MAGNETIC-RESONANCE-IMAGING OF MUSCLE IN AMYOTROPHIC-LATERAL-SCLEROSIS

Objective: To characterize leg muscle abnormalities in patients with A LS using MRI, and to correlate MRI with standard neurologic measures o f motor neuron dysfunction. Methods: Eleven ALS patients were studied twice (once at baseline and again after 4 months) and compared with ei ght normal control subjects. MRI data of the lower extremities were co mpared with tibialis anterior compound muscle action potential amplitu de (CMAPa) and foot dorsiflexion maximal voluntary isometric contracti on (MVIC). Results: Muscle MRI was abnormal by visual inspection in si x of 11 patients. The mean muscle T1 time and muscle volume were not d ifferent in patients compared with normal control subjects (p > 0.1). However, the mean T2 times were increased in the patients compared wit h normal control subjects (p = 0.009). T1 times did not correlate with CMAPa or MVIC. Muscle volume correlated with MVIC (r = 0.73 to 0.78, p < 0.02) but not with CMAPa (p > 0.05). There was a strong negative c orrelation (r < -0.8, p less than or equal to 0.01) between muscle T2 time and MVIC and CMAPa. Also, the change in T2 relaxation time correl ated with the change in CMAPa as the disease progressed (r = -0.63, p = 0.037). Conclusion: Of the MRI characteristics studied, T2 relaxatio n time was the best indicator of motor neuron dysfunction and may have a role in objective evaluation of motor neuron dysfunction.