ABSTRACT
Postural imbalance, abnormal axial posture, and axial rigidity are the characteristic features of Parkinson's disease (PD), and they are referred to as axial symptoms. The symptoms are difficult to manage since they are often resistant to both L-DOPA and deep brain stimulation. Hence, other treatments that can improve Parkinsonian axial symptoms without adverse effects are required. Vestibular dysfunction occurs in PD since neuropathological changes and reflex abnormalities are involved in the vestibular nucleus complex. Galvanic vestibular stimulation (GVS), which activates the vestibular system, is a noninvasive method. This review aimed to assess the clinical effect of GVS on axial symptoms in PD. To date, studies on the effects of GVS on postural instability, anterior bending posture, lateral bending posture, and trunk rigidity and akinesia in PD had yielded interesting data, and none of the patients presented with severe adverse events, and the others had mild reactions. GVS indicated a possible novel therapy. However, most included a small number of patients, and the sample sizes were not similar in some studies that included controls. In addition, there was only one randomized controlled clinical trial, and it did not perform an objective evaluation of axial symptoms. In this type of research, vestibular contributions to balance should be distinguished from others such as proprioceptive inputs or nonmotor symptoms of PD.
ABSTRACT
OBJECTIVE: Galvanic vestibular stimulation (GVS) activates the vestibular afferents, and these changes in vestibular input exert a strong influence on the subject's posture or standing balance. In patients with Parkinson's disease (PD), vestibular dysfunction might contribute to postural instability and gait disorders. METHODS: Current intensity was increased to 0.7 mA, and the current was applied to the patients for 20 minutes. To perform a sham stimulation, the current intensity was increased as described and then decreased to 0 mA over the course of 10 seconds. The patient's status was recorded continuously for 20 minutes with the patient in the supine position. RESULTS: Three out of 5 patients diagnosed with PD with postural instability and/or abnormal axial posture showed a reduction in postural instability after GVS. The score for item 12 of the revised Unified Parkinson's Disease Rating Scale part 3 was decreased in these patients. CONCLUSIONS: The mechanism of postural instability is complex and not completely understood. In 2 out of the 5 patients, postural instability was not changed in response to GVS. Nonetheless, the GVS-induced change in postural instability for 3 patients in our study suggests that GVS might be a therapeutic option for postural instability.
ABSTRACT
Galvanic vestibular stimulation (GVS) stimulates the vestibular system electrically with low-amplitude direct current through surface electrodes applied to the left and right mastoids. The effects of GVS on unilateral spatial neglect (USN) in poststroke patients were recently reported, but the influence of the current intensity and application duration of GVS on USN has not been sufficiently investigated. Here we explored the influence of these stimulus parameters on USN. We recruited seven patients with right-hemisphere stroke and left-sided USN (four female) for this single-blind, sham-controlled cross-over trial. Their scores on the line cancellation test were measured under three stimulation conditions [left-cathodal/right-anodal GVS (L-GVS), right-cathodal/left-anodal GVS, and sham] at three time points (before the start of GVS, 10 min after the start of GVS, and 20 min after the start of GVS). The GVS intensity was set below the sensory threshold and differed among the patients (0.4-2.0 mA). The cancellation scores were significantly increased after 10 and 20 min L-GVS, with a greater increase observed after the latter (P<0.0001). The other stimulus conditions had no significant effect. There was a significant positive correlation between the change in the increase in the cancellation score with L-GVS and the total charge (r=0.81, P=0.0004). The effect of GVS on USN may depend on its application duration, current intensity, and polarity.
Subject(s)
Electric Stimulation Therapy/methods , Perceptual Disorders/rehabilitation , Stroke/complications , Vestibular Nerve/physiopathology , Aged , Aged, 80 and over , Cross-Over Studies , Female , Functional Laterality/physiology , Humans , Male , Mastoid , Middle Aged , Perceptual Disorders/etiology , Sensory Thresholds , Treatment Outcome , Visual PerceptionABSTRACT
This study investigated the effects of binaural monopolar galvanic vestibular stimulation (GVS), which likely stimulates the bilateral vestibular system, on the anterior bending angle in patients with Parkinson's disease (PD) with anterior bending posture in a single-blind, randomized sham-controlled crossover trial. The seven PD patients completed two types of stimulation (binaural monopolar GVS and sham stimulation) applied in a random order 1 week apart. We measured each patient's anterior bending angles while he or she stood with eyes open and eyes closed before/after the stimulations. The anterior bending angles in both the eyes-open and the eyes-closed conditions were significantly reduced after the GVS. The amount of change in the eyes-closed condition post-GVS was significantly larger than that by sham stimulation. The amount of change in anterior bending angles in the GVS condition was not significantly correlated with Unified Parkinson's Disease Rating Scale motor score, disease duration, the duration of the postural deformities, and the anterior bending angles before the GVS. Binaural monopolar GVS might improve anterior bending posture in PD patients, irrespective of the duration and the severity of disease and postural deformities. Binaural monopolar GVS might be a novel treatment strategy to improve anterior bending posture in PD.
Subject(s)
Electric Stimulation Therapy/methods , Parkinson Disease/physiopathology , Parkinson Disease/therapy , Posture , Aged , Aged, 80 and over , Biomechanical Phenomena , Cross-Over Studies , Female , Humans , Male , Middle Aged , Posture/physiology , Severity of Illness Index , Single-Blind Method , Treatment Outcome , Vestibular Nerve , Vision, OcularABSTRACT
BACKGROUND: A recent study investigated the effects of galvanic vestibular stimulation (GVS) on pusher behavior (PB) in post-stroke patients. However, there have been no reports about the effects of multisession GVS on PB. OBJECTIVE: The purpose of this study was to investigate the feasibility and effects of multisession GVS combined with physical therapy for PB in stroke patients. METHODS: Two stroke patients who showed PB were enrolled. The ABAB single-case design was used. Each phase lasted 1 wk. In phases A1 and A2, the patients underwent a 60-min-long physical therapy session 5 days a week. In phases B1 and B2, they underwent GVS for 20 min before each physical therapy session, and then the same physical therapy program as in phases A1 and A2 were performed. PB was evaluated using the Scale for Contraversive Pushing (SCP) and the Burke Lateropulsion Scale (BLS). Outcomes were tested at the baseline and after each phase. RESULTS: In both patients, the SCP scores were reduced only during phase B2. Although the BLS scores improved at the A1 phase, a larger improvement was seen at the two B phases. CONCLUSIONS: Multisession GVS combined with physical therapy may have positive effects on PB in clinical setting.
