Modulation of auditory percepts by transcutaneous electrical stimulation.

Transcutaneous, electrical stimulation with electrodes placed on the mastoid processes represents a specific way to elicit vestibular reflexes in humans without active or passive subject movements, for which the term galvanic vestibular stimulation was coined. It has been suggested that galvanic vestibular stimulation mainly affects the vestibular periphery, but whether vestibular hair cells, vestibular afferents, or a combination of both are excited, is still a matter of debate. Galvanic vestibular stimulation has been in use since the late 18th century, but despite the long-known and well-documented effects on the vestibular system, reports of the effect of electrical stimulation on the adjacent cochlea or the ascending auditory pathway are surprisingly sparse. The present study examines the effect of transcutaneous, electrical stimulation of the human auditory periphery employing evoked and spontaneous otoacoustic emissions and several psychoacoustic measures. In particular, level growth functions of distortion product otoacoustic emissions were recorded during electrical stimulation with alternating currents (2 Hz, 1-4 mA in 1 mA-steps). In addition, the level and frequency of spontaneous otoacoustic emissions were followed before, during, and after electrical stimulation (2 Hz, 1-4 mA). To explore the effect of electrical stimulation on the retrocochlear level (i.e. on the ascending auditory pathway beyond the cochlea), psychoacoustic experiments were carried out. Specifically, participants indicated whether electrical stimulation (4 Hz, 2 and 3 mA) induced amplitude modulations of the perception of a pure tone, and of auditory illusions after presentation of either an intense, low-frequency sound (Bounce tinnitus) or a faint band-stop noise (Zwicker tone). These three psychoacoustic measures revealed significant perceived amplitude modulations during electrical stimulation in the majority of participants. However, no significant changes of evoked and spontaneous otoacoustic emissions could be detected during electrical stimulation relative to recordings without electrical stimulation. The present findings show that cochlear function, as assessed with spontaneous and evoked otoacoustic emissions, is not affected by transcutaneous electrical stimulation, at the currents used in this study. Psychoacoustic measures like pure tone perception, but also auditory illusions, are affected by electrical stimulation. This indicates that activity of the retrocochlear ascending auditory pathway is modulated during transcutaneous electrical stimulation.

Electrical vestibular stimulation after vestibular deafferentation and in vestibular schwannoma.

BACKGROUND: Vestibular reflexes, evoked by human electrical (galvanic) vestibular stimulation (EVS), are utilized to assess vestibular function and investigate its pathways. Our study aimed to investigate the electrically-evoked vestibulo-ocular reflex (eVOR) output after bilateral and unilateral vestibular deafferentations to determine the characteristics for interpreting unilateral lesions such as vestibular schwannomas. METHODS: EVOR was recorded with dual-search coils as binocular three-dimensional eye movements evoked by bipolar 100 ms-step at EVS intensities of [0.9, 2.5, 5.0, 7.5, 10.0] mA and unipolar 100 ms-step at 5 mA EVS intensity. Five bilateral vestibular deafferented (BVD), 12 unilateral vestibular deafferented (UVD), four unilateral vestibular schwannoma (UVS) patients and 17 healthy subjects were tested with bipolar EVS, and five UVDs with unipolar EVS. RESULTS: After BVD, bipolar EVS elicited no eVOR. After UVD, bipolar EVS of one functioning ear elicited bidirectional, excitatory eVOR to cathodal EVS with 9 ms latency and inhibitory eVOR to anodal EVS, opposite in direction, at half the amplitude with 12 ms latency, exhibiting an excitatory-inhibitory asymmetry. The eVOR patterns from UVS were consistent with responses from UVD confirming the vestibular loss on the lesion side. Unexpectedly, unipolar EVS of the UVD ear, instead of absent response, evoked one-third the bipolar eVOR while unipolar EVS of the functioning ear evoked half the bipolar response. CONCLUSIONS: The bidirectional eVOR evoked by bipolar EVS from UVD with an excitatory-inhibitory asymmetry and the 3 ms latency difference between normal and lesion side may be useful for detecting vestibular lesions such as UVS. We suggest that current spread could account for the small eVOR to 5 mA unipolar EVS of the UVD ear.

Vestibular perception following acute unilateral vestibular lesions.

Little is known about the vestibulo-perceptual (VP) system, particularly after a unilateral vestibular lesion. We investigated vestibulo-ocular (VO) and VP function in 25 patients with vestibular neuritis (VN) acutely (2 days after onset) and after compensation (recovery phase, 10 weeks). Since the effect of VN on reflex and perceptual function may differ at threshold and supra-threshold acceleration levels, we used two stimulus intensities, acceleration steps of 0.5°/s(2) and velocity steps of 90°/s (acceleration 180°/s(2)). We hypothesised that the vestibular lesion or the compensatory processes could dissociate VO and VP function, particularly if the acute vertiginous sensation interferes with the perceptual tasks. Both in acute and recovery phases, VO and VP thresholds increased, particularly during ipsilesional rotations. In signal detection theory this indicates that signals from the healthy and affected side are still fused, but result in asymmetric thresholds due to a lesion-induced bias. The normal pattern whereby VP thresholds are higher than VO thresholds was preserved, indicating that any 'perceptual noise' added by the vertigo does not disrupt the cognitive decision-making processes inherent to the perceptual task. Overall, the parallel findings in VO and VP thresholds imply little or no additional cortical processing and suggest that vestibular thresholds essentially reflect the sensitivity of the fused peripheral receptors. In contrast, a significant VO-VP dissociation for supra-threshold stimuli was found. Acutely, time constants and duration of the VO and VP responses were reduced - asymmetrically for VO, as expected, but surprisingly symmetrical for perception. At recovery, VP responses normalised but VO responses remained shortened and asymmetric. Thus, unlike threshold data, supra-threshold responses show considerable VO-VP dissociation indicative of additional, higher-order processing of vestibular signals. We provide evidence of perceptual processes (ultimately cortical) participating in vestibular compensation, suppressing asymmetry acutely in unilateral vestibular lesions.

Head direction cell activity in the anterodorsal thalamus requires intact supragenual nuclei.

Neural activity in several limbic areas varies as a function of the animal's head direction (HD) in the horizontal plane. Lesions of the vestibular periphery abolish this HD cell signal, suggesting an essential role for vestibular afference in HD signal generation. The organization of brain stem pathways conveying vestibular information to the HD circuit is poorly understood; however, recent anatomical work has identified the supragenual nucleus (SGN) as a putative relay. To test this hypothesis, we made lesions of the SGN in rats and screened for HD cells in the anterodorsal thalamus. In animals with complete bilateral lesions, the overall number of HD cells was significantly reduced relative to control animals. In animals with unilateral lesions of the SGN, directional activity was present, but the preferred firing directions of these cells were unstable and less influenced by the rotation of an environmental landmark. In addition, we found that preferred directions displayed large directional shifts when animals foraged for food in a darkened environment and when they were navigating from a familiar environment to a novel one, suggesting that the SGN plays a critical role in projecting essential self-motion (idiothetic) information to the HD cell circuit.

Auditory outcomes following implantation and electrical stimulation of the semicircular canals.

We measured auditory brainstem responses (ABRs) in eight Rhesus monkeys after implantation of electrodes in the semicircular canals of one ear, using a multi-channel vestibular prosthesis based on cochlear implant technology. In five animals, click-evoked ABR thresholds in the implanted ear were within 10 dB of thresholds in the non-implanted control ear. Threshold differences in the remaining three animals varied from 18 to 69 dB, indicating mild to severe hearing losses. Click- and tone-evoked ABRs measured in a subset of animals before and after implantation revealed a comparable pattern of threshold changes. Thresholds obtained five months or more after implantation--a period in which the prosthesis regularly delivered electrical stimulation to achieve functional activation of the vestibular system--improved in three animals with no or mild initial hearing loss and increased in a fourth with a moderate hearing loss. These results suggest that, although there is a risk of hearing loss with unilateral vestibular implantation to treat balance disorders, the surgery can be performed in a manner that preserves hearing over an extended period of functional stimulation.

Effects of vestibular prosthesis electrode implantation and stimulation on hearing in rhesus monkeys.

To investigate the effects of vestibular prosthesis electrode implantation and activation on hearing in rhesus monkeys, we measured auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE) in four rhesus monkeys before and after unilateral implantation of vestibular prosthesis electrodes in each of 3 left semicircular canals (SCC). Each of the 3 left SCCs were implanted with electrodes via a transmastoid approach. Right ears, which served as controls, were not surgically manipulated. Hearing tests were conducted before implantation (BI) and then 4 weeks post-implantation both without electrical stimulation (NS) and with electrical stimulation (S). During the latter condition, prosthetic electrical stimuli encoding 3 dimensions of head angular velocity were delivered to the 3 ampullary branches of the left vestibular nerve via each of 3 electrode pairs of a multichannel vestibular prosthesis. Electrical stimuli comprised charge-balanced biphasic pulses at a baseline rate of 94 pulses/s, with pulse frequency modulated from 48 to 222 pulses/s by head angular velocity. ABR hearing thresholds to clicks and tone pips at 1, 2, and 4 kHz increased by 5-10 dB from BI to NS and increased another ∼5 dB from NS to S in implanted ears. No significant change was seen in right ears. DPOAE amplitudes decreased by 2-14 dB from BI to NS in implanted ears. There was a slight but insignificant decrease of DPOAE amplitude and a corresponding increase of DPOAE/Noise floor ratio between NS and S in implanted ears. Vestibular prosthesis electrode implantation and activation have small but measurable effects on hearing in rhesus monkeys. Coupled with the clinical observation that patients with cochlear implants only rarely exhibit signs of vestibular injury or spurious vestibular nerve stimulation, these results suggest that although implantation and activation of multichannel vestibular prosthesis electrodes in human will carry a risk of hearing loss, that loss is not likely to be severe.

[Cochleovestibular disorders: approaches to diagnostics and treatment].

The aim of this work was to evaluate the efficacy of introduction of milgamma and milgamma compositum in the treatment of 52 patients with cochleovestibular disorders of different etiology. Thirteen patients enrolled in the study received standard therapy and 39 others were given its combination with milgamma preparations. Combined therapy with milgamma and milgamma compositum ensured faster vestibular compensation including posturographic characteristics than the standard treatment (within 3-4 weeks compared with 5 weeks in controls). The results of the study give reason to recommend milgamma and milgamma compositum as neurotropic medicines in addition to standard therapy for the management of the patients presenting with cochleovestibular disorders for the acceleration of the vestibular compensation.

[Computer-aided techniques for the treatment and rehabilitation of patients suffering vertigo and balance disorders].

A new computerized method is proposed for the correction and elimination of undesirable illusory sensations (dizziness), vestibulo-oculomotor (nystagmus), and vestibulo-postural (imbalance) reactions. The method allows to teach the subject about how to avoid generalization of afferent signals over the effector mechanisms in the central nervous system by developing a fixational reflex employing delayed biological feedback for the assessment of efforts being exerted (self-control of training results). Three variants of application of this technique were evaluated depending on the type of stimulation software intended to induce illusory and oculomotor reactions of a defined sensory modality (visual, vestibular or combined). The study involved 30 subjects divided into three groups. They had been taught using the visual (group 1), vestibular (group 2) or combined (group 3) methods. Each group was comprised of an approximately equal number of subjects with vestibulopathies of either peripheral or central origin. The study demonstrated that the proposed approach allows to invoke, with the use of a computer stimulation software, abnormal illusory and vestibulo-oculomotor responses and inhibit them by developing the adequate fixational reflex. Comparative analysis of the results obtained by teaching the patients with the help of the three different methods revealed the dependence of their effectiveness on the level of disturbances in the vestibular system. The visual method of correction proved to be especially efficacious for the patients with peripheral vestibulopathy, and the vestibular methods for the patients with central vestibulopathy. Patients with combined peripheral and central vestibulopathy required the choice of training modalities (either visual or vestibular) on an individual basis.

Molecular identity and functional properties of a novel T-type Ca2+ channel cloned from the sensory epithelia of the mouse inner ear.

The molecular identity of non-Cav1.3 channels in auditory and vestibular hair cells has remained obscure, yet the evidence in support of their roles to promote diverse Ca2+-dependent functions is indisputable. Recently, a transient Cav3.1 current that serves as a functional signature for the development and regeneration of hair cells has been identified in the chicken basilar papilla. The Cav3.1 current promotes spontaneous activity of the developing hair cell, which may be essential for synapse formation. Here, we have isolated and sequenced the full-length complementary DNA of a distinct isoform of Cav3.1 in the mouse inner ear. The channel is derived from alternative splicing of exon14, exon25A, exon34, and exon35. Functional expression of the channel in Xenopus oocytes yielded Ca2+ currents, which have a permeation phenotype consistent with T-type channels. However, unlike most multiion channels, the T-type channel does not exhibit the anomalous mole fraction effect, possibly reflecting comparable permeation properties of divalent cations. The Cav3.1 channel was expressed in sensory and nonsensory epithelia of the inner ear. Moreover, there are profound changes in the expression levels during development. The differential expression of the channel during development and the pharmacology of the inner ear Cav3.1 channel may have contributed to the difficulties associated with identification of the non-Cav1.3 currents.

Visual mental imagery during caloric vestibular stimulation.

We investigated high-resolution mental imagery and mental rotation, while the participants received caloric vestibular stimulation. High-resolution visual mental imagery tasks have been shown to activate early visual cortex, which is deactivated by vestibular input. Thus, we predicted that vestibular stimulation would disrupt high-resolution mental imagery; this prediction was confirmed. In addition, mental rotation tasks have been shown to activate posterior parietal cortex, which is also engaged in the processing of vestibular stimulation. As predicted, we also found that mental rotation is impaired during vestibular stimulation. In contrast, such stimulation did not affect performance of a low-imagery control task. These data document previously unsuspected interactions between the vestibular system and the high-level visual system.

Vestibular hypersensitivity to clicks is characteristic of the Tullio phenomenon.

OBJECTIVES: The frequency of pathologically reduced click thresholds for vestibular activation was explored in patients with the Tullio phenomenon (sound induced vestibular activation). METHODS: Seven patients (eight affected ears) with symptoms of oscillopsia and unsteadiness in response to loud external sounds or to the patient's own voice were examined. In all but one patient, vestibular hypersensitivity to sound was confirmed by the fact that eye movements could be produced by pure tones of 110 dB intensity or less. Conventional diagnostic imaging was normal in all cases and three of the patients had normal middle ears at surgical exploration. Thresholds for click evoked vestibulocollic reflexes were compared with those of a group of normal subjects. Galvanic stimulation was used as a complementary method of examining the excitability of vestibular reflexes. RESULTS: All the patients showed a reduced threshold for click activation of vestibulocollic reflexes arising from the affected ear. Short latency EMG responses to clicks were also present in posterior neck and leg muscles, suggesting that these muscles receive vestibular projections. Galvanic stimulation produced a normal pattern of body sway in four of the five patients tested. CONCLUSIONS: A pathologically reduced threshold to click activation (< or = 70 dB NHL (average normal hearing level)) seems to be a consistent feature of the Tullio phenomenon and a useful diagnostic criterion. This in turn is most likely to be due to an increased effectiveness of the transmission of sound energy to saccular receptors. Activation of these receptors probably contributed to the vestibular symptoms experienced by the patients.

Vestibulocollic reflexes evoked by short-duration galvanic stimulation in man.

1. Vestibular-dependent responses in leg muscles following transmastoid galvanic stimulation have been well characterized. Here we describe the properties of vestibulocollic responses evoked by transmastoid galvanic stimulation. 2. In twelve healthy human subjects we examined the averaged responses in unrectified sternocleidomastoid (SCM) EMG evoked by transmastoid stimulation using current pulses of 4 mA intensity and 2 ms duration. In ten subjects we also examined the effects of unilateral vestibular stimulation with the indifferent electrode at the vertex. In further experiments we studied the effects of different levels of background muscle activation, head position, current intensity and current duration. We compared these responses with click-evoked vestibulocollic responses in SCM. 3. A clearly defined biphasic response, beginning with a surface positivity, was recorded in the SCM ipsilateral to the side of cathode placement in all subjects. We refer to this as the p13/n23 [g] (galvanic) response, given the close similarity, in terms of waveform and latencies, to the previously described click-evoked p13/n23 vestibulocollic response. The amplitude of this response was linearly related to background muscle activation, current intensity and current duration, but independent of head position. Unilateral galvanic stimulation revealed the p13/n23 [g] response to be solely generated by the cathode. 4. A biphasic response beginning with a surface negativity (n12/p20 [g]) contralateral to the cathode was seen in all subjects and was generated by both the cathode contralaterally and the anode ipsilaterally. 5. Both the p13/n23 [g] and n12/p20 [g] potentials were abolished by selective vestibular nerve section and unaffected by severe sensorineural deafness. 6. We conclude that galvanic stimulation evokes short-latency vestibulocollic reflexes. These vestibulocollic reflexes have properties that are distinct from those described for galvanic-evoked vestibular reflexes in leg muscles, and which may be related to their differing physiological roles.

Physiological and anatomical study of click-sensitive primary vestibular afferents in the guinea pig.

We studied the sensitivity of primary vestibular afferents in anaesthetised guinea pigs to clicks. These vestibular neurons were also tested by their response to pitch and roll tilts and yaw-axis angular acceleration. The click intensity was referred to the threshold for evoking the auditory brainstem responses. Recording sites in the vestibular nerve were confirmed histologically using iontophoretic injection of FCF green dye. To confirm the site of labyrinthine origin of the click-sensitive neurons, we used retrograde tracing with biocytin. In all, 647 out of 2354 neurons in the vestibular nerves of 51 guinea pigs were activated by clicks. Most were irregularly discharging primary neurons, but some were regularly discharging. We studied responses to vestibular stimuli in 188 click-sensitive neurons. Of these, 86% responded to pitch and/or roll tilt, but none responded to yaw angular acceleration. Conversely we also recorded vestibular neurons which did not respond to clicks. None of 300 neurons sensitive to yaw angular acceleration were responsive to 80-90 dB SL clicks (0 dB SL = threshold for auditory brainstem response to clicks). The latencies of click-evoked action potentials of neurons in the vestibular nerve were very short (mean +/- SD = 0.82 +/- 0.22 ms). Changing click polarity caused a heterogeneous pattern of latency change. Thresholds for evoking spikes in primary vestibular neurons were high (62.0 +/- 12.2 dB SL, range 30-90 dB, n = 371). Retrograde tracing of the origin of the click-sensitive afferents using extracellular biocytin showed that most neurons originated in the medial (striola area) of the saccular macula.

Insulin-like growth factor-I regulates cell proliferation in the developing inner ear, activating glycosyl-phosphatidylinositol hydrolysis and Fos expression.

The role of insulin-like growth factors (IGF) was investigated during the early development of the inner ear. IGF-I stimulated growth of otic vesicles that were isolated and cultured in vitro. IGF-I induced DNA synthesis, increased cell number, and mitotic rate in a dose-dependent manner at concentrations between 0.1-10 nM. IGF-II also induced growth but with a lower potency, whereas insulin had no effect. In the presence of IGF-I, otic vesicles developed from stage 18 to stage 21 in 24-h cultures, mimicking the normal mitotic pattern and morphogenesis in vivo. IGF-I also stimulated growth in the cochleovestibular ganglion. Binding of 125I-IGF-I to specific receptors occurred with high affinity. An autoradiographic study of sections from otic vesicles showed radiolabeled IGF-I in the epithelium. Immunoreactivity to IGF-I was detected in the otic vesicle and in the cochleovestibular ganglion. Intracellular signaling mechanisms of IGF were explored by studying the turnover of glycosylated phosphatidylinositols and the expression of Fos oncoprotein. IGF-I rapidly increased Fos levels in cultured otic vesicles. Furthermore, antisense oligonucleotides complementary to c-fos were able to inhibit IGF-I-induced growth. Both IGF-I-induced cell proliferation and Fos expression were blocked by an antiinositol phosphoglycan (alpha-IPG) antibody. This work suggests that IGF-I may be a candidate to regulate proliferative growth of the otic primordium during normal development and that this action requires the sequential modulation of glycosyl-phosphatidylinositol turnover and Fos expression.

Myogenic potentials generated by a click-evoked vestibulocollic reflex.

Electromyograms (EMGs) were recorded from surface electrodes over the sternomastoid muscles and averaged in response to brief (0.1 ms) clicks played through headphones. In normal subjects, clicks 85 to 100 dB above our reference (45 dB SPL: close to perceptual threshold for normal subjects for such clicks) evoked reproducible changes in the averaged EMG beginning at a mean latency of 8.2 ms. The earliest potential change, a biphasic positive-negativity (p13-n23), occurred in all subjects and the response recorded from over the muscle on each side was predominantly generated by afferents originating from the ipsilateral ear. Later potentials (n34, p44), present in most but not all subjects, were generated bilaterally after unilateral ear stimulation. The amplitude of the averaged responses increased in direct proportion to the mean level of tonic muscle activation during the recording period. The p13-n23 response was abolished in patients who had undergone selective section of the vestibular nerve but was preserved in subjects with severe sensorineural hearing loss. It is proposed that the p13-n23 response is generated by activation of vestibular afferents, possibly those arising from the saccule, and transmitted via a rapidly conducting oligosynaptic pathway to anterior neck muscles. Conversely, the n34 and p44 potentials do not depend on the integrity of the vestibular nerve and probably originate from cochlear afferents.

Vestibulo-thalamic neurons give off descending axons to the spinal cord.

Vestibulo-thalamic (VT) neurons were physiologically studied in the anesthetized cat. Forty-seven VT neurons were recorded extracellularly. More than half of the VT neurons responded monosynaptically to vestibular nerve stimulation while the others responded polysynaptically. They were activated antidromically from one or two sites in the VPL. VPM, VL, VM, SG, and PO of the contralateral thalamus. Four fifths of the VT neurons were activated from the C1 segment of the spinal cord. Half of them were also activated from the C4 segment, but none were activated from the L5 segment. It is suggested that most VT neurons project descending axons to the cervical spinal cord. Axonal branching was shown by means of systematic microstimulation in the thalamus and the ventral horn in the C1 segment. The VT neurons were mainly located in the descending vestibular nucleus.

Recording of electrical-evoked responses from a remote field in the vestibular part of the eighth nerve. A preliminary technical report.

The paper discusses the results of the author's own studies concerning the recording of electrical responses evoked from a remote field in the vestibular part of the eighth nerve. The studies are of experimental nature and they were carried out repetitively in guinea pigs. Particular attention is paid to an apparatus specially designed and constructed, permitting to obtain stimulation of adequate quality of vestibular organs, and to receive and average short (up to 10 ms) evoked vestibular potentials. Different variants of elimination of bioelectrical muscular disturbances and of the auditory pathway are proposed.

Medical fitness examination of commercial pilots: new criteria for evaluation of vestibular tests.

In medical fitness examinations of commercial pilots, extensive vestibular investigations should be conducted. In particular, the pendular test, as a weak rotational stimulation method, can disclose central vestibular disorders. Thus, the central nystagmus tracing can be considered as a sign of irritation of vestibular centers, most frequently as a consequence of head trauma, a finding that may influence the decision in the enlistment of the pilot. In contrast, a small nystagmus amplitude tracing is observed in cases of insufficient blood supply, occurring mostly in elderly persons. Therefore, this finding helps to demonstrate and treat arteriosclerotic dizziness in elderly pilots. Cervical-nystagmus--elicited by neck-torsion while keeping the labyrinth fixed at rest--is an objective demonstration of a cervical-spine-syndrome. Aimed therapy, namely chiropractic manipulation, may help the pilot become fit to fly again. Further processing of the data from the vestibular investigations by means of a computer and plotting can provide the so-called cumulative eye position. This enables one to evaluate the compensation capacity which is a measure of the intensity of the vestibular response, important in the assessment of normal function of the vestibular system.

Tinnitus: diagnosis and treatment.

Few conditions are seen as commonly by the otologist and are more poorly understood than subjective tinnitus. Tinnitus has been reported in as high as 80% of patients seen in an otolaryngology practice. This symptom is especially marked in patients with a hearing problem and can be so severe that it becomes incapacitating. Careful diagnosis and classification of tinnitus is important for understanding of the problem. Identification of the frequency and intensity of masking, using a tinnitus analyzer, is useful in selecting the form of treatment. Analysis of the history, physical findings and the use of special electrocochleography and brain stem evoked response audiometry help to identify the site of lesion, which may be within the cochlea, cochlear nerve, cochlear nucleus, brain stem, midbrain or auditory cortex. Specific disease entities should be identified and treated. Lesions of the end-organ or cochlear nerve can be treated when necessary by translabyrinthine or middle cranial fossa section of the cochlear nerve. Tinnitus from cervical nerve lesions can be treated by rhizotomy. The use of a hearing aid or introduction of a sound with a tinnitus masker has been found to be 82% effective in suppressing tinnitus. Maskers can be combined with a hearing aid in some cases. The pathogenesis of tinnitus is discussed, but the method of action of tinnitus relief by auditory stimulation is still unclear. A thoughtful and complete examination with our new diagnostic tools and the judicious selection of therapy now makes it possible to give relief to the majority of patients suffering with disturbing tinnitus.

[Nystagmus as an objective assessment of the cervical spine syndrome and its treatment (author's transl)]. / Der Cervicalnystagmus als objektiver Befund beim HWS-Syndrom und seine Beeinflussbarkeit durch Manualtherapie.

Nystagmus together with the history, X-ray and palpation findings were used to confirm the diagnosis of the cervical spine syndrome. In patients with this disorder the nystagmus was controlled by manual treatment in 63%. Nystagmus therefore can be used objectively to assess the success of therapy in cervical spine syndrome.