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Biomedical subjects

H Aalto

Publications and source records attributed to H Aalto.

At least 37 records · Page 2Linked to original sources
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

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↗
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↗
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

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

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↗
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↗
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

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↗