Is the Frequency in Somatosensory Electrical Stimulation theKeyParameter in Modulating the Corticospinal Excitability of Healthy Volunteers and Stroke Patients with Spasticity?

Abstract

Somatosensory electrical stimulation (SES) has been proposed as an approach to treat patients with sensory-motor impairment such as spasticity. However, there is still no consensus regarding which would be the adequate SES parameters to treat those deficits. Therefore, the aim of this study was to evaluate the effects of applying SES over the forearm muscles at four different frequencies of stimulation (3, 30, 150, and 300 Hz) and in two intervals of time (5′ and 30′) by means of transcranial magnetic stimulation and Hoffmann's reflex (H-reflex) in healthy volunteers (Experiments I and II). A group of stroke patients (Experiment III) was also preliminary evaluated to ascertain SES effects at a low frequency (3 Hz) applied for 30′ over the forearm spastic flexors muscles by measuring the wrist joint passive torque. Motor evoked potentials and the H-reflex were collected from different forearm and hand muscles immediately before and after SES and up to 5′ (Experiment I) and 10′ (Experiments I and II) later. None of the investigated frequencies of SES was able to operate as a key in switching modulatory effects in the central nervous system of healthy volunteers and stroke patients with spasticity.

Can somatosensory electrical stimulation relieve spasticity in post-stroke patients? A TMS pilot study

“…without any fine tune adjustment from multiples of sensory threshold. Therefore, even though the recent literature [13,16] corroborates the hypothesis that the intensity of stimulation may lead to distinct effects on corticospinal modulation, the excitability of this neural pathway may be affected by other parameters such as pulse width, waveform, frequency and application time. Moreover, it seems reasonable to conjecture that not every resultant modulatory effect on corticospinal excitability (positive or negative deviations from baseline) will lead to the same effect on spasticity even in stroke patients with similar clinical signs.…”

“…All subjects were submitted to a single session of SES therapy for 30 min with a symmetrical biphasic pulse (3 Hz, 500 μs) [13,25].…”

“…botulin toxin) in treating this sensory motor disorder in post-stroke patients has been endorsed [8,13,22,25,26]. However, Current neurological deficits: P, present; A, absent; MPSO, months post-stroke onset; NIHSS(so), National Institute of Health Stroke Scale at stroke onset; mRS, current modified Rankin Scale;…”

“…Since SES intensity is set below the MT, it is understood to lead to the recruitment of somatosensory receptors which mobilize neural circuitries at the spinal and brain levels [8,13]. Accordingly, it is possible to hypothesize that the modulation of the corticospinal pathway may decrease the resistance of spastic muscles to a passive movement from neural drives.…”

A method of hand motor control assessment in patients with post-stroke spasticity

“…Kinesiotherapy methods used in these patients include, for instance, the NDT-Bobath Approach [28], a method of continuous passive motion metoda NDT Bobath [28], metoda ciągłego ruchu biernego w stawie promieniowo-nadgarstkowym i stawach rąk prowadzonego przez urządzenie mechaniczne (stretching device) [15] oraz kinezyterapia z elementami robotyki (robot Gloreha) [29]. Przykładem metody fizykoterapeutycznej jest stymulacja elektryczna somatosensoryczna (SES), polegająca na stosowaniu obwodowej stymulacji elektrycznej poniżej lub na poziomie progu pobudliwości czuciowej [30]. Stosuje się też funkcjonalną elektryczną stymulację (FES) połączoną z biofeedbackiem opartym o wizualizację zapisu EMG [31].…”