中文摘要：

目的 研究表现为上肢近端肌肉萎缩的平山病患者的临床表现和颈椎中立位、屈曲位MR影像特征.方法 3例临床上表现为上肢近端肌肉萎缩的平山病患者,行颈椎中立位及屈曲位MR检查,分析患者的临床表现及与影像学征象的关系,并与43例表现为手及前臂肌肉萎缩的平山病患者相比较.结果 （1）临床特点：3例患者均为青少年男性,表现为一侧胸大肌、三角肌、肱二头肌等上肢近端肌肉萎缩和肌无力,肌电图检查均提示双侧上肢神经源性损害.（2）颈椎MRI特点：3例患者中立位MRI示颈椎呈后凸畸形,脊髓未见压迫;屈曲位MRI示C3-5椎体水平的颈段脊髓和后方硬脊膜向前移位,C4.5椎体水平脊髓受到前方椎体或椎间盘和后方硬脊膜的压迫,硬脊膜外有扩张的椎管内静脉丛.43例表现为手及前臂肌肉萎缩的平山病患者也出现上述征象,脊髓受压部位在C6.7椎体水平.结论 平山病可表现为胸大肌、三角肌、肱二头肌等上肢近端肌肉的萎缩和无力,容易被误诊和漏诊;颈椎屈曲位MRI是本病早期诊断的重要依据.

英文摘要：

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 presenting proximal upper extremity muscular atrophy received cervical spine MRI on neutral and flexion position. The relationship between MRI findings and their clinical symptoms were analyzed. The outcomes were compared with those of 43 patients who were diagnosed as Hirayama disease with muscular atrophy at the hand and forearm. Results 1） Clinical features：three patients were young men. The disease was characterized by unilateral weakness and atrophy of the proximal upper limbs, such as pectoralis major muscle, deltoid muscle, and biceps brachii muscle. Electromyogram （EMG） showed bilateral upper extremities neurogenic damage. 2） Cervical spine MRI findings：cervical spine kyphosis without spinal cord compression was found on neutral position. On flexion position,anterior shifting of C3-C5 cervical cord and the posterior wall of dural sac were found; C4-C5 cervical cord was compressed by vertebral body or intervertebral disc or dural sac. Engorged posterior internal vertebral venous plexus were observed in epidural space. In the 43 patients who were diagnosed Hirayama disease with muscular atrophy at the hand and forearm, similar MRI findings were found, while cervical cords compression were at C6-C7 level. Conclusion Hirayama disease could present as proximal upper extremity muscular atrophy and weakness, such as pectoralis major muscle, deltoid muscle, and biceps brachii muscle.Neglecting of this will result in diagnostic errors or missed diagnosis. Flexion position MRI is an important base of early diagnosis of Hirayama disease.