Biomedical subjects

I Pyykkö

Publications and source records attributed to I Pyykkö.

At least 73 records · Page 4Linked to original sources

PubMed1998

Comparison between diagnoses of human experts and a neurotologic expert system.

The decision-making ability of a recently developed neurotologic expert system was compared with the diagnoses of six physicians. Five of the physicians were residents and one was a specialist in the field of otolaryngology. The test patients were randomly selected from vertiginous patients referred to an otolaryngology clinic. The expert system and the physicians first had identical information on patient history, symptoms, and tests. During the second phase of the study the physicians were allowed to use the full medical records. The correct diagnoses were certified by an experienced specialist in neurotology. The expert system did better in decision-making when both the expert system and the physicians had identical information on patients. However, when the physicians were allowed to use patient's complete medical records, they surpassed the expert system. The expert system diagnosed 65% of the cases, while the physicians first diagnosed 54% of the cases, and then with complete information, 69% of the cases. From the patients' medical records, the physicians obtained information on the time perspective of the symptoms and the progression of the disease. These aspects will be used to further improve the expert system.

Adult↗

PubMed1997

Computational problems in the analysis of eye movement signals in the determination of vestibulo-ocular reflex.

The vestibulo-ocular reflex preserves clear vision when the head is moving fast. Measurement of the vestibulo-ocular reflex during the head autorotation test is usually calibrated using a dynamic technique in which the initial part of the eye movement signal and the corresponding part of the stimulating head movement signal are matched. Dynamic techniques can, however, be prone to generate excessively small or large calibration coefficients if a calibration segment of such a signal is corrupted by saccades or artifacts of large amplitudes. We have implemented an effective improvement for computation of difficult signals, not infrequent in clinical data, by limiting influence of distorting parts in the eye movement signal. We also discuss pitfalls of parameter accuracy concerning gain and phase parameters of the vestibulo-ocular reflex that are used to differentiate abnormal results from the normal. Furthermore, we call the ubiquituous Fast Fourier Transform method into question with regard to these signals.

Adult↗

PubMed1997

Vestibulo-ocular reflex function as measured with the head autorotation test.

The vestibulo-ocular reflex (VOR) of 125 healthy subjects was examined over the frequency range of 0.5-5 Hz with the head autorotation test (HART). During the HART the subjects fixated at a steady target while moving their heads horizontally from side to side with increasing frequencies according to auditory signals. The gain was determined as the ratio between the amplitude of the eye and head movements in five frequency bands between 0.5 and 5 Hz. The phase difference between the eye and head movements was determined in both degrees and milliseconds. The ability to reach high-frequency bands was evaluated. The mean gain was close to unity up 5 Hz, when it decreased to 0.91. The mean phase difference showed a lead of approximately 5 degrees at frequencies below 2 Hz, and at frequencies above 2 Hz there was no phase difference within the resolution of the test. The frequency band of 5 Hz was reached by 78% of the subjects, and that of 4 Hz was reached by 94% of the subjects. In summary, the HART is a new approach with which to study VOR function and determine accurately the VOR for healthy subjects. The normal upper frequency limit is 4 Hz in the HART.

Acoustic Stimulation↗

PubMed1997

Non-surgical treatment of vestibular schwannoma patients.

The aim of the study was to evaluate the course of vestibular schwannoma (VS) when surgery was not attempted. The tumor may be slowly growing and surgery a risk for a patient. Twenty-eight patients out of 390 VS patients during years 1981-1995 were primarily recommended a non-surgical treatment. Another 3 patients refused the operation. Altogether 23 women and 8 men were evaluated. Their age varied from 30.6 to 74.6 years (median 56.7 years). Tumor size varied from 5 to 30 mm (median 15.0 mm) at the beginning of the follow-up. Patients symptoms, condition and other illnesses were recorded. Seven patients had neurofibromatosis 2 (3 of them had one hearing ear), 2 had severe mental problems, 5 patients had their only hearing ear and 11 patients were not recommended an operation because of their age and other illnesses. Patients were controlled with MRI at intervals from 1 to 3 years. The follow-up time varied from 1 to 20 years (median 2.0 years). The average tumor growth rate among unilateral VS patients was 0.035 cm/year and among bilateral tumors the average tumor growth rate was 0.015 cm/year. Two patients were later operated on, one 2 years after diagnosis because of the tumor growth and the other one 4 years after diagnosis-she had refused an operation earlier. Two patients could not be reached. Another patient had tumor growth but because of his illnesses he got a radiation beam instead of an operation. The majority of the patients could live fairly normal lives and required no treatment. Surgery is not the only alternative to VS patients. Wait-and-see policy is also a good alternative to those who have high operation risk or who refuse an operation.

Adult↗

PubMed1997

Azathioprine with cortisone in treatment of hearing loss in only hearing ear.

A sudden or progressive hearing loss in the only hearing ear is an otologic emergency, in which therapeutic possibilities are limited. We describe results of immunosuppressive therapy in 10 patients with one deafened ear either due to cochlear hydrops or Meniere's disease, who developed progressive or fluctuant hearing loss in the only hearing ear. The perilymphatic fistula was excluded with tympanoscopy. Azathioprine (25 mg t.i.d.) with prednisone (initial dose 20-40 mg with daily dose of 5-15 mg/day) was used. The hearing of 6 subjects responded to treatment. The initial pure tone audiogram (PTA) at speech frequencies of the "only hearing ear" was 57.3 dB HL with speech discrimination score (SDS) of 85%. The hearing improvement occurred successively within days or weeks. The average improvement of PTA was 22.4 dB HL after the mean treatment period of 5 weeks. In contralateral ear (the average PTA and SDS were 72.5 dB HL and 28%, respectively) the mean improvement in PTA was insignificant (4.4 dB). In 5 patients with vertigo it was improved in 3 cases. Cortisone alone or with combination of cyclophosphamide or ciclosporine was not effective in our hands.

Audiometry, Pure-Tone↗

PubMed1997

Postural stability, neck proprioception and tension neck.

We examined whether tension neck (TN) may due to inadequate proprioceptive and vestibular activation of the cervico-collic reflex (CCR). CCR and vestibulospinal responses (VSRs) were recorded from 106 forest workers by stimulating the neck, lumbar or calf proprioceptors by vibration. The VSRs were recorded with posturography. TN occurred in 27 out of 106 subjects. The subjects with TN (48.5 years) were older than those without TN (43.1). The mean body sway during quiet stance was the same in both groups during the neck stimulation. In subjects with tension neck stimulation of neck or lumbar proprioceptors caused excessive, unpredictable body excursion in the lateral and anteroposterior direction that continued after stimulation. Results from stimulation of lower limb proprioceptors did not significantly differ between the 2 groups. In logistic regression analysis a model to predict TN consisting of perstimulatory postural stability (odds ratio 1.4) and poststimulatory postural stability (odds ratio 1.8) turned out to be statistically significant. The anatomical findings of CCR in the medulla oblongata suggest that neck muscle afferents control the posture and muscle activity of the neck. The erroneus facilitation of proprioception in TN subjects indicate that TN may be raised by inadequate facilitation of CCR.

Adult↗

PubMed1997

Phase difference of vestibulo-ocular reflex in head autorotation test.

In the head autorotation test (HART) gain is commonly used to determine the vestibulo-ocular reflex (VOR). The purpose of this work was to evaluate the relevance of phase (the phase difference between the eye and corresponding head movement) in describing the VOR. The phase was determined in 5 frequency bands in both degrees and milliseconds (ms) in 4 groups: 30 healthy adults, 15 elderly subjects, 37 vestibular schwannoma (VS) patients, and 35 Meniere's disease (MD) patients. In healthy adults and in MD patients the phase was close to nil in the frequency bands of 3 and 4 Hz. In elderly subjects phase lead was between 5.0 and 15.5 ms in each frequency band. Patients with VS showed a phase lag of -4.2 to -7.6 ms. The mean phase of the elderly in the frequency band of 3 Hz differed statistically significantly from that of MD and VS patients, and in the frequency band of 4 Hz from that of healthy adults and VS patients. In summary, the elderly had phase lead and VS patients showed increased phase lag in the frequency bands higher than 2 Hz. The phase is useful parameter together with gain in evaluating VOR and it seems to change in aged subjects and in patients with permanent vestibular lesion.

Adult↗

PubMed1997

Stability limits for visual feedback posturography in vestibular rehabilitation.

Vestibular rehabilitation therapy (VRT) is used to enhance compensation after peripheral vestibular lesion. In visual feedback posturography (VFP) a patient can practice postural control actively on a force platform and progress in the VRT can be objectively measured. The aim of the study was to determine normative values for stability limits (SL) in the VFP. Eleven healthy subjects were measured with force platform in visual feedback condition. Subjects were instructed to move their center of gravity (COG) marker to given targets, which were displayed on a computer screen in front of them. Target distance from the center of the platform was increased step by step to determine the SL in 8 directions. Hit delays (HD) to the targets and hold percentages (HP) within the targets were measured to quantify the difficulty of the individual targets as a function of subject's shoe size. With fixed feet position the SL in anterior direction increased 1.2 times the absolute increase in shoe length. An almost similar increase was found in anterolateral direction. The knowledge of the mechanical SL is important, because targets near SL should be avoided for safety reasons.

Adult↗

PubMed1997

Changes in vestibulo-ocular reflex of elderly people.

Dizziness is a common symptom in elderly people. Head autorotation test (HART) has earlier shown no significant vestibulo-ocular reflex (VOR) disturbances in healthy elderly subjects. We used our recently developed HART to determine VOR in 14 elderly volunteers without otoneurological diseases and sedative medications. Gain and phase were determined in 5 frequency bands from 0.5 to 5 Hz. The gain of the elderly was significantly increased to 1.11-1.27 in the frequency range of 3-5 Hz compared with the controls. The phase lead of 7-8 degrees in the frequency bands of 2 and 4 Hz differed significantly from normative values of the controls. The percentage of the elderly to reach high-frequency head movements was diminished to 50% in the frequency band of 3 Hz and to 36% in the frequency band of 4 Hz (controls 100% and 95%, respectively). The individual HART results were abnormal in 86% of the elderly. The high-frequency VOR of the elderly was inaccurate in magnitude and timing. More than half of aged subjects were not able to generate voluntary fast head movements. These findings may explain the high prevalence of dizziness and falls in elderly subjects.

Accidental Falls↗

PubMed1997

Pediatric facial paralysis--a spirochetal infection with good prognosis?

The aim of the study was to investigate the possible signs of chronic spirochetal infection in 27 children with a history of facial paralysis with onset of symptoms during May-October 1985-1993. These children had not been studied at the time of facial paralysis for possible Lyme borreliosis and none of these children had received antimicrobial therapy at that time. The patients were interviewed with special reference to symptoms and signs of Lyme borreliosis and thereafter examined clinically and with laboratory tests. None of the patients showed signs or symptoms of chronic Lyme borreliosis. One child-now a 14-year old girl-had a 4-fold rise in serum Borrelia burgdorferi antibodies as a sign of a recent infection. According to our prospective studies on pediatric facial paralysis in Finland (over 50% of children presenting with facial paralysis during May-October have Lyme borreliosis), we have a reason to assume that at least some in our study group had a facial paralysis caused by Borrelia burgdorferi infection. The results of our study indicate that facial paralysis has a favorable prognosis and in short-term follow-up the children do not have symptoms or signs of chronic Lyme borreliosis.

Adolescent↗

PubMed1997

Hemangioblastoma and oculomotor pathology.

We examined voluntary eye movements of 20 ophtalmologically screened patients (mean age of 51 years) with operated hemangioblastoma (HAB) in the cerebellum. Constant and pseudo-random saccades and pseudo-random smooth pursuit eye movement (PRPEM) test (with 4 frequency combinations) were evaluated. As controls 38 healthy subjects were examined. In the logistic regression analysis latency and accuracy of constant saccades were the best predictors for operated HAB with correct overall classification rate of 79.3%. Accuracy was worse and latency longer in operated HAB group than in control group. In pseudo-random saccades correct classification between the groups was achieved in 82.8% of all cases with latency and accuracy as predictors. In PRPEM test the best frequency combinations in differentiating operated HAB patients from controls were 0.25 and 0.425 Hz for gain, and 0.3 and 0.7 Hz for phase and gain, the correct overall classification rate being 73.3% in both cases. The characteristic changes in voluntary eye movements after removal of cerebellar hemangioblastoma seem to be insufficient timing of initiating the eye movement.

Case-Control Studies↗

PubMed1997

Oculomotor pathology in Menière's disease.

In this study data of voluntary eye movements 62 patients (mean age was 49.6 years) with Meniere's disease and 38 healthy control subjects were examined. Pseudo-random smooth pursuit (PRPEM) tests were conducted with frequency combination of 0.25 and 0.425 Hz. Saccades at constant targets and pseudo-randomly shifting targets were evaluated. In logistic regression analysis constant saccades correctly classified the cases in 57% as saccadic latency discriminating the groups best, latency being longer in Meniere group. In pseudo-random saccades, correct classification was achieved in 75.4% of all cases as latency discriminating the groups best, and latency was longer in Meniere group. In PRPEM, correct classification was achieved in 65.3% of all cases as gain by amplitude (GA), discriminating the groups best, and GA was smaller in Meniere group. Pseudo-random saccade test is a demanding task and that may explain why a peripheral vestibular lesion may interfere visual tracking and scanning performance. Latency is the most vulnerable of parameters to be lesioned. Results indicate that a peripheral vestibular lesion influences the control of voluntary eye movements and may explain the complaints of visual targeting on objects that patients with Meniere's disease have.

Case-Control Studies↗

PubMed1997

Neural networks in neurotologic expert systems.

Artificial intelligence donates new possibilities to neurotologic research. Neural networks are a computer-based reasoning method which can be applied in expert systems created for clinical decision support. Neural networks have been used in medical imaging, in medical signal processing and to analyze both clinical and laboratory data. Principally, neural networks simulate the function of the brain. They have to be taught to make correct decisions from the input data. This learning process can be either supervised or unsupervised. The decision making is based on mathematical transformations and it occurs on a hidden level. Calculations are made on parallel manner and the decision making simulates pattern recognition method. Neural networks suit well in medical problems which cannot be defined in simple rules. A drawback of neural networks is that the decisions are irrational and cannot be motivated to the user. Another problem is neural networks' difficulty to handle incomplete input data, i.e., how to define some default or expected values for unknown input parameters. In a complex medical area, which would require multilayered neural networks, the neural networks require a large amount of solved cases for the learning process. In our experience neural networks seem not suitable for diagnosing vertigo and a better choice would be either case-based reasoning or possibly genetic algorithms or a combination of these.

Diagnosis, Computer-Assisted↗

PubMed1997

Impaired interferon production by leukocytes from patients with Bell palsy and lack of findings suggestive for a systemic viral involvement.

HYPOTHESIS: This study aimed to test the hypothesis that viral and other microbial infections cause Bell palsy and to use the interferon (IFN) alpha/beta-induced MxA protein as an indicator of systemic viral infection. BACKGROUND: Bell palsy has been previously associated with several viral infections. Recently, after this study was completed, herpes simplex virus DNA was detected in the endoneurial fluid of some patients with Bell palsy. METHODS: Serum and blood mononuclear cells were obtained from 30 patients with Bell palsy and 12 control subjects. The sera were tested for antibodies to 21 microbes. Mononuclear cells were assayed for (a) MxA protein using immunoblotting and (b) capacity to produce IFN in short-term culture after stimulation with influenza A virus. RESULTS: No significant differences were seen in serum antibodies or MxA protein between the patients and controls. The geometric mean of leukocyte IFN production in the convalescent phase of Bell palsy patients was higher than in the acute phase but remained still at significantly lower levels as compared with the control group (p < 0.05). In three patients there was no detectable IFN production. CONCLUSIONS: These results provide no evidence for a systemic viral involvement in Bell palsy, but the observed decreased IFN-producing capacity at the onset of Bell palsy could be a sign of transient immunosuppression or of an abnormal frequency of leukocyte subpopulations in the disease.

Adolescent↗

PubMed1997

Benign recurrent vertigo--true or artificial diagnosis?

The etiology of many diseases involving vertigo is still unknown although the same etiologic factors have been suggested for several diseases. In most cases the diseases are diagnosed on the basis of exclusion-other possible causes being ruled out before the diagnosis can be confirmed. Benign recurrent vertigo (BRV) has been defined as spells of vertigo characteristic of Menieres disease without auditory or clinical neurologic symptoms and signs. The etiology of this condition is also unknown. BRV has been linked to migraine and viral diseases. In a prospective study we collected the clinical history and the signs and results of neurotologic and audiologic tests from 33 patients with a BRV diagnosis. The clinical characteristics truly mimicked the vertigo seen in Menieres disease. The concept of vestibular Menieres disease is not widely accepted, and without auditory signs BRV is the only diagnosis that can be given to these patients. In other studies up to 25% of the patients initially diagnosed with BRV subsequently developed another peripheral vestibular disorder. Until the etiology of diseases involving vertigo is more clearly understood, artificial diagnoses like BRV, must be accepted.

Adult↗

PubMed1996

Psychomotor speed and postural control in chronic low back pain patients A controlled follow-up study.

STUDY DESIGN: Psychomotor speed (reaction time) and postural control (center point of force velocity) among healthy control volunteers and patients with chronic low back pain (LBP) were studied at the beginning of an active, functional, restoration back rehabilitation program and 5 months after the program. OBJECTIVES: To study cross-sectionally reaction times and center points of force velocity among control volunteers and patients with low back pain, and to evaluate the effects of the restoration on these measures of motor function in a follow-up examination. SUMMARY OF BACKGROUND DATA: Deficits of motor skills and of coordination have been reported in association with musculoskeletal disorders, but one can only speculate about an association between proprioceptive dysfunction and low back disorders on the basis of the currently available data. METHODS: Sixty-one healthy control volunteers and 99 patients with low back pain-68 of these patients experienced moderate pain; 31 experienced severe pain-participated in the study. Reaction times for upper and lower limbs were tested with a system based on a microcomputer. Postural stability was measured with a vertical force platform. RESULTS: A consistent trend was found in which patients with low back pain had reaction times slower than these of control volunteers. Man with severe low back pain had significantly longer hand reaction times than men in the control group (P = 0.03). Women with severe low back pain also had poorer postural control than women with moderate low back pain (P = 0.02) and women in the control group (P = 0.04). Functional restoration seemed to have an effect on reaction times. The restoration was considered successful if the condition of a patient with a disability that had resulted from low back pain improved during the follow-up examination and unsuccessful if the disability worsened. Patients who experienced these results were identified in groups called "good" and "poor," respectively. Among men, the reaction times improved in the control group and "good" groups, but they became slower in the "poor" group. The difference between "good" and "poor" groups was significant (P = 0.008). Women in the "good" group achieved the most improved reaction times, and the difference between these women and the control women almost reached significance (P = 0.076). CONCLUSION: The results indicate that patients with chronic low back pain have impaired psychomotor speed and, among women, impaired postural control. Psychomotor speed improved during an active, functional, restoration back rehabilitation program.

Adult↗

PubMed1996

Increased incidence of retching and vomiting during periovulatory phase after middle ear surgery.

PURPOSE: To assess the effect of the menstrual cycle on postoperative retching and vomiting (R&V) after middle ear surgery, and the efficacy of prophylaxis against R&V in female patients with transdermal scopolamine during either general or local anaesthesia and with intravenous ondansetron during general anaesthesia. METHOD: A post hoc analysis of the data on 85 female patients with normal menstrual cycles from three prospective studies on the prophylaxis of postoperative nausea and vomiting after middle ear surgery on 205 patients. RESULTS: Periovulatory period (menstrual dates 11-24) and history of motion sickness were predictors for R&V. During 2-24hr, both the percentage of patients needing droperidol and the mean number of doses were lower in the perimenstrual group (menstrual dates 25-10) than in the periovulatory group 27 vs 51% (P < 0.05) and 0.2 vs 0.7 (P < 0.01), respectively. Prophylaxis with transdermal scopolamine was a predictor for lowered R&V (P < 0.05) and resulted in fewer doses of droperidol (0.4 +/- 0.7 vs 1.4 +/- 1.5, P < 0.01). This reduction was significant during the periovulatory period (from 1.4 +/- 1.3 to 0.3 +/- 0.5, P < 0.005). Ondansetron reduced the mean need for droperidol from 1.4 +/- 1.5 to 0.6 +/- 0.8, (P < 0.05). CONCLUSION: The incidence of R&V after middle ear surgery was lower during the perimenstrual phase. In the periovulatory phase, transdermal scopolamine was more efficient as prophylaxis against R&V than ondansetron. All female patients scheduled for middle ear surgery should be considered individually to receive prophylaxis against R&V.

Adolescent↗

PubMed1996

Otoneurological expert system.

An otoneurological expert system was developed to help collect data and diagnose both central and peripheral diseases causing vertigo. Patient history and otoneurological and other examination results are used in the reasoning process. 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 the otoneurological expert system 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. Graphic displays illustrate the linear and nonlinear correlation between the symptoms and diseases. Emphasis is placed on diminishing the possibility of a wrong decision rather than maximizing the likelihood of reaching only one right decision, so that even rare diseases can be taken into consideration.

Diagnosis, Computer-Assisted↗