Characteristics of muscle MRI of lower limbs in patients with GNE myopathy

Abstract

Objective To summarize the characteristic of muscle MRI of lower limbs in patients with GNE myopathy and to explore the correlation between the fatty degenerative score of muscle MRI and clinical phenotype. Methods This was a prospective study. Seventeen patients with genetically confirmed GNE myopathy, having lower limb muscle MRI test and completed clinical and laboratory data.The degree of fatty degeneration in 18 muscles of lower limbs in each patient was grading. According to the GM-W score, these patients were divided into two groups. GM-W score ≤ 3 were divided into mild group (n=8) and GM-W score≥ 4 were divided into severe group(n=9). Kruskal-Wallis test was used to compare the fatty degenerative score in different muscles of the thigh and the calf level;Mann-Whitney U test was used to compare score of the same muscle between mild and severe group;Spearman rank correlation test was used to analysis the relationship between fatty degenerative score and the course of disease (year), GM-W score, creatinine kinase (IU/L), respectively. Results At the thigh level, the most severely involved muscle of GNE myopathy was semi-tendinosusand adductor, followed by semi-membranous, biceps femoris and gracilis. There was no statistically significant difference in the fatty degenerative score of the above-mentioned muscles (P=0.058). At the calf level, the most severely involved muscle was medial of soleus which score was 4.0(3.0, 4.0), followed by tibialis anterior,extensor digitorum longus and lateral of soleus. There was no significant difference of the above (P=0.259).The fatty degenerative score showed difference between the mild and severe group at sartorius and adductor (P<0.05).At the calf level, the fatty degenerative score in peroneus longus, medial of soleus, lateral of soleus, medial of gastrocnemius and lateral of gastrocnemius showed difference between groups(P<0.05).The total score of fatty degenerative of Lower limb muscles was positively correlated with GM-W score(r=0.730, P<0.05). There were positive correlations between the score of fatty degenerative of the sartorius, peroneal longus, lateral of soleus, medial of gastrocnemius, lateral of gastrocnemius and the GM-W scores(r=0.630, 0.845, 0.569, 0.591, 0.640, 0.659, P<0.05). The total score of fatty degenerative of Lower limb muscles was not correlated with the level of creatine kinase(P=0.582), course of disease(P=0.601) and age of onset(P=0.850). Conclusions GNE myopathy in the thigh level within the adductor muscle and posterior muscle involvement, calf level to the tibial anterior muscle early involvement. The total score of fatty degenerative of lower limb muscles is positively correlated with GM-W score, but not correlated with the level of creatine kinase, course of disease and age of onset. Key words: Magnetic resonance imaging; Comparative study; GNE myopathy