Timothy C. Hain

Practice parameter: therapies for benign paroxysmal positional vertigo (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology.

GLOSSARYAAN = American Academy of Neurology; BPPV = benign paroxysmal positional vertigo; CONSORT = Consolidated Standards of Reporting Trials; CRP = canalith repositioning procedure; NNT = number needed to treat.

Vocal responses to unanticipated perturbations in voice loudness feedback: An automatic mechanism for stabilizing voice amplitude

The present study tested whether subjects respond to unanticipated short perturbations in voice loudness feedback with compensatory responses in voice amplitude. The role of stimulus magnitude (+/- 1,3 vs 6 dB SPL), stimulus direction (up vs down), and the ongoing voice amplitude level (normal vs soft) were compared across compensations. Subjects responded to perturbations in voice loudness feedback with a compensatory change in voice amplitude 76% of the time. Mean latency of amplitude compensation was 157 ms. Mean response magnitudes were smallest for 1-dB stimulus perturbations (0.75 dB) and greatest for 6-dB conditions (0.98 dB). However, expressed as gain, responses for 1-dB perturbations were largest and almost approached 1.0. Response magnitudes were larger for the soft voice amplitude condition compared to the normal voice amplitude condition. A mathematical model of the audio-vocal system captured the main features of the compensations. Previous research has demonstrated that subjects can respond to an unanticipated perturbation in voice pitch feedback with an automatic compensatory response in voice fundamental frequency. Data from the present study suggest that voice loudness feedback can be used in a similar manner to monitor and stabilize voice amplitude around a desired loudness level.

Effectiveness of Particle Repositioning Maneuvers in the Treatment of Benign Paroxysmal Positional Vertigo: A Systematic Review

Background Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo. Purpose The purpose of this systematic review was to determine whether patients diagnosed with posterior canal (PC) BPPV, based on positional testing, and treated with a particle repositioning maneuver will show the resolution of benign paroxysmal positional nystagmus (BPPN) on the Dix-Hallpike Test performed 24 hours or more after treatment. Data Sources Data were obtained from an electronic search of the MEDLINE, EMBASE, and CINAHL databases from 1966 through September 2009. Study Selection The study topics were randomized controlled trials (RCTs), quasi-RCTs, the diagnosis of PC BPPV, treatment with the particle repositioning maneuver, and outcome measured with a positional test 24 hours or more after treatment. Data Extraction Data extracted were study descriptors and the information used to code for effect size. Data Synthesis In 2 double-blind RCTs, the odds in favor of the resolution of BPPN were 22 times (95% confidence interval=3.41–141.73) and 37 times (95% confidence interval=8.75–159.22) higher in people receiving the canalith repositioning procedure (CRP) than in people receiving a sham treatment. This finding was supported by the results reported in 8 nonmasked quasi-RCTs. Studies with limited methodological quality suggested that a liberatory maneuver (LM) was more effective than a control intervention; there was no significant difference in the effectiveness of the LM and the effectiveness of the CRP; the self-administered CRP was more effective than the self-administered LM; and the CRP administered together with the self-administered CRP was more effective than the CRP administered alone. The Brandt-Daroff exercises were the least effective self-administered treatments. Limitations The limitations included the methodological quality of the studies, the lack of quality-of-life measures, and confounding factors in reporting vertigo. Conclusions Randomized controlled trials provided strong evidence that the CRP resolves PC BPPN, and quasi-RCTs suggested that the CRP or the LM performed by a clinician or with proper instruction at home by the patient resolves PC BPPN. There were no data on the effects of the maneuvers on outcomes relevant to patients.

Antivertigo Medications and Drug-Induced Vertigo: A Pharmacological Review

SummaryThe approach to drug treatment of vertigo is almost exclusively symptomatic. There are 3 major goals for drug treatment of vertigo. The first one is to eliminate the hallucination of motion. Drugs with vestibular ‘suppressant’ properties are used for this purpose. The major vestibular suppressants are anticholinergic and antihistamine drugs. The second goal is to reduce the accompanying neurovegetative and psychoaffective signs (nausea, vomiting, anxiety). Antidopaminergics are used for this purpose. The third goal is to enhance the process of ‘vestibular compensation’ to allow the brain to find a new sensory equilibrium in spite of the vestibular lesion. Until now, the pharmacological manipulation of vestibular compensation has been assessed in animals but not in humans with vestibular lesions. Vestibular suppressant drugs delay rather than enhance compensation. A variety of other drugs is also used in the treatment of vertigo, including benzodiazepines, histaminergic agents, sympathomimetics and calcium antagonists. Their mechanism of action is poorly understood.The data base derived from clinical trials evaluating antivertigo medications is often questionable because of methodological limitations. This explains why habits of prescription are mainly empirical, and why striking differences can be noticed from one country to another. We can hope that new treatments may emerge from the present interest in receptor subclasses and neuromodulators of the vestibular system, and we must be ready to evaluate these potential new pharmacological agents with reliable clinical methods in humans.

Pharmacological Treatment of Vertigo

This review discusses the physiology and pharmacological treatment of vertigo and related disorders. Classes of medications useful in the treatment of vertigo include anticholinergics, antihistamines, benzodiazepines, calcium channel antagonists and dopamine receptor antagonists. These medications often have multiple actions. They may modify the intensity of symptoms (e.g. vestibular suppressants) or they may affect the underlying disease process (e.g. calcium channel antagonists in the case of vestibular migraine). Most of these agents, particularly those that are sedating, also have a potential to modulate the rate of compensation for vestibular damage. This consideration has become more relevant in recent years, as vestibular rehabilitation physical therapy is now often recommended in an attempt to promote compensation. Accordingly, therapy of vertigo is optimised when the prescriber has detailed knowledge of the pharmacology of medications being administered as well as the precise actions being sought.There are four broad causes of vertigo, for which specific regimens of drug therapy can be tailored. Otological vertigo includes disorders of the inner ear such as Ménière’s disease, vestibular neuritis, benign paroxysmal positional vertigo (BPPV) and bilateral vestibular paresis. In both Ménière’s disease and vestibular neuritis, vestibular suppressants such as anticholinergics and benzodiazepines are used. In Ménière’s disease, salt restriction and diuretics are used in an attempt to prevent flare-ups. In vestibular neuritis, only brief use of vestibular suppressants is now recommended. Drug treatments are not presently recommended for BPPV and bilateral vestibular paresis, but physical therapy treatment can be very useful in both. Central vertigo includes entities such as vertigo associated with migraine and certain strokes. Prophylactic agents (L-channel calcium channel antagonists, tricyclic antidepressants, β-blockers) are the mainstay of treatment for migraine-associated vertigo. In individuals with stroke or other structural lesions of the brainstem or cerebellum, an eclectic approach incorporating trials of vestibular suppressants and physical therapy is recommended. Psychogenic vertigo occurs in association with disorders such as panic disorder, anxiety disorder and agoraphobia. Benzodiazepines are the most useful agents here. Undetermined and illdefined causes of vertigo make up a large remainder of diagnoses. An empirical approach to these patients incorporating trials of medications of general utility, such as benzodiazepines, as well as trials of medication withdrawal when appropriate, physical therapy and psychiatric consultation is suggested.

Interactions between auditory and somatosensory feedback for voice F0 control.

Previous studies have demonstrated the importance of both kinesthetic and auditory feedback for control of voice fundamental frequency (F0). In the present study, a possible interaction between auditory feedback and kinesthetic feedback for control of voice F0 was tested by administering local anesthetic to the vocal folds in the presence of perturbations in voice pitch feedback. Responses to pitch-shifted voice feedback were larger when the vocal fold mucosa was anesthetized than during normal kinesthesia. A mathematical model incorporating a linear combination of kinesthesia and pitch feedback simulated the main aspects of our experimental results. This model indicates that a feasible explanation for the increase in response magnitude with vocal fold anesthesia is that the vocal motor system uses both pitch and kinesthesia to stabilize voice F0 shortly after a perturbation of voice pitch feedback has been perceived.

Compensation for pitch-shifted auditory feedback during the production of Mandarin tone sequences

Recent research has found that while speaking, subjects react to perturbations in pitch of voice auditory feedback by changing their voice fundamental frequency (F0) to compensate for the perceived pitch-shift. The long response latencies (150-200 ms) suggest they may be too slow to assist in on-line control of the local pitch contour patterns associated with lexical tones on a syllable-to-syllable basis. In the present study, we introduced pitch-shifted auditory feedback to native speakers of Mandarin Chinese while they produced disyllabic sequences /ma ma/ with different tonal combinations at a natural speaking rate. Voice F0 response latencies (100-150 ms) to the pitch perturbations were shorter than syllable durations reported elsewhere. Response magnitudes increased from 50 cents during static tone to 85 cents during dynamic tone productions. Response latencies and peak times decreased in phrases involving a dynamic change in F0. The larger response magnitudes and shorter latency and peak times in tasks requiring accurate, dynamic control of F0, indicate this automatic system for regulation of voice F0 may be task-dependent. These findings suggest that auditory feedback may be used to help regulate voice F0 during production of bi-tonal Mandarin phrases.

New therapeutic maneuver for anterior canal benign paroxysmal positional vertigo

This article describes the clinical features of anterior semicircular canal benign paroxysmal positional vertigo (AC-BPPV) and a new therapeutic maneuver for its management. Our study was a retrospective review of cases from an ambulatory tertiary referral center. Thirteen patients afflicted with positional paroxysmal vertigo exhibiting brief positional down-beating nystagmus in positional tests (Dix–Hallpike and head-hanging position) were treated with a maneuver comprised of the following movements: Sequential head positioning beginning supine with head hanging 30° dependent with respect to the body, then supine with head inclined 30° forward, and ending sitting with head 30° forward. All cases showed excellent therapeutic response to our repositioning procedure, i.e. relief of vertigo and elimination of nystagmus. The maneuver described is an option for AC-BPPV treatment.

Modified liberatory maneuver: Effective treatment for benign paroxysmal positional vertigo

A modification of the liberatory maneuver was used to treat 25 patients with benign paroxysmal positional vertigo (BPPV). The modified liberatory maneuver relieved symptoms without recurrence in 11 (44%) patients. A partial response was noted in 6 (24%) patients, and there was no improvement in 8 (32%) patients. Follow‐up ranged from 1 to 20 months (median 4.0 months). Patient age was not predictive of response to treatment. Duration of symptoms before treatment, however, was greater in nonresponders (median 15.5 months) than in complete (median 5.0 months) or partial (median 3.5 months) responders. The modified liberatory maneuver takes approximately 5 minutes to perform and provides effective treatment in two thirds of patients who suffer from BPPV.

A dynamical model for reflex activated head movements in the horizontal plane.

Abstract. We present a controls systems model of horizontal-plane head movements during perturbations of the trunk, which for the first time interfaces a model of the human head with neural feedback controllers representing the vestibulocollic (VCR) and the cervicocollic (CCR) reflexes. This model is homeomorphic such that model structure and parameters are drawn directly from anthropomorphic, biomechanical and physiological studies. Using control theory we analyzed the system model in the time and frequency domains, simulating neck movement responses to input perturbations of the trunk. Without reflex control, the head and neck system produced a second-order underdamped response with a 5.2 dB resonant peak at 2.1 Hz. Adding the CCR component to the system dampened the response by approximately 7%. Adding the VCR component dampened head oscillations by 75%. The VCR also improved low-frequency compensation by increasing the gain and phase lag, creating a phase minimum at 0.1 Hz and a phase peak at 1.1 Hz. Combining all three components (mechanics, VCR and CCR) linearly in the head and neck system reduced the amplitude of the resonant peak to 1.1 dB and increased the resonant frequency to 2.9 Hz. The closed loop results closely fit human data, and explain quantitatively the characteristic phase peak often observed.