidomast or thoracic paravertebral muscle. Changes in motor NCS were significantly correlated with muscle strength. Conclusions EMG detects diffused subclinical neurogenic lesion in a high proportion of patients with Hirayama disease. Results of our study challenge the hypothesis that Hirayama disease is a type of cervical myelopathy.

Neuroelectrophysiological characteristics of Hirayama disease： report of 14 cases

Background Hirayama disease is a juvenile muscular atrophy of the distal upper extremities and affects mainly young males. The present study aimed to investigate the neuroelectrophysiological characteristics of Hirayama disease. Methods We retrospectively analyzed the neural conduction velocity （NCV） parameters and needle-electrode electromyograms （EMG） of 14 patients with Hirayama disease. According to the clinical features of the patients, NCV was performed on affected upper-limb including median nerves and ulnar nerves, while EMG was selectively performed on upper and lower extremities, sternocleidomast and thoracic paraspinal muscles. Results The median nerves of all affected upper limbs of patients with Hirayama disease had normal conduction velocities and compound motor action potentials （CMAPs）. The ulnar nerves of all affected upper limbs also had normal conduction velocities. Of the 16 measured ulnar nerves of the affected upper limbs, eight had normal CMAPS, while the other eight showed CMAPs below the normal value by 〉20%. All patients had neurogenic injury on the affected side in muscles innervated by anterior horn cells at the lower cervical region （C7-8, T1）. Four patients had unilateral upper-limb muscle neurogenic injury on the affected side. Seven patients had bilateral upper-limb muscle neurogenic injury, while only two patients experienced bilateral upper-limb muscle atrophy / weakness. The other three patients showed extensive neurogenic injury （unilateral upper-limb muscle atrophy/weakness in one patient, bilateral symptoms in the other two patients）. Conclusions Electromyographic examination showed that the majority of Hirayama disease patients exhibited characteristic segmental injury in the anterior horn of the lower cervical region, while a few patients exhibited extensive neurogenic injury. These data suggest that the actual influence of Hirayama disease may be more extensive than indicated by the clinical presentations.

Pattern Differences of Small Hand Muscle Atrophy in Amyotrophic Lateral Sclerosis and Mimic Disorders

Background： Amyotrophic lateral sclerosis （ALS） and some mimic disorders, such as distal-type cervical spondylotic amyotrophy （LISA）, Hirayama disease （HD）, and spinobulbar muscular atrophy （SBMA） may present with intrinsic hand muscle atrophy. This study aimed to investigate different patterns of small hand muscle involvement in ALS and some mimic disorders. Methods： We compared the abductor digiti minimi/abductor pollicis brevis （ADM/APB） compound muscle action potential （（＇MAP） ratios between 200 ALS patients, 95 patients with distal-type CSA, 88 HD patients, 43 SBMA patients, and 150 normal controls. Results： The ADM/APB （？MAP amplitude ratio was significantly higher in the ALS patients （P 〈 0.001） than that in the normal controls. The ADM/APB CMAP amplitude ratio was significantly reduced in the patients with distal-type CSA （P 〈 0,001 ） and the H I） patients （P 〈 0.001 ） compared with that in the normal controls. The patients with distal-type CSA had significantly lower APB CMAP amplitude than the HD patients （P- 0.004）. The ADM/APB CMAP amplitude ratio was significantly lower in the HD patients （P 〈 0.001 ） than that in the patients with distal-type CSA. The ADM/APB CMAP amplitude ratio of the SBMA patients was similar to that of the normal controls （P = 0.862）. An absent APB CMAP and an abnormally high ADM/APB CMAP amplitude ratio （_〉4.5） were observed exclusively in the ALS patients. Conclusions： The different patterns of small hand muscle atrophy between the ALS patients and the patients with mimic disorders presumably reflect distinct pathophysiological mechanisms underlying different disorders, and may aid in distinguishing between ALS and mimic disorders.