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Biomedical subjects

J M Furman

Publications and source records attributed to J M Furman.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1985

Infantile cerebellar atrophy.

We describe a family whose members have a dominantly inherited, early-onset, nonprogressive syndrome that includes spontaneous upbeating nystagmus and mild gait ataxia. Magnetic resonance imaging showed localized atrophy of the cerebellar vermis. Several families described in the literature resemble our family but differ in mode of inheritance, age at onset, rate of progression, or clinical findings. We believe this family represents a unique type of inherited early-onset atrophy of the cerebellar vermis.

Adult↗
PubMed1985

Dorsal midbrain syndrome: clinical and oculographic findings.

We report clinical and oculographic findings in seven patients with the dorsal midbrain syndrome (Parinaud's syndrome). All presented with limited upward voluntary gaze and convergence nystagmus with attempted upward voluntary gaze. Quantitative analysis of vertical eye movements documented characteristic abnormalities of saccades with relative preservation of reflex eye movements (ie, vestibular, optokinetic, and visual-vestibular). Vertical saccade velocity was only slightly decreased in five patients with tumors, indicating that the vertical burst neurons in the mesencephalic reticular formation and their efferent pathways to the oculomotor neurons were minimally damaged. On the other hand, two patients with probable brainstem encephalitis exhibited marked slowing of vertical saccades, indicating that the burst neurons, or their efferent pathways to the oculomotor neurons, were severely damaged.

Adolescent↗
PubMed1985

Atypical brainstem encephalitis: magnetic resonance imaging and oculographic features.

A 50-year-old woman had primary position upbeating nystagmus, abnormalities of the lower cranial nerves, mild cerebellar signs, and CSF lymphocytosis. CT and MRI showed enlargement of the pons. Eye movement recordings revealed impaired pursuit and optokinetic nystagmus, and visual-vestibular interactions were absent. The patient improved spontaneously.

Brain Stem↗
PubMed1984

Head and eye movements in congenital nystagmus.

Patients with congenital nystagmus exhibit a wide range of unusual nystagmus waveforms and strategies to obtain maximum visual acuity. We investigated target acquisition strategies, head-eye coordination, and the effects of alteration of head position relative to gravity on congenital nystagmus waveforms in five patients. No changes in the nystagmus were found when patients' heads were placed in different positions relative to gravity. Two patients had distinctive abnormalities of head-eye coordination characterized both by failure of eye movement to precede head movement and by position of the eye in the orbit, after target acquisition, being in a direction opposite that of the head movement. We conclude that static changes in head position relative to gravity probably do not influence congenital nystagmus waveforms. In addition, some patients with congenital nystagmus may have abnormal head-eye coordination.

Adult↗
PubMed1983

Eye movements in Friedreich's ataxia.

Twenty-four patients with well-documented Friedreich's ataxia underwent quantitative oculomotor testing. A consistent pattern of eye movement abnormalities was observed. This pattern included fixation instability, inaccurate saccades with normal peak velocity, impaired smooth pursuit and optokinetic slow phases, decreased vestibulo-ocular reflex gain, and impaired visual-vestibular interaction. This pattern corresponds to the known pathologic changes of Friedreich's ataxia and can be useful in the differential diagnosis of cerebellar atrophy.

Adolescent↗
PubMed1981

Changes in the horizontal vestibulo-ocular reflex of the rhesus monkey with behavioral and pharmacological alerting.

It is well known that eye movements are influenced by an animal's state of arousal. Alterations in the dynamic characteristics of the horizontal vestibulo-ocular reflex of adolescent rhesus monkeys induced by changes in the animal's state of arousal were studied using linear system analysis employing both single frequency sinusoidal and white noise rotational stimulations. Arousal changes were induced by a behavioral task and/or the administration of amphetamines (0.5 mg/kg). Results indicate that highly alert animals display vestibulo-ocular reflex gains significantly different from less alert animals. Specifically, the gain of the vestibulo-ocular reflex is closer to unity over a wider range of frequencies in more alert animals. These changes were independent of the method used to maintain a high level of arousal.

Animals↗
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↗
PubMedDate not supplied

Long-latency rotational evoked potentials in subjects with and without bilateral vestibular loss.

Human subjects with and without profound bilateral vestibular loss were evaluated using repetitive rotational stimulation about an earth-vertical axis and signal averaging of vertex-recorded potentials. The stimulus events to which averaging was synchronized were acceleration/deceleration pulses produced by abrupt reversals in direction of angular velocity. In control subjects the long-latency rotational evoked potentials elicited via this paradigm were robust and reproducible. The responses of subjects with vestibular loss did not differ remarkably from those of the control subjects. We conclude that the long-latency rotational evoked potential elicited using a conventional rotary chair is not primarily of vestibular origin.

Adolescent↗