Juvenile Muscular Atrophy of Unilateral Upper Extremity (Hirayama Disease)

概要

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We have clinically examined 9 patients with juvenile muscular atrophy of unilateral upper extremity (Hirayama disease) , which is characterized by exclusive juvenile male occurrence, insudious onset, unilateral muscular atrophy of the hand and forearm, lack of definite sesory disturbances and non or very slow progressive course. Although the clinical features of our patients were basically consistent with those in previous reports, their ages at onset were slightly higher and cold paresis and fasciculation ossurred less frequently in our cases. Five patients were examined by cervical magnetic resonance imaging (MRI) at the anteflexed position in addition to the routine neutral position. As aresult, 4 were found to show both the spinal cord thinning and anterioi shifting of the dural sac at levels of C5-C7 ; especially in 2 patients, the findings were obtained only at the anteflexed position (not at the neutral one). The present results clearly provide the evidence that MRI at the anteflexed position was efficient for detection of Hirayama desease and strongly support the hypothesis that the desease is caused by chronic circulatory insufficiency due to compression of the spinal cord resulting from repeated anterior shifting of the dural sac.