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Biomedical subjects

R W Baloh

Publications and source records attributed to R W Baloh.

At least 19 recordsLinked to original sources
PubMed1992

Otolith-ocular testing in human subjects.

Assessment of the otolith-ocular reflex of human subjects involves linear acceleration and/or changes in the orientation of the head with respect to gravity. Several such stimuli are currently under investigation regarding their applicability to the evaluation of patients with dizziness and balance disorders. Discussed in this paper are off-vertical axis rotation, eccentric rotation, pitch and roll rotation, and linear acceleration. For each of these stimuli, basic principles, normative human data, and patient data are described. Although none of these methods are currently established for clinical use, each of them, especially off-vertical axis rotation and linear acceleration, have the potential for developing into a clinically useful method for assessing otolith function in man.

Electrooculography↗
PubMed1992

Optokinetic and vestibular interactions with smooth pursuit: psychophysical responses.

The effect was evaluated in normal subjects of the subjective perception of motion of a small visual target (VT) when combined with the effect of vestibular stimulation produced by different magnitudes of constant angular accelerations in the dark or the effect of optokinetic stimulation produced by different constant velocities of rotation. The visual target appeared to the subject to travel more slowly and for a shorter duration when it moved in the direction of the body's angular acceleration or against that of the optokinetic drum. The perceived error in motion was: (i) in the same direction as the subject's motion sensation produced by either of the two stimuli, and (ii) quantitatively related, although differently, to the magnitude of each of the two stimulus modalities; an heuristic model is proposed to account for these observations.

Acceleration↗
PubMed1992

Migraine-associated dizziness.

We reviewed the clinical histories, examinations and results of quantitative vestibular testing in 91 patients with migraine-associated dizziness. Nausea and vomiting, hypersensitivity to motion and postural instability accompanied the dizziness. In the majority of patients, the temporal profile of the dizziness was more typical of the headache phase of migraine than of the aura phase. Nineteen patients (20.9%) had unilateral hypoexcitability to caloric stimulation, which represents a modestly increased risk of damage to the peripheral vestibular apparatus. We propose two separate pathophysiologic mechanisms for the production of dizziness with migraine: Short-duration vertiginous attacks lasting minutes to 2 hours and temporally associated with headache are due to the same mechanism as other aura phenomena (spreading wave of depression and/or transient vasospasm). Longer-duration attacks of vertigo and motion sickness lasting days, with or without headache, result from the release of neuroactive peptides into peripheral and central vestibular structures, causing an increased baseline firing of primary afferent neurons and increased sensitivity to motion.

Adult↗
PubMed1992

Dizziness in older people.

Patients use the term dizziness to describe a sensation of altered orientation in space. Because visual, proprioceptive, somatosensory and vestibular signals provide the main information about the position of the head and body in space, damage to any of these systems can lead to a complaint of dizziness. Changes in the brain centers that integrate these orienting signals can also result in a sensation of dizziness. This review focuses on the pathophysiology, diagnosis, and management of the common causes of dizziness in older people.

Accidental Falls↗
PubMed1992

Vertigo and the anterior inferior cerebellar artery syndrome.

We present two patients with clinical features of infarction in the distribution of the anterior inferior cerebellar artery (AICA) who had vertigo as an isolated symptom for several months prior to infarction. Both had risk factors for cerebrovascular disease and other episodes of transient neurologic symptoms not associated with vertigo. At the time of infarction they developed vertigo, unilateral hearing loss, tinnitus, facial numbness, and hemiataxia. MRI identified hyperintense lesions in the lateral pons and middle cerebellar peduncle on T2-weighted images. Audiometry and electronystagmography documented absent auditory and vestibular function on the affected side. Since the blood supply to the inner ear and the vestibulocochlear nerve arises from AICA, a combination of peripheral and central symptoms and signs is characteristic of the AICA infarction syndrome. The vertigo that preceded infarction may have resulted from transient ischemia to the inner ear or the vestibular nerve.

Aged↗
PubMed1992

Posttraumatic cranial neuropathies.

Injury to cranial nerves is a common sequela of blunt head trauma. The olfactory, facial, and audiovestibular nerves are damaged most often, followed by the optic and ocular motor nerves. The trigeminal and lower cranial nerves are rarely involved. Chances of recovery are greatest for the facial nerve, intermediate for the ocular motor nerves, and least likely for the olfactory, optic, and audiovestibular nerves. Treatment is usually symptomatic, although steroids or surgical decompression of the optic and facial nerves can lead to dramatic results in selected patients.

Brain Concussion↗
PubMed1991

Gravity and the vertical vestibulo-ocular reflex.

We studied the vertical vestibulo-ocular reflex (VOR) and vertical visual-vestibular interaction induced by voluntary pitch in the upright and onside positions in eight normal human subjects. Subjects were trained to produce sinusoidal (0.4 to 1.6 Hz) pitch head movements guided by a frequency modulated sound signal. Eye and head movements were recorded with a magnetic search coil. There was no significant difference between the pooled average gain (eye velocity/head velocity) of the vertical VOR in the upright and onside positions. Vertical VOR gain in any position could be more or less than 1.0 for individual subjects. By contrast, gain with an earth-fixed visual target was always near 1.0. Asymmetries in the gain of upward and downward VOR, pursuit and fixation suppression of the VOR were found in individual subjects, but in the group of normal subjects there was no significant difference between gain of up and down eye movements induced by vestibular, visual or visual-vestibular stimulation in any position. We conclude that during voluntary pitch otolith signals are not critical for normal functioning of the vertical VOR.

Adult↗
PubMed1991

The electrically evoked vestibulo-ocular reflex: I. Normal subjects.

Recent animal studies indicate that electric currents applied through perilymphatic-space electrodes stimulate vestibular primary afferent neurons directly. These findings suggest that electrical stimulation may provide a testing method by which the vestibular nerve and central pathways could be evaluated separately from the vestibular end-organ. The goal of this study was to obtain normative data on human beings for an electrically evoked vestibulo-ocular reflex (EVOR). Sinusoidal electrical stimuli (0.0125 to 0.8 Hz, 4 mA peak intensity) were applied along the interaural axis through mastoid electrodes in 10 subjects. Horizontal eye movements were recorded by an infrared limbus-tracking device. The subjects also underwent rotational stimulation at the same frequencies so that their horizontal vestibulo-ocular reflex (VOR) could be evaluated. Nystagmus was observed in the EVOR at lower stimulus frequencies, whereas purely sinusoidal eye deviations occurred at higher frequencies. The phase of the EVOR slow-component eye velocity consistently lagged the stimulus. This contrasts with the phase measurements of the VOR in the same subjects, which exhibited a lead relative to head velocity. These findings suggest that currents applied to human beings may activate vestibular primary afferents independent of peripheral receptor mechanisms and thereby provide a "site-of-lesion" testing method by which the vestibular nerve and central pathways can be evaluated separately from the vestibular end-organ.

Adolescent↗
PubMed1991

Acetazolamide-responsive vestibulocerebellar syndrome: clinical and oculographic features.

Five patients who presented with long-standing episodic vertigo had ocular motor signs localizing to the vestibulocerebellum. In each patient, the episodic vertigo was either abolished or markedly decreased in frequency and severity with acetazolamide therapy. In 4, other family members had identical symptoms and signs. This syndrome is 1 of the few treatable causes of chronic episodic vertigo.

Acetazolamide↗
PubMed1990

Drop attacks with Menière's syndrome.

We report the clinical features of 12 patients with drop attacks associated with Meniere's syndrome. Each described a sensation of being pushed, thrown, or knocked to the ground or a sudden illusion of movement of the environment that led to a fall. These episodes were not accompanied by symptoms of their typical attacks of Meniere's syndrome. The drop attacks occurred early and late in the course of the disease; they were the initial manifestation in 1 patient. In the majority the episodes spontaneously remitted, although Meniere's syndrome continued to progress. These attacks probably result from a sudden mechanical deformation of the otolithic membrane of the utricle or saccule due to pressure gradients within the inner ear. They are important to recognize because their prognosis is relatively benign compared to other causes of drop attacks.

Accidental Falls↗
PubMed1990

Internuclear ophthalmoplegia in the Chiari type II malformation.

We describe 3 cases of Chiari type II malformation presenting with bilateral internuclear ophthalmoplegia (INO). Although prominent, the INO was not an isolated sign in any of the patients; superimposed abduction paresis was present in 2, and deficits in smooth pursuit, optokinetic nystagmus, and vestibulo-ocular responses were present in 3. Two had hydrocephalus: 1 was clinically unchanged without therapy after 5 years; the other did not improve with shunting. Findings in our 3 patients, along with the 4 previously reported, confirm that INO is 1 manifestation of widespread brainstem or cerebellar dysfunction. Its origin is probably multifactorial, related to hydrocephalus, vascular compromise, direct neuronal distortion, or congenital neural malformation.

Adult↗
PubMed1990

Wallenberg's syndrome following neck manipulation.

We describe 4 patients ages 28 to 41 with lateral medullary infarction (Wallenberg's syndrome) following chiropractic neck manipulation. In 3 patients, angiography documented dissection of the extracranial 3rd segment of the vertebral artery near the atlantoaxial joint. The onset of neurologic symptoms following manipulation varied from immediate to 4 days. All had good recovery with minor residual deficits. Although the association between chiropractic neck manipulation and vertebral-basilar artery distribution infarction is well known, we emphasize its occurrence in young healthy individuals without commonly regarded predisposing factors.

Adult↗