Neurophysiological Evaluation of Autonomic Dysfunction in Spinal Muscular Atrophy: A Case-Control Study

Introduction. Spinal muscular atrophy (SMA) is an autosomal recessive disorder causing lower motor neuron degeneration leading to weakness and muscle atrophy due to reduction of survival motor neuron (SMN) protein. Although SMA was considered an exclusively motor neuron disease, few reports indicate the involvement of nonmotor neurons. The aim of this study is to investigate autonomous nervous system (ANS) involvement in SMA. Materials and Methods. We investigated 9 SMA adult patients and 36 age- and sex-matched controls. ANS was evaluated by sympathetic skin response (SSR). Results. SSR was not elicited in 28% of measurements in cases and in 0% of measurements in controls (p<0.001). Both palmar (p<0.001) and plantar (p<0.001) SSR latencies were significantly longer in cases than controls. Palmar SSR amplitudes were smaller (p=0.036) in patients compared to controls. Conclusions. This study provides new evidence of ANS dysfunction in SMA patients.