Magnetic resonance imaging of muscle injury and atrophy in glycolytic myopathies

Exertional muscle pain, contractures, recurrent rhabdomyolysis, and pigmenturia are common in certain muscle glycolytic disorders. However, the frequency, distribution, and long-term significance of these findings are poorly understood. First we performed magnetic resonance imaging (MRI) of the extremities as a screening test for the detection of muscle abnormalities incurred in activities of daily living in four patients with myophosphorylase deficiency (MPD) and three with muscle phosphofructokinase deficiency (PFKD). MRI findings of abnormal muscles detected upon screening were next compared with changes observed in a prospective study of muscle contractures involving the forearms of four of the patients (two MPD, two PFKD). Screening revealed abnormalities of proximal thigh muscles in three of seven patients, in two of whom (one MPD, one PFKD) a recent history of exertional myalgia coincided with increases in T1 and T2 estimates of isolated thigh muscles. In the third patient (PFKD), focal atrophy of the adductor magnus was present bilaterally. In prospective studies, focal areas of prolonged T1 and T2 appeared in the flexor digitorum superificalis in all four cases and in the flexor digitorum profundus in two cases. Serial imaging suggested that the onset of MRI abnormalities begins within 24 hours of contracture and persists for at least several days and possibly for much longer, with complete recovery apparently the rule. These cases suggests a high prevalence of focal muscle abnormalities in patients with glycolytic myopathies and show the potential of MRI to detect them.