单肢肌萎缩/平山病:41例患者临床、电生理和颈椎MRI特征分析

Retrospective analysis of clinical,electrophysiologic and MRI features in 41 patients with monomelic atrophy / Hirayama disease

目的探讨单肢肌萎缩（MMA）/平山病患者的临床、肌电图及颈椎MRI特征。方法 2009年5月至2014年5月就诊本科,符合诊断标准的患者,连续登记并详细记录及分析人口学资料、临床、电生理和颈椎自然位和屈曲位MRI资料。结果 （1）共41例,男39例、女2例,发病年龄14~24岁、平均年龄（16.87±2.62）岁。病程1~121月、平均病程（22.13±26.25）月。双上肢均有临床症状者6例（14.6%）,症状局限单侧者35例（85.4%）;单侧者左12例（29.3%）、右23例（56.1%）。冷麻痹22例,指震颤9例,手麻木4例;41例均有手固有肌萎缩,均无感觉障碍;（2）症状侧尺和正中神经运动潜伏期延长,小指展肌、拇短展肌运动波幅减低,小指展肌/拇短展肌波幅比值减小;（3）症状侧针肌电图显示异常自发活动者的出现率,在第一骨间肌和小指展肌为100%、拇短伸肌90.1%、拇短展肌86.3%、肱桡肌16.8%、肱二头肌13.8%;在仅限于单侧症状的35例患者中,无症状侧手固有肌也显示异常自发活动者占51.4%;（4）32例患者完成颈椎MRI检查。自然位时32例均显示颈2-颈7椎体后方下缘连线与椎体相交;均显示下段颈髓萎缩变扁平,其中位于C5-C7节段14例,C5-C6节段6例,C6-C7节段7例,C5-T1节段5例;屈颈位时15例显示硬膜腔后壁前移,移位的硬膜后方可见硬膜外占位,内有流空信号,恢复自然位后占位消失。9例显示髓内可疑T_2异常高信号。结论 MMA/平山病主要见于青少年男性;电生理表现为低位颈髓前角细胞病变,且无症状侧可显示临床下神经源性损害;小指展肌/拇短展肌波幅比值减小,是有鉴别意义的电生理指标;屈颈位颈椎MRI对于诊断很重要。结合临床、神经电生理及影像表现,有助于更全面认识本病。

Objective To analyze the clinical,electromyographic and cervical MRI features in patients with monomelic atrophy（ MMA） / Hirayama disease. Methods The consecutive patients referral to our department between May 2009 and May 2014,who met the inclusion criteria were registered. The demographic data,clinical symptoms / signs,presentations,electrophysiological findings and cervical MRI scanning including sagittal and axial images with neutral-position and flexion of neck,were recorded with details and analyzed. Results There were totally 41 patents with 39 males and 2 females,the age of onset was 14 ~ 24 years with the average of 16. 87 ± 2. 62,and the illness duration was 1 ~ 121 months,with the average of 22. 13 ± 26. 25. There were 6 patients（ 14. 6%） with bilateral and 35（ 85. 4%） unilateral involvement in upper limb; among those with unilateral involvement,there were 12patients（ 29. 3%） occurred on the left side and 23（ 56. 1%） on the right side. Cold paresis was noted in 22 cases,tremulous movement of the extended fingers in 9,atrophy of hand intrinsic muscle in all 41 cases,and none had sensory impairment on neurologic examination.（ 2） On the symptomatic side of the upper limb,the distal motor latencies of ulnar and median nerve prolonged,the compund muscle action potential（ CMAP） amplitude of m. abductor digiti minimi（ ADM） and m. abductor pollicis brevis（ APB） decreased; the mean ADM / APB ratio decreased.（ 3）On the symptomatic side,the incidence rate of abnormal spontaneous activity in first interosseous muscle was 100%,ADM 100%,extensor pollicis brevis 90. 1%,APB 86. 3%,brachioradialis 16. 8% and biceps brachii 13. 8%; among the 35 patients whose clinical manifestations were restricted in one side of upper extremity,those with abnormal spontaneous activity on the unaffected side accounted for 50. 4%.（ 4） Among 32 patients whose cervical MRI were accomplished,MRI revealed part of the vertebral body met or crossed the line drawn from the dorsocaudal aspect of C_2 through C_7and lower cervical cord atrophy in all cases with neutral-position of neck,with 14 cases of localized cord atrophy at disk C5~ C7,6 at C_5~ C_6,7 at C_6~ C_7 and 5 at C_5~ T_1; anterior shifting of the posterior dura in 15 cases with neck flexion,in which an epidural mass posterior to the shifting dura mater was noted,with flow void signals inside it,and the posterior epidural mass disappeared and the shifting dura mater returned to its normal position;and intramedullary hyperdensity lesion on T_2-weighted images in 9 cases. Conclusions MMA / Hirayama disease is predominated by male adolescent; electrophysiologic studies show lesions of anterior horn cells at the level of low cervical cord,and subclinical neurogenic damage may occur on the asymptomatic side,in which the decreased ADM /APB CMAP ratio is a meaningful electrophysiological parameter in the patient with MMA; the cervical MRI findings is very important for diagnosis of MMA / Hirayama diseas,especially adequate flexion MRI. It is helpful for us to recognize MMA more comprehensively along with the clinical,electromyographic and imaging findings.