Triple stimulation technique (TST) in amyotrophic lateral sclerosis

Objective: The authors studied amyotrophic lateral sclerosis (ALS) patients using triple stimulation technique (TST) to detect upper motor neuron (UMN) involvement. Methods: Nineteen ALS patients (aged 45–72 years) were enrolled in the study. According to the El Escorial criteria, 6 diagnoses were suspected or possible, 6 probable, and 7 definite. Patients were examined clinically, with conventional (single-pulse) transcranial magnetic stimulation (TMS), and with TST (on one side only). Results: Among the whole group of patients, TST appeared to be more sensitive than conventional TMS techniques. In particular among suspected/possible ALS patients, TST area ratio was pathologic in 100%, while single-pulse TMS was abnormal only in 50% of cases. Overall, the use of TST area ratio was more sensitive than the analysis of TST amplitude ratio. Conclusions: The results suggest that TST might be more sensitive and useful in the diagnosis of subclinical UMN involvement than conventional TMS techniques, even if TST is performed on one side only.