Ten-year longitudinal study of the effect of impulse noise exposure from gunshot on inner ear function.

This longitudinal study investigated how chronic gunshot noise exposure affects cochlear and saccular function in police officers who engaged in regular target shooting practice using dual protection (ear plugs plus earmuffs) for >10 years. In 1997, 20 male police officers underwent audiometry before and two weeks after shooting. Twelve of the original subjects were re-examined by audiometry coupled with vestibular evoked myogenic potential (VEMP) test in 2007. Significant deterioration of mean hearing thresholds at frequencies of 500 Hz through 4000 Hz was noted ten years later, affecting both ears. However, only the frequencies of 4000 and 6000 Hz on the left ear revealed significant difference in mean hearing thresholds compared with healthy controls. Abnormal VEMP responses were evident in nine police officers (75%), including absent VEMPs 7 and delayed VEMPs 2. In conclusion, deterioration to hearing may occur after long term exposure to gunshots, even when double hearing protection is used. Further study is in progress regarding how to preserve both cochlear and saccular function during long term gunshot exposure.

An ipsilateral vestibulothalamic tract adjacent to the medial lemniscus in humans.

We examined 14 patients with acute anteromedial pontomesencephalic infarctions for signs of vestibular and ocular motor dysfunction. In all cases, an isolated ipsilateral deviation of the subjective visual vertical (mean: 4.1, range: 2.7- 6.6) was found without any further signs of vestibular or eye movement disorders like ocular torsion or skew deviation. Distinct lesions in thin-slice brainstem MRI showed an overlap zone in the medial portion of the medial lemniscus. The finding of putative ipsilateral vestibular projections running adjacent to or within the medial lemniscus was subsequently confirmed by a reanalysis of an anterograde tracer labelling study in the primate after tracer injection in the vestibular nucleus complex. The major conclusions of this study are as follows: (i) there is evidence for an ipsilateral graviceptive pathway running from the vestibular nuclei close to and within the medial lemniscus to the posterolateral thalamus [ipsilateral vestibulothalamic tract (IVTT)], (ii) this pathway might be the human homologue of the three-neuron sensory vestibulocortical tract described in primates and (iii) unilateral lesions of this pathway cause only vestibulo-perceptive dysfunction in the roll plane in contrast to lesions of the crossed graviceptive pathways (in the medial longitudinal fascicle), which were described earlier and which manifest as a combination of tilt of the subjective visual vertical, ocular torsion and skew deviation.

The effects of logon versus click on vestibular evoked myogenic potentials.

CONCLUSION: Logon is superior to click to trigger larger and more consistent vestibular evoked myogenic potentials (VEMPs). OBJECTIVES: To record and compare the parameters of VEMPs evoked by bone- and air-conducted logon (l-VEMPs) and click (c-VEMPs). SUBJECTS AND METHODS: Air- and bone-conducted l-VEMPs and c-VEMPs were recorded in 28 normal ears with an Amplaid MK12 (Amplaid, Milan) equipment. RESULTS: VEMPs response rate was 100% with both air-conducted logon and click, while l-VEMPs showed a higher response rate (79%) in comparison with c-VEMPs (21%) with bone-conducted stimuli. A significant (p<0.05) increase of P1, N1 and P1-N1 amplitude and augmented P1 and N1 latencies were noticed in l-VEMPs with respect to c-VEMPs.

Vestibular-evoked myogenic potential thresholds normalize on plugging superior canal dehiscence.

BACKGROUND: Diagnosis of the superior canal dehiscence syndrome (SCDS) relies on symptoms such as sound- or pressure-induced vertigo or oscillopsia, demonstration of sound or pressure-evoked vertical/torsional eye movements, and the presence of a defect in the bony roof overlying the superior semicircular canal. Lowered thresholds for eliciting vestibular-evoked myogenic potentials (VEMPs) provide additional conformation. OBJECTIVE: To examine VEMP characteristics before and after canal plugging for SCDS. METHODS: VEMPs evoked by air- and bone-conducted tones were measured from the sternocleidomastoid muscles (cVEMP) and periocular sites (oVEMP) of 20 normal volunteers, 10 newly diagnosed subjects with SCDS, and 12 subjects who underwent successful superior canal plugging. RESULTS: In all SCDS ears, thresholds for evoking VEMP using air-conducted tones were pathologically lowered, with average values of 83.85 +/- 1.40 dB sound pressure level (SPL) for cVEMP and 85.38 +/- 1.32 dB SPL for oVEMP, 20 to 30 dB below those of controls. Successful canal plugging resulted in normal reflex thresholds. For bone vibration, average thresholds in SCDS ears were 114.62 +/- 1.54 dB FL (force level) for cVEMP and 116.0 +/- 1.52 dB FL for oVEMP, 10 to 20 dB below controls, yet three SCDS ears had normal thresholds. CONCLUSIONS: Ocular and cervical vestibular-evoked myogenic potentials evoked by air-conducted sound are equally useful in the diagnosis and follow-up of superior canal dehiscence syndrome. Stimulus thresholds are consistently lowered upon presentation and normalize after corrective surgery. Thresholds for bone vibration, in contrast, have a lower diagnostic yield.

The recordability of two sonomotor responses in young normal subjects.

BACKGROUND: It has been reported that up to 40% of patients over age 60 fail to generate a vestibular evoked myogenic potential (VEMP; Su et al, 2004). When this occurs it is difficult to determine whether the absent VEMP represents evidence of bilateral impairment of the vestibulocollic reflex pathway or a normal age-related variant (i.e., idiopathic absence). PURPOSE: The purpose of the present investigation was to determine whether both VEMPs and PAMs could be recorded reliably in a sample of neurologically and otologically intact young adults. If both could be obtained with high reliability in normal subjects, then the bilateral presence of PAM in the bilateral absence of VEMP, at least in younger patients, could be used to support the contention that the absent VEMP represented evidence of bilateral impairment. RESEARCH DESIGN: A descriptive study. STUDY SAMPLE: Attempts were made to record both the VEMP and a second sonomotor response, the postauricular muscle potential (PAM) from 20 young adults. RESULTS: Results showed both the VEMP and the PAM were present in 90% of the ears. Both the VEMP and PAM responses were bilaterally absent for one subject. Also, the VEMP and PAM were unilaterally absent for two subjects. Subjects who generated VEMPs also generated a PAM in at least one ear. CONCLUSIONS: The present investigation represents an initial step in the determination of whether the presence of PAMs in the absence of VEMPs can be used as a method of validating the presence of an impairment affecting the vestibulocollic reflex pathway.

[Reorganization of the vestibular-thalamic projections following injury of the cerebellar interpositus and deiters vestibuar nuclei].

Plastic reorganization of the vestibular-thalamic system was studied in adult cats. It was shown, that preliminary (3 months before) injury of the cerebellar contralateral nucleus interpositus or lateral vestibular nucleus of Deiters leads to reorganization of vestibular-thalamic projections. Ipsilateral projections to the ventrolateral nucleus of thalamus arised from vestibular nuclear complex since the pattern of normal representations to mentioned thalamic nucleus were changed. The peculiarities of distribution and morphological structure of vestibular neurons forming new projections to the ventrolateral thalamic nucleus were studied as well.

Neurophysiological monitoring of brainstem function in a patient with Wallenberg syndrome, using Vestibular Evoked Myogenic Potentials.

PURPOSE: We evaluated the use of Vestibular Evoked Myogenic Potentials (VEMPs) in the assessment of neural function, following medullary lesions. METHODS: A 54-year-old male presented with symptoms and signs typical of right lateral medullary (Wallenberg) syndrome. He underwent brain MRI and three successive neurophysiological investigations, which included VEMPs, Brainstem Auditory Evoked Responses (BAERs) and the blink reflex. RESULTS: VEMPs amplitude on the left (unaffected) side was 256.8 microv in the first investigation and remained approximately equal to that value in the following two ones. Their amplitude on the right (affected) side was 37.9 microv, 154.2 microv and 235.2 microv correspondingly. At the same time vertigo, diplopia and nystagmus gradually improved. Right blink reflex comprised a normal R1, but delayed R2 ipsilateral and R2 contralateral responses, which remained unaltered during the follow-up period. Brain MRI disclosed a right dorsolateral medullary infarct. CONCLUSIONS: VEMPs amplitude progressively increased, parallel to the improvement of vestibular symptoms. The blink reflex evolved differently, while BAERs were not affected. As the three evoked responses are mediated by separate neural circuits, they provide information on different aspects of brainstem function. Thus, VEMPs seem to be a useful method that complements existing ones in the assessment of brainstem lesions.

Migrainous vertigo: development of a pathogenetic model and structured diagnostic interview.

PURPOSE OF REVIEW: Vestibular symptoms occur frequently in patients with migraine. This review refines recently proposed diagnostic criteria for migraine-related vestibular symptoms, and develops a pathophysiological model for the interface between migraine and the vestibular system. RECENT FINDINGS: The epidemiological link between migraine and vestibular symptoms and signs suggests shared pathogenetic mechanisms. Links between the vestibular nuclei, the trigeminal system, and thalamocortical processing centers provide the basis for the development of a pathophysiological model of migraine-related vertigo. During the last year, several studies have increased understanding of the relationship between migraine and vestibular symptoms. A study of motion sickness and allodynia in migraine patients supports the importance of central mechanisms of sensitization for migraine-related vestibular symptoms. A study has demonstrated effective treatment of vertigo with migraine therapy. The identification of migrainous vertigo, however, is hampered by a lack of standardized assessment criteria for both clinical and research practices. The application of published criteria for the diagnosis of migrainous vertigo allows the development of a standardized, structured assessment interview. SUMMARY: An understanding of the relationship between migraine and the vestibular system increases knowledge of the pathogenesis of both migraine and vertigo. In addition, studies have identified successful treatment, with standard migraine therapies, of vestibular symptoms in patients with both migraine and vertigo. The use of a standardized assessment tool to identify this unique population of patients will help future studies to test both the pathological model and effective treatment options.

Neurotological findings in a patient with narrow internal auditory canal: a case report.

We report neurotological findings in a patient with unilateral narrow internal auditory canal, as confirmed by computed tomography. The patient presented no auditory brainstem response on the affected side. Vestibular tests including vestibular-evoked myogenic potentials (VEMP) and caloric test revealed normal function of both inferior and superior vestibular neural pathways.

A short latency vestibular evoked potential (VsEP) produced by bone-conducted acoustic stimulation.

In this paper data are presented from an experiment which provides evidence for the existence of a short latency, acoustically evoked potential of probable vestibular origin. The experiment was conducted in two phases using bone-conducted acoustic stimulation. In the first phase subjects were stimulated with 6-ms, 500-Hz tone bursts in order to obtain the threshold V(T) for vestibular evoked myogenic potentials (VEMP). It was confirmed that the difference between bone-conducted auditory and acoustic vestibular thresholds was slightly over 30 dB. The estimated threshold was then used as a reference value in the second part of the experiment to stimulate subjects over a range of intensities from -6 to +18 dB (re: V(T)). Averaged EEG recordings were made with eight Ag/AgCl electrodes placed on the scalp at Fpz, F3, F4, F7, F8, Cz, T3, and T4 according to the 10-20 system. Below V(T) auditory midlatency responses (MLRs) were observed. Above V(T) two additional potentials appeared: a positivity at about 10 ms (P10) which was maximal at Cz, and a negativity at about 15 ms (N15) which was maximal at Fpz. Extrapolation of the growth functions for the P10 and N15 indicated a threshold close to V(T), consistent with a vestibular origin of these potentials. Given the low threshold of vestibular acoustic sensitivity it is possible that this mode may make a contribution to the detection of and affective responses to loud low frequency sounds. The evoked potentials may also have application as a noninvasive and nontraumatic test of vestibular projections to the cortex.

Developing prosthetics to treat cognitive disabilities resulting from acquired brain injuries.

Persistent cognitive disabilities represent the most troublesome consequences of acquired brain injury. Although these problems are widely recognized, few neuroprosthetic efforts have focused on developing therapeutic strategies aimed at improving general cognitive functions such as sustained attention, intention, working memory or awareness. If possible, effective modulation of these neuropsychologic components might improve recovery of interactive behaviors. The emerging field of neuromodulation holds promise that technologies developed to treat other neurological disorders may be adapted to address the cognitive problems of patients suffering from acquired brain injuries. We here discuss initial efforts at neuromodulation in patients in the persistent vegetative state and aspects of recent studies of the underlying neurobiology of PVS and other severe brain injuries. Innovative strategies for open-loop and closed-loop neuromodulation of impaired cognitive function are outlined. We discuss the possibilities of linking neuromodulation techniques to underlying neuronal mechanisms underpinning cognitive rehabilitation maneuvers. Ethical considerations surrounding the development of these strategies are reviewed.

[Treatment of hyperemesis gravidarum by electrostimulation of the vestibular apparatus]. / Die Behandlung der Hyperemesis gravidarum durch Elektrostimulation des Vestibular-Apparates

26 patients hospitalized with Hyperemesis Gravidarum were treated with electrical stimulation of the vestibular system, as the symptoms of Hyperemesis Gravidarum resemble the symptoms of motion sickness, where the electrical stimulation has been used successfully. The patients were treated for one hour daily, two hours before the standard infusion therapy. 89% reported a decrease in vomiting and nausea during the first application, 85% a lasting improvement. Theoretical considerations concerning the mechanism of the effect are discussed.