Introduction: Corticoespinal dysfunction is a common finding in primary and amyotrophic lateral sclerosis (PLS and ALS). AIM. To compare the behaviour of motor evoked potentials (MEP) with transcranial magnetic stimulation (TMS) in patients with ALS and PLS.
Patients and methods: It was performed a retrospective analysis of MEP recordings of 11 patients with PLS and 10 patients with sporadic ALS. Central motor conduction time and amplitude ratio were the selected variables for the statistical analysis of MEP from abductor pollicis brevis and tibialis anterior muscle from the four limbs, using non-parametric methods.
Results: As a general observation there was a high incidence of abnormal recordings in both groups of patients; in 30% of recording from ALS patients response to TMS was absent, but only the 4.5% in the group of PLS had the same characteristic. In PLS patients abnormal central motor conduction time was the most frequent finding, as it was the low amplitude ratio in ALS patients; both variables showed statistically significant differences between groups (Kruskall-Wallis, H = 6.32, p = 0.011; and Kruskall-Wallis, H = 5.777, p = 0.0163, respectively).
Conclusion: Corticoespinal dysfunction has different characteristics in ALS and PLS patients, and the analysis of MEP could add useful information for differential diagnosis of these diseases.