1/11. The incidence and waveform characteristics of periodic alternating nystagmus in congenital nystagmus.PURPOSE: To investigate the incidence and waveform characteristics of periodic alternating nystagmus, (PAN) in congenital nystagmus (CN). methods: In a prospective study, 18 patients with CN without associated sensory defects agreed to undergo eye movement documentation using binocular infrared oculography. Two of the 18 had a diagnosis of suspected PAN before entering the study. The patients sat in a dimly lit room and viewed an LED (4 min in diameter) located in the primary position, at a distance of 100 cm. During an 8-minute recording, patients were read a story of neutral interest to hold attention at a constant level. PAN was defined as a left-beating nystagmus, a transition phase, a right-beating nystagmus, and a final transition phase; the sequence was then repeated. RESULTS: Seven of the 18 patients had PAN (median cycle: 223 seconds, range 180-307 seconds). The periodicity of the cycles for each adult patient was regular, although the phases within a cycle were often asymmetric. Six of the seven patients had an anomalous head posture (AHP), and in five the AHP was in only one direction. Except for one patient, the PAN waveforms had an increasing slow-phase velocity in at least one phase of the cycle; in the other phase they were linear. CONCLUSIONS: The occurrence of PAN in CN is not as rare as previously thought and can be missed because of the long cycles and the use of only one AHP. The AHP was dependent on, and could be predicted from, the waveforms containing the longest foveation times. Although the waveforms and foveation times may differ among the phases of the PAN cycle, the periodicity of the cycle was usually regular and therefore predictable. Identification of PAN is essential in cases in which surgical treatment is considered for correction of AHPs.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
2/11. Periodic alternating nystagmus.Three patients with periodic alternating nystagmus (PAN) are described in detail. Digital computer methods were used to quantify their disordered eye movement in an attempt to understand the pathophysiology. One of the patients was unusual in showing rebound nystagmus with fixation and PAN without fixation. Each patient had hyperactive vestibular responses and the phase and gain of the PAN cycles were altered in a predictable fashion by vestibular stimuli. It is postulated that PAN represents cyclical firing between reciprocally connected groups of inhibitory neurons within the vestibular and oculomotor nuclei. The cyclical firing is initiated by a critical imbalance of tonic input to either group of normally functioning neurons.- - - - - - - - - - ranking = 0.14285714285714keywords = cycle (Clic here for more details about this article) |
3/11. Central nystagmus induced by deep-brain stimulation for epilepsy.PURPOSE: The goal of the present study was to describe the localization of central nystagmus induced as a side effect of electrical deep-brain stimulation for epilepsy. methods: Bilateral deep-brain stimulating electrodes were inserted in the centromedian nucleus of the thalamus to control seizures in a patient with intractable epilepsy. RESULTS: Cathodal high-frequency stimulation through the deepest contact of each electrode elicited cycles of slow ipsiversive conjugate eye deviations, each followed by rapid contralateral jerks. The involved electrode contacts were situated at the mesodiencephalic junction just inferior to the centromedian nucleus of the thalamus and rostral to the superior colliculus. Right-sided stimulation evoked left beating nystagmus and left-sided stimulation evoked right beating nystagmus. Stimulation through other electrode contacts did not induce nystagmus. electronystagmography showed the nystagmus to have constant velocity slow phases. CONCLUSIONS: A central nystagmogenic area exists in humans that appears to be homologous to the nucleus of the optic tract, a region described in nonhuman primates to play a role in the generation of optokinetic nystagmus.- - - - - - - - - - ranking = 0.14285714285714keywords = cycle (Clic here for more details about this article) |
4/11. primidone/phenobarbital-induced periodic alternating nystagmus.A 37-year-old man with a history of seizures developed periodic alternating nystagmus (PAN) along with other signs of primidone/phenobarbital toxicity. The PAN gradually diminished in cycle length and intensity, finally resolving with gradual discontinuation of the drugs.- - - - - - - - - - ranking = 0.14285714285714keywords = cycle (Clic here for more details about this article) |
5/11. Seesaw nystagmus. role of visuovestibular interaction in its pathogenesis.Elevation and intorsion of one eye and synchronous depression and extorsion of the other eye characterize a half cycle of seesaw nystagmus. Reversal of these movements constitutes the second half cycle, forming the "seesaw"-like movements. Based on analysis of the ocular oscillation characteristics of the cases of seesaw nystagmus reported in the literature, including the two new cases we present, we postulate that seesaw nystagmus is another type of ocular oscillation brought about by an unstable visuovestibular interaction control system. Nonavailability of retinal error signals to the inferior olivary nucleus essential for vestibuloocular reflex adaptation due to complete chiasmal dissection makes the system less stable. This system instability is further accentuated by the pursuit feedback element. The intact inferior olivary nucleus-nodulus connections in seesaw nystagmus would explain the 180 degrees phase difference that distinguishes it from the midline form of oculopalatal myoclonus, where these connections are likely disrupted.- - - - - - - - - - ranking = 0.28571428571429keywords = cycle (Clic here for more details about this article) |
6/11. Visual improvement in an albinotic patient with an alteration of congenital nystagmus.Biofeedback techniques were used to alter congenital nystagmus (CN) in an albino. In response to auditory cues, the patient was able to reduce the amplitude of the nystagmus by 50% or more. In response to a combination of auditory and visual cues, the patient was able to alter the waveform of the nystagmus in such a manner that progressively larger portions of each cycle of the nystagmus were spent with the eye relatively stationary. Presumably as a consequence of this alteration in waveform, the patient's visual acuity (VA) improved from 6/35 to 6/25. The results indicate that, although VA in albinos is limited ultimately by the presence of foveal hypoplasia, other components of the typical albinotic syndrome (such as the accompanying nystagmus) can add to the acuity reduction and should, therefore, be treated.- - - - - - - - - - ranking = 0.14285714285714keywords = cycle (Clic here for more details about this article) |
7/11. Ocular dipping.Ocular dipping consists of cycles of eye movements occurring spontaneously, which are characterized by a slow conjugated downward deviation followed after a delay by a quick return to mid position. Ocular dipping is only described in unconscious patients, especially in anoxic comata. Three new patients with this syndrome are described. Electronystagmographic registrations are shown.- - - - - - - - - - ranking = 0.14285714285714keywords = cycle (Clic here for more details about this article) |
8/11. Epileptic nystagmus associated with typical absence seizures.A 10-year-old girl was reported who showed horizontal nystagmus in association with typical absence and 3-cycles/s generalized, bisynchronous spike-and-wave discharges. In view of the general concept that epileptic nystagmus is a manifestation of partial seizures, the occurrence of such an association deserves documentation.- - - - - - - - - - ranking = 0.14285714285714keywords = cycle (Clic here for more details about this article) |
9/11. The relationship between head and eye movement in congenital nystagmus with head shaking: objective recordings of a single case.head shaking and congenital nystagmus were recorded in a patient presented with visual tasks. When she was at rest the nystagmus took a 6 cycles per second saw-tooth wave-form. When she was attentive the nystagmus beat at a 2 to 2.6 cycles per second with a saddle-shaped deformation which permitted foveation. The head shaking occurred occasionally when the patient was attentive and was phase-locked to the nystagmus with resemblances in wave form and direction. deceleration of the head shaking to zero velocity and peak displacement (to the left) coincided with the onset of the saddle of the nystagmus and hence assisted foveation; all other parts of the head-shaking cycle were detrimental to vision. It is proposed that the head shaking has a common pathological origin with the nystagmus and that, just as an isolated congenital nystagmus wave form becomes altered with attention to permit periods of foveal fixation, the pattern of combined head and eye nodding in this patient provided similar peroids of fixation.- - - - - - - - - - ranking = 0.42857142857143keywords = cycle (Clic here for more details about this article) |
10/11. Mechanism of rotatory eye movements in opsoclonus.'Rotatory nystagmus', in which the visual axis of the eye moves involuntarily in the horizontal and vertical planes describing a closed loop trajectory, was analysed by means of combined video and electro-oculography in a patient with multiple sclerosis having numerous ocular signs of cerebellar disease. The rotations were sporadic, isolated single cycles having stereotyped, crescentiform loop shapes. Each consisted of a combination of a single cycle of vertical ocular flutter, the onset of which was followed 40 to 50 milliseconds later by a single cycle of horizontal ocular flutter. The timing relationship between flutters suggest that the vertical and horizontal systems had become somehow entrained. Rotatory nystagmus is saccadic in nature and arises from a unique timing relationship between vertical and horizontal flutter.- - - - - - - - - - ranking = 0.42857142857143keywords = cycle (Clic here for more details about this article) |
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