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Biomedical subjects

J M Furman

Publications and source records attributed to J M Furman.

At least 37 records · Page 2Linked to original sources
PubMed2000

Characteristics of secondary phase post-rotatory nystagmus following off-vertical axis rotation in humans.

The nystagmus following yaw earth-vertical axis rotation often reverses direction, a phenomenon known as the "secondary phase". The purpose of this study was to examine the existence and the spatial and temporal properties of the secondary phase of post-rotatory nystagmus following off-vertical axis rotation (OVAR). Eleven normal human subjects were rotated at 120 or 180 degrees/s about an off-vertical axis and stopped in the left ear down or right ear down lateral position. Horizontal and vertical eye positions were recorded with a scleral search coil, and horizontal and vertical slow component eye velocities were computed. Our results indicate that (a) there is a robust secondary phase nystagmus following OVAR, and (b) the direction of the secondary phase nystagmus tends to align with earth-horizontal. These results can be explained by a minor modification of an existing VOR model that has been shown to produce secondary phase responses.

Adult↗
PubMed1999

Benign paroxysmal positional vertigo.

Benign paroxysmal positional vertigo is a common disorder of the inner ear that should be suspected in all patients with a history of positionally provoked vertigo. The condition appears to be caused by free-floating debris in the posterior semicircular canal. The diagnosis is confirmed by eliciting characteristic symptoms and signs during the Dix-Hallpike test. Although benign paroxysmal positional vertigo is usually a self-limited disorder, treatment with a specific bedside maneuver is effective and can provide the patient immediate and long-lasting relief. Although many patients with positionally provoked vertigo have typical benign paroxysmal positional vertigo, physicians should be aware of nonbenign variants.

Calcium Carbonate↗
PubMed1999

Postural sway with earth-fixed and body-referenced finger contact in young and older adults.

Sensory information from lightly touching a reference with the hand is known to influence postural sway in young adults. The primary aim of this study was to compare the influence of finger contact (FC) with an earth-fixed reference to the influence of FC with a body-fixed reference. A second goal of this study was to determine if FC is used differently by older adults compared to younger adults. Using a force plate, center of pressure at the feet was recorded from blindfolded young and older subjects during several conditions. Subjects either did or did not lightly touch a force-sensitive plate that was either earth-fixed or moved forward and backward in synchrony with body sway (that is, sway-referenced). In addition, support surface conditions were also varied, including a fixed floor and a sway-referenced floor using an Equitest. Results showed that the type of FC, floor condition, and age each had an effect on postural sway. Touching an earth-fixed plate decreased postural sway as compared to no touching, while touching a sway-referenced plate increased sway. This influence of FC was enhanced when the floor was sway-referenced. Although older subjects swayed more than young subjects overall, no age-FC interactions occurred, indicating that FC was not utilized differently between the age groups. This study suggests that FC cannot be disregarded as erroneous, especially when proprioceptive information from the legs is distorted. Further, FC is integrated with other sensory information by the postural control system similarly in young and older persons.

Adult↗
PubMed1999

Somatosensory cuing of head-only rotational testing.

Head-only rotational testing (HORT) is a method of assessing the vestibulo-ocular reflex (VOR) that can be performed at the bedside with inexpensive, transportable equipment. Previous studies of HORT using auditory cuing have suggested that test results are in large part independent of the method by which a subject's head is moved, that is, active versus passive. However, many subjects have difficulty moving their head at rotational frequencies of 3 Hz or greater. In an attempt to overcome this difficulty, and to learn more about HORT, we explored the possibility of providing subjects with a somatosensory, rather than an auditory cue for head movement. Somatosensory, cues were provided either by applying gentle pressure against a tightly-fitted headband or by lightly tapping on the shoulders. Our results with young, healthy subjects indicate that somatosensory cuing is an efficacious means of inducing periodic head rotation and that HORT results are unaffected by the type of cue provided. We conclude that somatosensory rather than auditory cuing may be the preferred method of performing HORT.

Adult↗
PubMed1999

The influence of dynamic visual environments on postural sway in the elderly.

Postural sway during stance has been found to be sensitive to moving visual scenes in young adults, children, and those with vestibular disease. The effect of visual environments on balance in elderly individuals is relatively unknown. The purpose of this study was to compare postural sway responses of healthy elderly to those of young subjects when both groups were exposed to a moving visual scene. Peak to peak, root mean squared, and mean velocity of the center of pressure were analyzed under conditions combining four moving scene amplitudes (2.5o, 5o, 7.5o, 10o) and two frequencies of scene movement (0.1 Hz, 0.25 Hz). Each visual condition was tested with a fixed floor and sway referenced platform. Results showed that elderly subjects swayed more than younger subjects when experiencing a moving visual scene under all conditions. The elderly were affected more than the young be sway referencing the platform. The differences between the two age groups were greater at increased amplitudes of scene movement. These results suggest that elderly are more influenced by dynamic visual information for balance than the young, particularly when cues from the ankles are altered.

Adult↗
PubMed1999

Voluntary movement strategies of individuals with unilateral peripheral vestibular hypofunction.

This study compared voluntary movement strategies of patients with unilateral peripheral vestibular hypofunction with those of age-matched healthy control subjects. All subjects performed three voluntary movement tasks with their dominant upper extremity: a forward flexion arm movement through 90 degrees, a reach to an overhead target, and a reach to a side target. Subjects performed the movement tasks sitting and standing (Body Position), and under precued and choice reaction time (RT) conditions (Task Certainty). Measures of motor planning and movement execution included RT and movement time (MT), respectively. Statistical analysis included separate Group x Task Certainty x Body Position ANOVA calculations for each task. Across tasks, results suggested no between group differences for RT. A Task Certainty main effect for the side and overhead tasks indicated that the choice RT situation resulted in longer RTs as compared to the precued RT condition. Movement time differed between the two groups. Across all three voluntary movement tasks, vestibular impaired subjects moved more slowly than control subjects. Providing vestibular subjects with a precue did not bring MT performance to the level of controls. Body position influenced MT for the side task only. Across both groups of subjects, MT for the side task was longer when performed in the standing position. The results of this study suggest that individuals with unilateral peripheral vestibular hypofunction initiate voluntary movement responses with similar timing as control subjects, but require more time to complete the movement. Vestibular rehabilitation should include goal-directed movement and should address issues of movement speed.

Adult↗
PubMed1998

Visual-induced postural sway in children with and without otitis media.

Children with otitis media with effusion (OME) have been shown to have a significantly higher velocity of sway than normal children. To further evaluate the effect of OME on balance, we studied visual dependency for balance by investigating the influence of optic flow on postural sway. The results of this preliminary study suggest that children with OME may be more visually dependent for balance than healthy age-matched controls. This was particularly evident for higher-frequency stimulus conditions (0.25 Hz) as opposed to lower-frequency stimulus conditions (0.10 Hz). These findings indicate that OME may affect vestibular function in children, thereby causing excessive reliance on other, nonvestibular sensory cues to maintain balance. Further studies are needed to define the role of vestibular function in the management of children with OME.

Child↗
PubMed1998

Treatment of benign positional vertigo using heels-over-head rotation.

Particle repositioning, using either bedside techniques or whole-body manipulation devices, has been used effectively to treat benign positional vertigo (BPV). We assessed the efficacy of particle repositioning using a device designed and built specifically to treat BPV that rotated patients 360 degrees heels-over-head in their sagittal body plane while their heads were turned to align the posterior semicircular canal with the plane of rotation. Eye movements were monitored during the maneuver by an infrared video recording system that allowed subsequent review of the induced nystagmus. Our results indicate that 1) heels-over-head rotation is an extremely efficacious procedure for treating patients with BPV and 2) the pattern of nystagmus during repositioning is consistent with the theory that free-floating debris is highly likely to account for BPV.

Adult↗
PubMed1997

Familial episodic ataxia: clinical heterogeneity in four families linked to chromosome 19p.

We describe the clinical and oculographic findings in 4 families with episodic ataxia and interictal nystagmus (EA-2) linked to chromosome 19p. Episodes varied from pure ataxia to combinations of symptoms suggesting involvement of the cerebellum, brainstem, and cortex. Some affected individuals exhibited a progressive ataxia syndrome phenotypically indistinguishable from the dominantly inherited spinocerebellar ataxia (SCA) syndromes. About one-half of the affected individuals had migraine headaches and several had episodes typical of basilar migraine. Oculographic findings were localizing to the vestibulocerebellum and posterior vermis. Additional genetic and environmental factors must account for the marked clinical heterogeneity in these families with an abnormal gene on chromosome 19p.

Adolescent↗
PubMed1997

Otolith-ocular responses in familial episodic ataxia linked to chromosome 19p.

We evaluated several members of a family with episodic ataxia type 2 linked to chromosome 19p by using a battery of vestibulo-ocular reflex (VOR) tests. Testing focused on the otolith-ocular reflex and semicircular canal-otolith interaction. Our aims were to improve understanding of the structures important for the VOR and to define further the range of vestibulo-ocular, in particular otolith-ocular, manifestations within a family with episodic ataxia. Ocular motor, semicircular canal-ocular, and semicircular canal-otolith interaction assessments suggested impairment of the vestibulo-cerebellum (ie, the flocculonodular lobe); the brainstem appeared to be relatively spared. Eye movements during constant velocity off-vertical axis rotation (OVAR), a pure otolith stimulus, indicated that the modulation component of the response was normal whereas the bias component was reduced or nearly absent. Based on these data, it appears that the cerebellum is not responsible for the generation of the modulation component of the response to OVAR. However, the bias component appears to depend on the caudal midline cerebellum.

Ataxia↗
PubMed1997

Computerized dynamic platform posturography.

Computerized dynamic platform posturography is defined in this technology assessment. The review discusses what computerized dynamic platform posturography measures, what the reliability and validity of the information are, and the uniqueness of the information provided. The clinical contribution and indications for testing are discussed. There are comments on future directions for research on computerized dynamic platform posturography and a summary and conclusion.

Diagnostic Techniques, Neurological↗
PubMed1997

Migraine-related vestibulopathy.

Migraine has been associated with specific vestibular disorders, including benign paroxysmal vertigo of childhood and benign recurrent vertigo in adults. Migraine may also play a role in chronic nonspecific vestibulopathy. Because scant data exist that describe the clinical findings and vestibular function abnormalities in suspected migraine-related vestibulopathy, we reviewed the history, physical examination, vestibular tests (electronystagmography, rotational chair, posturography), and response to treatment of 100 patients with diagnoses of migraine-related vestibulopathy. Dominant clinical features included chronic movement-associated dysequilibrium, unsteadiness, space and motion discomfort, and occasionally, episodic vertigo as an aura prior to headache, or true vertigo without headache. Common vestibular test abnormalities included a directional preponderance on rotational testing, unilateral reduced caloric responsiveness, and vestibular system dysfunction patterns on posturography. Treatment was usually directed at the underlying migraine condition by identifying and avoiding dietary triggers and prescribing prophylactic anti-migraine medications. Symptomatic relief was also provided using anti-motion sickness medications, vestibular rehabilitation, and pharmacotherapy directed at any associated anxiety or panic disorder.

Adolescent↗
PubMed1997

Vestibular compensation in a patient with a cerebellar infarction.

We report the case of a 67-year-old man who suffered a traumatic unilateral peripheral vestibular injury subsequent to an unrelated prior cerebellar infarction that occurred at least 2 years earlier. The patient's clinical course was marked by poor compensation for his peripheral vestibular loss. Four months after his vestibular injury, his symptoms of dizziness had not resolved. He had a spontaneous vestibular nystagmus, and laboratory testing indicated an asymmetric semicircular canal-ocular reflex. The otolith-ocular reflex, tested using off-vertical axis rotation, also was asymmetric but had a preserved modulation component. Visual-vestibular interaction and semicircular canal-otolith interaction were normal. An MRI indicated preservation of the flocculo-nodular lobe but infarction of the pyramis and uvula. Taken together, the findings in this case suggest that despite structural and functional preservation of the flocculo-nodular lobe, an anatomic region often labeled the "vestibulo-cerebellum", a lesion of the cerebellum that can impair CNS compensation for a unilateral peripheral lesion in humans.

Adaptation, Physiological↗
PubMed1997

Plasticity of responses to off-vertical axis rotation.

This study assessed whether a change in the magnitude of the angular vestibulo-ocular reflex (VOR) influences the magnitude of the linear VOR, thereby suggesting a common gain element for these reflexes. The responses to linear acceleration using yaw off-vertical axis rotation (OVAR) at 30 degrees tilt were recorded before and after an adaptation protocol designed to increase the angular VOR gain. Subjects included eight asymptomatic healthy young individuals. Eye movements, recorded with electro-oculography, were analyzed to yield gain of the horizontal angular VOR and the magnitude of the modulation and bias components of the response to OVAR. Results indicated that there was no consistent influence of angular VOR gain on the eye movement response to OVAR. Since previous studies have shown that responses to earth horizontal axis rotation are influenced consistently by angular VOR gain, our study suggests that high intensity otolithic stimulation is required to observe changes in the linear VOR following modification of the angular VOR.

Acceleration↗
PubMed1996

Galvanic-induced postural movements as a test of vestibular function in humans.

Galvanic stimulation produces a postural sway and eye movements in humans. Since galvanic currents are thought to exert their effect at the trigger zone of the vestibular nerve, an intact vestibular nerve should be necessary to produce a response. We have used galvanic stimulation in humans to test the hypothesis that intact vestibular nerve fibers are required to obtain a postural away response. Experimental subjects included normal subjects, patients who had undergone resection of an acoustic neuroma, and patients who had undergone vestibular neurectomy and surgical labyrinthectomy. Our results support the hypothesis that an intact vestibular nerve is necessary to produce a response. Moreover, two patients with recurrent vertigo following vestibular neurectomy and labyrinthectomy, who had absent ice-water caloric test responses in the operated ears, were found to have a positive galvanic response. This result suggested that their recurrent vertigo was based on intact residual vestibular nerve fibers. Although previous research has not yielded a routine clinical use for galvanic stimulation, our results suggest that galvanic stimulation of the vestibular system can provide unique and valuable diagnostic information.

Aged↗
PubMed1996

Time-varying characteristics of visually induced postural sway.

To study potential time-varying dynamics of postural sway as measured via center-of-pressure (COP) under the feet, we applied time-frequency analysis to COP data from ten vestibularly impaired subjects and 13 nonimpaired controls, during quiet stance and in response to visual perturbation. This analysis revealed that 1) the spectral characteristics of COP change over time; 2) there are time-dependent and frequency-dependent differences in COP between impaired and nonimpaired populations during visual perturbation, and 3) there is no difference in COP during quiet stance (eyes opne) between impaired and nonimpaired populations for the parameters investigated. A novel finding of this research is that controls appear to adapt to constant frequency visual perturbation, while vestibularly impaired subjects do not. This difference could not have been observed with conventional Fourier analysis, which is commonly used in COP data analysis, because time is not a parameter of the spectrum and adaptation is, by nature, a time-varying process. These results suggest that time-frequency analysis of COP data is useful for studying temporal dynamics of postural control, and in particular the differences between vestibularly impaired subjects and healthy controls during visual perturbation.

Adult↗
PubMed1996

Panic, agoraphobia, and vestibular dysfunction.

OBJECTIVE: Otoneurological abnormalities have been reported in panic disorder. The purpose of this investigation was to determine the prevalence of such findings in panic disorder with and without agoraphobia and to discern whether vestibular dysfunction was associated with specific symptoms. METHOD: Clinical audiological and vestibular tests were administered to 30 patients with uncomplicated panic disorder (without agoraphobia or with only mild agoraphobia), 29 patients with panic disorder with moderate to severe agoraphobia, 27 patients with anxiety but no history of panic attacks, 13 patients with depressive disorders but no history of anxiety or panic attacks, and 45 normal comparison subjects. Evaluators were blind to subjects' diagnostic group. Quantitative measures of subjects' discomfort with space and motion and of the frequency of certain symptoms between and during panic attacks were obtained. Anxiety state levels were measured during the vestibular tests. RESULTS: Vestibular abnormalities were common in all the groups but most prevalent in the patients with panic disorder with moderate to severe agoraphobia. Vestibular dysfunction was associated with space and motion discomfort and with frequency of vestibular symptoms between, but not during, panic attacks. There were no major differences between the two panic groups in anxiety levels during vestibular testing. There were no significant differences between groups on the audiological component of the test battery. Exploratory data analysis indicated that the constellation of vestibular tests most specific for agoraphobia was one indicating compensated peripheral vestibular dysfunction. CONCLUSIONS: Subclinical vestibular dysfunction, as identified by clinical tests, may contribute to the phenomenology of panic disorder, particularly to the development of agoraphobia in panic disorder patients.

Adult↗