[Research of upper arms muscle MRI in patients with Kennedy's disease].

Objective: To investigate whether or not the involvement degree of extensor and flexor muscles in patients with Kennedy's Disease (KD) was different by measuring the diameter of biceps and triceps brachii muscles using Magnetic Resonance Imaging (MRI). Methods: All the subjects were outpatients or hospitalized patients from Department of Neurology, the Third Hospital of Peking University, 2011-2015. Subjects included 30 KD patients and 30 amyotrophic lateral sclerosis (ALS) patients. The right upper arms of all subjects were examined by muscle MRI. The diameters of biceps and triceps brachii muscles were measured, then the ratios were calculated. Additionally, the forces of these muscles were recorded. Results: The ratio of diameters of biceps to triceps brachii muscles were 1.08±0.14 in KD patients and 0.99±0.15 in ALS patients. The difference was statistically significant (P<0.05). The ratio of forces of biceps to triceps were 1.17±0.12 in KD patients and 0.98±0.28 in ALS patients. The difference was statistically significant (P<0.01). In KD patients, the fatty infiltration was more serious in triceps than biceps. At the same time, in ALS patients, the fatty infiltration was similar in triceps and biceps. Conclusion: The involvement degree of extensor and flexor muscles in KD patients is different.