A tentative interpretation of electromyographic regional differences in bulbar- and limb-onset ALS.

Electromyography (EMG) could be useful in defining regional motor neuron vulnerability in ALS. We performed EMG in 36 sporadic ALS patients (9 with bulbar-onset and 27 with limb-onset symptoms). Active denervation was more frequent in limb than in corresponding paraspinal muscles, in the thoracic paraspinal, and in the bulbo-cervical muscles in patients with bulbar-onset symptoms. These results are consistent with a regional motor neuron vulnerability along with a nerve length-dependent liability.