Objective: to investigate the clinical feature and dynamic changes of the cervical dural sac and spinal cord during neck flexion in Hirayama disease (juvenile muscular atrophy of distal upper extremity).
Methods: Clinical data were taken and MRI in neutral neck position and a fully flexed neck position were performed on 27 cases of Hirayama disease.
Results: (1) All patients were consistent with the diagnostic criteria of Hirayama disease who had asymmetric muscular atrophy and weakness of the hand and forearm. All patients were young males and right handed of whom 77.8% had initial symptoms before they were 19 years old. More patients(20 cases,74%é had muscular atrophy in the right hand than in the left at onset. The duration after disease onset was from 2-72 months[(26.48+/-15.57) months]. (2) In neutral neck position by MIR examination, 16 patients showed abnormal cervical curvature, 14 showed atrophy of the lower cervical cord and 2 patients had intramedullary abnormal high signal. (3) In a fully flexed position of the neck, all patients showed forward displacement and flattening of the lower cervical cord, and a crescent-shaped high signal area behind the cord. (4) The crescent shaped area was enhanced on T1-weighed imaging and disappeared after the patient returned to a neural position in one case.
Conclusion: Hirayama disease occurs mainly in young males. There are obviously dynamic changes of the cervical cord during neck flexion in Hirayama disease by MRI examination, which can help the doctor make diagnosis in the early stage.