Objective: To explore the relationship between the clinical onset locations and the electrophysiological characteristics of different spinal segments in amyotrophic lateral sclerosis (ALS) patients. To develop a rapid examination method using electromyographs (EMGs) for the diagnosis of ALS.
Methods: The clinical symptoms and electrodiagnostic examination results of 150 patients with definite or probable ALS were retrospectively analyzed. The patients were divided into four groups according to the primary onset locations (arms and legs onset, arms onset, legs onset, and bulbar onset groups). The differences between the onset locations and the electrophysiological characteristics revealed the lower motor neuron dysfunction in EMGs.
Results: The most affected onset location was the lower limbs (36.7%), particularly in the distal muscles. Nerve conduction showed that the sensory system was damaged in 22 patients (14.7%). The positive diagnostic rate of EMGs varied due to different onset locations. EMG abnormalities were seen in approximately 40% of asymptomatic limb muscles. Distal limb muscles showed higher electrodiagnostic sensitivity (78.4%) than proximal limb muscles. Cervical muscles showed the highest electrodiagnostic sensitivity (86.3%).
Conclusions: The sensory system in ALS patients was commonly impaired. Cervical muscles showed the highest electrodiagnostic sensitivity. The highest positive rate was generated from detecting the spinal segment onset and the special distal muscles onset ALS in our optimized test method. Through this improved examination based on the most affected individual muscles, physicians can greatly optimize the test duration and significantly reduce patient discomfort.
Keywords: Amyotrophic lateral sclerosis; Electromyography; Lower motor neuron; Onset location; Spinal segment.