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Biomedical subjects

I Pyykkö

Publications and source records attributed to I Pyykkö.

At least 109 records · Page 6Linked to original sources
PubMed1995

Culturing of acoustic neuroma--methodological aspects.

We have been able to culture acoustic neuroma (AN) tissues by taking small tumor pieces during surgery from the cisternal or, preferably, metal part of the tumor where macroscopic tissue degeneration is not prominent. The AN pieces were transported in culture tubes to our cell laboratory where they were sliced and transferred to culture medium. The AN tissue demands a crude culture suspension containing laminin. We have been successful in culturing 15 successive ANs. The cells have different morphological features with characteristics of type Anthony A and B. Four main cell types were recognized: ameboid microglia-like cells, spindle-shaped cells, racket-shaped cells, and kite-shaped cells. However, no immortal cell line could be established. Some of the cultures were viable for up to 4 months.

Culture Media↗
PubMed1994

Intratympanic gentamicin in bilateral Menière's disease.

Treatment of bilateral Menière's disease is a delicate task. Streptomycin has demonstrated its ability to successfully control the vertigo attacks, but in some cases it results in oscillopsia and transforms the periodic attacks to permanent instability. If the site of the active labyrinth can be determined, a more specific treatment can be tried. We have treated 14 patients with intractable bilateral Menière's disease with intratympanic gentamicin (Garamycin, 40 mg/ml) administered initially in either 1, 2, 3, or 4 injections. The patients were tested at frequent intervals and followed up for 2 years. The work capacity, severity of vertigo, and gait difficulties were scored before treatment and during each test occasion. The postural stability was evaluated on a force platform and sway velocity was analyzed. Before treatment, moderate or severe reduction of work capacity was experienced by all of the subjects, which correlated to severity of vertigo and gait problems. Two years after treatment, the vertigo attacks were eliminated in 11 subjects and controlled in three subjects. The work capacity of three subjects was still moderately or severely reduced. This reduction depended on gait disturbance and Tumarkin attacks. The average postural stability returned to pretreatment level 2 years after the treatment was begun. The outcome of the caloric responses did not correlate with the outcome of the treatment. Hearing was not significantly affected by the treatment. Intratympanic gentamicin treatment is a relatively safe and effective way to treat bilateral Meniere's disease when the symptoms can be localized to one ear.

Adolescent↗
PubMed1994

Recovery of the sutured facial nerve after removal of acoustic neuroma in patients with neurofibromatosis-2.

The authors compared the long-term recovery of sutured facial nerves after the removal of 8 neurofibromatosis-2 (NF2)-associated and 22 non-NF2 acoustic neuromas. The patients were from a series of 270 patients operated on for an acoustic neuroma between 1979 and 1989. The assessment was done with a modified House and Brackmann scale from video recordings. At least some facial movement or tone was achieved (Grade 5 or better) in all but three patients, but in none was the recovery excellent. The facial function, judged by the overall appearance in movement, recovered less in patients with NF2 (P = 0.048); a moderately good recovery (Grade 3 or better) was seen in one patient of eight with NF2, as compared with 13 of 22 with non-NF2. In conclusion, if the tumor cannot be peeled off easily from the facial nerve in patients with NF2, leaving a fragment of tumor behind is preferable to cutting and suturing the facial nerve.

Adolescent↗
PubMed1994

Interface between the facial nerve and large acoustic neurinomas. Immunohistochemical study of the cleavage plane in NF2 and non-NF2 cases.

In acoustic neurinoma surgery, the surgeon is required to find a cleavage plane between the facial nerve and the tumor, and with the aid of the operating microscope this is usually achieved by fine dissection. A histological specimen of the nerve-tumor interface is available only if the facial nerve was hopelessly adherent to the tumor (usually a large or giant neoplasm) and the surgeon decided to sever the nerve to obtain a complete removal. The authors have examined immunohistochemically the nerve-tumor interface of 20 such facial nerves (six cases of neurofibromatosis 2 (NF2) and 14 of non-NF2) in a series of 351 acoustic neurinomas. The largest extrameatal dimension of the 20 tumors ranged from 20 to 51 mm (median 39 mm). In all of these 20 instances the nerve-tumor contact area was at least partially devoid of a clear-cut histological cleavage plane. Where the facial nerve trunk was attached to the surface of the tumor, nerve fibers of the contact areas either abutted directly against tumor cells or nerve fibers were seen to penetrate into the tumor tissue. Frank embedding of nerve fibers was more frequent in NF2.

Adult↗
PubMed1994

Effect of hand-arm vibration on inner ear and cardiac functions in man.

To evaluate distant effects of hand-arm vibration we studied Finnish forestry workers using chain saw during the years 1972 through 1990. The hearing was tested annually and individual regression curves for sensorineural hearing loss (SHL) were calculated. Robinson's model was used in prediction of SHL. The heart rate variation (HRV) indexes at rest and during deep breathing test were analyzed to measure autonomic nervous function. In Robinson's model the measured SHL (17.8 dB) respected the predicted SHL (17.2 dB). The subjects with VWF had on average, 10 dB greater hearing loss than those who did not have VWF. The regression model based increase of hearing loss during follow up correlated with ageing, not to VWF. The intercept differed significantly in those with VWF from those without VWF. We found a significant difference between HRV indexes during deep breathing test in those with the shortest and those with the longest vibration exposure. The HRV decreased with age, but multiple regression analysis showed that the total exposure time to vibration had an independent negative association with HRV indexes. Our results suggest that prolonged exposure to vibration caused by chain saw has negative effects an autonomic functions. The aggravated hearing loss in subjects with VWF may be due to vibration induced changes in the autonomic nervous system or internal factors of the blood vessels.

Arm↗
PubMed1994

Vibration exposure and prevention in Finland.

The number of annually compensated occupational diseases due to exposure to hand-arm vibration (HAV) has decreased during the last 15 years. The number of exposed workers has been declining in Finland, especially in forestry work, as harvesters have increasingly replaced manual chain saw operations. During the entire 1970s, forest work caused more cases of vibration-induced occupational diseases than all industrial branches together. The decrease is mainly due to the technical development of chain saws, but also to the effective health care services in Finland. Other factors such as warm transport, warm rest cabins in which to take pauses at work, warm meals, adequate protective clothing, and vocationally adjusted early medical rehabilitation have helped to cut down health hazards, especially in forest work. The number of new cases has been decreasing in Finland not only in forestry but also in other industries. In Finland a considerable amount of research has been conducted to hand-arm vibration, resulting in the increased awareness of the health risks related to certain occupations. This has helped to carry out the Primary Health Care Act (1972) followed by the Occupational Health Care Act (1979) which obligates employers to arrange occupational health care for their employees. We believe that the research activity has contributed significantly to achieving the present health in Finnish work places. The purpose of the present paper is to describe the cases of occupational exposure to HAV, and the effectiveness of different preventive measures in Finland.

Finland↗
PubMed1993

Vibration stimulus induced EEG bursts in isoflurane anaesthesia.

The EEG and heart rate reactions to vibration stimulus were studied in 14 patients during moderately deep surgical isoflurane anaesthesia, at a level when EEG showed a burst suppression pattern. Vibration applied to the palm of the hand induced bursts in EEG in 12 patients, usually with a latency of about 0.5 sec from the onset, or from the end of the 3 sec stimulus. Increases in heart rate were seen at bursts related to both vibration onset and offset, as well as at spontaneous bursts. With spontaneous bursts, an initial positive wave was frequently seen. In 6 patients the vibration induced bursts were different in shape from the spontaneous bursts; no initial positive wave was seen before the negative DC shift in Cz-Fz recording. We conclude that EEG bursts can be evoked by a non-noxious stimulus such as vibration in patients during isoflurane anaesthesia.

Adult↗
PubMed1993

Evaluation of postural stability by computerised posturography following outpatient paediatric anaesthesia. Comparison of propofol/alfentanil/N2O anaesthesia with thiopentone/halothane/N2O anaesthesia.

Simple clinical tests, like Romberg's test or a walking test, have proved to be inadequate guidelines for safe discharge after outpatient anaesthesia. A randomised study was therefore planned to compare postural stability measured by computerised posturography in 31 oral midazolam-atropine premedicated children aged 6.9 (s.e. 0.4) years who had been anaesthetised with either propofol/alfentanil/N2O or thiopentone/halothane/N2O. The sway velocity of the children was measured before premedication and 1, 2 and 3 h after the end of anaesthesia. Results show that sway velocity had returned to baseline values 3 h after the end of anaesthesia in all children who had received propofol/alfentanil/N2O and in 12 of the 15 children who had received thiopentone/halothane/N2O. The quantified version of the Romberg test performed with eyes open or closed was not impaired after anaesthesia, compared with the control values, indicating that in children poor equilibrium is not compensated by vision. The clinical recovery with respect to the times to eye opening, to responding to command or to being fully awake did not differ between the two anaesthesia methods. On the basis of recovery assessed by postural stability, propofol/alfentanil/N2O anaesthesia was not preferable to thiopentone/halothane/N2O anaesthesia after minor paediatric otolaryngological surgery.

Alfentanil↗
PubMed1993

Neuroborreliosis in the etiology of vestibular neuronitis.

Symptoms and incidence of neuroborreliosis (NB) were studied in ambulatory patients visiting the ENT clinic in Helsinki. Especially we tried to search for possible markers indicating the connection between vestibular neuronitis and NB. A total of 350 patients were screened with the enzyme-linked immunosorbent assay (ELISA) technique for possible antibodies against Borrelia burgdorferi (BB). Twelve patients had positive serological reactions for BB with sera titer levels ranging from 640-14700 (normal < 500). In 2 additional cases, NB was clinically confirmed. In 7 cases a history of tick bite and in 4 cases erythema chronicum migrans was confirmed. In 9 cases, vertigo was the predominant symptom, and in 3 cases the symptoms were linked to facial nerve paresis. Six patients suffered from hearing loss. In 7 cases, the diagnosis was initially settled as vestibular neuronitis. NB seems to be present in about 4% of cases with apparent otologic diseases in Finland. In the majority of the cases, the disease resembles vestibular neuronitis in the acute stage. Since NB is tractable, all patients visiting the ENT clinic, especially those with vertigo, should be screened.

Antibodies, Bacterial↗
PubMed1993

Human spumaretrovirus in the etiology of sudden hearing loss.

The etiology of sudden sensorineural hearing loss, so called sudden deafness, has for long puzzled researchers. Recently we have studied the possibility that a hitherto relatively unknown retrovirus group consisting of human spumaretroviridae (HSRV) might be the causative agent of sudden deafness. During the last 3 months we have screened about 30 cases of sudden deafness. In 4 of them antibodies against HSRV were detected. Three of them had suffered from a flu-like condition about 2 weeks before the onset of hearing loss. In 2 cases the hearing of both ears was involved, in 1 case a relapsing hearing loss was observed, and 1 case developed a Meniere-like symptomatology with a fluctuant hearing loss. Vertigo was present in 3 patients and all suffered from tinnitus. Full recovery of hearing was observed in 4 of 6 affected ears whereas 2 ears became practically deaf with poor speech discrimination. At present it seems likely that a significant part of sudden deafness is caused by HSRV infection. The course of infection follows the spontaneous course of sudden deafness described by many authors. We encourage otologic units to screen for HSRV when assessing the etiology of sudden deafness.

Adult↗
PubMed1993

Postural control and age.

We quantified the effect of vision, pressoreceptor function and proprioception on the postural stability at different ages. Altogether 212 healthy volunteers (ages from 6 to 90 years) were examined by using a computerised force platform. The sway velocity (SV) was measured with eyes open and eyes closed during quiet stance on a bare platform and a foam plastic covered surface. In addition, to study the proprioceptive system, pseudorandom vibration perturbation was applied on the calf muscles. The SV showed a U-shaped curve: the children and the oldest swayed most. Equilibrium was most stable around 50 years. The visual system was of most importance for balance control in the old. The children were sensitive of pressoreceptor and proprioceptive perturbation, indicating the importance of these systems for their postural control.

Adult↗
PubMed1993

The site of impulse generation in transcranial magnetic stimulation of the facial nerve.

The facial nerve can be stimulated in its intracranial course through transcranial magnetic stimulation (TMS). We studied the site of impulse generation produced by TMS by comparing the latencies of the muscle evoked potentials (MEPs) elicited with TMS and intracranial electrical stimulation (IES) of the facial nerve during neurosurgical posterior fossa procedures. In a series of 25 patients, the mean latency of the TMS elicited MEPs, recorded in the orbicularis oris muscle, was 5.0 ms (SD 0.58). Also IES of the distal part of the facial nerve in the internal acoustic meatus showed a mean latency of 5.0 ms (SD 0.68). Proximal IES in the root entry zone of the facial nerve, and intermediate IES between root entry zone and meatus, produced MEPs with significantly longer latencies compared to TMS and distal IES (p < 0.05). The findings suggest that the TMS induced facial nerve activation, leading to a MEP response, takes place within the internal acoustic meatus.

Adult↗
PubMed1993

Hearing loss risk from exposure to shooting impulses in workers exposed to occupational noise.

The effect of shooting impulses on hearing was analysed in 150 professional forest workers exposed to noise from chain saws. The exposure to shooting impulses (Lesi) was designed to take into account the peak levels of shooting impulses, their number and use of hearing protectors. Hearing loss was dependent on Lesi even after allowing for the age of subjects and their exposure to chain saw noise. Hearing threshold levels were compared between pairwise matched groups with high and low Lesi. Proper matching was achieved for age, chain saw noise, salicylate consumption, blood pressure, cholesterol, smoking and vibration-induced white finger symptoms. The workers with high Lesi had 9 dB greater hearing loss at 4 kHz and 10 dB greater hearing loss at 8 kHz than those with low Lesi, the difference being significant at P < 0.05 level. In evaluation of noise-induced hearing loss the exposure to shooting impulses from different calibre weapons should be determined since they increase the extent of hearing loss. The present study describes the Lesi method which more accurately evaluates the harmful effects of shooting noise impulses on hearing.

Adult↗
PubMed1993

A measurement system of head movements for the vestibulo-ocular reflex.

This paper describes an efficient technique to record head movement signals for the computer analysis of vestibulo-ocular reflex. The technique has essentially lower costs than the method of rotatory chair. It is easy to operate and yields recordings of high quality. The system is connected to our analysis program of vestibulo-ocular reflex, the results of which are briefly presented.

Costs and Cost Analysis↗
PubMed1993

Postural stabilization on a moving platform oscillating at high frequencies.

The effect of a fore-aft oscillating platform on postural stability was studied in nine healthy volunteers. The force platform technique was used with automatic analysis that evaluated the position of the center point of force as a function of time. The duration of stimulation lasted 90 s and the perturbation frequencies ranged from 8 to 24 Hz, and were given at constant rms acceleration of 4 m/s2. When compared with a vibration-free baseline stance, horizontal vibration of the platform caused significantly worse postural stability in all subjects. Test frequencies of 8 and 10 Hz produced greater sway velocities than perturbation at frequencies of 14 and 16 Hz. The results indicate that horizontal perturbation of the support surface leads to postural instability that is frequency-dependent.

Adult↗
PubMed1992

Vibration syndrome among Finnish forest workers between 1972 and 1990.

A longitudinal study on vibration syndrome among professional forest workers was carried out in Finland from 1972 to 1990. In the course of the follow-up the weighted vibration acceleration of chain saws decreased from about 14 to 2 m/s2. The prevalence of vibration-induced white finger (VWF) decreased gradually from 40% to 5%. Numbness occurred mainly at night, and its prevalence decreased from 78% to 28%. During part of the follow-up period (1975-1990) the complaints of hand muscle weakness decreased from 19% to 9%. Disorders of the musculoskeletal system were considered to cause more disability than VWF. The decreased vibration acceleration and the lighter weight of chain saws were considered the main reasons for the decrease in the prevalence of vibration-induced symptoms.

Adult↗
PubMed1992

On identification of saccades from sinusoidal eye movement signals.

Sinusoidal eye movements and potential saccadic eye movements are examined using the syntactic pattern recognition method presented previously. A few computer tests are presented for the verification of potential saccades from signals of sinusoidal eye movements. The technique was developed and tested with electro-oculographic signals. The verification of saccades consists of three tests: the estimation of average noise peaks in an eye movement signal; an angular velocity threshold; and the comparison between a sinusoidal eye movement signal and the corresponding stimulus signal. The technique is also efficient for noisy signals of eye movements, which were stimulated by both predictive and non-predictive sinusoidal stimulus movements.

Calibration↗