Computed tomography in dystrophia myotonica.

The calves and thighs of ten patients with dystrophia myotonica and four normal controls were studied by CT. The morphology of the anterior and posterior muscle groups of the calf and the extensor, flexor and adductor groups of the thigh were studied and their attenuation values analysed. Clinical measurement of muscle force was compared with attenuation values in each muscle group. The principal morphological change observed in diseased muscle was fatty infiltration. The amount of fatty infiltration in the calf muscles paralleled the severity of clinically apparent disease. However, in the thigh, fatty infiltration was observed in the extensors of three of the five patients who clinically had involvement of calf muscles alone. Detailed analysis of attenuation values was no better in detecting diseased muscle except of the adductor group of the thigh in those patients with both proximal and distal lower limb involvement. Comparison between muscle force and attenuation values showed a significant correlation in only the anterior muscle group of the calf in the normal controls and in those patients with clinically apparent disease of the calf muscles alone.