Biomedical subjects

J M Furman

Publications and source records attributed to J M Furman.

At least 91 records · Page 5Linked to original sources

PubMedDate not supplied

Eighth nerve signs in a case of multiple sclerosis.

We evaluated a 25-year-old woman with multiple sclerosis who presented with the acute onset of a profound unilateral high-frequency, sensorineural hearing loss that resolved clinically within 10 days. Click-elicited brain stem-evoked responses were abnormal at the time of presentation and demonstrated only limited recovery over a follow-up period of 11 months. Magnetic resonance imaging disclosed a lesion in the eighth nerve root-entry zone and the cochlear nucleus. Our findings in this case support the hypothesis of eighth nerve root-entry zone involvement in sudden hearing loss in multiple sclerosis and reinforce the notion that click-elicited brain stem-evoked responses are useful primarily to evaluate the high-frequency regions of the auditory system.

Adult↗

PubMedDate not supplied

A clinical taxonomy of dizziness and anxiety in the otoneurological setting.

Dizziness can be associated with otologic, neurologic, medical, and psychiatric conditions. This paper focuses on the interface between otologic and psychiatric conditions. Because dizziness often is situation specific, concepts of space and motion sensitivity (SMS), space and motion discomfort (SMD), and space and motion phobia (SMP) are needed to understand the interface. We present a framework involving several categories of interactions between balance and psychiatric disorders. The first category is that of dizziness caused by psychiatric disorder (psychiatric dizziness), including hyperventilation-induced dizziness during panic attacks. The second category involves chance cooccurrence of a psychiatric disorder and a balance disorder in the same patient. The third category involves problematic coping with balance symptoms (psychiatric overlay). The fourth category provides psychological explanations for the relationship between anxiety and balance disorders, including somatopsychic and psychosomatic relationships. The final category, neurological linkage, focuses on the overlap in the neurological circuitry involved in balance disorders and anxiety disorders.

Anxiety Disorders↗

PubMedDate not supplied

Vestibular rehabilitation for patients with agoraphobia and vestibular dysfunction: a pilot study.

This study examined whether physical therapy with vestibular rehabilitation exercises would benefit patients with agoraphobia and vestibular dysfunction. Nine patients went through a 2-week no-treatment baseline phase, a 4-week behavioral treatment phase focusing on self-directed exposure, and an 8-12-week vestibular rehabilitation phase (weekly sessions). On the main outcome measure, clinical global impressions (CGI) ratings of severity, behavioral treatment was accompanied by a reduction in severity (effect size d=0.8; P<.10). On the supplementary measures, the Hamilton Anxiety Scale (Hamilton-A) and the Chambless Mobility Inventory (MI), no significant improvements were noted. After vestibular rehabilitation therapy, further improvement occurred in CGI severity (d=0.65; two-tailed P<.10), and significant improvements occurred in the supplementary measures. The physical therapist identified motion-induced dizziness and disturbances in balance in most patients. These improved with rehabilitation. Although the results can be attributed to other explanations, they are not inconsistent with the hypothesis that vestibular dysfunction maintains agoraphobic symptoms in some patients.

Adult↗

PubMedDate not supplied

Testing of vestibular function: an adjunct in the assessment of chronic fatigue syndrome.

Patients with chronic fatigue syndrome (CFS) often complain of dysequilibrium that is nonspecific. The basis of this complaint is unknown but may be related to vestibular system abnormalities, in that an association between inner-ear deficits and infectious mononucleosis has been established in the medical literature. An overview of quantitative vestibular function testing is given, including vestibulo-ocular and vestibulospinal tests. The basic principles of caloric and rotational testing are provided, including the interaction between vision and the vestibular system. Moving-platform posturography is described. Preliminary results from quantitative vestibular function testing of a small group of individuals with CFS are provided.

Fatigue Syndrome, Chronic↗

PubMedDate not supplied

Surface dependence: a balance control strategy in panic disorder with agoraphobia.

OBJECTIVE: Previous studies have reported vestibular dysfunction and impaired balance in patients with agoraphobia. Vestibular dysfunction may lead to an information processing strategy focusing on spatial stimuli from two nonvestibular sensory channels, vision and proprioception. This nonvestibular balance control strategy may in turn lead to discomfort in situations involving inadequate visual or proprioceptive spatial cues (space and motion discomfort). The objective of this study was to examine sensory integration of spatial information in agoraphobia. Because of previous findings that space and motion discomfort and vestibular dysfunction are common in agoraphobia, we hypothesized that agoraphobics would use a nonvestibular balance control strategy. METHOD: Using computerized dynamic posturography, we examined balance performance in patients with panic disorder with agoraphobia, uncomplicated panic disorder, nonpanic anxiety disorders, and depression without anxiety, as well as healthy subjects for comparison. The posturography procedure included six sensory conditions in which visual and proprioceptive balance information was manipulated experimentally by permutations of sway-referencing the support surface or the visual surround or by having patients close their eyes. RESULTS: The agoraphobics had impaired balance when proprioceptive balance information was minimized by sway-referencing the support surface (p < 0.02). This pattern, called surface dependence, tended to be more pronounced in agoraphobics who reported space and motion discomfort, including fear of heights or boats. CONCLUSION: Agoraphobics rely on proprioceptive cues for maintenance of upright balance. This strategy may lead to intolerance of situations characterized by unstable support.

Adult↗

PubMedDate not supplied

Alternate and simultaneous binaural bithermal caloric testing: a comparison.

This study compares the results from simultaneous binaural bithermal and alternate binaural bithermal caloric testing of 652 patients with dizziness. Also compared are the abilities of these tests to distinguish between a population of healthy asymptomatic subjects and our patient population. Caloric testing used a closed-loop irrigation system. Eye movements were monitored with electro-oculography. The agreement between the results from the two tests was low. Also, while the simultaneous test was more sensitive, the alternate test was more specific. Using receiver-operator characteristic methodology, it was found that the ability of the alternate test to distinguish between a healthy population and a patient population was superior to that of the simultaneous test. There was no improvement in the ability to distinguish between a healthy population and a patient population when the results from the two tests were combined as compared to using the alternate caloric test alone.

Algorithms↗

PubMedDate not supplied

Dynamic range of the frequency response of the horizontal vestibulo-ocular reflex of the alert rhesus monkey.

The vestibulo-ocular reflex (VOR) of the alert rhesus monkey was studied using rotational acceleration in the horizontal plane. Both sinusoidal and pseudorandom binary sequence (PRBS) stimuli were used to perform parameters. Results from sinusoidal studies over the frequency range 0.01 to 1.28 Hz, with stimulus amplitudes ranging from 16 to 256 degrees/second were consistent with a linear model of the VOR. Results PRBS stimuli whose bandwidths extended from 0.008 to 0.45 Hz with amplitudes of 4 to 256 degrees corroborated the sinusoidal results. Sinusoidal data obtained at high rotational frequencies indicated that a peak VOR gain occurred at approximately 4 Hz. Close agreement between sinusoidal and PRBS data suggested that the rhesus VOR does not manifest the predictive behavior reported in studies of smooth pursuit eye movements.

Acceleration↗

PubMedDate not supplied

Modulation of mean eye position during vestibular induced eye movements of the rhesus monkey.

Vestibular induced nystagmus in the dark was measured during sinusoidal rotational stimulation in three male monkeys using electrooculography. A periodic modulation of mean eye position was observed. This periodic modulation was quantified by least squares fitting through the nystagmus a sinusoid whose frequency was the same as that of the stimulus. The magnitude and the phase of the best fitting sinusoid were used to determine gain and phase delay at various combinations of stimulus amplitudes and frequency. Results indicate that the mean eye position in the alert animals is predominantly modulated in the direction of the fast component of nystagmus. The magnitude of this modulation of mean eye position is independent of the amplitude of the stimulus. The phase relationship of this modulation is dependent on the frequency of stimulation. In drowsy animals, the modulation of mean eye position is predominantly in the direction of the slow component of nystagmus. We conclude that the modulation of mean eye position during vestibular induced nystagmus operates as an automatic gain control system which is sensitive to the animal's level of alertness. The quantitative data in this report are useful in refining current models of vestibular nystagmus.

Animals↗

PubMedDate not supplied

Eye movement abnormalities in a family with cerebellar vermian atrophy.

We report the oculographic findings in a family whose members have a dominantly inherited, early onset, non-progressive syndrome which includes spontaneous upbeating nystagmus and mild cerebellar ataxia associated with cerebellar vermian atrophy seen on magnetic resonance scanning. Eye movements recorded with electro-oculography and a magnetic scleral search coil revealed severely impaired horizontal and vertical smooth pursuit, optokinetic nystagmus and visual-vestibular interaction, symmetrical horizontal but asymmetrical vertical vestibulo-ocular reflex, and normal saccades. The midline cerebellum appears to be essential for both horizontal and vertical visual tracking and visual modification of the vestibulo-ocular reflex in man.

Adult↗

PubMedDate not supplied

Nystagmus responses in a group of normal humans during earth-horizontal axis rotation.

Horizontal eye movement responses to earth-horizontal yaw axis rotation were evaluated in 50 normal human subjects who were uniformly distributed in age (20-69 years) and equally divided by gender for each decade. The subjects were rotated with eyes open in the dark, using clockwise and counterclockwise 60 degree/s velocity trapezoids. The nystagmus slow component velocity (SCV) was analysed using four parameters: Amp, Bias, Mod and Tau. Amp and Tau characterize the canal-ocular reflex to constant velocity steps, while Mod and Bias characterize the "AC" and "DC" components of the otolith-ocular reflex. Results indicated that intersubject variability was larger than that seen in earth-vertical axis data. Tau depended significantly (p less than 0.05) upon subject gender, while Mod increased monotonically with age decade. Linear regression showed a positive correlation between pairs of SCV magnitude parameters (Amp, Bias and Mod), suggesting a common scaling effect. In addition, there was a negative correlation between the value of the decay time constant Tau and each of the three magnitude parameters. Thus, despite large intersubject variability, parameters that describe earth-horizontal yaw axis responses are loosely interrelated and some of them vary significantly with gender and age.

Adaptation, Physiological↗

PubMedDate not supplied

Rotational responses in patients with bilateral caloric reduction.

Caloric irrigation and earth vertical axis rotation, both horizontal semicircular canal stimuli, occasionally provide conflicting information about the presence of bilateral vestibular loss. The caloric and rotational responses of an unselected group of 1274 dizzy patients were compared to identify discrepancies between the two tests. Results indicated a poor correlation between the magnitude of response to caloric and rotational stimuli; about half of patients with reduced caloric responses (total eye speed less than or equal to 10 degrees per second) had rotational response magnitudes (at 0.05 Hz and above) that were within normal limits. Our findings confirm that bilateral caloric reduction is not sufficient evidence for diagnosing bilateral vestibular loss and indicate that, in some case, caloric responses may be absent despite apparent normal vestibular sensitivity as assessed by rotational testing.

Adolescent↗

PubMedDate not supplied

Visual-vestibular interaction in humans during earth-horizontal axis rotation.

Visual-vestibular interaction (VVI) using 60 degrees/s constant velocity earth horizontal axis (EHA) yaw rotation was measured in 7 human subjects. This so-called 'barbecue spit' rotation stimulated both the horizontal semicircular canals and the otolith organs. Subjects were tested with their eyes open in the dark (EOD), while fixating upon a target rotating with them (FIX), and while observing stationary optokinetic stripes (VVR). The resulting nystagmus slow component velocity (SCV) was analyzed. During EOD, subjects showed an exponentially decaying SCV response with a time constant of between 10 and 15 s that decayed to a non-zero baseline value (bias). Superimposed was a cyclic activity, modulation, whose period equalled the time for a complete revolution of the subject. During FIX, the average value of SCV was nearly zero indicating almost complete abolition of the exponential decay and bias components. The modulation component was reduced by half. During VVR, an exponential decay was observed in most subjects and the average value of the bias component nearly equalled that of the velocity of rotation. Modulation during VVR varied on a cycle-by-cycle basis. On average, the modulation component was nearly twice that for the EOD condition. We conclude that visual-vestibular interactions during EHA differ significantly from those during rotation about the vertical; specifically, there is a non-linear interaction between linear acceleration and optokinetic nystagmus.

Adult↗

PubMedDate not supplied

Visual-vestibular interaction during OVAR in the elderly.

This study assessed visual-otolith interaction in healthy older humans and compared responses from older subjects to those of younger subjects. Using off-vertical axis rotation (OVAR) to stimulate the otolith organs, eye movement responses, measured using electro-oculography, were recorded during rotation in the dark, rotation with an earth-fixed lighted visual surround, and rotation with a subject-fixed fixation target. Results indicated that older subjects, like young subjects, exhibit a modulation component that was as large during rotation with a lighted earth-fixed visual surround as that seen in the dark and a modulation component during rotation with a subject-fixed visual target that was incompletely suppressed. The modulation component was, in general, larger in the older subjects. This study confirms findings from a previous study of visual-otolith interaction in young subjects and suggests that older subjects, like young subjects, have difficulty visually suppressing the modulation component induced by off-vertical axis rotation.

Adult↗

PubMedDate not supplied

Recent advances in clinical neurotology.

In recent years, owing to significant technological developments and an increased number of investigators entering the field, there have been spectacular advances in our understanding of the basic anatomy and physiology of the vestibular system. Unfortunately, these advances in basic science are slow to impact the clinical management of patients. We have selected a few important advances in clinical neurotology that have impacted the diagnosis and treatment of patients with vestibular disorders. This material was originally presented at the "Mechanisms of Vestibular Function and Dysfunction" symposium of the 1994 Neural Control of Movement meeting in Waikoloa, Hawaii.

Humans↗

PubMedDate not supplied

Head-only rotational testing: influence of volition and vision.

Head-only rotational testing has been suggested as a method of assessing the vestibuloocular reflex in patients with reduced vestibular function as a result of ototoxicity. The purpose of this study was to investigate the influence of vision and volition on horizontal vestibuloocular reflex responses during head-only rotation in normal subjects to better define the test parameters for future clinical application. Ten asymptomatic, healthy subjects were tested using various combinations of volitional and visual conditions during head-only rotation. Results indicated that visual fixation enhanced responses slightly and that response dynamics were altered somewhat by volition. These findings provide motivation for future studies to further define head-only rotation test parameters for patients with suspected vestibular abnormalities.

Adult↗

PubMedDate not supplied

Reorientation of poststimulus nystagmus in tilted humans.

Recent studies indicate that the direction of postrotatory nystagmus and optokinetic afternystagmus reorients toward earth-horizontal in tilted subjects. To further examine this phenomenon in humans, we studied 8 adults (4M, 4F) with no history of neurologic or otologic disease. Vestibular stimulation consisted of yaw off-vertical axis rotation (OVAR) trapezoids with eyes open in the dark at 60 degrees/s constant velocity with a tilt angle of 30 degrees and a deceleration at 100 degrees/s2 to a stop in either the right-ear-down or the left-ear-down position. The optokinetic stimulus consisted of 5 degrees wide black and white stripes projected against a cylindrical visual surround 1 m in diameter rotated at a constant velocity of 30 degrees/s. The projector, visual surround, and subject were all tilted by 30 degrees; subjects were placed either in the right-ear-down or left-ear-down position. Eye position was measured using the magnetic scleral search coil technique. Each trial was scrutinized for the presence of reorientation of nystagmus in the subject's roll plane by looking for vertical nystagmus in the appropriate direction. Results indicated that reorientation of postrotatory nystagmus following OVAR was variable but often present. Reorientation of optokinetic afternystagmus was neither as consistent nor as robust as that seen following OVAR. These findings confirm that humans exhibit a predilection for eye rotations in the earth-horizontal plane.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

Postural sway of patients with vestibular disorders during optic flow.

Patients with vestibular orders often complain of sensitivity to moving visual environments, leading to dizziness and imbalance. This study investigated standing postural sway of healthy adults and patients with vestibular disorders in response to optic flow in the central field. Visual conditions of varying properties were presented monocularly with a 60 degrees viewing field. The conditions included: eye open-no flow, eye closed, sinusoidal expansions/contractions at 0.3 Hz, a constant flow giving the appearance of tunnel, and a vertically translating checkerboard. Postural sway, defined in this study as movement of the center of pressure, was recorded using a force platform during presentation of the visual stimuli. Patients with vestibular disorders were found to have a significantly higher magnitude of postural sway than control subjects while viewing central optic flow stimuli. Sinusoidally expanding and contracting optic flow induced postural sway at the stimulus frequency in both the patients and controls; patients, however, had a much larger increase in sway at frequencies near the stimulus frequency. These results suggest that postural control in patients with vestibular disorders is particularly affected by optic flow stimuli to the central region of the visual field.

Adult↗

PubMedDate not supplied

Influence of otolith organs, semicircular canals, and neck afferents on post-rotatory nystagmus.

The duration of post-rotatory nystagmus is known to be shortened by head tilt, a phenomenon that has been attributed to rapid discharge of the velocity storage mechanism. The relative importance of the various sensory signals associated with post-rotatory head tilt is unknown. Using both earth-vertical axis and off-vertical axis rotation, we investigated this issue in humans by combining sudden termination of constant velocity rotation with several post-rotatory maneuvers that stimulated combinations of otolith organ, somatosensory, and vertical semicircular canal afferents. Results indicated that horizontal post-rotatory nystagmus was shortened by maneuvers that move the head from upright to off-vertical and by cessation of dynamic otolith stimuli. Somatosensory, neck afferent, and transient vestibular stimulation had no consistent effect. We conclude that tilt suppression of postrotatory nystagmus and the short time constant following off-vertical axis rotation is primarily a function of otolith influence on the velocity storage system.

Adult↗