The Galvanic whole-body sway response in health and disease

Objective: To explore the galvanic-evoked vestibulospinal reflex in health and disease. Methods: Vestibular-evoked whole-body movement was measured in 60 controls and eight patients with bilateral vestibular impairment, using 1 mA X2 s Galvanic Vestibular Stimulation (GVS). The displacement (s) and velocity (v) of 7 markers placed on the head, neck, shoulders, mid-thorax and hips and ground reaction forces (F) were recorded. Results: Monaural GVS evoked anterolateral whole-body movement away from the cathode. For controls, peak response magnitudes were 22.3 +/- 12.4 mm, 25.9 +/- 14.3 mm s(-1) and 3.2 +/- 1.3 N for s, v and F. Left right asymmetry measured using the Jongkee's formula was 12.59 +/- 8.64%, 11.94 +/- 11.09% and 11.68 +/- 8.99% for s, v and F. All three measures were symmetrical for left and right mastoid stimulation and showed good to excellent test retest reliability. Patients with bilateral vestibular failure had absent or attenuated responses. For this patient group, the ("R/B'') ratios between the "response period'' and baseline body-sway for s, v and F were 2.1 +/- 0.8, 1.7 +/- 1.1 and 1.3 +/- 0.6, which were significantly lower than 5.4 +/- 4.2, 4.1 +/- 2.5 and 2.3 +/- 0.8 for controls, with s and v providing better separation between controls and patients. There were no significant correlations between the amplitudes of galvanic body sway responses and vestibular-evoked myogenic potentials (VEMPs). Conclusion: GVS enables non-invasive assessment of the vestibulospinal reflex. Significance: This method offers a clinically applicable, test of vestibular contributions to standing balance. (C) 2013 Published by Elsevier Ireland Ltd. on behalf of International Federation of Clinical Neurophysiology

The Galvanic whole-body sway response in health and disease

Objective: To explore the galvanic-evoked vestibulospinal reflex in health and disease. Methods: Vestibular-evoked whole-body movement was measured in 60 controls and eight patients with bilateral vestibular impairment, using 1 mA X2 s Galvanic Vestibular Stimulation (GVS). The displacement (s) and velocity (v) of 7 markers placed on the head, neck, shoulders, mid-thorax and hips and ground reaction forces (F) were recorded. Results: Monaural GVS evoked anterolateral whole-body movement away from the cathode. For controls, peak response magnitudes were 22.3 +/- 12.4 mm, 25.9 +/- 14.3 mm s(-1) and 3.2 +/- 1.3 N for s, v and F. Left right asymmetry measured using the Jongkee's formula was 12.59 +/- 8.64%, 11.94 +/- 11.09% and 11.68 +/- 8.99% for s, v and F. All three measures were symmetrical for left and right mastoid stimulation and showed good to excellent test retest reliability. Patients with bilateral vestibular failure had absent or attenuated responses. For this patient group, the ("R/B'') ratios between the "response period'' and baseline body-sway for s, v and F were 2.1 +/- 0.8, 1.7 +/- 1.1 and 1.3 +/- 0.6, which were significantly lower than 5.4 +/- 4.2, 4.1 +/- 2.5 and 2.3 +/- 0.8 for controls, with s and v providing better separation between controls and patients. There were no significant correlations between the amplitudes of galvanic body sway responses and vestibular-evoked myogenic potentials (VEMPs). Conclusion: GVS enables non-invasive assessment of the vestibulospinal reflex. Significance: This method offers a clinically applicable, test of vestibular contributions to standing balance. (C) 2013 Published by Elsevier Ireland Ltd. on behalf of International Federation of Clinical Neurophysiology

Superior semicircular canal dehiscence syndrome:Diagnostic criteria consensus document of the committee for the classification of vestibular disorders of the Barany Society

This paper describes the diagnostic criteria for superior semicircular canal dehiscence syndrome (SCDS) as put forth by the classification committee of the Barany Society. In addition to the presence of a dehiscence of the superior semicircular canal on high resolution imaging, patients diagnosed with SCDS must also have symptoms and physiological tests that are both consistent with the pathophysiology of a 'third mobile window' syndrome and not better accounted for by another vestibular disease or disorder. The diagnosis of SCDS therefore requires a combination of A) at least one symptom consistent with SCDS and attributable to 'third mobile window' pathophysiology including 1) hyperacusis to bone conducted sound, 2) sound-induced vertigo and/or oscillopsia time-locked to the stimulus, 3) pressure-induced vertigo and/or oscillopsia time-locked to the stimulus, or 4) pulsatile tinnitus; B) at least 1 physiologic test or sign indicating that a 'third mobile window' is transmitting pressure including 1) eye movements in the plane of the affected superior semicircular canal when sound or pressure is applied to the affected ear, 2) low-frequency negative bone conduction thresholds on pure tone audiometry, or 3) enhanced vestibular-evoked myogenic potential (VEMP) responses (low cervical VEMP thresholds or elevated ocular VEMP amplitudes); and C) high resolution computed tomography (CT) scan with multiplanar reconstruction in the plane of the superior semicircular canal consistent with a dehiscence. Thus, patients who meet at least one criterion in each of the three major diagnostic categories (symptoms, physiologic tests, and imaging) are considered to have SCDS

Repeatability of sound evoked triceps myogenic potentials

Objective: To investigate the repeatability of sound-evoked vestibular evoked myogenic potentials recorded from the triceps (tVEMPs) with and without visual feedback. Design: tVEMP responses to 95 dB nHL 500-Hz tone bursts were recorded in a longitudinal, repeated measures study where P1 and N1 latencies and amplitudes were measured on three separate occasions from the same individuals. Analysis of variance, intra-class correlations, and limits of repeatability analyses were used to assess tVEMP repeatability and effects of visual feedback. Study sample: Fifteen participants (nine women) aged between 18 and 41 years took part. Results: Response rates of 63% and 68% were obtained for tVEMPs with eyes open and closed, respectively. When present, tVEMP latencies and amplitudes exhibited fair to good repeatability. Repeatability of tVEMP latencies and amplitudes measured using Bland-Altman methods was poorer with eyes closed. Conclusions: Sound-evoked tVEMP response rates are too low to support their clinical utility at the moment. tVEMP response rate may be improved by refining the balance task to include a force related target. Better tVEMP repeatability with eyes open supports the hypothesis that the response is modulated by visual feedback, and is consistent with studies reporting triceps responses to galvanic stimulation

Classification of vestibular signs and examination techniques: Nystagmus and nystagmus-like movements

This paper presents a classification and definitions for types of nystagmus and other oscillatory eye movements relevant to evaluation of patients with vestibular and neurological disorders, formulated by the Classification Committee of the Bar´ any Society, to facilitate identification and communication for research and clinical care. Terminology surrounding the ´ numerous attributes and influencing factors necessary to characterize nystagmus are outlined and defined. The classification first organizes the complex nomenclature of nystagmus around phenomenology, while also considering knowledge of anatomy, pathophysiology, and etiology. Nystagmus is distinguished from various other nystagmus-like movements including saccadic intrusions and oscillations