Altered activation of the tibialis anterior in individuals with Pompe disease: Implications for motor unit dysfunction.

INTRODUCTION: Pompe disease is a progressive disease that affects skeletal muscles and leads to loss of ambulation. We investigated the activation of the tibialis anterior (TA) in late-onset Pompe disease (LOPD) individuals during maximal voluntary contraction (MVC) and evoked involuntary responses. METHODS: Four LOPD patients and matched control subjects performed MVC of the TA using dorsiflexion and TA evoked responses. Activation of the TA was recorded with surface electromyography. RESULTS: The Pompe patients exhibited greater power at frequencies below 60 Hz and reduced power above 100 Hz. They also exhibited a reduced increase in M-wave and prolonged M-wave latency and duration in response to stimulation. CONCLUSIONS: These results provide evidence that LOPD individuals have an altered activation pattern of the TA during maximal contractions. The observed activation pattern may reflect impairments in voluntary command, neuromuscular junction pathology, or compensatory drive due to a reduced number of functional motoneurons.