Imaging of Temporal Bone

Multidetector computed tomography has been the benchmark for visualizing bony changes of the ear, but has recently been challenged by cone-beam computed tomography. In both methods, all inner ear bony structures can be visualized satisfactorily with 2D or 3D imaging. Both methods produce ionizing radiation and induce adverse health effects, especially among children. In 3T magnetic resonance imaging, the soft tissue can be imaged accurately. Use of gadolinium chelate (GdC) as a contrast agent allows the partition of fluid spaces to be visualized, such as the bulging of basilar and Reissner's membranes. Both intravenous and intratympanic administration of GdC has been used. The development of positive endolymph imaging method, which visualizes endolymph as a bright signal, and the use of image subtraction seems to allow more easily interpretable images. This long-awaited possibility of diagnosing endolymphatic hydrops in living human subjects has enabled the definition of Hydropic Ear Disease, encompassing typical Meniere's disease as well as its monosymptomatic variants and secondary conditions of endolymphatic hydrops. The next challenge in imaging of the temporal bone is to perform imaging at the cellular and molecular levels. This chapter provides an overview of current temporal bone imaging methods and a review of emerging concepts in temporal bone imaging technology.

Application of metrics constructed from vibrotactile thresholds to the assessment of tactile sensory changes in the hands

Two tools for assessing tactile sensory disturbances in the hands have been constructed from mechanoreceptor-specific vibrotactile threshold shifts, and thresholds changes with time, and employed in a prospective study of forest workers (N=18). Statistically significant positive threshold shifts (i.e., reductions in sensitivity compared to the hands of healthy persons) were found in five hands at study inception (13.9%), and 15 hands at follow-up (41.7%). Four patterns of threshold shift could be identified, involving selectively the median and/or ulnar nerve pathways and/or end organs. Statistically significant positive threshold changes (i.e., reductions in sensitivity with time) were recorded in 69.4% of the hands over a five-year period, even though a majority of the workers remained symptom free. If the thresholds recorded from subjects not working with power tools are used to control for aging, lifestyle, and environmental factors during the five year period, then 40% of the remaining subjects are found to be experiencing work-related threshold changes in their hands. The ability of the threshold shift metric to predict the numbness reported by these subjects shows that it is closely associated with the tactile sensory changes occurring in their hands.

Contribution of the N-acetyltransferase 2 polymorphism NAT2*6A to age-related hearing impairment

BACKGROUND

Age-related hearing impairment (ARHI) is the most common sensory impairment in older people, affecting 50% of those aged 80 years. The proportion of older people is increasing in the general population, and as a consequence, the number of people affected with ARHI is growing. ARHI is a complex disorder, with both environmental and genetic factors contributing to the disease. The first studies to elucidate these genetic factors were recently performed, resulting in the identification of the first two susceptibility genes for ARHI, NAT2 and KCNQ4.

METHODS

In the present study, the association between ARHI and polymorphisms in genes that contribute to the defence against reactive oxygen species, including GSTT1, GSTM1 and NAT2, was tested. Samples originated from seven different countries and were combined into two test population samples, the general European population and the Finnish population. Two distinct phenotypes for ARHI were studied, Z(low) and Z(high), representing hearing in the low and high frequencies, respectively. Statistical analysis was performed for single polymorphisms (GSTM1, GSTT1, NAT2*5A, NAT2*6A, and NAT2*7A), haplotypes, and gene-environment and gene-gene interactions.

RESULTS

We found an association between ARHI and GSTT1 and GSTM1 in the Finnish population sample, and with NAT2*6A in the general European population sample. The latter finding replicates previously published data.

CONCLUSION

As replication is considered the ultimate proof of true associations in the study of complex disorders, this study provides further support for the involvement of NAT2*6A in ARHI.

Method for detecting small changes in vibrotactile perception threshold related to tactile acuity

Two metrics, expressing the change in mechanoreceptor-specific vibrotactile thresholds at a fingertip over a time interval of months or years, and the shift in threshold from the mean values recorded from the fingertips of healthy persons, have been constructed for thresholds measured from individual fingers. The metrics assume the applicability of the acute adaptation property of mechanoreceptors, which has been confirmed by thresholds obtained from 18 forest workers on two occasions, separated by 5 years. Hence, when expressed in decibels, both threshold changes and threshold shifts may be averaged at frequencies mediated by the same receptor population to improve precision. Differences between threshold changes at frequencies mediated by the same receptor population may be used to identify inconsistent subject performance, and hence potentially erroneous results. For this group of subjects, the threshold changes and threshold shifts at frequencies believed mediated by the slowly adapting type I (SAI) (4 and 6.3 Hz) and rapidly adapting type I (FAI) (20 and 32 Hz) receptors within each finger were correlated. In these circumstances, which may be expected to occur for some work-induced and systemic peripheral neuropathies, both threshold changes and threshold shifts may be summed over SAI and FAI receptors to improve precision, and hence the potential for interpretation.

Familial aggregation of tinnitus: a European multicentre study

INTRODUCTION AND AIM

Tinnitus is a common condition affecting approximately 20% of the older population. There is increasing evidence that changes in the central auditory system following cochlear malfunctioning are responsible for tinnitus. To date, few investigators have studied the influence of genetic factors on tinnitus. The present report investigates the presence of a familial effect in tinnitus subjects.

METHODS

In a European multicentre study, 198 families were recruited in seven European countries. Each family had at least 3 siblings. Subjects were screened for causes of hearing loss other than presbyacusis by clinical examination and a questionnaire. The presence of tinnitus was evaluated with the question "Nowadays, do you ever get noises in your head or ear (tinnitus) which usually last longer than five minutes". Familial aggregation was tested using three methods: a mixed model approach, calculating familial correlations, and estimating the risk of a subject having tinnitus if the disorder is present in another family member.

RESULTS

All methods demonstrated a significant familial effect for tinnitus. The effect persisted after correction for the effect of other risk factors such as hearing loss, gender and age. The size of the familial effect is smaller than that for age-related hearing impairment, with a familial correlation of 0.15.

CONCLUSION

The presence of a familial effect for tinnitus opens the door to specific studies that can determine whether this effect is due to a shared familial environment or the involvement of genetic factors. Subsequent association studies may result in the identification of the factors responsible. In addition, more emphasis should be placed on the effect of role models in the treatment of tinnitus.

The use of hearing protectors among forest, shipyard and paper mill workers in Finland--a longitudinal study

From 1953 to 1995 the usage rate of hearing protective devices (HPD) was tracked at a paper mill, a shipyard, and in selected areas of forestry work. For each work period, observations were made of HPD use among workers. In the paper mill, the usage rate increased steadily from 1965. In 1990, 39% of workers used HPDs full-time. At the shipyard, the usage rate remained low up to the mid-1980s, but thereafter the proportion of full-time users rose to 70%. A similar trend was noted in forest workers, with the full-time use at 97% by the 1990s. Due to the increased usage rate in all measured industries, the mean effective noise level at the ear has decreased to below 85 dB.

Postural instability in Meniere's disease

In order to characterize the postural instability by duration of Meniere's disease (MD) we present the results of 180 MD patients tested on posturography. The duration of the disease varied from 4 weeks to 36 years. The patients were clinically examined and they had filled a questionnaire concerning their symptoms. Postural instability was examined by a force platform posturography and the results are expressed as sway velocities (SV). There was no statistically significant difference in the mean SV between groups of different duration of MD. The number of the patients with normal eyes open SV declined by duration of the illness from 73% to 38% but the decline was not statistically significant. The mean age in the different duration groups of MD varied from 47 to 61 years. In general 58% of the patients had their eyes open SV in normal range and 55% when measured eyes closed. When examining the SV between the 4 different hearing stages of MD we found that those belonging into the group III (pure tone average [PTA] 41–70 dB) had significantly higher eyes open and eyes closed SV's than the patients in the group I (PTA under 25 dB).

Can low frequency sound stimulation during posturography help diagnosing possible perilymphatic fistula in patients with sensorineural hearing loss and/or vertigo?

Perilymphatic fistula (PLF) is often difficult to diagnose because of the similar symptomatology, such as vertigo, tinnitus and hearing loss, which is found in several inner ear diseases. We attempted to correlate a positive result of low frequency sound (LFS) stimulation tests in posturography with the presence or absence of a PLF confirmed by transtympanic endoscopy in 209 patients with various inner ear diseases (Meniere's disease ( n=128), vestibulopathy ( n=41), cochleopathy ( n=28) and sudden deafness ( n=12). LFS provoked unsteadiness in posturography without PLF in 24 patients with Meniere's disease, in 5 patients with vestibulopathy, in 3 patients with cochleopathy and in 2 patients with sudden deafness. In one patient, tympanoscopy revealed fistula in the round window membrane that was covered with a fibrinous layer. In four cases there was abnormal light reflex in the round window but without PLF. In eight cases, Hennebert's sign was present with nystagmus, without PLF. We conclude that pathological responses to the LFS test in posturography can also be encountered in other inner ear diseases without PLF.

Postural instability in Meniere's disease

In order to characterize the postural instability by duration of Meniere's disease (MD) we present the results of 180 MD patients tested on posturography. The duration of the disease varied from 4 weeks to 36 years. The patients were clinically examined and they had filled a questionnaire concerning their symptoms. Postural instability was examined by a force platform posturography and the results are expressed as sway velocities (SV). There was no statistically significant difference in the mean SV between groups of different duration of MD. The number of the patients with normal eyes open SV declined by duration of the illness from 73% to 38% but the decline was not statistically significant. The mean age in the different duration groups of MD varied from 47 to 61 years. In general 58% of the patients had their eyes open SV in normal range and 55% when measured eyes closed. When examining the SV between the 4 different hearing stages of MD we found that those belonging into the group III (pure tone average [PTA] 41-70 dB) had significantly higher eyes open and eyes closed SV's than the patients in the group I (PTA under 25 dB).

Impulse noise and risk criteria

Impulse noise causes evidently more severe hearing loss than steady state noise. The additional effect of occupational impulse noise on hearing has been shown to be from 5 to 12 dB at 4 kHz audiometric frequency. Reported cases for compensated for hearing loss are prevalent in occupations where noise is impulsive. For impulse noise two measurement methods have been proposed: the peak level method and energy evaluation method. The applicability of the peak level method is difficult as even the recurrent impulses have different time and frequency characteristics. Various national risk criteria differ from international risk criteria. In France the maximum A-weighted peak level is 135 dB, and in the United Kingdom the C-weighted peak sound pressure is limited to 200 Pa (140 dB). This criterion of unweighted 200 Pa (140 dB) is used in European Union (EU) directive 86/188 and ISO 1999-1990 regardless of the number of impulses. The American Conference of Governmental Industrial Hygienists (ACGIH) has recommended that no exposure in excess of a C-weighted peak sound pressure level of 140 dB should be permitted. At work places these norms do not cause any practical consequences since the impulses seldom exceed 140 dB peak level. In several occupations the impulses are so rapid that they contribute only a minimal amount to the energy content of noise. These impulses can damage the inner ear even though they cause reduced awareness of the hazard of noise. Based to the present knowledge it is evident that there is the inadequacy of the equal energy principle in modelling the risk for hearing loss. The hearing protectors attenuate industrial impulse noise effectively due to the high frequency contents of impulses. Directive regarding the exposure of workers to the risks arising from noise requires that in risk assessment attention should be paid also to impulsive noise. So far there is no valid method to combine steady state and impulse noise. A statistical method for the measurements of industrial impulse noise is needed to get a preferably single number for risk assessment. There is an urgent task to develop risk assessment method and risk criteria for impulsive noise to meet the requirements of the upcoming European Union noise directive.

Role of transtympanic endoscopy of the middle ear in the diagnosis of perilymphatic fistula in patients with sensorineural hearing loss or vertigo

BACKGROUND

The diagnosis of perilymphatic fistula (PLF) is often difficult, and therefore the condition can be overlooked. Tympanoscopy presents an alternative procedure for visualising the middle ear anatomy, and it may help to diagnose PLF.

AIM

The aim of this study was to evaluate the use of middle ear endoscopy in establishing the diagnosis of PLF and in defining its incidence in patients with sensorineural hearing loss and/or vertigo and tinnitus.

SUBJECTS AND METHODS

Two hundred and sixty-five patients (22-80 years of age, mean 48 years) were prospectively and consecutively referred for middle ear examination with tympanoscopy. Tympanoscopy was performed using endoscopes with visual angles of 5 and 25 degrees and an outer diameter of 1.7 mm. The round window niche (with its secondary membrane), the oval window with a stapes superstructure, a part of the facial recess and the area in the fissula ante fenestram were examined and video-recorded.

RESULTS

For 1 patient, tympanoscopy revealed fistula in the round window membrane that was covered with a fibrinous layer. In 4 cases abnormal mucosal shining appeared in the round window, but no PLF was present. In 7 cases the tympanic cavity could not be visualised because of the adhesive tympanic membrane, abnormal anatomy or the prominent exostoses of the external ear canal. In 6 cases a postendoscopic middle ear infection was found. No permanent tympanic membrane perforation occurred in any of the patients in this study.

CONCLUSIONS

Tympanoscopy is a rapid examination tool with which to verify certain areas of the middle ear anatomy, but it is of limited value for ruling out the presence of PLF.

Age and noise-induced hearing loss

The purpose of the study was to evaluate the effect of noise, age and confounders in noise-induced hearing loss (NIHL). Information about work exposure, the use of hearing protective devices, audiogram, environmental and biological factors was collected from 406 paper mill workers exposed to noise levels of 91-94 dB(A), 124 forest workers exposed to noise levels of 96-99 dB(A) and 176 shipyard workers exposed to noise levels 95-97 dB(A). In addition to noise exposure, we collected the following confounders: smoking habits, serum cholesterol, systolic or diastolic blood pressure and use of analgesics. Subjects were classified based on median values, into high- and low-risk groups. The confounders were a significant source of hearing loss (HL) in younger and elderly groups of subjects, serum cholesterol level being the most important. In risk analysis the confounders partly masked the effects of noise in the development of HL. For subjects with less than two confounders, occupational noise exposure determined the development of NIHL. As the number of confounders increased, the noise exposure was overruled by these factors in the development of HL. In analysis where the subjects were matched with pairs by age, exposure, blood pressure and serum cholesterol level, the elderly subjects were more susceptible to NIHL than younger subjects. Factors independently but causally related to age were important in the development of NIHL among workers exposed to noise levels below 98 dB(A).

Hearing loss and tinnitus in Meniere's disease

OBJECTIVES

To characterize hearing loss, tinnitus and associative factors in Meniere's disease.

METHODS

From our vertigo database consisting of 1356 patients, we retrieved 243 patients with Meniere's disease (MD).

RESULTS

Hearing loss was the initial symptom in 13% of cases. Altogether 64% (n=133) of the patients stated that their hearing was reduced during the vertigo attack. The hearing deteriorated more likely during the vertigo attack if the vertigo attack was very intense [r(206)=0.19]. Tinnitus was the initial symptom in 5% of cases. The tinnitus was mild in 38% (n=90), moderate in 32% (n=76) and severe in 30% (n=72) of patients. The intensity of tinnitus correlated with the occurrence of drop attacks [r(237)=0.29], vertigo provoked by head positioning [r(235)=0.25], by physical activity [r(230)=0.33], or by pressure changes [r(239)=0.27].

CONCLUSION

Prolonged disease causes deterioration of hearing. Intense tinnitus is common in MD and is more often seen in late stage of the disease.

Postural control as assessed with virtual reality

We studied the use of virtual reality technology as a stimulus in balance examinations. A pilot study was made using a small group of healthy subjects to investigate the effect of alcohol and virtual reality stimulus on the subjects' balance. The tests showed that blood alcohol concentration accounted for almost 50% of the increased lateral body sway velocity. The new stimulus technique based on virtual reality technology seems to be effective and flexible for postural investigations.

Classification of patients on the basis of otoneurological data by using Kohonen networks

Machine learning methods such as neural networks, decision trees and genetic algorithms can be useful to aid in the classification of patients. We tested Kohonen artificial neural networks, which are known to be effective for classification tasks. Our sample included patients with six different diseases. The Kohonen network algorithm recognized the four largest groups reliably, but the two smallest groups were too small for the method. Neural networks seem to be promising for the computer-aided classification of otoneurological patients provided that the number of patients used is sufficiently large.

Cochlear blood flow measurement in patients with Ménière's disease and other inner ear disorders

To identify an eventual vascular aetiology in different diseases with sensorineural hearing loss (SNHL), the cochlear blood flow (CoBF) was measured using laser Doppler flowmetry (LDF) in 69 patients with Ménière's disease (MD), 38 patients with progressive SNHL and 8 patients with sudden deafness. The mean CoBF amplitude at rest was 0.70 mV (SD 0.25) for patients with MD, 0.66 mV (SD 0.21) for patients with SNHL and 0.69 mV (SD 0.23) for those with sudden deafness. No statistically significant difference was observed between the groups with respect to the CoBF amplitudes at rest or during the Valsalva manoeuvre. There was a statistically significant correlation (r = -0.4, p < 0.05) between the hearing level and CoBF amplitude in the SNHL group only. It is concluded that the reduction in vascular flow may not be the main aetiological factor in Ménière's disease or sudden deafness. In SNHL the correlation of hearing level with the level of the LDF amplitude can be secondary to the progression of hearing loss.

Towards virtual reality stimulation in force platform posturography

We developed a stimulation technique on the basis of virtual reality methods for balance investigation performed in balance laboratories of otorhinolaryngological clinics and institutes of occupational health. Such a stimulation technique is greatly progressive in the sense that by creating virtual moving views and "virtual worlds" inside which the subject is located it is possible to make effective stimuli that would be very difficult or even impossible to set in any real environment. We tested our system on healthy subjects and found out that this kind of virtual reality stimulation system is very useful for balance analysis.

Causes of persistent postoperative headache after surgery for vestibular schwannoma

Our aim was to elucidate the aetiology of persistent postoperative headache, a common sequel for several years after vestibular schwannoma surgery through the retrosigmoid approach. Twenty-seven patients with reported major postoperative headache were tested for vestibular responses and cervico-collic reflexes. The role of local anaesthesia injected into the neck muscle insertions or around the occipital nerves was evaluated. Sixteen patients operated on for vestibular schwannoma, but without headache, and 12 healthy volunteers served as control groups. Vestibular responses and cervico-collic reflexes deteriorated equally in the patients regardless of whether or not they had a postoperative headache. Local anaesthesia did not alter the results. The posturography results were increased among both patient groups. Sumatriptan alleviated pain in nine patients and abolished it completely in one out of these nine patients. Vestibular imbalance or abnormal activation of neck muscles do not explain postoperative headache. Occipital nerve entrapment or neuralgia explains the headache in a few patients. The relatively pronounced sumatriptan effect may, however, suggest a trigeminal nerve mediated cause for postoperative headache.

Application of artificial intelligence in audiology

In this paper, machine learning methods based on artificial intelligence theory are applied to the computer-aided decision making of some otoneurological diseases, for example Ménière's disease. Three methods explored are decision trees, genetic algorithms and neural networks. By using such a machine learning method, the decision-making program is trained with a representative training set of cases and tested with another set. The machine learning methods are useful also for our otoneurological expert system, One, which is based on a pattern recognition approach. The methods are able to differentiate most of the cases tested between the six diseases included, provided that a sufficiently large training set is available.

Using decision tree induction to model oculomotor data

Decision tree induction is a machine learning method used to generate classification models from data sets. Numerous decision trees were constructed to examine relationships between oculomotor test parameters and lesion sites in a data set containing cases with operated cerebello-pontine angle tumour, operated hemangioblastoma, infarction of cerebello-brainstem and Ménière's disease, and control subjects. The aim was to find useful parameter combinations with discriminatory power. Decision trees constructed using both pursuit eye movements and saccadic eye movements yielded the best classification results. This is reasonable: oculomotor test results vary according to the site of the lesion and so the performance ability of subjects has to be taken into account in the classification. The decision tree program was able to generate classification models from the oculomotor data set. Generated decision trees were intelligible and can be utilized in physicians' research work.

Autosomal dominant midfrequency hearing impairment

At present, 48 different gene loci have been localised and nine gene mutations have been characterised for non-syndromic hearing impairment. We have identified a large five-generation family with mid-and high-frequency hearing impairment. Family members were considered to be affected only if they had bilateral sensorineural hearing loss below the 90th percentile of an age and sex-dependent control audiometric curve of ISO class B. The inheritance of hearing impairment was autosomal dominant. Of seven affected individuals, six were females and one was male. The hearing loss among affected family members was bilateral, sensorineural and varies from mild to moderate. The type of audiogram was U-shaped. Genetic linkage studies are in progress and our preliminary data show exclusion in chromosome 6, chromosome 11 and chromosome 19 in already known loci for midfrequency hearing impairment. This means, we are mapping a novel locus for autosomal dominant midfrequency hearing impairment.

Effects of peak levels and number of impulses to hearing among forge hammering workers

The purpose of the study was to (1) compare measured and estimated hearing loss among forge hammering workers by applying models for risk assessment based on measurements of impulse noise, and (2) model the hazardous effects of impulse noise on hearing. Noise exposure and hearing loss among forge hammering workers were studied at two forge workshops of an automobile company, where the equivalent sound pressure levels (104 and 105 dB) were the same, but the peak levels and degree of impulsiveness were significantly different. The hearing threshold levels of selected groups of workers (97 and 235 workers) were determined. Comparison between the measured and expected hearing losses defined according to the ISO standard revealed 2 dB difference in excessive hearing loss (1 dB and 3 dB for the workers of workshop 1 and 2, respectively). The excessive hearing loss equals an increase of 3.5 years of exposure. The hearing loss of workers exposed to low impulsive noise could be predicted well using ISO 1999-1990. The hearing loss of workers exposed to high impulsive noise correlated significantly with the peak levels and the number of impulses in combination.

Basic fibroblast growth factor in nasal polyps immunohistochemical and quantitative findings

Basic fibroblast growth factor (bFGF) is a mediator with potent mitogenic properties. Increased amounts of this mediator have been demonstrated in damaged lung tissue, and it has been suggested to increase the healing of gastro-duodenal ulcers. In order to quantify the amounts and document the localization of bFGF in nasal polyps, polyp tissue from 12 patients undergoing polypectomy was analyzed by ELISA and immunohistochemistry. Mucosa from the inferior turbinate was analyzed in the same manner for comparison. The amount of bFGF detected in polyp tissue was significantly higher than that in turbinate mucosa. The amount of bFGF was also significantly higher in the group of patients with high degree of inflammation. The immunohistochemical findings demonstrated abundant bFGF activity mainly in the glandular acini, in the epithelium, in infiltrating inflammatory cells and in the vessel walls. We propose that bFGF may contribute in a significant way to the formation of nasal polyps.

Short-lasting drop attacks in Meniere's disease

OBJECTIVES

To study the vertigo attacks known as Tumarkin attacks or drop attacks (DA). DA are characterized by sudden loss of balance with or without falls but with preserved consciousness, and they are supposedly triggered by changes in the otolith function of Meniere's disease (MD).

STUDY DESIGN AND SETTING

Data from 243 consecutive MD patients were collected into a database of an otoneurologic expert system.

RESULTS

DA was experienced by 72% (n = 173) of the patients with MD. It correlated with visually provoked vertigo. Gait difficulties, tinnitus, and anxiety were more common in the DA group. Long lasting vertigo attacks were more frequently provoked in the DA subjects by physical strain (58% vs 14%), head movements or changes in head position (71% vs 48%), pressure changes (54% vs 12%), or rapid movements in visual surroundings (65% vs 35%) than in the non-DA subjects.

CONCLUSION

DA are common in MD patients. The abrupt occurrence of DA make them poorly tolerated.

SIGNIFICANCE

DA are more common in advanced MD.

Evaluating training data suitability for decision tree induction

Decision tree induction, as well as other inductive learning methods, requires training data of high quality to be able to generate accurate and reliable classification models. Example cases should form a representative sample from the application area, and the attributes used to describe example cases should be relevant and adequate for the classification task to be solved. In this paper, measures of the strength of association and an entropy-based approach have been used to assess the quality of the training data. Studied classification tasks related to three otological data sets: a conscript data set, a vertigo data set, and a postoperative nausea and vomiting data set. The paper suggests that the studied approaches give some guidelines about the quality of the training data, but other approaches are also needed to guide training data building.

Tinnitus and vestibular schwannoma surgery

The aim of this study was to evaluate the effect of operation on tinnitus in vestibular schwannoma (VS) patients. Altogether, 251 VS patients who underwent surgery during the years 1979 to 1993 at Helsinki University Central Hospital were included in the study. Information on preoperative tinnitus was collected from previously acquired data and postoperative tinnitus was evaluated. Preoperatively, 62.6% of the patients had experienced tinnitus. Of those with preoperative tinnitus, 47.4% also had it postoperatively, but of those 93 patients without preoperative tinnitus, 39.8% had tinnitus postoperatively. Tinnitus is one of the primary symptoms of VS, together with hearing impairment and disequilibrium. The risk of postoperative tinnitus is almost 40%, and with preoperative tinnitus, the risk is 7.6% higher. In the majority tinnitus was not related to the surgery. Only a few patients had severe problems with tinnitus; difficulty understanding speech was the major complaint.

Laser-assisted myringoplasty--technical aspects

At lower power, lasers fuse collagen fibres and weld tissues. Welded collagen fibres make a solid bond and allow tissue growth along the bonded edges. Our aim was to study applicability of lasers in myringoplasty. We used a KTP-532 laser in outpatient myringoplasty. The laser beam was delivered through a micromanipulator connected to a microscope or through a 200-400-micron silica fibre. The perichondrium was used for transplantant and harvested from the tragus. The margins of the perforation in the eardrum were evaporated, with the laser operating in a continuous mode at 2-4 W. The middle ear was filled with gelfilm to provide support for the transplant. The perichondrium was placed under the margins of the tympanic membrane and lazed at low power (0.2-1.5 W) in continuous mode. In pale tissues, venous blood, methylene blue or fluorescein was used to enhance the tissue admittance of laser energy. Surgical failures were linked to thermal tissue damage due to excessive energy during lazing. In two cases, visibility via microscope into the anterior edge was not complete and the transplantant did not adhere in the relatively limited area. One patient had epidermal growth under the tympanic membrane and developed local cholesteatoma. Laser-assisted myringoplasty provides several advantages over traditional myringoplasty: it is minimally invasive, no manipulation of the ossicles is needed and it is convenient in anterior perforations, where it can be done endoscopically. We prefer a fibre delivery system to a micromanipulator, as lazing with endoscopes is possible and thermal damage is easier to prevent.

Lyme borreliosis, an etiological factor in sensorineural hearing loss?

The incidence of Lyme borreliosis was studied prospectively in 165 patients with acute idiopathic sensorineural hearing loss. The prevalence of positive levels of antibodies against Borrelia burgdorferi was sixfold higher in patients with sensorineural hearing loss than in the general population in Finland. Four patients fulfilled the criteria for Lyme borreliosis. No specific risk factors were found with which to predict the occurrence of Lyme borreliosis among patients with hearing loss. In logistic regression modeling the poor outcome of hearing loss was best explained by advanced age, high-frequency or flat-type hearing loss, and absence of positive levels of antibodies against B. burgdorferi. Although the causal relationship between Lyme borreliosis and sensorineural hearing loss is difficult to verify, we suggest that Lyme borreliosis is a rare but potentially treatable cause of sudden deafness. We propose that in endemic areas antibodies against Lyme borreliosis should be determined in patients with idiopathic sensorineural hearing loss.

Vestibular schwannoma surgery and headache

The aim of the study was to evaluate aetiological factors for postoperative headache after vestibular schwannoma (VS) surgery with respect to asymmetric activation of vestibular reflexes. After surgery, 27 VS patients with persistent postoperative headache, 16 VS patients without headache and 9 healthy controls were examined. The vestibular, cervicocollic and cervicospinal reflexes were evaluated to study whether asymmetric activation of vestibular reflexes could cause headache. The effect of neck muscle and occipital nerve anaesthesia and the effect of sumatriptan on headache were also evaluated. The vestibular function of VS patients with headache did not differ from that of VS patients without headache, but was abnormal when compared to that of normal controls. The cervicospinal and cervicocollic reflexes did not differ in the patient groups. Injection of lidocaine around the operation scar gave pain relief to two patients, and one of them had occipital nerve entrapment. Infiltration of lidocaine deep in the neck muscles in the vicinity of the C2 root did not alleviate headache, but caused vertigo. Nine patients with musculogenic headache got pain relief from supportive neck collars, and two patients with cervicobrachial syndrome got pain relief from manual neck traction. The study shows that asymmetric activation of cervicocollic reflexes does not seem to be the reason for headache. Headache seems to be linked to neuropathic pain, allegedly caused by trigeminal irritation of the inner ear and the posterior fossa, which has recently been linked to vascular pain.

Basic fibroblast growth factor (bFGF) in saliva--physiological and clinical implications

Basic fibroblast growth factor (bFGF) has significant properties in wound healing, tissue regeneration and ulcer repair of the upper digestive tract. The purpose of the present study was to identify and analyse factors affecting the concentration of bFGF in saliva from healthy human individuals. A commercially available enzyme-linked immunosolvent assay kit (ELISA) was used for the analyses of bFGF in saliva. In total, 56 samples were collected from 28 healthy subjects, 15 male and 13 female. Determination of bFGF was performed by spectrophotometer (wavelength 490 nm). bFGF was detected in all samples. Mean bFGF concentration was 0.87 pg/ml (SD 0.49) and the concentration ranged from 0.3 to 1.9 pg/ml. In subjects aged 22 to 49 years, no age-dependent variation in bFGF was present, females did not differ from males, and no difference was evident between European and Asian subjects. Smokers had significantly higher saliva concentrations of bFGF than non-smokers. Since bFGF, together with other growth factors, is involved in wound healing and tissue repair, we suggest that bFGF in saliva is involved in the reparative processes of mucous membranes.

Vestibular schwannoma mimicking Ménière's disease

We retrieved information on 128 patients with vestibular schwannoma (VS) and 243 patients with Ménière's disease (MD) from the database of the otoneurologic expert system (ONE). The patients filled in a questionnaire concerning their symptoms, earlier diseases, accidents and tobacco and alcohol use. This information was then integrated with results of audiometric, otoneurologic and imaging studies. Forty-nine (38%) of the VS patients had the full triad of vertigo, hearing loss and tinnitus. The vertigo mimicked that in MD in 18 (14%) patients. The mean age of these patients was 48 years. There were 7 men and 11 women. The tumour was small (< 2 cm) in eight patients and medium-sized (2-4 cm) in seven patients. The mean attack duration in these 18 patients ranged from 5 min to 4 h. The attacks most commonly (69%) occurred only once or twice a year. Their intensity was moderate. Half of the patients had spontaneous nystagmus. Caloric asymmetry > 25% was detected in 61% of the patients. Tinnitus in these patients was mostly (49%) mild. Intense tinnitus was present only in 12% of patients. Headache was present in 25% of these patients.

Betahistine effects on cochlear blood flow: from the laboratory to the clinic

The development of laser Doppler flowmetry techniques has contributed greatly to the study of cochlear blood flow (CBF). In animal models, intravenous betahistine dihydrochloride clearly increased CBF in a dose-dependent manner. This effect was greater in the cochlear vasculature than in the systemic vascular bed. The effects of betahistine were blocked by the alpha 2-antagonist idazoxan, thus suggesting an interaction between histaminergic and presynaptic adrenergic receptors. This was further supported by studies investigating the effects of electrical stimulation on CBF. Local (round window membrane) application of betahistine did not affect CBF, but had a non-specific effect on cochlear electrophysiology. This indicates that the receptors for betahistine vascular effects in the inner ear are most likely located in the modiolar artery. More recently, laser Doppler flowmetry techniques have been applied to human subjects. It has been shown that intratympanic application of adrenaline affects CBF and that this blood flow is under vigorous sympathetic control. Electrical stimulation has also been used to obtain measures of dynamic responsiveness in human subjects. This results in an increase in CBF, which is dependent on the intensity of the stimulation. Preliminary evidence indicates that this procedure can provide a standardized measure of the dynamic properties of CBF and may provide a means to differentially identify patients with compromised vasculature.

Is hearing preservation worthwhile in vestibular schwannoma surgery?

The purpose of the study was to evaluate the usefulness of hearing preservation in vestibular schwannoma (VS) surgery. Hearing preservation was attempted in 123 of 383 patients operated on during the years 1979 to 1993 at Helsinki University Hospital. Hearing was preserved in 47 cases. Pure-tone averages (PTA) better than 30 dB were found in 12 cases postoperatively. Seventy percent of the patients rated their hearing preservation as valuable or very valuable. Only 8% did not find hearing preservation useful. Postoperatively, tinnitus was present in 62% of the patients, and it was a moderate problem in only 23% of the patients. In only one subject was the tinnitus a handicap that reduced the quality of life. Based on these experiences, we encourage surgeons to continue efforts to preserve hearing in VS surgery.