Sonographic evaluations of the skeletal muscles in patients with Pompe disease

Pompe disease usually has muscle weakness due to glycogen accumulation. Heckmatt scale is commonly used to grade the pertinent findings of ultrasound. Nonetheless, it is difficult to detect subtle changes of the muscle. Besides, no ultrasonographic parameter has been proposed to predict the motor functions of Pompe disease. Therefore, we aimed to find out an ultrasonographic parameter that can quantify the muscle involvement and correlate with the motor functions in Pompe disease.

Eighteen patients with Pompe disease were enrolled. The echo heterogeneity index (standard deviation divided by mean echogenicity values by ImageJ analysis) and shear modulus were recorded from rectus femoris, biceps femoris, tibialis anterior, medial gastrocnemius, biceps brachii and triceps brachii muscles. Motor functions, including manual muscle strength, 6-min walk and four-limb stair climb tests were assessed. Correlations between ultrasonographic parameters and Heckmatt scale and motor functions were analyzed.

The echo heterogeneity index, but not the shear modulus, was negatively correlated with the Heckmatt scale rating in all muscles. The echo heterogeneity indices of tibialis anterior (r = 0.698, p = 0.008) and medial gastrocnemius (r = 0.615, p = 0.025) muscles showed positive correlations with the walking distance. Besides, the echo heterogeneity indices of four lower limb muscles were negatively correlated with the duration of stair climbing.

The echo heterogeneity index but not the shear modulus can be used to quantitatively describe the muscle involvement in Pompe disease. In addition, lower echo heterogeneity indices of lower limb muscles are associated with worse motor functions in these patients.