强直性肌营养不良1型前臂肌肉MRI特点

The MRI characters of forearm muscles in patients with myotonic dystrophy type1

目的分析强直性肌营养不良1型(myotonic dystrophy type1,DM1)前臂肌肉MRI改变规律及其与临床表现的关系。方法收集基因检查确诊DM1患者的临床表现、电生理和病理资料,进行前臂肌肉MRI检查,分析T1WI序列上前臂肌肉脂肪化和短反转时间恢复序列水肿规律,对前臂各肌肉的脂肪化及水肿程度进行评分,并计算与年龄、病程、上肢远端无力之间的关系。结果23例患者发病年龄17~60岁,平均(34.3±12.2)岁,病程5(3,9)年,临床主要表现双手远端的发僵及无力,伴随脱发和多睡。肌肉MRI显示指深屈肌脂肪化评分为4.0(3.0,4.0)分、拇长屈肌4.0(3.0,4.0)分、拇短伸肌2.0(1.0,2.5)分、拇长展肌2.0(0.5,2.5)分、拇长伸肌2.0(1.0,2.0)分、指浅屈肌2.0(0.5,2.5)分、旋后肌2.0(1.0,2.0)分,其他肌肉1.0分,其中旋前圆肌为1.0(0.0,1.0)。9例出现指深屈肌萎缩,6例出现拇长屈肌萎缩,11例出现旋前圆肌肥大。肌肉水肿以指深屈肌、拇长屈肌、指浅屈肌最为明显,而肱桡肌、旋前圆肌未见水肿。骨骼肌MRI平均脂肪化评分与年龄、病程无相关,与肌力总评分(r=-0.590,P<0.01)相关;指深屈肌和拇长屈肌平均脂肪化评分分别与握力存在相关(r=-0.754,P<0.01和r=-0.699,P<0.01),与年龄、病程无相关。结论DM1患者前臂肌肉MRI检查可见相对特异的选择性肌肉受累分布,并可以评估肌无力严重程度。

Objective This study aimed to investigate the MRI features of forearm muscles from myotonic dystrophy type 1(DM1)and to evaluate the correlation between clinical factors and muscle MRI.Methods We retrospectively reviewed the medical records of genetic-confirmed DM1 patients including the clinical manifestations,the electromyography and the muscle pathology results.MRI scan was used to examine forearm muscles.Analysis of T1weighed images and short inversion time inversion recovery images were used to evaluate muscle fatty infiltration and muscle edema,respectively.The correlation between the fatty infiltration and age,disease duration and muscle strength were investigated.Results Twenty-three DM1 patients from different family were enrolled.The onset age was 17~60 year-old,mean age was(34.3±12.2)year-old,and the mean course of disease was 5(3,9)years.Their main symptoms were hand weakness and stiffness,accompanying with alopecia and excessive daytime sleepiness.The median fatty infiltration scores were recorded as follows:flexor digitorum profundus(FDP)4.0(3.0,4.0),flexor pollicis longus(FPL)4.0(3.0,4.0),extensor pollicis brevis 2.0(1.0,2.5),abductor pollicis longus 2.0(0.5,2.5),extensor pollicis longus 2.0(1.0,2.0),flexor digitorum superficialis 2.0(0.5,2.5),supinator(S)2.0(1.0,2.0).Other muscles scores were less than 1 of which the pronator teres(PT)was 1.0(0.0,1.0).Atrophy of FDP was detected in nine,atrophy of FPL in six and hypertrophy of PT in 11 patients.The muscle edema was evident in FDP,FPL,and the flexor digitorum superficialis,while brachioradialis and pronator teres were normal.There was no significant correlation between mean muscle fat infiltration score and age or course of disease.The mean muscle fat infiltration was significantly correlated with muscle strength score(r=-0.590,P<0.01).The mean fatty infiltration scores of FDP and FPL were not correlated with age nor course of disease,but correlated with grip strength(r=-0.754,P<0.01 and r=-0.699,P<0.01).Conclusion The forearm MRI in DM1 patients exhibit a relatively specific distribution of selective muscle involvement and can be used to assess muscle weakness.