EFFETTI DELLA STIMOLAZIONE MAGNETICA TRANSCRANICA RIPETITIVA (rTMS) A BASSA FREQUENZA DELLA CORTECCIA MOTORIA SULLA ECCITABILITÀ DEL BLINK REFLEX: STUDIO SPERIMENTALE SU SOGGETTI SANI

Objective: To evaluate the after-effects of low frequency, sub-threshold repetitive Transcranial Magnetic Stimulation (rTMS) of primary motor cortex, on the excitability of Blink Reflex (BR) in healthy subjects. Methods: The BR recovery cycle was carried out in 10 healthy volunteers in basal conditions, immediately after rTMS (30 s), 15 and 60 min later. A paired electric supraorbital stimulus paradigm with inter-stimulus intervals (ISI) of 100–600–1000–1500 ms was used. The ‘‘real” rTMS consisted of a 200 stimuli long train delivered at 1 Hz and intensity 80% of rest Motor Threshold of the FDI muscle, using a focal coil applied over the primary motor cortex region. The basal BR recovery cycle was also compared with that obtained after a ‘‘sham” rTMS. Results: The recovery of the R2 component of the BR was significantly suppressed 30 s after rTMS. This effect was also observed at 15 min, though of lower magnitude and only at long ISIs (1000-1500 ms). No significant effect on R2 recovery was observed 60 min after real rTMS as well as after sham rTMS. Conclusions: Slow (1 Hz), sub-threshold rTMS of motor cortex can modulate the BR excitability determining a long-lasting inhibitory effect probably through its action on the cortical excitability and the cortico-bulbar facilitatory drive to the BR pathways.