1/33. 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 = 1keywords = nucleus (Clic here for more details about this article) |
2/33. Opsoclonus in three dimensions: oculographic, neuropathologic and modelling correlates.Opsoclonus is a dyskinesia consisting of involuntary, arrhythmic, chaotic, multidirectional saccades, without intersaccadic intervals. We used a magnetic scleral search coil technique to study opsoclonus in two patients with paraneoplastic complications of lung carcinoma. Eye movement recordings provided evidence that opsoclonus is a three-dimensional oscillation, consisting of torsional, horizontal, and vertical components. Torsional nystagmus was also present in one patient. Antineuronal antibody study revealed the presence of anti-Ta (Ma2 onco-neuronal antigen) antibodies in one patient, which had previously been associated only with paraneoplastic limbic encephalitis and brainstem dysfunction, but not opsoclonus, and only in patients with testicular or breast cancer. Neuropathologic examination revealed mild paraneoplastic encephalitis. Normal neurons identified in the nucleus raphe interpositus (rip) do not support postulated dysfunction of omnipause cells in the pathogenesis of opsoclonus. computer simulation of a model of the saccadic system indicated that disinhibition of the oculomotor region of the fastigial nucleus (FOR) in the cerebellum can generate opsoclonus. Histopathological examination revealed inflammation and gliosis in the fastigial nucleus. This morphological finding is consistent with, but not necessary to confirm, damage to afferent projections to the FOR, as determined by the model. Malfunction of purkinje cells in the dorsal vermis, which inhibit the FOR, may cause opsoclonus by disinhibiting it.- - - - - - - - - - ranking = 1keywords = nucleus (Clic here for more details about this article) |
3/33. See-saw nystagmus and brainstem infarction: MRI findings.A patient with see-saw nystagmus had a lesion localized by magnetic resonance imaging (MRI) to the paramedian ventral midbrain with involvement of the right interstitial nucleus of Cajal. This the first MRI study of see-saw nystagmus associated with a presumed brainstem vascular event. Our findings support animal and human studies suggesting that dysfunction of the interstitial nucleus of Cajal or its connections is central in this disorder.- - - - - - - - - - ranking = 0.66666666666667keywords = nucleus (Clic here for more details about this article) |
4/33. Perverted head-shaking nystagmus: a possible mechanism.The authors describe a patient with acute MS who developed vertigo (tumbling) and downbeat nystagmus upon horizontal head oscillation (perverted head-shaking nystagmus). The only abnormality on brain MRI was a hyperintense signal in the caudal medulla that contains the nucleus Roller and nucleus intercalatus. These nuclei project to structures involved in the velocity storage system for horizontal vestibulocular reflex (VOR) and vertical VOR, and also to the vestibular cerebellum. The authors offer possible mechanisms for perverted nystagmus in this patient.- - - - - - - - - - ranking = 0.66666666666667keywords = nucleus (Clic here for more details about this article) |
5/33. Convergence retraction nystagmus: a disorder of vergence?The pathological mechanism of convergence retraction nystagmus (CRN) is not known. To determine whether CRN is a disorder of vergence or of the saccadic system, the scleral search coil technique was used to record binocularly the three-dimensional components of CRN in a patient with a left mesencephalic infarction involving the nucleus of the posterior commissure and the rostral interstitial nucleus of the medial longitudinal fascicle. CRN had disconjugate horizontal and torsional components. The horizontal amplitude/velocity relationship of CRN aligned with the main sequence of vergence responses of normal control subjects but not with that of saccades. Vergence responses of the right eye and left eye were not asynchronous. The slow phases of CRN showed an exponential decay with a time constant of 70 milliseconds. Thus, CRN is probably a disorder of vergence rather than of opposing adducting saccades.- - - - - - - - - - ranking = 0.66666666666667keywords = nucleus (Clic here for more details about this article) |
6/33. Metastatic brainstem tumor manifesting as hearing disturbance--case report.A 53-year-old male, who had undergone a left upper lung lobectomy for cancer 2 years previously, presented with metastatic brainstem tumor manifesting as hearing disturbance. At first an otorhinolaryngologist treated him for senile sensorineural hearing disturbance. However, he suffered gait ataxia and was referred to our department. On admission, neurological examination found mild cerebellar ataxia on the left and gait unsteadiness. Neurootological analysis revealed central-type sensorineural hearing disturbance on the left both in the pure tone audiogram and speech discrimination test. neuroimaging studies revealed a ring-like enhanced mass centered in the ventral left middle cerebellar peduncle, partly extending to the inferior cerebellar peduncle. Peritumoral edema extending to the ipsilateral cochlear nucleus was recognized. He underwent surgery via a left lateral suboccipital transcondylar approach. The histological diagnosis was adenocarcinoma identical with the primary lung cancer. Intra-axial brainstem metastatic lesion can be a cause of hearing disturbance, so should be included in the differential diagnosis for a patient complaining of hearing disturbance, especially with a past history of cancer.- - - - - - - - - - ranking = 0.33333333333333keywords = nucleus (Clic here for more details about this article) |
7/33. Pathophysiologic mechanism of convergence nystagmus.The convergent eye movements in convergence nystagmus are reported to be opposed adducting saccades under excessive convergence drive. What occurs is a horizontal saccade of the adducting eye and a quick reversal of the abducting eye immediately after initiation of the original saccade. Accordingly, the opposed adducting saccades of the abducting eye have been explained by the dynamic overshoot mechanism. However, by electro-oculographic analysis of eye movements in a patient with convergence nystagmus, we found that the opposed adducting saccades of the abducting eye occurred not only after but also just before initiation of the original saccade. Our observation indicates that the opposed adducting saccades can occur without dynamic overshoot as the starter mechanism. Possibly, cessation of the discharge of omnipause neurons may lead to firing of the burst neurons for the medial rectus subnucleus via activation by the excessive convergence drive.- - - - - - - - - - ranking = 0.33333333333333keywords = nucleus (Clic here for more details about this article) |
8/33. Internuclear ophthalmoplegia associated with transient torsional nystagmus.The association of internuclear ophthalmoplegia (INO) with torsional nystagmus is rare. We report the case of a 63-year-old man presenting with sudden onset of diplopia. On ocular examination, he had left INO and a torsional nystagmus with counter-clockwise quick-phases from the patient's point of view in the primary position, ipsiversive to the side of the medical longitudinal fasciculus (MLF) lesion at the pontomesencephalic junction on magnetic resonance images. Neither skew deviation nor head tilting was noted at that time. Two days later, the torsional nystagmus disappeared, although the limitation of adduction in the left eye remained. We speculate that with sparing of the rostral interstitial nucleus of the MLF, a small lesion in the MLF may involve the ipsilateral vertical integrator, the interstitial nucleus of Cajal, producing an INO associated with a transient ipsiversive torsional nystagmus.- - - - - - - - - - ranking = 0.66666666666667keywords = nucleus (Clic here for more details about this article) |
9/33. Saccadic lateropulsion and upbeat nystagmus: disorders of caudal medulla.A patient developed a primary position upbeat nystagmus and a left saccadic lateropulsion. magnetic resonance imaging demonstrated a probable cavernoma at right caudal paramedian medullary level. Anatomical correlations are discussed. Saccadic lateropulsion is attributed to olivocerebellar pathway impairment but usually is described in more rostral medullar lesions. Our case would still support this hypothesis because the lesion could have involved the olivocerebellar pathway at its very caudal level. Upbeat nystagmus could be attributed to impairment of the nucleus intercalatus and/or cell groups of the paramedian tract.- - - - - - - - - - ranking = 0.33333333333333keywords = nucleus (Clic here for more details about this article) |
10/33. paresis of contralateral smooth pursuit and normal vestibular smooth eye movements after unilateral brainstem lesions.Pursuit and vestibular smooth eye movements were measured in patients with lesions of the caudal brainstem tegmentum identified by magnetic resonance imaging (MRI) and computed tomography (CT), with neuropathological correlation in 1 patient. Contralateral smooth pursuit gain was significantly lower than ipsilateral gain in each patient. Ipsilateral smooth pursuit gain was also subnormal in patients with unilateral pontine damage that caused slowing of ipsilateral saccades. Horizontal vestibulo-ocular reflex gain and phase were normal. These quantitative correlations indicate that lesions of the pontine tegmentum that paralyze ipsilateral saccades can spare the vestibulo-ocular reflex, and that smooth pursuit movement and the vestibulo-ocular reflex can be impaired independently by pontine or medullary lesions. In contrast to lesions at other sites, unilateral lesions of the pontine or medullary tegmentum impair contralateral smooth pursuit more than ipsilateral pursuit movements. These findings provide evidence that a double decussating pathway mediates smooth pursuit; the first decussation is from the pons to the cerebellum, and the second decussation is from the vestibular nucleus to the contralateral abducens nucleus.- - - - - - - - - - ranking = 0.66666666666667keywords = nucleus (Clic here for more details about this article) |
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