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Biomedical subjects

J M Furman

Publications and source records attributed to J M Furman.

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

Off-vertical axis rotation: a test of the otolith-ocular reflex.

The vestibulo-ocular reflex was studied via off-vertical axis rotation (OVAR) in the dark. The axis of the turntable could be tilted from vertical by up to 30 degrees. Eye movements were measured with electro-oculography. Results from healthy asymptomatic subjects indicated that 1) a reliable otolith-induced response could be obtained during constant velocity OVAR using a velocity of 60 degrees/s with a tilt of 30 degrees; 2) constant velocity OVAR rotation was nausea-producing and, especially if subjects were rotated in the dark about an earth-vertical axis prior to being tilted, disorienting; and 3) sinusoidal OVAR produced minimal nausea; the eye movement response appeared to be the result of a combination of semicircular canal and otolith components. We conclude that OVAR has the potential of becoming a useful method for clinically assessing both the otolith-ocular reflex and semicircular canal-otolith interaction.

Adult↗
PubMed1992

Plasticity of the human otolith-ocular reflex.

The eye movement response to earth vertical axis rotation in the dark, a semicircular canal stimulus, can be altered by prior exposure to combined visual-vestibular stimuli. Such plasticity of the vestibulo-ocular reflex has not been described for earth horizontal axis rotation, a dynamic otolith stimulus. Twenty normal human subjects underwent one of two types of adaptation paradigms designed either to attenuate or enhance the gain of the semicircular canal-ocular reflex prior to undergoing otolith-ocular reflex testing with horizontal axis rotation. The adaptation paradigm paired a 0.2 Hz sinusoidal rotation about a vertical axis with a 0.2 Hz optokinetic stripe pattern that was deliberately mismatched in peak velocity. Pre- and post-adaptation horizontal axis rotations were at 60 degrees/s in the dark and produced a modulation in the slow component velocity of nystagmus having a frequency of 0.17 Hz due to putative stimulation of the otolith organs. Results showed that the magnitude of this modulation component response was altered in a manner similar to the alteration in semicircular canal-ocular responses. These results suggest that physiologic alteration of the vestibulo-ocular reflex using deliberately mismatched visual and semicircular canal stimuli induces changes in both canal-ocular and otolith-ocular responses. We postulate, therefore, that central nervous system pathways responsible for controlling the gains of canal-ocular and otolith-ocular reflexes are shared.

Adaptation, Physiological↗
PubMed1991

Asymmetrical ocular pursuit with posterior fossa tumors.

We report two patients with posterior fossa neoplasms who demonstrated asymmetrically impaired horizontal ocular pursuit documented with electrooculography. One patient had impaired pursuit contralateral to a pontomedullary lesion, whereas the second patient had impaired pursuit ipsilateral to a pontocerebellar lesion. These patients demonstrate that posterior fossa lesions may impair ocular pursuit either contralaterally or ipsilaterally unlike cerebral hemispheric lesions, which impair ocular pursuit ipsilaterally or bilaterally.

Adenocarcinoma↗
PubMed1991

Familial sensorineural hearing loss: a correlative study of audiologic, radiographic, and vestibular findings.

A multidisciplinary approach to the study of a family with autosomal dominant sensorineural hearing loss is presented. The affected family members underwent extensive clinical and laboratory evaluation. They were found to have various degrees of bilateral congenital inner ear anomalies as imaged by computed tomography. The degree of structural abnormalities in the inner ears correlated with the severity of hearing impairment. Vestibular testing revealed nonspecific abnormalities generally correlating with audiologic and radiographic findings. This report presents a unique form of sensorineural hearing loss not previously described and is the first in-depth clinical study of nonsyndromal "Mondini dysplasia" occurring in a family.

Adult↗
PubMed1990

Epileptic nystagmus.

We report a 52-year-old woman with episodes of vertigo accompanied by right beating nystagmus and left posterior temporoparietal sharp waves and spikes on electroencephalogram without change in level of consciousness. Electrooculography demonstrated that the episodes of nystagmus were not preceded by gaze deviation and that nystagmus slow component velocities were linear. This patient's epileptic nystagmus may have been the result of excitation of cerebral ocular pursuit pathways.

Electroencephalography↗
PubMed1990

Characteristics of the memory loss of a patient with Wernicke-Korsakoff's syndrome without alcoholism.

The memory loss in alcoholic Wernicke-Korsakoff syndrome has been well characterized. However, it has been suggested that some of the neuropsychological defects seen in these patients are due to frontal lobe dysfunction resulting from chronic alcohol abuse. The present report details the nature and extent of the amnesia in a Wernicke-Korsakoff patient who did not have a history of alcoholism. In spite of her normal performance on measures of frontal lobe function, this patient showed many characteristics similar to those seen in alcoholic Wernicke-Korsakoff syndrome including a graded loss of remote memories and abnormal semantic information processing. Thus, the extent of the "core" features of this amnesic syndrome may be greater than was previously thought.

Alcohol Amnestic Disorder↗
PubMed1990

Vestibular function in periodic alternating nystagmus.

The vestibulo-ocular reflex of 4 patients with periodic alternating nystagmus (PAN) was studied in detail. Rotational testing was used to investigate the horizontal semicircular canal-ocular reflex, canal-otolith interaction, and the dynamic otolith-ocular reflex. Results indicated abnormal gain and phase of the horizontal semicircular canal-ocular reflex during sinusoidal rotation and a variable rate of decay of postrotatory responses. Each patient had abnormal canal-otolith interaction. An enlarged modulation component of the dynamic otolith-ocular response was observed in each patient. This study supports the idea that PAN is caused by an instability in the velocity storage element, a hypothetical neural circuit that perseverates the eye movement response to both vestibular and optokinetic stimulation. Further, we postulate that PAN may be caused by lesions of the cerebellar uvula and nodulus or their connections with the brainstem vestibular nuclei.

Adult↗
PubMed1990

Vestibular recruitment in Meniere's disease.

The aim of this study was to search for vestibular recruitment in a sample of patients with Meniere's disease. Recruitment was defined as an abnormal growth of response with increasing stimulus intensity. Twenty-nine patients were tested with sinusoidal rotation of three different magnitudes at four different frequencies. We also searched for auditory recruitment in each patient via tests of auditory brain stem responses, acoustic reflexes, and loudness balance and discomfort level. Analysis of vestibular responses indicated, on average, a linear relationship between stimulus magnitude and response magnitude, ie, doubling the stimulus magnitude resulted in twice the response magnitude. Meniere's patients did not yield results significantly different (although they were more variable) from those of the normal subjects. The vestibular responses of patients with auditory recruitment did not differ systematically from those of patients without auditory recruitment. We conclude that vestibular recruitment, if it exists in patients with Meniere's disease, is not demonstrated by sinusoidal rotational testing.

Adult↗
PubMed1989

Vestibular responses in Wernicke's encephalopathy.

Two patients with Wernicke's encephalopathy were evaluated with quantitative vestibulo-ocular reflex and ocular motor testing. Vestibulo-ocular reflex testing included caloric irrigation, earth vertical axis rotational sinusoids, and rotational impulses. Both patients demonstrated hypoactive vestibular responses to both caloric and rotational stimuli at the time of presentation. One patient had unbeating nystagmus that diminished with upgaze, downgaze, or convergence. Following treatment with thiamine, both patients' vestibular responses improved but remained abnormal, with a short vestibulo-ocular reflex time constant and increased low-frequency rotational phase lead. Impairment of the velocity storage element attributable to damage to the vestibular nucleus and nucleus prepositus hypoglossi may account for this permanent effect on the vestibulo-ocular reflex.

Female↗
PubMed1989

Central adaptation models of the vestibulo-ocular and optokinetic systems.

A theoretical analysis of two models of the vestibulo-ocular and optokinetic systems was performed. Each model contains a filter element in the vestibular periphery to account for peripheral adaptation, and a filter element in the central vestibulo-optokinetic circuit to account for central adaptation. Both models account for 1 adaptation, i.e. a response decay to a constant angular acceleration input, in both peripheral vestibular afferent and vestibulo-ocular reflex (VOR) responses and 2 the reversal phases of optokinetic after-nystagmus (OKAN) and the VOR and 3 oscillatory behavior such as periodic alternating nystagmus. The two models differ regarding the order of their VOR transfer function. Also, they predict different OKAN patterns following a prolonged optokinetic stimulus. These models have behavioral implications and suggest future experiments.

Adaptation, Physiological↗
PubMed1989

Earth horizontal axis rotational responses in patients with unilateral peripheral vestibular deficits.

We evaluated the vestibulo-ocular reflex (VOR) of five patients with surgically confirmed unilateral peripheral vestibular lesions. Testing used both earth vertical axis (EVA) and earth horizontal axis (EHA) yaw rotation. Results indicated that the patients had short VOR time constants, asymmetric responses to both EVA and EHA rotation, and normal EHA modulation components. These findings suggest that unilateral peripheral vestibular loss causes a shortened VOR time constant even with the addition of dynamic otolithic stimulation and causes an asymmetry in semicircular canal-ocular reflexes and one aspect of otolith-ocular reflexes.

Aged↗
PubMed1989

Eyes open versus eyes closed: effect on human rotational responses.

The effect of eyelid closure on the response to rotational vestibular stimulation was assessed by evaluating 16 normal human subjects with both earth vertical axis (EVA) and earth horizontal axis (EHA) yaw rotations with either eyes closed (EC) or eyes open in the dark (EOD). Results indicated that for EVA rotation, the subjects' responses were of larger magnitude and less variable with EOD than with EC. However, for EHA rotation, responses were of larger magnitude and equally variable with EC as compared to EOD. Our data also indicated that the quality of the EHA response with EC was altered because eyelid closure influenced the amount of periodic gaze. We conclude that eyelid closure has an effect upon both canalocular and otolithocular reflexes and suggest that both EVA and EHA rotational testing be performed with EOD rather than with EC.

Adult↗
PubMed1989

Modern vestibular function testing.

Current tests of vestibular function concentrate on the horizontal semicircular canal-ocular reflex because it is the easiest reflex to stimulate (calorically and rotationally) and record (using electro-oculography). Tests of the other vestibulo-ocular reflexes (vertical semicircular canal and otolith) and of the vestibulospinal reflexes have yet to be shown useful in the clinical setting. Digital video recording of eye movements and vestibular-evoked responses are promising new technologies that may affect clinical testing in the near future.

Electronystagmography↗
PubMed1988

Spontaneous remission of paraneoplastic ocular flutter and saccadic intrusions.

We report two women with ocular flutter and saccadic intrusions, documented by electro-oculography, who had complete spontaneous remission of their ocular motor findings prior to the appearance of a primary neoplastic process remote from the nervous system. Transient elevation of blood HVA and VMA levels was detected in one patient who subsequently had breast cancer. These cases indicate that spontaneous remission of saccadic oscillations does not necessarily imply a benign outcome. Patients with this ocular motor abnormality should be followed closely for signs of a remote neoplasm even if initial investigation is negative.

Adult↗
PubMed1979

Application of linear system analysis to the horizontal vestibulo-ocular reflex of the alert rhesus monkey using pseudorandom binary sequence and single frequency sinusoidal stimulation.

Horizontal eye movements of the alert rhesus monkey resulting from both pseudorandom binary sequence (PRBS) and single frequency sinusoidal rotational stimulation were analyzed using a PDP 11/40 computer in order to generate gain, phase, and coherence estimates at discrete frequencies between 0.008 and 1.28 Hz. A computer simulation of vestibular induced eye movements was used to validate our analysis procedures and to determine the effects of digital noise. Frequency domain transfer functions derived from gain and phase estimates revealed that the responses to PRBS stimulation and to single frequency sinusoids were not appreciably different. PRBS testing was accomplished in approximately one third the time required for sinusoidal testing and yielded highly reproducible data. We conclude that PRBS stimulation is a reliable and efficient method for assessing linear system parameters of the horizontal vestibulo-ocular reflex. PRBS testing may be particularly advantageous in studies of vestibulo-oculomotor plasticity in which rapid assessment of alterations in system dynamics is essential.

Animals↗