Unilateral long-lasting vibration was applied to the sternomastoid muscle to assess the influence of asymmetric neck proprioceptive input on body orientation during stepping-in-place. Blindfolded s...

https://www.physiology.org/doi/pdf/10.1152/jn.00198.2002

Neck muscle vibration and spatial orientation during stepping in place in humans

OBJECTIVE: Our goal was to clarify the clinical significance of vibration-induced nystagmus (VIN). METHODS: One hundred patients with unilateral vestibulocochlear disorders were enrolled into this study. However, patients with spontaneous nystagmus were excluded. Vibratory stimuli (approximately 100 Hz) were presented to the mastoids and the forehead. Patients also underwent caloric testing and vestibular evoked myogenic potential testing.RESULTS: Of the 100 patients, 60 (60%) showed VIN. The nystagmus was mainly horizontal. VIN was more frequently evoked on the mastoids than the forehead. In the majority of patients, the direction of VIN was toward the healthy side, whereas some patients, especially patients with Meniere's disease, showed nystagmus toward the affected side. VIN was frequently evoked in patients with severe unilateral vestibular damages (canal paresis >50%) (39 of 43, or 90%).CONCLUSION: VIN testing is a simple and sensitive clinical test that indicates unilateral vestibular dysfunction.

Vibration-induced nystagmus in patients with vestibular disorders.

Dizziness is a nonspecific term that refers to various abnormal sensations of body orientation in space; patients often find these sensations difficult to describe. The prevalence of dizziness in the community ranges from 1.8% among young adults to over 30% among the elderly. Yearly consultation

https://www.cmaj.ca/content/cmaj/182/13/E621.full.pdf

Tests used to evaluate dizziness in primary care

Neck proprioceptive input, as elicited by muscle vibration, can produce destabilizing effects on stance and locomotion. Neck muscle fatigue produces destabilizing effects on stance, too. Our aim was to assess whether neck muscle fatigue can also perturb the orientation in space during a walking task. Direction and amplitude of the path covered during stepping in place were measured in 10 blindfolded subjects, who performed five 30-s stepping trials before and after a 5-min period of isometric dorsal neck muscle contraction against a load. Neck muscle electromyogram amplitude and median frequency during the head extensor effort were used to compute a fatigue index. Head and body kinematics were recorded by an optoelectronic system, and stepping cadence was measured by sensorized insoles. Before the contraction period, subjects normally stepped on the spot or drifted forward. After contraction, some subjects reproduced the same behavior, whereas others reduced their forward progression or even stepped backward. The former subjects showed minimal signs of fatigue and the latter ones marked signs of fatigue, as quantified by the dorsal neck electromyogram index. Head position and cadence were unaffected in either group of subjects. We argue that the abnormal fatigue-induced afferent input originating in the receptors transducing the neck muscle metabolic state can modulate the egocentric spatial reference frame. Notably, the effects of neck muscle fatigue on orientation are opposite to those produced by neck proprioception. The neck represents a complex source of inputs capable of modifying our orientation in space during a locomotor task.

/pdf/neck-muscle-fatigue-and-spatial-orientation-during-stepping-5a0ssaa4wa.pdf

Neck muscle fatigue and spatial orientation during stepping in place in humans

Dizziness in general practice is very common, especially in elderly patients. The empirical evidence for diagnostic tests in the evaluation of dizziness is scarce. Aim of our study was to determine which set of diagnostic tests should be part of a diagnostic protocol for evaluating dizziness in elderly patients in general practice. We conducted a Delphi procedure with a panel of 16 national and international experts of all relevant medical specialities in the field of dizziness. A selection of 36 diagnostic tests, based on a systematic review and practice guidelines, was presented to the panel. Each test was described extensively, and data on test characteristics and methodological quality (assessed with the Quality Assessment of Diagnostic Accuracy Studies, QUADAS) were presented. The threshold for in- or exclusion of a diagnostic test was set at an agreement of 70%. During three rounds 21 diagnostic tests were selected, concerning patient history (4 items), physical examination (11 items), and additional tests (6 items). Five tests were excluded, although they are recommended by existing practice guidelines on dizziness. Two tests were included, although several practice guidelines question their diagnostic value. Two more tests were included that have never been recommended by practice guidelines on dizziness. In this study we successfully combined empirical evidence with expert opinion for the development of a set of diagnostic tests for evaluating dizziness in elderly patients. This comprehensive set of tests will be evaluated in a cross-sectional diagnostic study.

/pdf/development-of-a-diagnostic-protocol-for-dizziness-in-m0meh00uxv.pdf

Development of a diagnostic protocol for dizziness in elderly patients in general practice: a Delphi procedure

On subjects with unilateral vestibular dysfunction, the application of a vibratory stimulation (100 Hz) to the two mastoids and the vertex, and to the right and left dorsal neck muscles produces a nystagmus directed towards the good ear in 85% of patients Fixation must be suppressed by Frenzel's glasses or video nystagmoscopy To be significant this nystagmus must appear in at least 3 of the 5 vibratory stimulated sites On healthy subjects nystagmus is present in 6% of cases but never in those below 30 years In subjects affected by central vertigo, nystagmus was elicited in 10% of cases and in subjects suffering from vertigo of unknown origin in 6% of cases Vibration nystagmus which stops immediately after stimulation differs from head shaking nystagmus which is present in only 34% of unilateral vestibular dysfunctions Vibration occasionally produces a pseudo-caloric nystagmus which persists after stimulation We believe that vibratory stimulation is a useful test, quick and easy to perform In conjunction with questionnaires, clinical examination, positional testing and the results of audiometry, it gives an immediate indication of a peripheral lesion when the vertigo is seen for the first time With unilateral deafness, a positive test leads one to suspect an acoustic neuroma Conversely if the test becomes negative after a vestibular neuritis when it was initially positive, it is a sign of recovery

Diagnostic value of vibration-induced nystagmus obtained by combined vibratory stimulation applied to the neck muscles and skull of 300 vertiginous patients.

Fifty two patients with positioning nystagmus were studied with the V.N.G. three-dimentional device of ULMER. In benign paroxysmal positional vertigo (BPPV) the torsionnal component is not pure: a vertical and a less important horizontal components also exist. They are not of the same amplitude on both eyes. The torsionnal and horizontal components are more important on the eye ipsilateral to the BPPV. The vertical component is more important on the contralateral eye. The horizontal canal B.P.V. (2% of the cases of B.P.V.) is so defined by the absence of vertical and torsionnal components. Three-D Eye Movement Analysis is helpful for differential diagnosis with the positional protocol described. The characteristics of central and peripheral paroxysmal positional nystagmus are given. The head Tilt and the ocular counter rolling reflex (O.C.R.) can be quantified with this device. It will be useful in the future to better explore the inferior root of the eighth nerve and the otolith organ. For clarity we propose to describe the torsionnal nystagmus so that the results are expressed with respect to the patient: clockwise nystagmus (in reference to the patient) would thus be also right rotatory nystagmus while left rotatory nystagmus would be also anticlockwise.

Benign positioning vertigo (BPV) and three-dimensional (3-D) eye movement analysis.

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Diagnostic value of vibration-induced nystagmus obtained by combined vibratory stimulation applied to the neck muscles and skull of 300 vertiginous patients.

Benign positioning vertigo (BPV) and three-dimensional (3-D) eye movement analysis.