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Biomedical subjects

R W Baloh

Publications and source records attributed to R W Baloh.

At least 217 records · Page 12Linked to original sources
PubMed1978

Vestibular-optokinetic interactions in normal subjects and in patients with peripheral vestibular dysfunction.

The vestibulo-ocular reflex (VOR) during rotation, optokinetic nystagmus (OKN), and interactions between the vestibulo-ocular and optokinetic systems were studied quantitatively in 10 normal human subjects, 15 patients with unilateral horizontal semicircular canal paralysis (UP), and 11 patients with bilateral horizontal semicircular canal paralysis (BP). The OKN gain (eye velocity/drum velocity) was not significantly different between the normal subjects and the patient groups. During tests in which rotatory and visual stimuli were presented simultaneously, the contribution to the observed eye movements by the VOR was only one-fourth to one-third of its gain during rotation in the dark in the normal subjects and UP patients. These interactive tests did not differentiate UP patients from normal subjects but did separate BP patients from normal subjects.

Adult↗
PubMed1978

The spectrum of audiologic and vestibular findings in patients with Meniere's disease.

A retrospective study of 55 patients with Meniere's disease suggested a subgrouping based on presentation of auditory symptoms. Patients were defined as "definite" (documented fluctuating hearing loss and episodic vertigo), "probable" (history of fluctuating hearing loss and episodic vertigo) and "possible" (history of fluctuating tinnitus and episodic vertigo). An in-depth discussion of the natural history, audiometric and vestibular findings is presented.

Adult↗
PubMed1977

Primary position upbeat nystagmus. A clinicopathologic study.

Eye movements were studied with electro-oculography in a patient with primary position, large amplitude, upbeat nystagmus. The upbeat nystagmus increased in amplitude on upward gaze, decreased on downward gaze, and was not altered by loss of fixation. The patient could not produce smooth pursuit movements upward or to the left, but had normal saccadic and vestibular induced eye movements in all directions. At necropsy, a low grade glioma was found involving primarily the medulla and caudal pons. The inferior olives and prepositus hypoglossal nuclei were diffusely infiltrated with tumor. These results suggest (1) primary position upbeat nystagmus is due to a defect in the upward smooth pursuit system, (2) the lower brain stem at the level of the inferior olives and nucleus prepositus hypoglossi is important in the mediation of vertical pursuit, and (3) primary position upbeat nystagmus can result from damage to several nuclei and interconnecting pathways in the caudal brain stem and midline cerebellum involved in control of vertical smooth pursuit.

Ataxia↗
PubMed1977

Subclinical eye movement disorders in patients with multiple sclerosis.

Eye movements were quantitatively evaluated in 16 patients with well-documented multiple sclerosis who had minimal or no clinically apparent eye movement disorder. Induced saccade and pursuit eye movements were recorded with electro-oculography and analyzed with newly developed programs on a laboratory digital computer. Thirteen of the 16 patients had significant (p less than 0.05) impairment of saccades and/or smooth pursuit when compared with 25 normal subjects tested in our laboratory. The type and frequency of abnormalities were as follows: saccade dysmetria, eight; delayed saccade reaction time, five; bilateral saccade slowing, four; slowing of adducting saccades only (medial longitudinal fasciculus syndrome), one; and impaired smooth pursuit, both directions, three, and one direction only, three. In addition, four patients had vestibular nystagmus with eyes closed, and one patient had typical rebound nystagmus. These data suggest that quantitative assessment of eye movements in patients with suspected multiple sclerosis can help in identifying the important "second lesion."

Adult↗
PubMed1976

Cerebellar-pontine angle tumors. Results of quantitative vestibulo-ocular testing.

A new quantitative vestibulo-ocular test battery was evaluated in 12 patients with surgically confirmed cerebellar-pontine angle tumors. The battery consisted of precise vestibular and visual stimuli and digital computer analyses of responses. Eleven of 12 patients, including all patients with acoustic neurolemmomas, had significant vestibular deficits on the tumor side (P less than .01). Contrary to previous reports, rotatory tests (impulse and sinusoidal acceleration) reliably identified the side and magnitude of vestibular deficit. Eight of nine patients with surgically confirmed brain stem compression had significantly impaired smooth pursuit (P less than .05). Optokinetic nystagmus was impaired in five of nine patients with brain stem compression (P less than .05). By combining the results of the entire test battery with standard clinical evaluation, a good prediction of tumor size, location, and type was possible.

Adolescent↗
PubMed1976

Rapid eye movements in myasthenia gravis. II. Electro-oculographic analysis.

Voluntary saccades were studied by electro-oculography in ten patients with myasthenia gravis (MG) and in eight patients with other types of ophthalmoplegia. Despite limited range of eye movements, maximum velocities of 20 degree and 40 degree saccades in patients with MG were not significantly different from those in normal individuals, whereas maximum velocities in patients with other types of ophthalmoplegia were significantly decreased. In some myasthenic patients, small amplitude saccades were hypermetric and had high velocities, appearing clinically as "quiver" movements characteristic of MG. In MG the preservation of saccades with high initial velocities, even in the presence of severe ophthalmoplegia, suggests that muscle fibers generating rapid movements during saccades (twitch fibers) can be relatively spared when muscle fibers responsible for maintenance of excentric gaze (tonic fibers) are severely affected.

Adolescent↗
PubMed1976

Periodic alternating nystagmus.

Three patients with periodic alternating nystagmus (PAN) are described in detail. Digital computer methods were used to quantify their disordered eye movement in an attempt to understand the pathophysiology. One of the patients was unusual in showing rebound nystagmus with fixation and PAN without fixation. Each patient had hyperactive vestibular responses and the phase and gain of the PAN cycles were altered in a predictable fashion by vestibular stimuli. It is postulated that PAN represents cyclical firing between reciprocally connected groups of inhibitory neurons within the vestibular and oculomotor nuclei. The cyclical firing is initiated by a critical imbalance of tonic input to either group of normally functioning neurons.

Adult↗
PubMed1976

Saccade fatigue and response to edrophonium for the diagnosis of myasthenia gravis.

Maximum velocity and amplitude of repetitive ( 1-per-second) 30 degrees saccadic eye movements were quantitatively assessed for 4 minutes before and after intravenous edrophonium chloride as a diagnostic test for myasthenia gravis. Atropine was given initially to suppress muscarinic side effects. Eye movements were recorded by electrooculography and a digital computer identified saccadic eye movements and plotted amplitude-velocity relationships. When compared with control subjects, eleven of twelve patients with proven MG had a significant increase in saccade amplitude and/or maximum velocity after edrophonium chloride. Only three of twelve proven MG patients had clinically apparent extraocular muscle weakness. The initial period of fatigue improved the sensitivity of the test in those patients who began with normal saccade amplitude and maximum velocity. Two of the patients with positive saccade fatigue tests had no change in optokinetic nystagmus amplitude before and after edrophonium chloride. It is concluded that, quantitative assessment of repetitive large angle saccades before and after edrophonium chloride is a sensitive test for extraocular muscle involvement in MG.

Adolescent↗
PubMed1976

A study of congenital nystagmus: waveforms.

Eighteen patients with congenital nystagmus were studied with the techniques of electronystagmography and computer analysis. We found several complex wave forms of congenital nystagmus in the primary position of gaze above those of jerk and pendular nystagmus as defined clinically. An etiologic classification of motor fixation defect and sensory fixation defect nystagmus based on waveforms is not justified. Ocular tracking studies demonstrate that the smooth pursuit system is operational in congenital nystagmus and substantiate the belief that the fast component of jerk nystagmus is a corrective movement generated by the saccadic system. Patients with congenital nystagmus are able to produce voluntary saccades with normal velocity-amplitude relationships.

Adolescent↗
PubMed1976

Pathologic nystagmus: a classification based on electro-oculographic recordings.

The widespread availability of eye movement recording systems has added a new dimension to our ability to accurately describe nystagmus. Electrooculography (EOG) is the simplest and most readily available system. With EOG the effect of loss of fixation (either with eyes closed, or eyes open in darkness) can be accurately assessed and quantitative evaluation of nystagmus speed, frequency and amplitude is easily made. Of equal importance, it provides a permanent record that can be compared with nystagmus recorded in other patients. By comparing clinical observation with paper recordings, both students and experienced clinicians can become more efficient in recognizing different varieties of nystagmus.

Electrooculography↗
PubMed1976

Algorithm for analyses of saccadic eye movements using a digital computer.

An algorithm for digital computer analyses of electro-oculographically recorded saccardic eye movements is presented. From a brief, 4-min recording session detailed statistical information about saccade velocity, accuracy, and delay time can be obtained. Since this data is not significantly altered by practice of motivational factors, it provides a sensitive functional test of the extra-ocular muscles and their brain control system.

Animals↗
PubMed1976

Positional vertigo with cerebellar astrocytoma.

The authors present two surgically verified cases of cerebellar astrocytoma extending into the fourth ventricular floor. Each patient presented with positional vertigo, and electronystagmography revealed positional nystagmus indicative of a central lesion. The findings in these cases emphasize the need of looking for positional nystagmus in patients with suspected posterior fossa lesions.

Adolescent↗
PubMed1975

Neuropsychological dysfunction in children with chronic low-level lead absorption.

To investigate the relation between low-level absorption and neuropsychological function, blind evaluations were under-taken in forty-six symptom-free children aged 3-15 years with blood-lead concentrations of 40-68 mug. per 100 ml. (mean 48 mug. per 100 ml.) and in seventy-eight ethnically and socioeconomically similar controls with levels greater than mug. per 100 ml. (mean 27 mug. per (100 ml). All children lived within 6-6 km. of a large, lead-emitting smelter, and in many cases residence there had been lifelong. Mean age in the lead group was 8-3 years and in the controls 9-3. Testing with Wechsler intelligence scales for schoolchildren and preschool children (W.I.S.C. and W.P.P.S.I.) showed age-adjusted performance I.Q. to be significantly decreased in the group with higher lead levels (mean scores, W.I.S.C. plus W.P.P.S.I., 95 v. 103). Children in all ages in the lead group also had significant slowing in a finger-wrist tapping test. Full-scale I.Q., verbal I.Q., BEHAVIOUR, AND HYPERACTIVITY RATINGS DID NOT DIFFER.

Absorption↗
PubMed1975

Quantitative measurement of saccade amplitude, duration, and velocity.

A method for rapid, accurate measurement of saccade amplitude, duration, and velocity (average and maximum) was developed as a functional test of the extraocular motor system. Recordings were made with a direct-current electro-oculographic system, and data analysis was performed on a laboratory digital computer. Saccade amplitude and duration were found to be linearly correlated in 25 normal subjects, with a mean slope of 2.7 msec per degree over a large amplitude range. In the same subjects, saccade amplitude and velocity (maximum or average) had a nonlinear relationship that was best fit by an exponential equation. The two constants of this equation adequately characterized the relationship between saccade amplitude and velocity and permitted rapid statistical comparison between normal and abnormal subjects.

Electrooculography↗
PubMed1975

The saccade velocity test.

Scatter plots showing the amplitude versus velocity (maximum and average) relationship of horizontal saccades in 25 normal subjects and four groups of patients were statistically compared. Three patients with "subclinical" medial longitudinal fasciculus syndromes had significant slowing of adducting saccades, and two of these patients had unsuspected slowing of abducting saccades (although to a lesser degree). Five patients with olivopontocerebellar degeneration and three patients with myotonic dystrophy had significant slowing of saccades in both directions. Five patients with surgically documented acoustic neuromas did not have significant slowing despite brain-stem compression in three. It is concluded that the saccade velocity test can be a useful clinical tool in addition to its potential in clinical research.

Adult↗
PubMed1975

Vestibulo-ocular function in patients with cerebellar atrophy.

Eye movement abnormalities were quantiatively assessed in four patients with clinically pure cerebellar atrophy (group A), six patients with brainstem plus cerebellar atrophy (group B), and five patients with Friedreich's ataxia (group C). Twelve patients had one or more types of spontaneous nystagmus; eight gaze nystagmus, three rebound nystagmus, wo positional nystagmus, and one vestibular nystagmus. Catoric-induced and rotatory-induced nystagmus was hyperactive in group A and diminished in group C. Group B had mixed responses. All patients demonstrated significant fixation instability and impaired smooth pursuit. There was dysmetria of voluntary saccades, with flutter and "rebound" saccades. Nine of 15 patients had significant slowing of induced saccades, including two patients in group A. It is concluded that quantitative vestibulocular tests can be useful in classifying the cerebellar atrophy syndromes.

Cerebellar Ataxia↗