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Biomedical subjects

I Pyykkö

Publications and source records attributed to I Pyykkö.

At least 91 records · Page 5Linked to original sources
PubMed1996

The noise level in magnetic stimulation.

The noise generated by stimulating coils may jeopardize the hearing of the patients as well as the hearing of the examiner. To evaluate the potential risk caused by the impulse noise of stimulating coils, we examined the A-weighted peak sound pressure levels from five different types of magnetic stimulator coils. At a distance of 10 cm, with 100% stimulation intensity, the coils with Dantec and Magstim stimulators created maximum peak sound pressure levels of 110 dB. Correspondingly, Cadwell MES-10 created maximum peak sound pressure levels of 132 dB. The decrease in the peak levels followed the distance rule quite closely. At a distance of 40 cm, the decrease in peak level was on average 14 dB (range -1-(+)1 dB). Based on American Conference of Governmental Industrial Hygienists (ACGIH) threshold limits of impact noise, the permitted maximum daily number of magnetic stimuli would be 1000 to 10,000. The permitted number of daily stimuli may be difficult to exceed in clinical practice. We consider the risk as small for the patients that are being examined and the operator using magnetic stimulation. The potential risk can be further diminished by even very light weighted hearing protectors providing proper attenuation to the coil impulses.

Hearing Disorders↗
PubMed1995

Abrupt unilateral deafness modifies function of human auditory pathways.

We studied nine patients with unilateral abrupt deafness caused by acoustic neuroma surgery. Cortical responses to tones delivered to the intact ear were recorded postoperatively with a 122-channel whole-scalp neuromagnetometer. In three patients, followed for 12 months with 2-4 measurements, evoked responses originating in the auditory cortices were weak and delayed one month after the operation in both hemispheres. During the follow-up, the amplitudes reached the control level. No response abnormalities were found in patients who were studied 1.5-4.5 years after the operation. Our findings suggest that abrupt unilateral deafness causes immediate changes in the function of auditory pathways of adult humans and that reorganization takes place within 1 year.

Adolescent↗
PubMed1995

A comparison of static and dynamic calibration techniques for the vestibulo-ocular reflex signal.

We investigated two calibration techniques commonly used with eye movement signals pertaining to the vestibulo-ocular reflex. Eye movement signals were recorded electro-oculographically as usual and calibrated using both static and dynamic calibration techniques. The calibration values of normals and patients were computed and compared to each other. Also gain parameters of vestibulo-ocular reflex which depend on the calibration were computed. We found that both techniques are chiefly equally valid, and there are no considerable differences in results computed with either one.

Algorithms↗
PubMed1995

Graphical user interface for the analysis of noise induced hearing loss.

We have developed a Windows-based computer program which will help the user to collect data needed for calculation models of noise induced hearing loss (NIHL). The program has a graphical user interface and it includes several methods to calculate NIHL. We have tried to make our system to cover all the factors concerning NIHL and also to take into account other possible reasons of hearing loss. The system is used not only for estimating noise induced hearing loss, but also as a systematic way to collect data for future evolution of new models and for other research purposes. For this sake the program asks some questions that are not currently included to these models, but which have been shown to have some impact on noise induced hearing loss.

Computer Graphics↗
PubMed1995

Prognosis of falls among elderly nursing home residents.

The survival rate of 207 nursing home residents who fell during a two-month study period was followed for 12 months and compared with that of 94 residents of the same nursing home who did not fall during the same period. One year after the fall, 74 fallers and 13 controls had died. In the group of fallers, the main factors associated with mortality were male gender, dementia, Parkinsonism, the use of antidepressants, diuretics and vasodilators. Among the controls, the main factors associated with mortality were Parkinsonism, diabetes and the use of diuretics. Thirty-eight fallers (33 women and 5 men) and one (female) control suffered a fracture; 32 of them required hospital attention, and 15 (47%) died during the same hospital stay. These results indicate that falls are an ominous sign, particularly if the subject has dementia, depression or Parkinsonism, or uses diuretics. The male subjects in this study had a lower injury rate than females, but their mortality rate was higher. In terms of prevention, the major concern should be the effective treatment of depression and Parkinsonism. Withdrawal of diuretics, when possible, may have an effect on mortality. Physical training and other stimulating activities should be beneficial, but subjects with severe dementia seem to be beyond this kind of prevention.

Accidental Falls↗
PubMed1995

Database for vertigo.

An interactive database has been developed to assist the diagnostic procedure for vertigo and to store the data. The database offers a possibility to split and reunite the collected information when needed. It contains detailed information about a patient's history, symptoms, and findings in otoneurologic, audiologic, and imaging tests. The symptoms are classified into sets of questions on vertigo (including postural instability), hearing loss and tinnitus, and provoking factors. Confounding disorders are screened. The otoneurologic tests involve saccades, smooth pursuit, posturography, and a caloric test. In addition, findings from specific antibody tests, clinical neurotologic tests, magnetic resonance imaging, brain stem audiometry, and electrocochleography are included. The input information can be applied to workups for vertigo in an expert system called ONE. The database assists its user in that the input of information is easy. If not only can be used for diagnostic purposes but is also beneficial for research, and in combination with the expert system, it provides a tutorial guide for medical students.

Anxiety↗
PubMed1995

Presymptomatic DNA and MRI diagnosis of neurofibromatosis 2 with mild clinical course in an extended pedigree.

Neurofibromatosis 2 (NF2), a dominantly inherited disorder, typically manifests as bilateral vestibular schwannomas and predisposes to other nervous system tumors. In this study, we present a large pedigree with a benign course of NF2 (mild Gardner type) characterized by slowly growing vestibular schwannomas but few other manifestations. The family was thoroughly investigated with neurologic, ophthalmologic, and neuro-otologic methods including gadolinium-enhanced MRI of the head and spine and DNA linkage analysis. In the clinical analysis of 22 family members, MRI was superior to neuro-otologic methods in the detection of asymptomatic tumors. Based on the DNA linkage analyses we identified the NF2 mutation carriers with a high degree of certainty. These DNA markers (CRYB2, NEFH, D22S268, and D22S280) can also be used for presymptomatic diagnosis in other NF2 families. Early detection of NF2 gene mutation carriers has become possible using linkage analysis in familial NF2. MRI screening of carriers will reveal presymptomatic vestibular schwannomas (and other CNS tumors), making early intervention possible, but an efficient treatment strategy to prevent deafness has not yet been established.

Adult↗
PubMed1995

Postural control in Menière's disease and acoustic neurinoma when studied on a linearly oscillating platform.

We investigated the effect of visual control on postural stability on a moving platform in 36 patients with Menière's disease (MD) in 25 patients with operated acoustic neurinoma (AN) and in 19 healthy controls. The force platform was placed on rails and oscillated linearly at frequencies from 0.2 to 5 Hz at a constant velocity of 30 mm/s. In all subjects, the support surface oscillation produced postural instability that differed significantly from the base line stability. The body sway velocity increased almost linearly with the increase of stimulation frequency. The MD patients swayed more than the AN patients at base line measurements in non-visual conditions but not during platform movement. In visual conditions the AN patients stabilized their posture significantly better than the MD patients, who showed deteriorating visual control of posture during platform movement. The controls differed from the patients in all test conditions except 5 Hz stimulation, which causes the body segment to fall into resonance. The Romberg quotients (RQ) in MD patients was significantly poorer during platform movement than in controls, except at 5 Hz stimulation. The AN patients had higher RQ values than controls, and mainly used vision to compensate their vestibular deficit. Thus, patients with MD fail to control their posture efficiently with vision during movement which may explain the visually induced dizziness in MD patients.

Adult↗
PubMed1995

Predictable and pseudo random saccades in patients with acoustic neuroma.

We studied predictive and pseudo random saccades in patients with cerebellopontine angle tumor. Target for the saccades was a laser beam which was reflected on the wall in front of the subject, and the stimulus was controlled by a computer. The fixed target was spaced at a distance of +/- 30 to each side of the subject. The random saccades jumped 20 degrees/40 degrees/60 degrees in an unpredictable manner. The saccade analysis program was based on pattern recognition. In the random saccade test none of the mean values of saccadic reaction time (SRT), saccadic accuracy (SA) and saccadic peak velocity (SPV) to the right or left differed significantly between the two groups. In the predictable saccade test there was statistically significant differences for certain variables: in right SRT (p < 0.01) and in left SRT (p < 0.01); in right SA (0.001 < p < 0.01) and in left SA (p < 0.001). The mean peak velocity (right SPV and left SPV) did not differ significantly between the two groups. When the stimulus is predictable, the saccades in a healthy subject are more timely spaced and accurate than in a patient. When the stimulus is unpredictable, "the memory of the past" has no importance and cannot help in saccade programming, and variability in the healthy subjects increases.

Adult↗
PubMed1995

Vestibular evoked responses in man: methodological aspects.

We have developed a stimulation method where the subject is sitting and the head is rotated with shock bursts elicited by a shaker with a repetition rate of 2 Hz. The head movement is monitored with an accelerometer mounted on the cheek by a head band. The maximum amplitude of the head movement is 3 degrees. The electrodes were places on vertex with a negative electrode on the mastoid. During stimulation, 90 dB white noise was applied to the ears to mask the noise generated by the stimulus. We recorded following responses: i) VER from ipsilateral ear, ii) VER from contralateral ear, iii) eye movement with EOG, and iv) movement of the head. Amplification and averaging of the signal were made with an evoked response recorder (Nihon Kohden, Neuropac four). From 200 to 2,000 averaged responses were collected and stored for further analysis on a floppy disc. During second stage filtering the data were fed into a microcomputer where appropriate programs were used to eliminate the EMG and movement artifacts.

Acceleration↗
PubMed1995

Effect of intratympanically administered gentamicin on hearing and tinnitus in Menière's disease.

We have examined the effect of intratympanic gentamicin on hearing and tinnitus in 69 patients with intractable Menière's disease. Tinnitus was scored from 1 to 4 depending on its severity. The mean pure tone audiometry level before treatment was 57.5 dB and 1 year after treatment 63.5 dB Five subjects became deaf in the treated ear, and in 13 subjects hearing loss was > 10 dB and in 21 subjects 0 10 dB. In 25 subjects significant improvement (> 10 dB) was gained, and in 5 patients. Tinnitus was significantly reduced after treatment with gentamicin. A total of 66 patients had tinnitus before treatment and tinnitus relief was rated as good. Four percent of the subjects had no tinnitus, 30% had slight tinnitus. 27% moderate tinnitus. 18% severe and 8% handicapping tinnitus.

Administration, Topical↗
PubMed1995

Computer assisted data collection in vestibular disorders.

We have developed an interactive database for vertigo than can be used to assist in the diagnostic procedure and to store the data in a form of a database. The database offers the possibility to split and reunite the collected information in a desired way. The database contains detailed information about patient history, symptoms and findings in neurotological, audiological and imaging tests. The symptoms are classified into three sets of questions: vertigo (including postural instability), hearing loss and tinnitus, and provoking factors. Confounding disorders are screened. The neurotological tests involve saccades, smooth pursuit, posturography and caloric test. In addition, findings in specified antibody testing, clinical neurotological tests. MRI, brain stem audiometry and electrocochleography are included. The input information can be applied in an expert system ONE for vertigo work-up. The database is user-friendly. Besides diagnostic purposes the database is excellent for research purposes, and combined with the expert system it works as a tutorial guide for medical students.

Artificial Intelligence↗
PubMed1995

Reasoning in expert system ONE for vertigo work-up.

An otoneurological expert system (ONE) was developed to help collect data and diagnose the work-up of vertigo of both central and peripheral diseases causing vertigo. Patient history and otoneurological and other examination results are used in the reasoning process. The history is interactively collected and is complemented with clinical examination results. The case history data can be either mandatory or supportive. Mandatory questions are used to confirm a diagnosis, and conflicting answers are used to reject an unlikely disease. Supportive questions support or suppress a diagnosis, but their presence is not obligatory. The reasoning procedure of ONE scores every question independently for different diagnoses, depending on how well they agree with the symptom entity of a disease. Diagnostic criteria are set for each disease, in Meniere's disease, for example, the full triad is required. Graphic displays illustrate the linear and nonlinear correlation between the symptoms and diseases. For instance, both second-long Tumarkin-type attacks and attacks lasting hours give a high score while intermediately long attacks score much lower in Meniere's disease. To be able to take even rare diseases into consideration we try to diminish the possibility of a wrong decision rather than maximize the likelihood of reaching only one right decision.

Artificial Intelligence↗
PubMed1995

Middle ear imaging in neurotological work-up.

Middle ear imaging constitutes a homogeneous test battery for evaluation of neurotological disease. The imaging comprises infra-sound fistula test, ABR, tympanoscopy, ECoG, and trans-promontiorial cochlear blood flow measurement. We used a fistula test with infra-sound loading on posturography. In tympanoscopy we used 5 degrees and 25 degrees endoscopes with a diameter of 1.9 mm and length of 125 mm. In blood flow measurement we used laser-Doppler system with a stainless steel tip placed on the basal turn against stira vascularis. The flux was analyzed with a computer with custom-made software. In ECoG, a silver ball electrode was placed on the round window. In 64 cases evaluated we were not able to verify a spontaneous PLF by tympanoscopy. Symptoms typical for spontaneous PLF with positive fistula test turned out to be caused by endolymphatic hydrops. Sudden deafness usually did not show reduced cochlear blood flow, but often an endolymphatic hydrops. Fistula test was positive in about 25% of cases with endolymphatic hydrops. Tympanoscopy caused very few complication. The procedure takes about one hour and is done ambulatorily.

Adolescent↗
PubMed1995

Using magnetic coil signals with EOG signals in computer analysis of vestibulo-ocular reflex.

Since EOG signals are rather noisy, but magnetic coil signals almost noiseless, the latter type is a good reference to the former which is much easier to record. Concurrently recording magnetic coil and EOG signals we could verify some details as saccades which are often difficult to detect in noisy signals. It is important to recognise such phenomena in eye movement signals, because these affect the gain parameter computed between the vestibulo-ocular reflex signal and the head movement signal.

Algorithms↗
PubMed1995

Pseudo random smooth pursuit test in patients with acoustic neuroma.

We examined the pseudo random smooth pursuit test in patients with cerebellopontine angle (CPA) tumors. Four different frequency combinations of sinusoids 0.15-0.35 Hz, 0.25-0.425 Hz, 0.3-0.7 Hz and 0.45-0.7 Hz were tested. Gain was calculated by comparing the smooth pursuit amplitude with stimulus after the supporting saccades had been removed. Phase was calculated by comparing maximum excursion of the eyes and stimulus. Gain was in the patients lower than in the controls in different frequency combinations, and the difference was statistically significant/highly significant in different frequency combinations. In the phase shift the differences were highly significant in the two higher frequency combinations and significant in the second frequency combination (0.25-0.425 Hz), while in the first frequency combination (0.15-0.35 Hz) the difference was not significant. The gain method was a somewhat better analyzing method than the phase shift method.

Adolescent↗
PubMed1995

Cochlear vascular pathology and hydrops in otosclerosis.

Three ears with otosclerosis were found incidentally in a series of human temporal bones examined to evaluate cochlear sensorineural degeneration. Otosclerosis was identified with microdissection, surface preparation technique and transmission electron microscopy. Vascular abnormalities were present in all ears, and otosclerosis involved the cochlear endosteum extensively, mainly in the scala tympani of the basal turn. In the scala tympani of the lower half of the basal turn, shunts had formed so that venules deviated abruptly from their normal radiating course towards the spiral vein, left the scala and entered into otosclerotic foci. There was a marked loss of radiating venules in areas where otosclerosis affected the endosteum of the scala. In the pair of bones capillaries in the stria vascularis were extremely dilated, the widest being 80 microns in diameter. The third single bone from a patient with Meniere's disease had severe cochleo-saccular hydrops. Ten serially sectioned temporal bones with known otosclerosis were reviewed. Two of the bones, one of which had cochleo-saccular hydrops, displayed vascular shunts in the scala tympani and enormously dilated strial capillaries with a maximum diameter of 139 microns.

Adult↗