Background
Needle electromyography (EMG) and motor evoked potential (MEP) of the genioglossus (tongue) aredifficult to perform in evaluations of the craniobulbar region in amyotrophic lateral sclerosis (ALS). Therefore, weinvestigated the yields of needle EMG and MEP recorded from the upper trapezius, since it receives innervation fromthe lower medulla and upper cervical cord.Methods: Needle EMG and MEP of the upper trapezius were obtained in 17 consecutive ALS patients. The needleEMG parameters recorded included abnormal spontaneous activity and motor unit action potential (MUAP) morphology.An upper motor neuron (UMN) lesion was presumed when either response to cortical stimulation was absent, or thecentral conduction time was delayed (>mean+2SD).Results: Of the five patients with bulbar-onset ALS, four had abnormalities in the upper trapezius and four in thetongue by needle EMG. In contrast, of the 12 patients with limb-onset ALS, 11 had abnormalities in the upper trapezius,and only five in the tongue. When MEP was performed, it was found that three of the five patients with bulbar symptomsand three of the six patients with isolated limb involvement had abnormal MEP findings.Conclusions: Electrophysiological studies of the upper trapezius are more sensitive those of the tongue in patientswithout bulbar symptoms. Thus, needle EMG and MEP of the upper trapezius are alternative tools for assessing bulbarand rostral neuraxial involvement in the diagnosis of ALS.
