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.

Neurotrophic factor intervention restores auditory function in deafened animals

A primary cause of deafness is damage of receptor cells in the inner ear. Clinically, it has been demonstrated that effective functionality can be provided by electrical stimulation of the auditory nerve, thus bypassing damaged receptor cells. However, subsequent to sensory cell loss there is a secondary degeneration of the afferent nerve fibers, resulting in reduced effectiveness of such cochlear prostheses. The effects of neurotrophic factors were tested in a guinea pig cochlear prosthesis model. After chemical deafening to mimic the clinical situation, the neurotrophic factors brain-derived neurotrophic factor and an analogue of ciliary neurotrophic factor were infused directly into the cochlea of the inner ear for 26 days by using an osmotic pump system. An electrode introduced into the cochlea was used to elicit auditory responses just as in patients implanted with cochlear prostheses. Intervention with brain-derived neurotrophic factor and the ciliary neurotrophic factor analogue not only increased the survival of auditory spiral ganglion neurons, but significantly enhanced the functional responsiveness of the auditory system as measured by using electrically evoked auditory brainstem responses. This demonstration that neurotrophin intervention enhances threshold sensitivity within the auditory system will have great clinical importance for the treatment of deaf patients with cochlear prostheses. The findings have direct implications for the enhancement of responsiveness in deafferented peripheral nerves.

Functional and morphological effects of styrene on the auditory system of the rat

The effect of inhaled styrene on the structure and function of the auditory organ of the male Wistar rat was studied. The animals were exposed either to 600, 300 or 100 ppm styrene (12 h/day, 5 days/week, for 4 weeks). Auditory sensitivity was tested prior to and after the exposure by auditory brain stem audiometry (ABR) at frequencies of 1.0, 2.0, 4.0 and 8.0 kHz. Inner ear morphological changes were studied by light- and electron-microscopy. Exposure to 600 ppm styrene caused a 3 dB hearing loss only at the highest test frequency (8 kHz). Quantitative morphological analysis of cochlear hair cells (cytocochleograms) showed that 600 ppm styrene caused a severe outer hair cell (OHC) loss particularly in the third OHC row of the upper basal and lower middle coil. The inner hair cells were usually intact. Exposure to lower styrene concentrations (100 and 300 ppm) caused no unequivocal functional deficit or hair cell damage. We conclude that there appears to be a concentration threshold for styrene ototoxicity in rats (between 300 and 600 ppm).

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.

Nearest neighbour classification of otoneurological data

We studied the nearest neighbour classification of patient cases with benign positional vertigo, Meniere's disease, sudden deafness, traumatic vertigo, vestibular neuritis, and vestibular schwannoma. The classification results were compared to the inference results obtained by an otoneurological expert system ONE whose inference mechanism somewhat resembles the classical nearest neighbour method. With respect to the predictive accuracy, the classification results of these two systems agreed. The best predictive accuracy for the expert system ONE was 79.7% and for the nearest neighbour method 80.5%. However, differences in the true positive rates for sudden deafness, traumatic vertigo, vestibular neuritis, and vestibular schwannoma were found. The nearest neighbour classification results will be used in the refinement of ONE's knowledge base.

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.

Hereditary hearing loss--the role of environmental factors

A large family with mid onset sensorineural hearing loss (HL) was used to study the effect of environmental factors on progression HL. Data from five-generations of one family were traced and 104 living members were included in the study. Audiograms were measured for 60 family members. We used an expert program to study the individual risk factors, which included the known risk factors for sensorineural HL. The pattern of inheritance in this HL family was autosomal dominant and 22 individuals were affected. The HL among affected individuals was symmetrical and varied from mild to severe. The mean age at onset of HL was 22 years. The mean deterioration of hearing at 2 kHz frequency was 1 dB/year. In the risk analysis the use of NSAID-analgetics and military noise exposure correlated with HL. There was no correlation between occupational and free time noise-exposure and HL. Analgetics may aggravate the HL in subjects with inherited HL. This type of genetic lesion is new and is not in those chromosomal areas already documented in the literature.

Vertigo in patients with benign paroxysmal positional vertigo

We retrieved information on 59 patients, 19 men and 40 women, with benign paroxysmal positional vertigo (BPPV) from the database of the otoneurologic expert system (ONE). The original number of patients was greater, but we excluded all those with hearing loss of any origin. 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. The mean age at onset of symptoms was 44 years. Most patients had had vertiginous spells for < 1 year. None of the patients had hearing loss. Tinnitus was experienced by 32% of patients, and these patients experienced more anxiety than the others [r(53) = 0.40, p < 0.01]. The mean duration of the vertigo attacks ranged from a few seconds to 5 min, and they were fairly mild (26%) or moderate (41%) in intensity. The attacks were perceived as more intense if vertigo was rotational [r(54) = 0.60, p < 0.01] or if it was accompanied by nausea [r(58) = 0.42, p < 0.01]. Patients with headache had more intense attacks [r(58) = 0.36, p < 0.01]. The vertigo attacks occurred in spells; patients had several attacks a week (23%) or during the course of 1 day (52%). The vertigo was rotational in 80% of patients, and 47% experienced a floating sensation. The floating vertigo was most often provoked by pressure changes [r(54) = 0.41, p < 0.01] or changes in visual surroundings [r(54) = 0.52, p < 0.01].