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Biomedical subjects

D Hydén

Publications and source records attributed to D Hydén.

At least 37 records · Page 2Linked to original sources
PubMed1985

Response of the human vestibulo-ocular reflex following long-term 2x magnified visual input.

This study examines the contribution of predictive motor programming to the adjustment of vestibulo-ocular reflex (VOR) gains after exposure to spectacles with a 2X magnification. When fully adapted, subjects exhibited two-fold gain increases with a 3 Hz sinewave stimulus with both an imaginary earth-fixed and imaginary moving target. Before complete adaptation was achieved, quick phases embedded in the slow component were observed intermittently which compensated for insufficient VOR gain. At 0.5 Hz in the same state of full adaptation during fixation of an imaginary earth-fixed target subjects exhibited a gain increase of only approximately 75% indicating that the contribution of VOR adjustment is not sufficient for perfect visual stabilization at lower frequencies. Over the range of random stimulation (0.5-5 Hz), the VOR failed to exhibit complete adaptation. The degree of adaptation derived with a VOR-cancellation task was less overall than that with a task requiring perfect compensatory eye movements. These findings indicate that central motor programmes are required in the adaptive process to achieve visual stability.

Adaptation, Physiological↗
PubMed1985

Peripheral facial palsy in children. A cerebrospinal fluid study.

Seven children and five adults with acute, peripheral facial palsy were investigated by clinical, blood and cerebrospinal fluid (CSF) examinations. Routine blood examinations and blood and CSF serological tests were normal. In all children studied the CSF showed an increased number of mononuclear white cells despite the absence of clinical signs of meningitis in all but one. Two of the twelve patients studied had normal CSF. Contrary to that in adults the outcome in children was excellent, all recovered totally within three months. The present study indicates that acute, peripheral facial palsy is a manifestation of a generalized disorder with subclinical pathology of the central nervous system, and that in children a lumbar puncture should be done, even if there are no signs of meningitis.

Adult↗
PubMed1984

Quantification of compensatory eye movements in light and darkness.

A broad frequency-band rotatory test has been used to quantify compensatory eye movements in 13 healthy subjects during light and darkness conditions. Eye movements were recorded by EOG. Head movements were recorded either by a potentiometer attached to the chair's axis of rotation or by an angular rate sensory attached to a bite-board. Gain and phase values between eye and head velocity were calculated. A systematic error in the higher frequency range is introduced in the results by assuming head movement equal to chair movement. Different instructions in the dark can alter the gain values at lower frequencies (up to 2 Hz) during sinusoidal stimulation. During pseudorandom stimulation no such differences can be obtained. During all test conditions with the rate sensor the gain values approach unity at about 3 Hz.

Adolescent↗
PubMed1983

Impairment of visuo-vestibular interaction in humans exposed to toluene.

15 healthy volunteers were investigated in a vestibulo-oculomotor test battery during toluene exposure. The concentration was comparable to the threshold limit value. The results were compared to an identical air experiment. The intoxication caused an impaired visual suppression during a pseudo-random oscillatory swing test and also an increased saccade speed. Other vestibular-oculomotor parameters were normal. The findings are in accordance with our earlier study on styrene in humans, showing that the visual suppression test and the saccade test are sensitive parameters assessing neurotoxic influences by organic solvents.

Adult↗
PubMed1983

Vestibulo-oculomotor disturbances caused by industrial solvents.

Animal experiments show that intoxication with hydrocarbon solvents influences the vestibulo-oculomotor reflex arc and indicate that the solvents block the inhibition of the vestibulo-oculomotor reflex presumably exerted by the cerebellum. The blood concentrations necessary to elicit oculomotor disturbances in animals were smaller than those that disturbed the vestibular function. Accordingly, in human experiments styrene and toluene exposure did not elicit any positional nystagmus but caused an increased saccade speed and a diminished visual suppression of vestibular nystagmus. Some cerebellar clinical pathologic process in patients who suffer from a psycho-organic syndrome caused by solvents leads us to believe that the cerebellum might be the most vulnerable part of the brain. Some patients had a positional nystagmus, but the most prominent pathologic signs were elicited by the visual suppression test. Our findings compare well with the increased saccade speed and diminished visual suppression in patients with cerebellar tumors and infarctions.

Benzene Derivatives↗
PubMed1981

Bell's palsy - part of a polyneuropathy?

Some authors have suggested that Bell's palsy should be considered a part of a polyneuritis cranialis and others, reporting Bell's palsy in patients with diabetes mellitus, proposed that it is an overt sign of a subclinical polyneuropathy. To study whether nerves other than the facial nerve were affected, the clinical findings of 112 patients with Bell's palsy were correlated with a quantitative EMG done on an asymptomatic leg muscle. The electromyographic results obtained from these leg muscles showed changes similar to those occurring in peripheral nerve lesions, and the changes correlated well with the degree of facial palsy. The results indicate that the patients with symptomatic facial dysfunction have an acute subclinical polyneuropathy.

Adolescent↗
PubMed1979

The influence of trichloroethylene and related drugs on the vestibular system.

A previously described experimental model for studying the effect of industrial solvents on the vestibular system of rabbits has been applied to trichloroethylene. Estimation of trichloroethylene and its metabolites in blood and cerebrospinal fluid was performed by gas chromatography. Vestibular function was studied by recording nystagmus, induced by positional changes or accelerated rotation. At blood levels of trichloroethylene above 30 p.p.m. "positional nystagmus" develops. Two metabolites of trichloroethylene, chloral hydrate and trichloroethanol, which are known as central nervous system (CNS) depressants, did not induce this abnormal nystagmus. However, alpha-chloralose, a derivative of chloral hydrate, induced positional nystagmus and also a markedly exaggerated nystagmus developed during rotatory acceleration. It is suggested that solvents like trichloroethylene elicit vestibular disturbances by stimulation of central subcortical vestibulo-oculomotor connections. The stimulation may be caused by a blockage of inhibitory systems.

Animals↗
PubMed1979

Vestibular symptoms in mumps deafness.

Deafness appears in as many as 4% of adult cases of epidemic parotitis. It is often severe, though reversible and is usually unilateral. Vertigo has been reported in mumps, as have occasional cases with impaired caloric reaction. Twenty cases of unilateral hearing impairment in mumps have been investigaed with audiometry and electronystagmography in order to determine the degree of permanent lesions. Nine of the patients had noted vertigo when falling ill with protitis. Five of these had normal calorics, 3 were impaired and one was without response in the deaf ear. No certain correlation between vertigo and permanent caloric impairment was found. An interesting finding was that 5 cases without vertigo showed an impaired or absent caloric responsiveness, which might confuse future diagnostics. Presumably, most patients with hearing impairment in mumps suffer vesticular damage, but the acute vertigo in early childhood is easily overlooked. No certain correlation between age at the onset of mumps and any permanent caloric disturbance was found. One mumps case is described, in which a severe hearing loss and caloric impairment returned to normal.

Adolescent↗
PubMed1978

Exposure of rabbits to styrene. Electronystagmographic findings correlated to the styrene level in blood and cerebrospinal fluid.

Objective methods for critically evaluating the toxic effect of industrial solvents are highly desirable. As many of these solvents are suspected to cause vertigo, an animal experimental model was set up for studying the effects of solvents on the vestibular systems. The vestibular function was studied by registration of involuntary eye movements--nystagmus--which are elicited via central vestibulo-oculomotor connections. During exposure to styrene a so-called positional nystagmus was demonstrated that indicated vestibular disturbances. Nystagmus is normally elicited by rotatory acceleration. During exposure to styrene the direction of this rotatory nystagmus was reversed. The incidence of the positional nystagmus correlated well with the blood level of the solvent, measured by gas chromatography. Kinetic studies also demonstrated a rapid equilibration between the level of the solvent in arterial blood and cerebrospinal fluid, and therefore suggested that estimation of the arterial level reliably indicates the level in the central nervous system.

Animals↗
PubMedDate not supplied

Acute "idiopathic" peripheral facial palsy: clinical, serological, and cerebrospinal fluid findings and effects of corticosteroids.

INTRODUCTION: The causes for peripheral facial palsy remain obscure in many patients. Evidence exists suggesting viruses, especially those belonging to the herpesvirus group, may be causative. This study was developed to evaluate this theory. METHODS: One hundred forty-seven patients with acute peripheral facial palsy of primarily unknown origin were studied. All were examined within 1 week of onset. Subsequent follow-up was undertaken until the palsy had recovered or become static. Paried cerebral spinal fluid and serum samples were obtained for serological evaluation to detect herpes simplex, varicella zoster, cytomegalovirus, measles, mumps, rubella, tick-borne encephalitis, adenovirus, Epstein-Barr virus, and human immunodeficiency virus, as well as the antibodies to Borrelia burgdorferi. RESULTS: Elevated antibiotic titers to Borrelia burgdorferi were observed in 11% of patients, whereas 9% of patients demonstrated elevated viral titers. Antibody pattern consistent with Epstein-Barr virus reactivation was present in 13%. A total of 67% were classified as idiopathic. CONCLUSION: Patients with reactivated Epstein-Barr virus were characterized by having a higher incidence of auricular pain and displayed diabetes mellitus in a higher frequency than in other groups. In the Borrelia group, neck/back pain was more common. Healing was less favorable in the Borrelia group despite an equal rate of palsy at onset and adequate antibiotic treatment. Corticosteroid treatment used in 44% of the patients did not significantly improve the functional outcome.

Acute Disease↗
PubMedDate not supplied

Mumps labyrinthitis, endolymphatic hydrops and sudden deafness in succession in the same ear.

Acute sensorineural hearing loss, mostly unilateral and reversible, is a well-known complication to mumps. Secondary endolymphatic hydrops, Ménière's syndrome, has rarely been associated with a previous mumps infection. This paper presents the case report of a woman who experienced unilateral hearing loss, vestibular symptoms and a caloric depression on the same ear during mumps. The symptoms and findings were reversible. Twelve years later she developed Ménière's symptoms in the same ear. This continued for 2 years after which she suddenly had a sensorineural hearing loss. This was localized in the mid- and high-tone area and was almost identical with the initial hearing loss 14 years earlier. Viral damage to the resorptive structures of the inner ear seems to have caused the hydrops. It also seemed to have weakened the neuronal structures of the ear, letting the initial damage become overt after repeated attacks of pathological pressure changes.

Adult↗
PubMedDate not supplied

Electronystagmographic and gaschromatographic studies in rabbits.

Complaints of vertigo from people who are exposed to industrial solvents have focused interest on their toxic effect on the nervous system. In order to evaluate the influence of an organic solvent, xylene, on the mammalian vestibular system, a series of rabbit experiments were performed. To achieve a constant concentration, the xylene was infused as a lipid emulsion. Blood concentrations were estimated by gas chromatography. Electronystagmography in darkness revealed that at blood xylene concentrations of 30 ppm all rabbits had a positional nystagmus. The beat direction was the opposite of positional alcohol nystagmus. Another difference between the alcohol and the xylene reaction was that rotatory nystagmus responses were exaggerated. The relations between the present findings and the reactions and blood concentrations in people exposed to industrial solvents are discussed.

Aerosols↗
PubMedDate not supplied

Human visuo-vestibular interaction as a basis for quantitative clinical diagnostics.

Visuo-vestibular interaction during randomized and sinusoidal head oscillations (0.5-5.0 Hz) was measured by power spectral analysis. It was shown that visual eye movement programmes can adjust the vestibulo-ocular reflex (VOR) gain at frequencies exceeding the dynamic range of visual tracking: above 3 Hz, gains exceeded unity during attempted fixation of a target moving with the subject whereas unity gains prevailed during fixation of an earth-fixed target. At low frequencies, fixation suppression was more efficient (-10 dB) when sinusoidal stimuli rather than randomized oscillations (-3 dB) were employed. Identical results were obtained when the fixation target moved with a total visual surround or against an earth-fixed visual background. Therefore, peripheral vision is normally not important for visual suppression of the VOR, which is dominated by foveal visual tracking at low frequencies.

Adult↗
PubMedDate not supplied

Prognosis in Bell's palsy based on symptoms, signs and laboratory data.

A prognostic study was performed in 197 consecutive cases of Bell's palsy. The patients were investigated soon after onset, after one week, after one month and then every second month until total recovery or one year had elapsed. Case histories, clinical findings, and laboratory data were noted. Facial EMG, pure tone audiometry, stapedius reflex test and electrogustometry were performed. The healing time, quality of final healing and amount of sequelae were noted. All data were fed to a computer and correlations were calculated. The final degree of healing was well correlated to the initial EMG, the stapedial reflex test and the electrogustometry but also to the clinical evaluation of the degree of motility at the first visit. A combination of EMG, electrogustometry, stapedial reflex test and evaluation of lacrimation showed a high rate of prognostic value.

Adult↗