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Query: UMLS:C0028738 (nystagmus)
 7,431 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rotatory stimulation is a physiological stimulation of the vestibular canalicular organs. In every day's neurootological routine it is applied in sinusoidal, triangular and trapezoidal shape. The rotatory intensity damping test (RIDT) applies a perrotatory and postrotatory test combination of a trapezoidal stimulus pattern. Thus the perrotatory as well as the postrotatory nystagmus can be recorded during several phases of the after phenomena. In terms of acceleration/time plots the supraliminal perrotatory acceleration exhibits a rectangular or step-like stimulus characteristic. The supramaximal postrotatory stimulus however has a needle-like impulse pattern. The nystagmus reaction being recorded by the ENG is evaluated according to frequency or beat-rate distributions. The perrotatory nystagmus can be linearily optimalized in a linear to linear plot during its maximal reactional dynamics. The postrotatory nystagmus distribution can also be linearily graphed in a nomogram. However this nomogram is a log.log intensity/time-chart. This paper clinically compares per- and postrotatory reactions of the rotatory intensity damping test. It can be seen that this test adds important information to the clinical study of the dizzy patient.
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PMID:[Clinical comparison of perrotatory and postrotatory nystagmus characteristics (author's transl)]. 14 30

The above effect was studied in 65 subjects with normal vision (mean age 20 years) in investigations in which the following factors were successively changed: distance of optokinetic stimuli from the eyes; this distance and angular velocity of stimuli; distance and frequency of stimuli or finally distance and accommodation level. The angular velocity of the pursuit nystagmus phase was found to be by far the highest and simultaneously the closest to the angular velocity of optokinetic stimuli when the latter are 1.5m from the eyes. With shorter distances, the velocity of the pursuit movements lags steadily behind that of stimulus velocity. This change is conditioned by changes in OKN amplitude since its frequency as a whole does not change. Even though the accommodation level significantly affects the velocity of the pursuit nystagmus phase, the dependence on the distance of optokinetic stimuli from the eyes persists even after atropinization. The interpretation of these findings must take into account sepcifically the demands on accommodation, convergence, and on visual attention which are increased with shorter distances.
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PMID:Effect of the distance of optokinetic stimuli from the eyes on certain parameters of the optokinetic nystagmus. 15 Dec 94

The orthopaedic surgeon is often the first consultant to whom a patient with syringomyelia is referred. The disease is not as rare as he may suppose, but its early presenting features are very variable; if he relies solely on such familiar features as pes cavus and scoliosis, he may well miss the diagnosis. The commonest presenting symptom is pain in the head, neck, trunk or limbs; headache or neckache made worse by straining is particularly significant. A history of birth injury also may suggest the possibility of syringomyelia, especially if any spasticity subsequently worsens. Neurological features which may be diagnostic include nystagmus, dissociated sensory loss, muscle wasting, spasticity of the lower limbs or Charcot's joints. Radiographic features include erosion of the bodies of cervical vertebrae and widening of the spinal canal; if, at C5, the size of the canal exceeds that of the body by 6 millimetres in the adult, pathological dilatation is present. The presence of basilar invagination or other abnormalities of the foramen magnum, of spina bifida occulta and of scoliosis are further pointers. Thermography is a useful way of showing asymmetrical sympathetic involvement in early cases. A greater awareness of the prevalence of syringomyelia may lead to earlier diagnosis and to early operation, which appears to hold out the best hope of arresting what is all too commonly a severely disabling and progressive condition.
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PMID:Orthopaedic features in the presentation of syringomyelia. 15 24

1. Nystagmus in the horizontal plane is evoked in fish by mechanical stimulation of the ampulla of the horizontal semicircular canal or by electrical stimulation of the nerve from this canal. The movements are conjugate and the slow phase is away from the side of stimulation. 2. Medial rectus motoneurons were recorded from intracellularly, during nystagmus. During the slow phase (induced by ipsilateral stimulation), impulses arise abruptly from the base line and appear to arise at a distance from the cell body. During the fast phase (evoked by contralateral stimulation), impulses appear to arise from large PSPs that must be generated at or near the cell body. 3. In the curarized fish, stimulation of the nerve from the contralateral horizontal canal evokes spikes that arise from large EPSPs and that are blocked relatively easily by hyperpolarizing currents. Stimulation of the nerve from the ipsilateral horizontal canal evokes spikes that arise abruptly from the base line and that are much more difficult to block by hyperpolarizing currents. Little if any underlying PSP is observed when these impulses are delayed or blocked. Thus impulses evoked by stimulation of contralateral and ipsilateral side are initiated near to and far from the cell soma, respectively. 4. If impulses evoked by contralateral stimulation fail to excite the cell body due to injury, antidromic spikes are not occluded. Thus contralateral stimulation initiates impulses in the dendrites. 5. Cell bodies of neighboring motoneurons are coupled electrotonically, and graded antidromic stimulation evokes graded depolarizing potentials which result from electrotonic spread of spike activity from adjacent neurons. These depolarizing potentials are adequate to excite the cells in the presence of a background EPSP evoked by contralateral canal stimulation. In this manner coupling tends to synchronize cells during the fast phase of the nystagmus. 6. Antidromic responses of neighboring cells fail to interact with dendritic inputs to a particular cell, although indirect evidence indicates antidromic spikes invade the impulse-initiating regions in the dendrites. Thus coupling between dendrites is negligible and dendritic inputs can mediate the smoothly graded movements of the slow nystagmic phase. Coupling between somata is too weak to cause significant interaction between dendritically evoked impulses (unless the cell bodies are depolarized by EPSPs). 7. Rhythmic firing can be recorded in a single presynaptic fiber corresponding to either the slow or the fast phase of nystagmus, but not to both. Oculomotor neurons appear to be "relay cells" that, during the fast phase of the nystagmus receive a synchronized synaptic input which is initiated in a higher level command nucleus.
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PMID:Vestibular nystagmus and teleost oculomotor neurons: functions of electrotonic coupling and dendritic impulse initiation. 16 74

Eye movements (with closed lids) were studied in a group of highly hypnotizable experimental subjects experienced in self-hypnosis, and compared with a random sample of control subjects that had never been hypnotized and were low in waking suggestibility. Approximately half the experimental subjects rolled their eyes upwards to a greater extent when hypnosis was induced than during eye closure while awake. In some subjects eye flutter occurred during hypnosis, but not in the awake condition. During passive hypnosis the mean rates of rapid eye movements were lower, but those of slow eye movements were higher than during the resting awake condition of the same subjects or the random control subjects. The mean rates of horizontal eye movements during suggestions about begin in a train and watching passing telephone poles were higher for the experimental subjects in the hypnosis and 'imagination' sessions than that of the random control group in the imagination session. A proportion of the experimental subjects made more lateral eye movements during hypnosis than during the imagination session, but an equal proportion did not differ between the two conditions. The mean rates and durations of horizontal eye movements during dreaming about a tennis match were greater during hypnosis ('hypnotic' dream), than during the awake condition a few minutes later ('natural' dream), or the awake condition in the imagination session ('imagination' dream) of the same subjects or random controls. The performance and subjective involvement of the experimental subjects during the Barber suggestibility scale, 'nystagmus' suggestions and 'dreaming' did not differ significantly between the two hypnosis sessions, but in most cases were significantly greater during hypnosis than during the imagination session of the same group or the random control group.
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PMID:Hypnosis and eye movements. 16 21

A class of direction-selective (DS) units, histologically localized within the nucleus of the optic tract (NOT) was isolated in the rabbit's pretectum. These units typically had a maintained discharge of 25-50 action potentials/sec and large receptive fields (up to 40 X 150 degrees) in the visual streak area of the contralateral eye. They were excited by a visual pattern moving in one direction and inhibited by motion in the opposite direction. The reactions were sustained. Excitatory and inhibitory acceptance angles were each 180 degrees. Most units were excited by anterior motion of the stimulus and reacted to a wide range of velocities (0.01-20 degrees/sec). Random checkerboard patterns (elements 0.8 degrees), grids of black and white stripes (1, 2 and 4 degrees wide) and single black and white edges were all effective, with a decreasing response magnitude in roughly this order. A stimulus area of 2 X 2 degrees was already effective; response increased with area and was maximal for 15 X 15 degrees and larger stimuli. Latency for visual stimulation was 60 +/- 10 (S.D.) msec, for electrical stimulation of the chiasm 2.2 +/- 0.3 (S.D.) msec. Synaptic latency and presynaptic conduction velocity were estimated at 0.7 msec and 13m/sec, respectively. A strong convergence of retinal DS fibers upon NOT units is postulated. Since most properties of NOT units are compatible with those of optokinetic nystagmus, and electrical stimulation of the NOT elicits vigorous nystagmus, these data suggest that these cells are the essential afferent link in the optokinetic reflex arc.
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PMID:Direction-selective units in the rabbit's nucleus of the optic tract. 17 94

The effects of eyelid closure on oculomotor function was examined in 11 patients with palatal myoclonus. In eight patients, eyelid closure induced gross rhythmic vertical or almost oscillatory movements of the globes, which were synchronous with the rhythmic beat of the palatal myoclonus. The rhythmic vertical ocular movements induced by eyelid closure replaced calorically induced or spontaneous horizontal nystagmus present when the lids were open. Vertical ocular motions persisted during some stages of slow-wave sleep and reappeared during each stage of rapid eye movement. The physiologic basis of the palato-ocular synchrony may be similar to the eyelid closure, vertical eye movements, and palatal myoclonus that occurs in monkeys on stimulation of the central tegmental fasciculus.
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PMID:Palato-ocular synchrony during eyelid closure. 17 83

Two children are described with congenital abnormalities (microcephaly, nystagmus, deafness, hepatomegaly) and the anomalous feature of triglyceride deposits in peripheral adipose tissue associated with severe malnutrition. Peripheral adipose tissue of one of these children displayed: (a) reduced sensitivity of adenyl cyclase to stimulation by noradrenaline (b) no response in tissue levels of cyclic AMP when stimulated by isoprenaline and (c) impaired release of glycerol following stimulation with isoprenaline. The other child, with similar clinical features, showed abnormal deposits of glycogen in the liver. It is postulated that a primary metabolic defect occurs in peripheral adipose tissue (and possibly at other sites such as the liver) that interferes with triglyceride (and glycogen) mobilization during prolonged malnutrition.
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PMID:Triglyceride storage disease. A report of two affected children associated with neurological abnormalities. 18 5

Posturally-evoked vomiting (PEV) dissociated from vertigo was present in two patients with proven posterior fossa mass lesions. In both instances PEV was a major aspect of the patients' symptomatology before other findings clearly indicated the presence of an infratentorial mass lesion. A distinction is drawn between benign postural vertigo, which almost always indicates a benign disorder of the peripheral vestibular apparatus, and PEV which indicates a central lesion within the posterior fossa. A possible anatomic-physiologic basis is offered for PEV, based on the dissociation of the "vestibular syndrome," in which PEV increases while vertigo and nystagmus diminish.
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PMID:Posturally-evoked vomiting; Association with posterior fossa lesions. 18 65

After control studies, using electrodes permanently implanted in the central visual system, squirrel monkeys and macaques were in most instances blinded by acute glaucoma. This permitted subsequent observation of eye movements. Ocular nystagmus developed in all cases. Beginning immediately upon recovery from anesthesia, and persisting for at least 1 year, the EEG of the striate cortex was characterized by totally flat periods up to several seconds in duration which were ended abruptly by a sharp "spike" trailed in turn by a ragged high voltage, slow pattern for another second or two. The great majority of these "spikes" from the blind striate cortex occurred within 60-200 msec after a saccadic eye movement, made either in nystagmus or attempted fixation. They were not dependent upon proprioception from the extraocular muscles. It is suggested that they represent a "corollary discharge" for movement of the eyes. The blind striate cortex was judged to be hyperexcitable on the basis of these saccade-associated "spikes", not often observable in intact monkeys, and from the increase both in response evoked by electrical stimulation of optic radiation and amplitude of the EEG in sleep.
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PMID:EEG of striate cortex in blind monkeys: effects of eye movements and sleep. 18 14


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