62. Transcutaneous trigeminal nerve stimulation (TNS) induces a long-term potentiation (LTP)-like plasticity of the blink reflex (BR) in patients with blepharospasm (BS)

Abstract

TNS induces a long-term depression (LTD)-like plasticity of the BR in healthy subjects (controls). BS have an hyperexcitability of the BR recovery cycle (BRRC) and an altered brainstem plasticity [2;3]. TNS effects on BR and BRRC of BS was investigated in the present study. Seven BS and seven controls underwent BR and BRRC (inter-stimulus intervals: 200, 300, 500 ms) assessment before and at 0 (T0), 15 (T15) and 30 (T30) min after TNS delivery (120 Hz; 30 s ON, 30 s OFF for 20 min). R2 areas of the BR were similar in BS and controls at baseline but were significantly different (p < 0.001) following TNS administration, with a significant facilitation in BS at T15 (p = 0.006) and a significant inhibition in controls at T15 and T30 (p < 0.05). At baseline, the BRCC was significantly enhanced in BS compared with controls (p < 0.05) and appeared unchanged after TNS, in both groups. The BRRC was unaffected by TNS in both controls and BS, while the TNS-induced LTD of R2 circuits observed in controls was inverted into a LTP-like effect in BS. These preliminary data suggest that TNS may be a useful tool to evaluate an altered brainstem plasticity of brainstem circuits.