Postural control and vestibular function in patients selected for cochlear implantation

Postural control and vestibular and eye motor function were evaluated in 7 postlingually deaf patients before cochlear implantation as vibration toward the calf muscles or galvanic electrical stimulation of the vestibular nerves perturbed stance. The patients were compared with 21 control subjects. Vibration-induced bodysway was increased in the patients compared to the normals. Galvanic stimulation induced a bodysway that was not significantly different from that of the control group suggesting that the patients selected for cochlear implantation, and with otherwise reduced postural control, are sensitive to electrical stimulation of the vestibular nerve. This finding may contribute with a complementary hypothesis to the causes of dizziness among cochlear implant patients.

Three-dimensional (3-D) eye movement analysis in patients with positioning nystagmus

Benign paroxysmal positioning vertigo (BPPV), and nystagmus (BPPN) is the commonest type of rotational vertigo. Typical BPPN is generally believed to arise from one posterior semicircular canal. If this is true, the syndrome would offer the unique possibility to study vestibular responses when just one single semicircular canal is excited. In this study we used search coils to measure 3-D eye positions in 3 patients with BPPN. We present a complete 3-D description of the eye movements induced in BPPN. We found that in our patients the eyes rotate rather precisely in the plane of one posterior semicircular canal, suggesting that BPPN in our cases is indeed solely produced by the posterior semicircular canal.

Atypical "reversed" paroxysmal positioning nystagmus in benign paroxysmal positional vertigo

An atypical paroxysmal positioning nystagmus (PPNy), "reversed" in its directional components, is a rare finding in patients suffering from benign paroxysmal positioning vertigo (BPPV). It poses problems of pathophysiogenetic interpretation, differential diagnosis with a CNS lesion and therapeutic strategy. Such a finding was observed in 7 patients (out of a total of 450 BPPV) and took on the typical PPNy pattern after repeated diagnostic manoeuvres. These aspects are incompatible with the "heavy cupula" mechanism (cupulolithiasis) and are better explained by the presence of "free endolymph aggregates" (canalolithiasis) within the posterior semicircular canal (p.s.c). Moreover, canalolithiasis would also permit a more convincing interpretation of all the clinical findings observed in typical p.s.c.-BPPV.

Menière's disease

Menière's disease is the most common cause of true vertigo and it affects about 2.4 million Americans. Episodic tinnitus, hearing loss, vertigo, and aural fullness are the classic findings. The symptom which is most debilitating and which causes most people to seek treatment is vertigo. Most patients respond extremely well to medical management and only rarely is surgery necessary. This paper discusses the symptoms, diagnosis, and clinical course of Menière's disease. Medical and surgical therapeutic options are discussed.

3DFT-magnetic resonance imaging of the inner ear in Meniére's disease

Three dimensional Fourier transformation constructive interference in steady state (3DFT-CISS) magnetic resonance imaging (MRI) allows a detailed visualization of the membranous labyrinth of the inner ear. In this study the endolymphatic duct and sac is investigated in patients with Menière's disease using 3DFT-CISS MRI. In addition, the distance between the vertical part of the posterior semicircular canal and the fossa posterior is quantified.

Dynamic platform sway measurement in Menière's disease

Fourteen patients in the latent phase of Menière's disease and 14 control subjects were tested on a moving platform apparatus as part of a protocol of investigations for Menière's disease. Subjects were tested under 3 different visual conditions (eyes open, eyes closed, sway feedback) and 2 proprioceptive conditions (fixed platform and ankle stabilization). There was a significant interaction between subject group and visual condition, Menière's patients had a larger RMS sway amplitude than controls with their eyes open and closed, but this difference was abolished by sway feedback. Loss of either visual or proprioceptive sensory information increased sway amplitude, indicating that both cues influence postural control, and in different ways, but patients were able to use these cues to maintain upright posture almost as effectively as controls. More patients than controls lost balance with ankles stabilized and eyes closed, but the difference was not statistically significant (P = 0.0516). There was no detectable relationship between clinical ratings of disease severity and sway scores. The dynamic platform tests described in this report are more suitable for tests involving comparisons between groups of subjects rather than for diagnostic testing of individuals.

Surgical treatment of Menière's disease

Surgical treatment is used only for patients with Menière's disease in cases that do not respond to medical therapy. At the present time, the endolymphatic sac shunt operation is performed in cases where the auditory threshold is fluctuant around 30 dB. When the auditory threshold is between 40 and 70 dB we use the vestibular neurectomy by the retrosigmoid approach. In patients with Menière's disease with profound hearing loss the translabyrinthine neurectomy is used. The advantages of the vestibular neurectomy by the retrosigmoid approach compared to the retrolabyrinthine and middle fossa approaches will be described.

[Noninvasive assessment of intracochlear pressure and patency of the cochlear aqueduct in normal probands with TMD (tympanic membrane displacement) analysis]

The intracochlear pressure cannot yet be evaluated in patients with certain audiological neuro-otological diseases. However, it seems to be of importance in the diagnosis and pathogenesis of Ménière's disease and related disorders. The present paper is aimed at introducing a setup to indirectly assess intracochlear and intracranial pressure changes and the design and philosophy of this technique. It is possible to describe a normal range of the measured values in healthy controls although large interindividual variations occur. In addition, the positional changes of the registered parameters enable assessment of the patency of the cochlear aquaeduct. This seems to be important in some diseases, such as stapes gusher.

[Cervicogenic hearing loss]

Existing investigations of cervical hearing disorders have been carried out predominantly in patients in whom those with vertebrobasilar insufficiencies (VBI) could not be distinguished from patients suffering from functional deficit of the upper cervical spine. Since two different syndromes exist, no statement can be made about cervical hearing disorders. That deafness can occur in VBI is uncontested. In contrast, there remains a dispute whether a "vertebragenic hearing disorder" exists. This latter disorder is believed accompanied by tinnitus, a feeling of ear pressure, otalgia and deafness as symptoms of a functional deficit of the upper cervical spine. In reviewing the medical findings of 259 patients with well-defined functional deficits of the upper cervical spine and symptoms of cervical vertigo, subjective hearing disorders occurred in 15%. Audiometric threshold shifts of 5-25 dB, most often in lower frequencies, were observed in 40%. Additionally, results of click-evoked otoacoustic emissions (OAE) were negative in spite of approximately normal hearing. Findings in 62 patients suffering from vertebragenic hearing disorders are reported before and after chiropractic management. Results indicate that these hearing disorders are reversible, as demonstrated by audiometry and OAE. The therapy of choice is chiropractic manipulation of the upper cervical spine. The commoness of vertebragenic hearing disorders emphasizes their clinical and forensic importance.

[Effect of head rotation on the vertebrobasilar system. A transcranial Doppler ultrasound contribution to the physiology]

Examination of the vertebrobasilar system until a short time ago was possible only by invasive and therefore potentially harmful techniques. The results of these studies were also contradictory. The objective of the present study was to determine how blood flow velocity differed in the vertebral arteries during head rotation in normal subjects. The origin of cervical vertigo essentially involves three components that are difficult to distinguish. There are the sensory proprioceptive, vascular and sympathicotonic components. Use of transcranial Doppler sonography (TCD) has now made it possible to measure the flow velocity of the vertebral arteries. In 17 normal probands without vertigo or cervical nystagmus, the mean diameters of the vertebral arteries were measured by means of duplex scanning. TCD was used to determine the mean flow velocities of the vertebral arteries in a median position and after head rotations of 30 degrees and 60 degrees to the left and right. Blood flow velocities in both vertebral arteries were not altered by head rotation. This observation contrasted with that of other publications, which were mainly based on cadaver findings. The results of this study form the basis for further investigations on symptomatic patients with recurring cervical nystagmus and cervical vertigo.

Benign positional vertigo produces a specific pattern of abnormalities with high frequency vestibulo-ocular reflex testing

The vestibulo-ocular reflex was studied at high frequencies of active head rotation (2 to 6 Hz) in twenty-three patients with benign positional vertigo (BPPV). Gain and phase measurements were obtained in the vertical and horizontal planes, and the results were compared to those of a control group consisting of 19 asymptomatic age-matched subjects. In the horizontal plane, the phase lead was significantly smaller in patients with BPPV as compared to controls (p < 0.01 at all frequencies). Vertical results did not differ from normals. These findings challenge "cupulolithiasis" as an explanation of the mechanism of BPPV's symptoms.

Vestibular rehabilitation improves daily life function

This article reviews recent research that addresses the functional outcomes of intervention for vestibular disorders. Vestibular impairments cause disequilibrium, blurred vision, disorientation, and vertigo. These sensory disturbances and motor impairments in turn cause dysfunction in many activities of daily living and in social interactions that traditional medical treatments do not address. The motor sequelae of some vestibular disorders can be treated successfully with programs of graded exercises and activities, the functional implications of which are described herein. The functional impairments caused by other vestibular disorders, which cannot be treated with graded activities, are also described. These disorders include bilateral vestibular loss caused by connective tissue disorders or by the use of ototoxic medications, tumors of the labyrinth or vestibular nerve, and Meniere's disease. Occupational therapy intervention for these conditions may involve providing adaptive equipment, teaching alternative strategies for performing activities of daily living, and psychological intervention for depression and anxiety.

Reproducibility of the electric response components in clinical electrocochleography

The reproducibility of transtympanic electrocochleographic components was investigated in normal-hearing subjects and in patients with Menière's disease. The electric responses to short clicks and long tone bursts were studied using repeated stimuli within the same test (intratest), and after replacement of all electrodes (intertest). The parameters of the response to clicks, such as the SP/AP (summating potential/action potential) ratio and the width of the complex as well as the amplitudes of the response to clicks presented at fast repetition rate, were analyzed. Absolute amplitudes of the SP were measured using long tone bursts of 4, 2 and 1 kHz. It was found that the intratest reproducibility of the responses was good for all the parameters. The intertest responses showed a larger variability, particularly when long bursts were used. Parameters obtained from hydroptic ears, which could be considered mainly representative for the SP, showed the largest variability of the responses. The effect of replacement of the electrodes amounted to less than 35% of the total intertest variability which would indicate that replacement of the electrodes did not significantly influence the recordings obtained at different measurement occasions in the same patient. The upper normal limit value indicating changes which could be contributed to biological fluctuations and the method of measurements were calculated for each response parameter. Changes exceeding these values could thus be attributed to a real change in the electric cochlear potentials, at the 95% confidence level.

[The characteristics of vestibular-visual interaction in patients with cochleovestibular disorders under galvanic stimulation]

The paper deals with the problem of vestibular-visual interactions in pathogenesis of cochleovestibular diseases. The investigations were made on the original unit for registration of visual illusions in response to galvanic stimulation of vestibular structures. The examination covered patients with Meniere's disease, peripheral and central cochleovestibular syndrome, otogenic arachnoiditis. Emergence of visual illusions was related to the degree of vestibular abnormality and threshold stimulation. The greatest compensation of the equilibrium function at the expense of vision was reported in patients with central vestibular disorders. Further studies into the vestibular reactions seem important for elucidation of cochleovestibulopathy pathogenesis.

[Distortion products in Menière's disease]

Distortion Product Otoacoustic Emissions (DPOAEs) are elicited by simultaneous application of two tones to the ear canal. These emissions are a result of nonlinear mechanical characteristics of the cochlea at a specific point and have a precise mathematical relation with the frequencies of the two eliciting primary tones f1 and f2. This frequency-selective property of DPOAEs suggests that they should be regarded as useful monitor of localized cochlear function at any predetermined frequency. The present study was designed to investigate DPOAEs in patients with Menière's disease. DPOAEs were recorded before and after glycerol administration to verify if the fluctuation of the hearing threshold induced by this hyperosmotic agent causes selective changes in the activity of the outer hair cells. DPOAEs were present in patients in which the mean duration of the disease was shorter compared to those patients without measurable DPOAEs. An improvement of DPOAEs after glycerol intatte was observed in a half of our cases. The improvement of DPOAEs does not appear to be brought about by modifications of the auditory threshold induced by glycerol.

[Benign paroxysmal positional vertigo. Differential diagnosis of posterior, horizontal and anterior canalolithiasis]

Evidence is presented that all typical features of benign paroxysmal positioning vertigo can be explained by canalolithiasis rather than by cupulolithiasis. A free floating clot of "heavy" inorganic particles gravitates to the most dependent part of the canal as soon as the patient's head is moved in a way that alters the angle between the canal's plane and the gravity vector. Based on the canalolithiasis mechanism we describe how characteristics of the thus elicited nystagmus differ if the posterior, the horizontal or the anterior semicircular canal is causative.

Impedance measurement as a noninvasive technique for the monitoring of intracranial pressure variations

In previous reports it has been demonstrated that jugular compression causes a modification of middle ear acoustic impedance; this phenomenon has been named the jugulotympanic reflex (JTR). The aim of the present study was to contribute to the understanding of the origin of this reflex. We have analyzed the middle-ear impedance modifications induced by unilateral and bilateral jugular compression in 12 normal subjects, in 12 patients afflicted with otosclerosis, in 3 patients with Menière's disease and in 6 patients demonstrating intracranial hypertension. In the latter group, the cerebrospinal fluid (CSF) pressure was simultaneously recorded. The JTR was elicited in each normal subject and in each patient affected by Menière's disease and intracranial hypertension, while it was usually absent or modified in otosclerotic patients. The absence of the JTR in otosclerotic patients and, above all, the correspondence between CSF pressure and the middle-ear impedance modification induced by jugular compression suggest that it is due to the transmission of pressure changes from the CSF to the perilymph through the cochlear aqueduct.

Neural conduction velocity of the human auditory nerve: bipolar recordings from the exposed intracranial portion of the eighth nerve during vestibular nerve section

We measured the conduction velocity of the intracranial portion of the auditory nerve in 3 patients undergoing vestibular nerve section to treat Ménière's disease. The conduction velocity varied from patient to patient, with an average value of 15.1 m/sec. The latency of peak III of the brain-stem auditory evoked potentials (BAEPs) increased by an average of 0.5 msec as a result of exposure of the eighth nerve, and if that increase is assumed to affect the entire length of the auditory nerve (2.6 cm) evenly, then the corrected estimate of conduction velocity would be 22.0 m/sec. Estimates of conduction velocity based on the interpeak latencies of peaks I and II of the BAEP, assuming that peak II is generated by the mid-portion of the intracranial segment of the auditory nerve, yielded similar values of conduction velocities (about 20 m/sec).

Dizziness in childhood

There is a scant literature regarding vestibular evaluation of children with complaints of dizziness or vertigo. Considerable time and effort are expended on the problem and prevention of hearing loss in children, yet we often ignore concurrent or subsequent vestibular disorders. This neglect could be due to several factors, perhaps the most common being the fact that vertiginous crises in childhood are often attributed to problems of behavior or incoordination. In this article, we offer an approach to the dizzy child based on presenting symptoms. We discuss features of the history, examination, and laboratory evaluation key to determining the cause of dizziness. Finally, we discuss management, which varies according to the diagnosis.

[Extratympanic electrocochleography during glycerol dehydration test in unilateral Ménière's diseases]

Extratympanic electrocochleography and pure-tone audiometry were performed in unilateral Ménière's disease patients before and 1, 2 and 3 hours after oral administration of glycerol. The mean electrocochleographic response from 12 recordings at 80 dBnHL click stimuli was determined to obtain stable values. The electrocochleographic response during the glycerol dehydration test was compared with that in normal subjects (28 ears). A positive result on a pure-tone audiogram was determined by an improvement of at least 10 dB in two octave bands. In 25 involved ears with Ménière's disease, the action potential (AP) amplitudes gradually decreased during the test, but there were no significant differences. The summating potential (SP) amplitudes decreased during the test and there was a significant difference at 2 hours after administration. The negative SP/AP ratios were unchanged. The Ménière's disease patients were classified into two groups; one with a positive response on the audiogram and the other negative responses including deterioration. According to multiple comparison testing, there were significant differences in AP amplitudes and SP amplitudes between the positive group and normal controls at 2 and 3 hours after administration, and between the positive group and the negative group at 3 hours. Electrocochleographic changes in the positive audiogram group were significant. Then, the patients were classified into three groups by negative SP/AP ratio before administration. The first group consisted of negative ears whose negative SP/AP ratios were less than 0.36, which was the upper 95% confidence limit for 40 normal hearing ears, the second consisted of slightly positive ears (0.36 < or = negative SP/AP ratio < 0.40), the last consisted of severely positive ears whose ratios were more than 0.4, which was the upper 99% confidence limit. There was a significant difference for the SP amplitudes between the slightly positive group and normal controls at 2 hours after administration. Electrocochleographic changes in the slightly positive group with a negative SP/AP ratio were significant at this SP amplitude. In 18 normal ears with Ménière's disease, electrocochleographic changes showed no significant difference. However, the SP amplitudes in 3 ears and the negative SP/AP ratios in 4 ears decreased to less than 80% of the pre-administration value, although they had not fallen below that in the normal controls. These decreases indicate that some normal ears with Ménière's disease already had the distinctive features of involved ears. Whether the fluctuation in hearing will appear in the normal ears with decreasing SP amplitudes or negative SP/AP ratios, as in the involved ears, remains to be determined.

Ménière's disease

Even more than a century after the first description of Ménière's disease, Portmann (1927) said: 'Ménière's is one of the least understood disorders both by doctors in general and specialists. It is variable in clinical presentation, imprecise in diagnosis, and because the effectiveness of treatment is doubtful, leaves the clinician disillusioned, depriving the patient of the potential cure that has become the rule.'

An experimental evaluation of the effects of transcutaneous nerve stimulation (TNS) and applied relaxation (AR) on hearing ability, tinnitus and dizziness in patients with Menière's disease

In 20 patients diagnosed with Menière's disease, transcutaneous nerve stimulation (TNS) and applied relaxation (AR) were used as a treatment aimed at reducing tinnitus and dizziness and increasing hearing ability. The main aim of the study was to examine whether TNS could be regarded as a more beneficial treatment regimen than AR. An experimental between-group cross-over design was used. The results from the experimental phase (group comparisons) showed a significantly increased ability to hear for the TNS group when measured on visual analogue scales. During the same period, the AR-group showed a significant hearing improvement for the ear not primarily affected by Menière's disease as measured with pure tone audiometry. The vestibular tests did not reveal any significant changes either after TNS or AR intervention. Tinnitus matching showed changes of pitch and loudness before and after both TNS and AR intervention. However, no statistically significant changes between treatment regimes were found on these measures. The results from this study did not show TNS to be superior to AR in reducing tinnitus, dizziness or increasing hearing ability.

Transitory endolymph leakage induced hearing loss and tinnitus: depolarization, biphasic shortening and loss of electromotility of outer hair cells

There are types of deafness and tinnitus in which ruptures or massive changes in the ionic permeability of the membranes lining the endolymphatic space [e.g., of the reticular lamina (RL)] are believed to allow potassium-rich endolymph to deluge the low [K+] perilymphatic fluid (e.g., in the small spaces of Nuel). This would result in a K+ intoxication of sensory and neural structures. Acute attacks of Ménière's disease have been suggested to be an important example for this event. The present study investigated the effects of transiently elevated [K+] due to the addition of artificial endolymph to the basolateral cell surface of outer hair cells (OHC) in replicating endolymph-induced K+ intoxication of the perilymph in the small spaces of Nuel. The influence of K+ intoxication of the basolateral OHC cell surface on the transduction was then examined. Intoxication resulted in an inhibition of the physiological repolarizing K+ efflux from hair cells. This induced unwanted depolarizations of the hair cells, interfering with mechanoelectrical transduction. A pathological longitudinal OHC shortening was also found, with subsequent compression of the organ of Corti possibly influencing the micromechanics of the mechanically active OHC. Both micromechanical and electrophysiological alterations are proposed to contribute to endolymph leakage induced attacks of deafness and possibly also to tinnitus. Moreover, repeated or long-lasting K+ intoxications of OHC resulted in a chronic and complete loss of OHC motility. This is suggested to be a pathophysiological basis in some patients with chronic hearing loss resulting from Ménière's syndrome.

Electrocochleographic monitoring in endolymphatic sac surgery for Menière's disease

OBJECTIVE

To determine the efficacy of intraoperative electrocochleographic monitoring during endolymphatic sac-ballooning surgery for Menière's disease.

DESIGN

At each of five surgical steps, the eighth nerve action potential (AP) amplitude and latency, summating potential (SP) amplitude, and SP/AP amplitude ratio were recorded. Data were analyzed using repeated measure analysis of variance.

PATIENTS

Electrocochleographs were successfully recorded in 97 patients during endolymphatic sac-ballooning surgery. Forty patients had an abnormal baseline ratio (group 1), and 57 patients had a normal baseline ratio.

RESULTS

Data showed that the SP/AP amplitude ratio reductions were significant only in group 1 patients. The SP/AP amplitude ratio was reduced in two thirds of the group 1 patients and unchanged in roughly the same proportion of group 2 patients. A significant reduction of SP/AP amplitude ratios was found to be always associated with prominent SP/AP ratios at the baseline, irrespective of glycerol test results, and only in cases of classic Menière's disease, indicating that this dominant ratio is a very reliable indicator of Menière's disease and endolymphatic hydrops. Importantly, reductions of SP/AP amplitude ratios were observed at every step to be consistently due to AP increase rather than SP decrease.

CONCLUSIONS

It is theorized that the dominant SP/AP amplitude ratio found in patients with Menière's disease and endolymphatic hydrops is caused by the inhibition of AP activity rather than by the enhancement of the SP resulting from the displacement of the basilar membrane toward the scala tympani owing to hydropic endolymph, as is generally believed. We conclude that electrocochleograpic monitoring is useful during endolymphatic sacballooning surgery to provide a definitive delineation of the endolymphatic sac and its lumen; this delineation is the key to the success of such surgery.

On the role of the olivocochlear bundle in hearing: a case study

A young patient with normal pure-tone thresholds in both ears underwent a unilateral vestibular neurotomy in January 1992 to relieve severe vertigo ascribed to Ménière's disease. Evidence is provided that the whole vestibular nerve including the olivocochlear bundle (OCB) was sectioned. Just prior to the surgery, the patient was examined in several psychoacoustic tests involving mainly signal detection and selective attention. Over the next 20 months, he was reexamined in those same tests. The patient's ability to detect expected tones in the quiet (including audiograms) or in noise was the same as before the surgery. The one change was a marked improvement in the detection of unexpected signals in noise, which appears to reflect impaired selective attention. During those 20 months, new tests were also performed on discrimination, loudness, pitch, lateralization, and temporary threshold shift. On these tests, the only differences between the operated and unoperated ears concerned binaural diplacusis and loudness adaptation close to threshold, but these differences may well have been present prior to the surgery. Except with respect to what is probably selective attention, we uncovered no other clear role for the OCB in hearing. This outcome agrees with limited measurements on other patients, with their subjective reports, and with a number of published neurophysiological observations.