Objective    To study clinical characteristics of juvenile muscular atrophy of the distal upper extremity, for early diagnosis　and treatment.    Methods    The clinical data, neuro-electrophysiological features, clinical anatomy and　MRI features of 13 patients diagnosed by the criteria of　Hirayama Disease were retrospectively analyzed.    Results    The mean age of onset was about 18.6 years old. Hirayama disease was characterized by muscular atrophy in the hand and forearm. The brachioradialis was spared (oblique amyotrophy). EMG indicated that the impairment of spinal　anterior cells　was limited to the arm relevant segments and both sides were involved. During neck flexion, the spinal cord was placed forward and flattened. The diameter of cervical spine cord in the sixth cervical vertebra along the horizontal in juvenile muscular atrophy of the distal upper extremity was smaller than that in normal volunteers significantly (P＜0.05). Conclusions 　Juvenile muscular atrophy of the distal upper extremity may be a special type of cervical　myelopathy. The neuro-electrophysiological check and the neck flexion　MRI check are valuable to the clinical　diagnosis and differential diagnosis. Cervical collar therapy is recommended the sooner the better and avoiding long time neck flexion position is very important for the patients.