11/33. Upbeat nystagmus due to a small pontine lesion: evidence for the existence of a crossing ventral tegmental tract.We report a patient with an isolated large upbeat nystagmus (UBN) in the primary position of gaze. eye movements were filmed and recorded using electro-oculography. The upward vestibulo-ocular reflex gain, evaluated by pitching the head forward, was markedly reduced compared to when pitching the head back. The lesion was a probable lacunar infarction located in the paramedian and posterior part of the basis pontis, at the upper pons level. This UBN case, with one of the smallest brainstem lesions reported so far, supports the existence in humans of the crossing ventral tegmental tract, described in the cat and transmitting excitatory upward vestibular signals to the third nerve nucleus. It is also suggested that the decussation of this tract lies at the same upper pons level as in the cat but in a slightly more ventral location, i.e. in the posterior basis pontis.- - - - - - - - - - ranking = 1keywords = nucleus (Clic here for more details about this article) |
12/33. Impairment of vertical motion detection and downgaze palsy due to rostral midbrain infarction.We present two cases with acute onset of vertical gaze palsy, mainly consisting of impaired downgaze and apraxia of downward head movements, together with neuropsychological deficits (hypersomnia, impaired attention and disorders of memory and affective control). CT and MRI revealed bilateral post-ischaemic lesions in the dorsomedial thalamus and the mesodiencephalic junction, dorsomedial to the red nucleus, thus being restricted to the territory of the posterior thalamosubthalamic paramedian artery, which includes the region of the rostral interstitial nucleus of the medial longitudinal fascicle as the main premotor nucleus for the generation of vertical saccades. In our patients, oculographic examination with electro-oculography and magnetic search coil recording showed severe impairment of downward more than upward saccades and only minor deficits of vertical pursuit and the vestibulo-ocular reflex. Visual functions were normal, with one exception: a psychophysical test of motion perception revealed a significant deficit in the detection of vertical movements. This could be due to a central adaptive mechanism which, in order to minimize oscillopsia, might elevate thresholds for vertical motion perception in cases of vertical gaze palsy. As an alternative explanation, lesions within the midbrain tegmentum could have damaged subcortical visual pathways involved in motion perception.- - - - - - - - - - ranking = 3keywords = nucleus (Clic here for more details about this article) |
13/33. Downbeating nystagmus and other ocular motor defects caused by lithium toxicity.We report the clinical and neuropathologic findings of a 63-year-old woman who died following an accidental lithium overdose that produced coma, respiratory depression, horizontal gaze palsy, and downbeating nystagmus. She also had mild hypomagnesemia. The pathology was cytotoxicity, predominantly in the regions of the nuclei prepositus hypoglossi and medial vestibular nucleus. Damage to this area with kainate and ibotenate in rhesus monkeys has produced horizontal gaze palsy and downbeating nystagmus. In addition, we report our clinical experience during the past 6 years with other examples of downbeating nystagmus in patients receiving lithium.- - - - - - - - - - ranking = 1keywords = nucleus (Clic here for more details about this article) |
14/33. 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.- - - - - - - - - - ranking = 2keywords = nucleus (Clic here for more details about this article) |
15/33. 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 = 2keywords = nucleus (Clic here for more details about this article) |
16/33. Monocular downbeat nystagmus.Two patients with acute unilateral infarction of the medial thalamus and upper mesencephalon exhibited ipsilateral nuclear involvement of the third nerve, contralateral skew deviation with weakness of eye elevation, and monocular downbeat nystagmus. Monocular downbeat nystagmus is a rare manifestation of combined nuclear-supranuclear ophthalmoparesis that is seemingly secondary to dysfunction of cerebellar-modulated crossed oculovestibular fibers of the brachium conjunctivum, integrator neurons, or posterior commissure crossing fibers originating at the interstitial nucleus of Cajal and mediating vertical ocular reflexes.- - - - - - - - - - ranking = 1keywords = nucleus (Clic here for more details about this article) |
17/33. Primary position upbeat nystagmus. A clinicopathologic study.eye movements were studied with electro-oculography in a patient with primary position, large amplitude, upbeat nystagmus. The upbeat nystagmus increased in amplitude on upward gaze, decreased on downward gaze, and was not altered by loss of fixation. The patient could not produce smooth pursuit movements upward or to the left, but had normal saccadic and vestibular induced eye movements in all directions. At necropsy, a low grade glioma was found involving primarily the medulla and caudal pons. The inferior olives and prepositus hypoglossal nuclei were diffusely infiltrated with tumor. These results suggest (1) primary position upbeat nystagmus is due to a defect in the upward smooth pursuit system, (2) the lower brain stem at the level of the inferior olives and nucleus prepositus hypoglossi is important in the mediation of vertical pursuit, and (3) primary position upbeat nystagmus can result from damage to several nuclei and interconnecting pathways in the caudal brain stem and midline cerebellum involved in control of vertical smooth pursuit.- - - - - - - - - - ranking = 1keywords = nucleus (Clic here for more details about this article) |
18/33. Periodic alternating skew deviation.A 78-year-old hypertensive woman suddenly developed blurred vision, followed shortly by dizziness, difficulty walking with a tendency to veer to the left, and vertical diplopia. Examination 3 weeks later revealed a unique neuro-ophthalmologic motility pattern, which may be described as periodic alternating skew deviation. This previously unreported motility disturbance was associated with downbeat nystagmus in our patient, and a focal lesion at the level of the interstitial nucleus of Cajal was demonstrated on computed tomography. The spectrum of physiologically related motility patterns--including periodic alternating nystagmus, cyclic oculomotor paralysis, see-saw nystagmus, periodic alternating gaze deviation, "ping-pong" gaze, and intermittent aperiodic alternating skew deviation--has been considered and is helpful in topical neuro-ophthalmologic diagnosis.- - - - - - - - - - ranking = 1keywords = nucleus (Clic here for more details about this article) |
19/33. Primary position upbeat nystagmus. Another central vestibular nystagmus?Recent studies of the vestibulo-ocular reflex have revealed a distinct pathway from the anterior semicircular canal to the contralateral oculomotor nucleus via the superior vestibular nucleus. axons of this pathway ascend in the brachium conjunctivum, while axons of the other semicircular canal pathways ascend in the medial longitudinal fasciculus (MLF). We report two cases of primary position upbeat nystagmus where lesions of the brachium conjunctivum were suggested by computed tomography (CT) scans. One of these lesions was confirmed at autopsy. We concluded that primary position upbeat nystagmus, like downbeat nystagmus, is a type of central vestibular nystagmus resulting from an imbalance of vertical vestibulo-ocular reflex activity.- - - - - - - - - - ranking = 2keywords = nucleus (Clic here for more details about this article) |
20/33. Periodic nonalternating ocular skew deviation accompanied by head tilt and pathologic lid retraction.A 60-year-old black male with a 13-year history of adult onset diabetes mellitus and hypertension with a previous lacunar stroke suddenly developed a periodic head and eye movement disorder characterized by nonalternating skew deviation, rotatory nystagmus, head tilt, and lid retraction. On CT scan, the patient had a lacunar infarct in the right midbrain in the region of the interstitial nucleus of Cajal, an anatomical area involved with head tilt, torsional eye movement, and skew deviation.- - - - - - - - - - ranking = 1keywords = nucleus (Clic here for more details about this article) |
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