The MRI characters of forearm muscles in patients with myotonic dystrophy type1 / 中国神经精神疾病杂志

ABSTRACT

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.