Comparison of Selective surface stimulation in Unilateral Vocal Fold Paresis and Facial Paralysis

Background Functional electrical stimulation (FES) with surface electrodes can increase muscle tone and reduce atrophy until motor function is restored in fully or partly denervated areas. We compare the stimulation parameters of two studies that investigated FES in both unilateral vocal fold paresis (UVFP) and facial paralysis (FP).

Methods 53 adult UVFP patients and 10 FP were evaluated. For laryngeal stimulation, a pair of surface electrodes with moistened sponge pockets were attached at the level of the paretic (cathode) and healthy (anode) thyroarytenoid muscle. In FP, two 6×4cm adhesive electrodes were placed over the paralyzed zygomaticus muscle. Triangular pulses of 1 Hz, each 500, 250, 100, 50, 25, 10, 1 ms phase duration (PD) and 1-20 mA were delivered with an external stimulator. Stimulus threshold, side effects, and muscle contraction were recorded.

Results For both UVFP and FP, the most effective PD for a selective muscle contraction of the paretic muscle was between 50 and 100 ms at a stimulus intensity of approximately 7 mA on average. In FP, the best results were observed with triangular pulses, a PD of 100-250 ms, and an amplitude of ≤ 5mA. In UVFP, an amplitude above 6 mA and a PD of 250 or 500 ms often elicited a swallowing reflex. Nonspecific contraction of musculi infrahyoidei or platysma in UVFP or masseter muscle in FP was elicited with short PD of 1, 10, or 25 ms.

Conclusions In both UVFP and FP, the paretic muscles are selectively triggered with PD of 100ms. Higher PD are more likely to trigger the swallowing reflex in UVFP, and lower PD are more likely to cause unwanted contraction of innervated muscles in both settings.

Med-EL Elektromedizinische Geräte GmbH

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Artikel online veröffentlicht:
24. Mai 2022