Search PubMed⌕ Search

Biomedical subjects

R D Yee

Publications and source records attributed to R D Yee.

At least 19 recordsLinked to original sources
PubMed1992

Abnormal eye movements in Gerstmann-Sträussler-Scheinker disease.

Gerstmann-Sträussler-Scheinker disease is a familial disorder of progressive ataxia and dementia in adulthood with extrapyramidal signs in some families. Neuro-ophthalmic examinations and eye movement recordings were performed in members of a large Indiana kindred. Five affected members and 11 members at risk were studied. Eye movements were recorded with videotape, electro-oculography, and/or magnetic scleral search coil. All affected members had abnormal eye movements characteristic of extrapyramidal diseases and cerebellar disorders. Nine members at risk had normal eye movements, but two others had slightly abnormal eye movements. Neuro-ophthalmic examination and eye movement recordings might be helpful in detecting early signs of Gerstmann-Sträussler-Scheinker disease in persons at risk.

Adolescent↗
PubMed1991

Analysis of electro-oculographic artifact during vertical saccadic eye movements.

The analysis of vertical saccades by electrooculography (EOG) is limited by the presence of waveform artifacts that occur with both upward and downward saccades. The artifacts have been shown to increase the calculated velocities of upward saccades. For better evaluation of the nature of these artifacts, voluntary vertical saccades were recorded by EOG and magnetic search coil in five normal subjects and by EOG only in two patients who had previously undergone enucleation. All subjects demonstrated peaked EOG artifacts during vertical saccades. The amplitude of these artifacts was decreased but not completely eliminated by eyelid or eyeball fixation during the attempted saccade. Peak saccadic velocities were also decreased by eyelid fixation, but EOG measurements were generally less accurate than those obtained by search coil. There is evidence that these artifacts may be the result of a combination of eyelid electrical activity and resistance effects.

Electrooculography↗
PubMed1991

Electrooculography and discriminant analysis in Duane's syndrome and sixth-cranial-nerve palsy.

Eye-movement recordings may be helpful in the differentiation of Duane's syndrome from sixth-cranial-nerve palsy. Voluntary horizontal saccades were recorded and quantitated by electrooculography in 18 patients with unilateral type I Duane's syndrome and in 25 patients with sixth-nerve palsy. When ranges of abduction were matched, the peak velocities of abducting saccades in affected eyes were decreased equally in both groups. However, the peak velocities of adducting saccades in sound eyes were slowed in patients with Duane's syndrome. Because the standard deviations in saccadic velocities are large, computer-based, stepwise discriminant analyses were performed to identify the variables that proved to be useful in differentiating the two disorders. By entering these variables into the discriminant functions that were created, we could distinguish Duane's syndrome from sixth-nerve palsy in a statistically significant manner.

Abducens Nerve↗
PubMed1991

Vertical saccades in superior oblique palsy.

Vertical saccadic velocities in 10 patients who had unilateral superior oblique muscle palsy and 14 normal subjects were measured with the magnetic scleral search coil. The authors sought to determine whether downward saccades in patients who had superior oblique palsy are slow. Peak velocities of 10 degrees and 20 degrees saccades performed in the superior and inferior fields of the orbit, and 10 degrees, 20 degrees, and 30 degrees saccades performed across the center of the orbit were recorded with the eye in center gaze, 30 degrees of adduction, and 30 degrees of abduction. Paired t-tests did not show statistically significant differences between upward and downward saccades in patients with superior oblique palsy; no effects of orbital field or position of horizontal gaze were found (P greater than 0.01). Comparison of similar saccades between normal subjects and patients with superior oblique palsy by two-sample t-tests did not show significant differences between the two groups (P greater than 0.01).

Adult↗
PubMed1990

Visual motion response properties of neurons in dorsolateral pontine nucleus of alert monkey.

1. In this study we sought to characterize the visual motion processing that exists in the dorsolateral pontine nucleus (DLPN) and make a comparison with the reported visual responses of the middle temporal (MT) and medial superior temporal (MST) areas of the monkey cerebral cortex. The DLPN is implicated as a component of the visuomotor interface involved with the regulation of smooth-pursuit eye movements, because it is a major terminus for afferents from MT and MST and also the source of efferents to cerebellar regions involved with eye-movement control. 2. Some DLPN cells were preferentially responsive to discrete (spot and bar) visual stimuli, or to large-field, random-dot pattern motion, or to both discrete and large-field visual motion. The results suggest differential input from localized regions of MT and MST. 3. The visual-motion responses of DLPN neurons were direction selective for 86% of the discrete visual responses and 95% of the large-field responses. Direction tuning bandwidths (full-width at 50% maximum response amplitude) averaged 107 degrees and 120 degrees for discrete and large-field visual motion responses, respectively. For the two visual response types, the direction index averaged 0.95 and 1.02, indicating that responses to stimuli moving in preferred directions were, on average, 20 and 50 times greater than responses to discrete or large-field stimulus movement in the opposite directions, respectively. 4. Most of the DLPN visual responses to movements of discrete visual stimuli exhibited increases in amplitude up to preferred retinal image speeds between 20 and 80 degrees/s, with an average preferred speed of 39 degrees/s. At higher speeds, the response amplitude of most units decreased, although a few units exhibited a broad saturation in response amplitude that was maintained up to at least 150 degrees/s before the response decreased. Over the range of speeds up to the preferred speeds, the sensitivity of DLPN neurons to discrete stimulus-related, retinal-image speed averaged 3.0 spikes/s per deg/s. The responses to large-field visual motion were less sensitive to retinal image speed and exhibited an average sensitivity of 1.4 spikes/s per deg/s before the visual response saturated. 5. DLPN and MT were quantitatively comparable with respect to degree of direction selectivity, retinal image speed tuning, and distribution of preferred speeds. Many DLPN receptive fields contained the fovea and were larger than those of MT and more like MST receptive fields in size.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Internuclear ophthalmoplegia in the Chiari type II malformation.

We describe 3 cases of Chiari type II malformation presenting with bilateral internuclear ophthalmoplegia (INO). Although prominent, the INO was not an isolated sign in any of the patients; superimposed abduction paresis was present in 2, and deficits in smooth pursuit, optokinetic nystagmus, and vestibulo-ocular responses were present in 3. Two had hydrocephalus: 1 was clinically unchanged without therapy after 5 years; the other did not improve with shunting. Findings in our 3 patients, along with the 4 previously reported, confirm that INO is 1 manifestation of widespread brainstem or cerebellar dysfunction. Its origin is probably multifactorial, related to hydrocephalus, vascular compromise, direct neuronal distortion, or congenital neural malformation.

Adult↗
PubMed1989

Downbeat nystagmus: characteristics and localization of lesions.

Clinical examinations and eye movement recordings of 91 consecutive patients with DBN were analyzed to describe the characteristics of DBN and to localize the lesions producing this abnormality. Horizontal and vertical eye movement recordings were made with EOG and/or magnetic search coil. The most frequent causes were infarction, cerebellar and spinocerebellar degeneration syndromes, MS and developmental anomalies affecting the pons and cerebellum. Toxicity from anticonvulsant drugs probably caused nystagmus in a few patients. Clinical examinations, excluding electronic eye movement recordings, were used to localize lesions. Localizations included the cerebellum in 88% of the patients. However, localizations to structures outside of the cerebellum were made in several patients. The effects of DBN of gaze position, convergence, blockage of fixation, and positioning of the head and body were observed. Almost all patients had DBN in some position of gaze while sitting and fixating a distant target. A few patients demonstrated DBN only with convergence, in the dark, or with positioning of the head and body. Horizontal gaze increased DBN in most patients. The nystagmus slow components usually had constant-velocity or increasing-velocity waveforms. The effects of vertical gaze on DBN were variable. In general, statistically significant differences in the frequencies of these effects among the various causes and localizations of lesions were not found. Horizontal eye movements were electronically recorded in DBN patients, in a group of normal subjects, and in a group of patients with isolated cerebellar atrophy who did not have DBN. The pattern of abnormal horizontal eye movements characteristic of damage to the midline structures of the cerebellum (impaired pursuit, impaired OKN, and inability to suppress VOR) was found in almost all DBN patients (99%), including patients with lesions localized to structures outside the cerebellum by clinical examination. DBN is usually produced by lesions in the cerebellum that also damage pathways that control horizontal tracking and visual-vestibulo-ocular interactions.

Adolescent↗
PubMed1989

Spontaneous vertical nystagmus.

We reviewed the clinical and oculographic features of 106 patients with spontaneous vertical nystagmus evaluated at the UCLA Eye Movement Laboratories over the past 10 years. Downbeat nystagmus typically occurred with lesions involving the caudal midline cerebellum whereas upbeat nystagmus was most often associated with lesions of the central medulla. Since the vestibular systems is the main source of tonic input to the oculomotor neurons and since the up and down vestibulo-ocular pathways separate beginning at the level of the vestibular nuclei asymmetric involvement of these pathways can explain spontaneous vertical nystagmus.

Brain Diseases↗
PubMed1979

Modification of constant optokinetic nystagmus by vestibular stimuation.

Experiments were conducted to quantify the effect of a vestibular stimulation of known magnitude on a constant optokinetic nystagmus (OKN). Ten normal human subjects were tested with varying magnitudes of vestibular stimuli that were superimposed on a constant 30 degrees optokinetic stimulus. The gain of the vestibular system in the dark was 0.42 +/- 0.11, and the gain in the light during superimposition testing was 0.12 +/- 0.02. From these results, predictions were made that the degree of vestibular imbalance necessary to produce an asymmetric OKN would generate a spontaneous nystagmus in the dark, which would be equivalent to 20 to 30 degrees. Data from a large group of patients were used for corroboration of the results.

Adult↗
PubMed1979

Opticociliary veins in a primary optic nerve sheath meningioma.

A 59-year-old man developed painless visual loss in his left eye over a one-year period, with rapid progression to blindness over three months. Ocular examination of the left eye revealed proptosis, marked optic disk pallor, dilated retinal veins, and congeries of vessels at the disk margin (opticociliary veins). His right eye was unremarkable. Fluorescein angiography and histopathologic examination confirmed the presence of opticociliary veins communicating between branches of the central retinal vein and the adjacent choroidal vasculature. Primary orbital optic nerve meningioma associated with opticociliary veins was diagnosed.

Cranial Nerve Neoplasms↗
PubMed1979

Uniocular nystagmus in monocular visual loss.

Uniocular nystagmus was studied by electro-oculography in ten patients with monocular visual loss caused by ocular and optic nerve lesions. In these patients, visual loss was congenital or acquired in childhood or adult life. In all patients the oscillations were present in the primary position of gaze and were vertical, pendular, and of variable and low frequency (less than, or equal to, 1.0 HZ) and amplitude (usually less than 5 degrees). Refixation saccades, smooth pursuit, optokinetic nystagmus, and vestibuloocular responses to rotation in the horizontal and vertical planes were within normal limits. The irregularity, low frequency, and low amplitude of this form of nystagmus cause it to often be missed during casual clinical examination, but easily differentiate it from other causes of uniocular nystagmus.

Adolescent↗
PubMed1979

Visual-vestibular interaction and cerebellar atrophy.

The vestibular and optokinetic ocular control systems were studied in 10 patients with cerebellar atrophy and in 10 normal subjects using (1) constant velocity optokinetic stimulation, (2) sinusoidal rotation in the dark, and (3) sinusoidal rotation in the light with a surrounding fixed optokinetic drum. The gain (maximum slow component velocity/maximum head or drum velocity) of induced nystagmus was calculated from electro-oculographic recordings. Optokinetic nystagmus was abnormal in seven patients and the average optokinetic gain in the patients was significantly (p less than 0.01) less than that of the normal group. Three patients with "clinically pure" cerebellar atrophy had increased vestibular responses, and one patient with clinical signs of peripheral neuropathy had decreased responses, probably due to associated vestibular nerve disease. The average vestibulo-ocular reflex gain in patients did not differ significantly from controls (p greater than 0.05). Three patients had normal vestibular and optokinetic responses when tested independently, but had abnormal visual-vestibular interaction. These patients probably had selective disorders of the midline cerebellar pathways that mediate visual-vestibular interaction. By studying each system, both independently and during interaction, all patients were identified as abnormal, and a more precise anatomic localization of the atrophy was obtained.

Adolescent↗
PubMed1979

Slow build-up of optokinetic nystagmus associated with downbeat nystagmus.

Eye movement recordings in two patients with downbeat nystagmus demonstrated an unusual finding of severely impaired smooth pursuit and relatively unimpaired optokinetic nystagmus (OKN). OKN was characterized by a remarkable, slow build-up of slow-component velocity, similar to that found in afoveate animals. Optokinetic after-nystagmus (OKAN), or transient persistence of nystagmus after cessation of visual stimulation, typical of the optokinetic response of normal human subjects, was also preserved in these patients. These observations suggest that the normal contribution of smooth pursuit to the ocular motor response to rotation of the visual environment can be selectively removed by a lesion at the level of the craniocervical junction.

Adult↗
PubMed1978

Internuclear ophthalmoplegia. I. Saccades and dissociated nystagmus.

Saccades (horizontal and vertical) and dissociated nystagmus were quantitatively assessed in four patients with internuclear ophthalmoplegia. Two patients had bilateral medial longitudinal fasciculus (MLF) lesions associated with multiple sclerosis and two had unilateral lesions associated with brain stem vascular disease. Adducting saccades made on the side of an MLF lesion were slowed in each patient (P less than .01). At the same time, abducting saccades in the contralateral eye had normal velocity, but consistently overshot the target. After the overshoot, the eye returned to the target with an exponentially decaying course. With large angular deviations (usually more than 15 degrees), the abducting eye developed nystagmus characterized by slow components that moved toward the midposition with an initially high velocity followed by a segment of slower velocity. The adducting eye had either no nystagmus or a low-amplitude nystagmus characterized by a rounded junction between the fast and slow component. The saccade abnormalities and waveform of the dissociated nystagmus can be explained by a pulse-step mismatch at the agonist motoneurons.

Adult↗
PubMed1978

Internuclear ophthalmoplegia. II. Pursuit, optokinetic nystagmus, and vestibulo-ocular reflex.

Smooth pursuit, optokinetic nystagmus (OKN) and the vestibulo-ocular reflex (VOR) were studied in four patients with internuclear ophthalmoplegia (two with bilateral and two with unilateral lesions). Horizontal smooth pursuit by an adducting eye on the side of a medial longitudinal fasciculus (MLF) lesion was normal in three of four patients; vertical pursuit was abnormal in all four. The horizontal VOR gain of slow components made by an adducting eye on the side of an MLF lesion was normal in all four patients. The vertical VOR gain was decreased in the two patients tested. It is concluded that either there are pathways independent of the MLF for horizontal pursuit and vestibular signals that are not available to vertical signals, or vertical pursuit and vestibular eye movements require a higher rate of oculomotor neuron firing than equal-velocity horizontal eye movements.

Adult↗
PubMed1978

Histochemistry and acetylcholine receptor distribution in normal and denervated monkey extraocular muscles.

In monkey extraocular muscles (EOM), a battery of histochemical reactions delineates three muscle fiber types, coarse, fine, and granular. Normal EOM are compared with EOM denervated by intracranial oculomotor nerve section. The experimentally denervated EOM fibers did not show the constellation of histologic responses typical of denervated limb muscle, making a diagnosis of a denervation process in EOM muscle very difficult. Although the denervated fine and granular fibers (but not the coarse fibers) develop diffuse extrajunctional acetylcholine receptors (AChR) following experimental denervation, this is not a reliable criterion of denervation because not all of those fibers developed it and they did not show it beyond a 12-week period following nerve section; moreover, myopathic mechanisms have previously been shown capable of provoking diffuse extrajunctional AChR in limb-muscle fibers.

Acetylcholine↗
PubMed1978

Eye movements in ataxia-telangiectasia.

The spectrum of eye movement disorders in six patients with ataxia-telangiectasia at different stages of progression was assessed quantitatively by electrooculography. All patients demonstrated abnormalities of voluntary and involuntary saccades. The youngest and least involved patient had significantly increased reaction times of voluntary saccades, but normal accuracy and velocity. The other patients demonstrated increased reaction times and marked hypometria of horizontal and vertical voluntary saccades. Saccade velocity remained normal. Vestibular and optokinetic fast components (involuntary saccades) had normal amplitude and velocity but the eyes deviated tonically in the direction of the slow component. We conclude that patients with ataxia-telangiectasia have a defect in the initiation of voluntary and involuntary saccades in the earliest stages. These findings are distinctly different from those in other familial cerebellar atrophy syndromes.

Adolescent↗