DISTRIBUTION OF MUSCLE DEGENERATION IN WELANDER DISTAL MYOPATHY - A MAGNETIC-RESONANCE-IMAGING AND MUSCLE BIOPSY STUDY

Seven patients with Welander distal myopathy were subjected to magneti c resonance imaging (MRI) of the lower extremity, and muscle biopsies of the tibialis anterior, soleus and vastus lateralis muscles. MRI rev ealed abnormalities in both the anterior and posterior compartments of the lower leg in three of the patients, and in only the posterior com partment in the rest of the patients. No MRI abnormalities were found in either the proximal muscles of the leg or in the peroneal or poster ior tibial muscle groups. Affected muscles had T1- and T2-values indic ating a replacement of muscle fibres with fat tissue. Muscle biopsies showed pathological changes varying from slight to severe in tibialis anterior and soleus muscles in all patients. No muscle fibre abnormali ties were seen in the vastus lateralis muscle in any of the patients. In accordance with earlier reports from patients with Welander distal myopathy, there was muscle degeneration of tibialis anterior muscles c orresponding to the weakness of dorsal extension of the feet, but also degeneration in the muscles of the posterior compartment. The patient s did not, however, show any clinical signs of weakness related to pos terior muscle groups. There is no evidence of involvement of proximal muscles of the leg clinically, with MRI or in muscle biopsies.