Biomedical subjects

Ilmari Pyykkö

Publications and source records attributed to Ilmari Pyykkö.

10 recordsLinked to original sources

PubMed2003

The ototoxic interaction of styrene and noise.

The interaction between noise and 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 ppm, 300 ppm or 100 ppm styrene (12 h/day, 5 days/week, for 4 weeks) alone or in combination with a simultaneous 100-105 dB industrial noise stimulant. Auditory sensitivity was tested by auditory brainstem audiometry at 1.0, 2.0, 4.0 and 8.0 kHz frequencies. Inner ear changes were studied by light microscopy. Exposure to 600 ppm styrene alone caused a 3 dB hearing loss only at the highest test frequency (8 kHz). Quantitative morphological analysis of cochlear hair cells (cytocochleograms) showed a severe outer hair cell (OHC) loss particularly in the third OHC row of the upper basal and lower middle coil. Exposure to noise alone caused only a mild hearing loss (2-9 dB), and only an occasional loss of OHCs (<1% missing). Exposure to the combination of noise and 600 ppm styrene caused a moderate flat hearing loss of 23-27 dB. The cytocochleograms showed a more severe damage of the OHCs than after exposure to 600 ppm styrene alone. The inner hair cells were found to be destroyed in some animals in the upper basal turn only after the combination exposure. Only in combination with noise exposure, the lower styrene concentrations (100 and 300 ppm) induced a hearing loss which was equivalent to that seen after exposure to noise alone. We conclude that: (1) There is an ototoxic interaction between styrene and noise. (2) Synergism is manifested only if styrene is applied in concentrations above the critical level (between 300 and 600 ppm in this study).

Animals↗

PubMed2002

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.

Acoustic Stimulation↗

PubMed2002

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).

Administration, Inhalation↗

PubMed2002

Protection and treatment of sensorineural hearing disorders caused by exogenous factors: experimental findings and potential clinical application.

During the last decade, there have been numerous interesting findings regarding the roles of neurotrophins, nitric oxide, reactive oxygen species, glutamate receptors, and shock protein in the auditory system. These findings have provided a scientific basis for the development of techniques to protect the auditory system against trauma as well as for the treatment of peripheral hearing disorders. This review focuses on recent advances in experimental prevention and treatment of hearing impairment which are expected to be of clinical value in the near future. Viral vector and non-viral vector gene therapy and transplantation of stem cells are discussed as potential treatments of irreversible sensorineural inner ear damage.

Animals↗

PubMed2002

Generating decision trees from otoneurological data with a variable grouping method.

When medical data sets are modelled by machine learning methods, wealth of variables may be available. This paper deals with variable selection for decision tree induction in the context of two otoneurological data sets: vertigo data, and postoperative nausea and vomiting data. First, a variable grouping method based on measures of association and graph theoretic techniques was used to gain insight into data. Then, representations of learning data were defined using the information from discovered variable groups, and decision trees were generated. The use of variable grouping method was beneficial by revealing interesting associations between variables and enabling generation of accurate and reasonable decision trees that modelled the application areas from different viewpoints.

Data Collection↗

PubMed2002

Use of electrocochleography for assessing endolymphatic hydrops in patients with Lyme disease and Ménière's disease.

From an otological standpoint, Lyme disease can manifest itself as Ménière's disease both clinically and electrophysiologically. The aim of this study was to describe the findings of routine clinical, auditory and vestibular tests in patients with Ménière's and Lyme disease and to use electrocochleography (ECoG) to assess the presence of endolymphatic hydrops (EH) in both diseases. Transtympanic ECoG was performed in 91 patients with Ménière's disease and in 11 patients with confirmed Lyme disease. In both diseases the majority of patients had more than one complaint. There was one case with isolated hearing loss in the Lyme disease group. Typical clinical manifestations of Ménière's disease (vertigo, sensorineural hearing loss and tinnitus) were found in 6/11 patients (54.5%) in the Lyme disease group. The ECoG results indicated that there were 65/91 patients (71.4%) with Ménière's disease and 5 patients (45.5%) with Lyme disease who presented with EH. No statistically significant difference was found between the incidence of different symptoms of Ménière's and Lyme disease. On the basis of these results, patients with Lyme disease should undergo careful examination and investigation, especially in endemic regions. The presence of EH does not exclude the presence of infection with borreliosis as a cause of Ménière's disease-like symptoms.

Adult↗

PubMed2002

Basic fibroblast growth factor in human saliva decreases with aging.

OBJECTIVE: Basic fibroblast growth factor (bFGF) has significant properties in wound healing and tissue repair and is suggested to be of importance for the maintenance of mucosal integrity in the upper digestive tract. The purpose of the present study was to identify any age-dependent variations in the concentration of bFGF in human saliva. STUDY DESIGN: Nonprospective, cross-sectional pilot study. METHODS: The study was based on findings from 182 healthy volunteers with ages ranging from 4 to 97 years. Mixed saliva samples were obtained by drooling. The saliva concentration of bFGF was determined with a commercially available enzyme-linked immunosorbent assay kit. RESULTS: The mean saliva concentration of bFGF was 0.41 pg/mL with no gender differences. In persons aged 4 to 19 years, the mean concentration was 0.72 pg/mL; in those aged 20 to 65 years, 0.33 pg/mL; and in those aged 66 to 97 years, 0.005 pg/mL. These age-dependent differences were highly significant. In the youngest group the saliva concentration of bFGF varied more than in the other groups. CONCLUSIONS: The saliva concentration of bFGF varies with individual age, with the highest levels among young individuals, even levels during a mature phase of life, and low levels toward the end of the life cycle. This strongly suggests a physiological implication of bFGF in saliva.

Adolescent↗

PubMed2002

Is hearing preservation useful in vestibular schwannoma surgery?

The goal of our study was to examine the usefulness of preserved hearing after unilateral vestibular schwannoma removal. The patients were assessed by clinical evaluation, preoperative and postoperative audiometric evaluation, operative findings, and postoperative functional results. Hearing was preserved in 47 of 119 patients. The postoperative hearing was better than 30 dB in 10 patients. During the follow-up, the hearing decreased 5 dB on average, and almost all of the decrement occurred during the first 6 months. Subjectively, the preserved hearing assisted in understanding of speech in 62% of the patients. Tinnitus did not interfere with understanding of speech. The age of the patients was the most significant factor associated with preserved hearing. Sixty-six percent of the patients with hearing preservation rated their preserved hearing as valuable. Neither tinnitus nor speech distortion reduced the appreciation for hearing preservation. We conclude that efforts to preserve hearing are worthwhile.

Audiometry↗

PubMed2000

Individual Risk Factors in the Development of Noise-Induced Hearing Loss.

We have analysed the association of noise-induced hearing loss with various risk factors among 685 workers in forest, shipyard, and paper mills. Occupational histories, health, environmental factors, and noise exposures of each worker were retrieved from the database of NoiseScan, our expert program on hearing. The mean hearing level at 4 kHz was 21.5 dB +/- 20.3 dB HL. It correlated significantly with age, noise emission level and noise exposure level. However, these factors could only explain about 2 dB HL of the variation in hearing level. Impulse noise in the shipyard work caused increase in hearing level of 12 dB HL at 4 kHz when compared to steady state noise exposure of forest work. Hearing level correlated with serum cholesterol levels, use of analgesics, blood pressure and smoking. An elevated cholesterol level increased hearing loss in both the high- and low-exposure groups. The use of analgesics did not increase a permanent threshold shift in the low-exposure group, but did in the high-exposure group. Systolic blood pressure, smoking, cholesterol level and the use of painkillers explained 36 % of the variation in hearing level at 4 kHz, whereas noise exposure alone explained 25 % of the corresponding variation.

Journal Article↗

PubMedDate not supplied

Lyme borreliosis and facial paralysis--a prospective analysis of risk factors and outcome.

PURPOSE: To evaluate the incidence of Lyme borreliosis in patients with acute idiopathic facial paralysis with special emphasis on the risk factors that explain the poor outcome of facial paralysis and occurrence of Lyme borreliosis. MATERIALS AND METHODS: During a 2-year period, we prospectively studied 503 consecutive patients with acute idiopathic facial paralysis for the presence of Lyme borreliosis. We screened the patients for antibodies to Borrelia burgdorferi and for symptoms or signs related to Lyme borreliosis. Chi-square and logistic regression tests were used for the statistical analysis. Special attention was paid to strict criteria for the diagnosis of Lyme borreliosis. RESULTS: Eleven (2.2%) of the 503 patients with facial paralysis had Lyme borreliosis. Fever, headache, pharyngalgia, enlarged cervical lymph nodes, bilateral paralysis, and arthralgia were more common in patients with Lyme borreliosis than in those without it. In the logistic regression modeling the best combination of explanatory variables for predicting the occurrence of Lyme borreliosis included summer season at the onset of facial paralysis, presence of enlarged cervical lymph nodes, and arthralgia. The best combination of explanatory variables to predict the poor outcome of facial paralysis was total paralysis of facial nerves, recurrent facial paralysis, and hyperacusis. CONCLUSIONS: Lyme borreliosis is an important infectious cause of facial paralysis. In our study, 11 of 503 patients with acute idiopathic facial paralysis had Lyme borreliosis. The screening for serum antibodies in addition to the thorough evaluation of the history of the patient and of the patient's clinical signs or symptoms possibly linked with Lyme borreliosis, are essential when diagnosing Lyme borreliosis.

Acute Disease↗