Hypertrophic obstructive cardiomyopathy.
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Aged↗
Biomedical subjects
R D Yee
Publications and source records attributed to R D Yee.
Gastric eosinophilia in rats immunized with stomach.
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Animals↗
Autoenucleation.
Autoenucleation is a rare occurrence. An unusual case is presented of a young woman who manually extracted her right globe and was left with a temporal hemianopsia in the remaining eye. Legends surrounding autoenucleation and the medical literature are reviewed, with emphasis on psychiatric aspects and pathologic findings in ocular avulsion.
Adult↗
Vestibulo-ocular reflexes in peripheral labyrinthine lesions: I. Unilateral dysfunction.
Measurements were made of the lesion-induced changes in vestibulo-ocular reflexes to rotatory stimuli in a group of patients with total unilateral labyrinthine paralysis and in a group with partial unilateral labyrinthine paralysis. Significant differences were found in the amplitude and phase of the response to low-frequency rotation and in the time constant of the post-rotatory response to impulsive rotation between normal subjects and patients with total unilateral labyrinthine paralysis. The results were evaluated by the use of a simplified model of vestibular function that allows the parametric evaluation of the characteristics of vestibular responses. It was found that changes in vestibulo-ocular reflex characteristics take place in parallel in both the time constant and the sensitivity of the system parameters used to describe the responses. The physiologic significance of the changes and their implication for diagnostic purposes are discussed.
Electrooculography↗
Vestibulo-ocular reflexes in peripheral labyrinthine lesions: II. Caloric testing.
In a group of patients with unilateral labyrinthine dysfunction, the maximal velocity of the slow component response to caloric stimulation was compared with that to horizontal vestibular rotatory stimulation by a low-frequency stimulus. It was found that the larger the magnitude of the caloric response, the larger were the gain and sensitivity of the vestibulo-ocular reflex induced by physiologic stimuli. Rotary stimulation of patients with only one functioning inner ear provides information equivalent to that obtained from caloric stimulation and allows more rigorous quantification of the state of the vestibulo-ocular reflex.
Caloric Tests↗
Vestibulo-ocular reflexes in peripheral labyrinthine lesions: III. Bilateral dysfunction.
Measurements were made of the lesion-induced changes in vestibulo-ocular reflexes (VOR) to rotatory stimuli in a group of patients with bilateral peripheral labyrinthine lesions. All the patients had caloric responses that were below the confidence levels used for normal responses in our laboratory. Responses to rotatory stimuli were greatly decreased or absent at low frequencies of stimulation, but present to a much greater degree at the higher frequencies. Phase measurements showed an increase in relationship to the velocity of the stimulus; there was a corresponding shortening of the time constant as obtained from impulse response measurements. A parametric study indicated that the changes in the responses can be described by a decrease in the sensitivity coefficient and in the basic time constant of a simplified pendulum model equation of vestibular function. A theoretical analysis of the data using a new model for the organization of the vestibular pathways indicated that the preservation of the high-frequency responses was the result of adaptive changes brought about in the central vestibular pathways and/or changes in the receptor-neuron transduction characteristics. Thus, despite the almost complete absence of any caloric response, the vestibular system reflexes remained adequate to maintain gaze during normal head movements.
Adult↗
Comparison of vestibular subjective sensation and nystagmus responses during computerized harmonic acceleration tests.
A comparison was made between the phase of vestibulo-ocular reflex (VOR) responses to sinusoidal rotatory tests and the phase of the subjective sensation (SS) to rotation. A parallelism was found between the results of both sets of data such that they behaved in accordance with the prediction of the pendulum model of vestibular function. The time constant of the VOR (17.5 seconds) was longer, however, than that of the SS (13 seconds). Measurements in patients with unilateral labyrinthine pathology also showed comparable changes in both responses. One group of patients with complete unilateral labyrinthine paralysis showed an advance of the phase of the VOR and of the SS. However, phase measurements in the group of patients with only partial unilateral labyrinthine paralysis were not significantly different statistically from those of normal subjects.
Caloric Tests↗
Voluntary control of the human vestibulo-ocular reflex.
The ability of normal subjects to increase their vestibulo-ocular reflex (VOR) gain with an imagined stationary frame of reference was dependent on their strategy and the test conditions. With large amplitude sinusoidal rotation (greater than 50 degrees) subjects could not increase their VOR gain regardless of the strategy used. With small amplitude excursions (less than 50 degrees) they could significantly increase their VOR gain if they used a 'single stripe' strategy. Accompanying this increase in VOR gain was an increase in the phase lead of VOR slow phase velocity relative to head velocity. Apparently the signal used to augment the VOR gain with an imagined stationary surround had phase characteristics similar to those of primary vestibular afferent neurons.
Eye Movements↗
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↗
Congenital nystagmus in identical twins: discordant features.
Identical twins with congenital nystagmus were examined and studied with eye movement recordings and videotaping. The nystagmus differed in its location of the null zone, its frequency and amplitude, the degree of persistence in the dark, and the degree of impairment of pursuit and optokinetic nystagmus. As the two boys have the identical genetic constitution, we postulate that the discordant features of the nystagmus represent variable expressivity or, alternatively, the influence of environmental factors.
Diseases in Twins↗
Congenital double elevator palsy: vertical saccadic velocity utilizing the scleral search coil technique.
Four patients with congenital double elevator palsy were studied who had clinically brisk elevation of the affected eye from downgaze to the midline position of rest, but severely limited or absent elevation above primary position. Forced duction tests were negative and Bell's phenomenon was present preoperatively in all patients. To clarify why upgaze saccades clinically seemed intact below but not above midline, vertical saccadic velocities were measured using the scleral search coil technique. The tracings of three cases suggest sufficient superior rectus function to generate a normal upward saccadic trajectory. A supranuclear lesion is the most likely etiology of the inability to elevate the eye well above primary position in these three patients. In a fourth patient, the reduced ability to elevate the affected eye above primary position is caused by a superior rectus paresis with decreased upward saccadic velocities. We suggest at least three distinct groups of patients present clinically as double elevator palsy: primary inferior rectus restriction, primary superior rectus paresis or palsy, and congenital supranuclear elevation deficiency.
Adolescent↗