Sensory changes in pediatric patients with spinal muscular atrophy: an electrophysiologic study

Abstract

Spinal muscular atrophy (SMA) is well known to be a pure motor neuron disease. However, it was reported that sensory neuron degeneration can also occur in pediatric SMA. The aim of the present study was to assess peripheral and central sensory abnormalities in pediatric SMA patients. The present study included 29 type I and 11 type II SMA patients diagnosed on the basis of clinical history and typical electromyographic patterns, and 25 age-matched and sex-matched healthy pediatric participants, who comprised the control group. Sensory and motor conduction studies were carried out for both groups. Sensory conduction studies of sural and median nerves assessed peak latency, sensory nerve action potential (SNAP) amplitude, and sensory nerve conduction velocity. Mixed posterior tibial somatosensory evoked potential latency and amplitude were also assessed for both groups. SMA I patients had lower sural and median SNAP amplitudes, as well as lower peroneal and femoral compound muscle action potential amplitudes, slower tibial motor conduction velocity (MCV), and prolonged femoral and peroneal distal latency compared with the control group. SMA II patients had lower sural SNAP amplitude, slower sural sensory nerve conduction velocity, lower tibial somatosensory evoked potential amplitude, and lower tibial peroneal and femoral compound muscle action potential amplitudes, as well as slower tibial motor conduction velocity and prolonged peroneal distal latency, compared with the control group. Sensory neuron and/or axonal affection have been demonstrated in the studied series of pediatric SMA patients suggesting that the pathological changes in SMA may also involve the sensory system.