Ocular neuromyotonia secondary to a cavernous sinus meningioma.
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Acetazolamide↗
Biomedical subjects
Caroline Tilikete
Publications and source records attributed to Caroline Tilikete.
Saccadic lateropulsion in Wallenberg syndrome: a window to access cerebellar control of saccades?
Saccadic lateropulsion is characterized by an undershoot of contralaterally directed saccades, an overshoot of ipsilaterally directed saccades and an ipsilateral deviation of vertical saccades. In Wallenberg syndrome, it is thought to result from altered signals in the olivo-cerebellar pathway to the oculomotor cerebellar network. In the current study we aimed to determine whether saccadic lateropulsion results from a cerebellar impairment of motor related signals or visuo-spatial related signals. We studied the trajectory, the accuracy, the direction and the amplitude of a variety of vertical and oblique saccades produced by five patients and nine control subjects. Some results are consistent with previous data suggesting altered motor related signals. Indeed, the horizontal error of contralesional saccades in patients increased with the desired horizontal saccade size. Furthermore, the initial directional error measured during the saccadic acceleration phase was smaller than the global directional error, suggesting that the eye trajectory curved progressively. However, some other results suggest that the processes that specify the horizontal spatial goal of the saccades might be impaired in the patients. Indeed, the horizontal error of ipsilesional saccades in patients did not change significantly with the desired horizontal saccade size. In addition, when comparing saccades with similar intended direction, it was found that the directional error was inversely related to the vertical saccade amplitude. Thus we conclude that the cerebellum might be involved both in controlling the motor execution of saccades and in determining the visuo-spatial information about their goal.
Aged↗
Prism adaptation in the rehabilitation of patients with visuo-spatial cognitive disorders.
PURPOSE OF REVIEW: The traditional focus of neurorehabilitaion has been on the patients' attention on their deficit, such that they should become aware of their problems and gain intentional control of compensatory strategies (descending approach). We review prism adaptation as one of the approaches that emphasize ascending rather than descending strategies to the rehabilitation of visuo-spatial disorders. The clinical outcome of prism adaptation highlights the need for a theoretical reconsideration of some previous stances to neurological rehabilitation. RECENT FINDINGS: Recent years have given rise to a growing body of experimental studies showing that the descending strategy is not always optimal, especially when higher-level cognition is affected by the patients' condition. Ascending approaches have, for example, used visuo-manual adaptation for the rehabilitation of visuo-spatial deficits. A simple task of pointing to visual targets while wearing prismatic goggles can produce remarkable improvements of various aspects of unilateral neglect. SUMMARY: The neural mechanisms underpinning visuo-manual plasticity can be viewed as a powerful rehabilitation tool that produces straightforward effects not only on visual and motor parameters, but on visuo-spatial, attentional and higher cognitive neurological functions. The use of prism adaptation therapy in neglect and other visuo-spatial disorders has just started to reveal its potential, both at a practical and theoretical level.
Adaptation, Physiological↗
[Vertigo (including treatment)].
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Diagnosis, Differential↗
Beware of neuro-syphilis.
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Diagnosis, Differential↗
Anti-GAD antibodies and periodic alternating nystagmus.
BACKGROUND: Autoantibodies directed against glutamic acid decarboxylase (GAD-Ab) have recently been described in a few patients with progressive cerebellar ataxia, suggesting an autoimmune physiopathologic mechanism. OBJECTIVE: To determine the exact role of GAD-Ab and gamma-aminobutyric acid (GABA)-ergic neurotransmission in the pathogenesis of cerebellar ataxia. DESIGN: Case report. SETTING: University neurological hospital. PATIENT: We report the case of a patient with subacute cerebellar ataxia associated with GAD-Ab showing periodic alternating nystagmus (PAN). INTERVENTION: Baclofen, a GABAergic medication, was given to the patient. MAIN OUTCOME MEASURES: Eye movement recording of spontaneous nystagmus and postrotatory vestibular responses. RESULTS: Baclofen was effective in suppressing PAN and improving postrotatory vestibular responses but not for improving cerebellar ataxia. CONCLUSION: The presence of PAN and the response to baclofen provide a unique opportunity to suggest a direct role of GAD-Ab in cerebellar dysfunction in this patient.
Aged↗
Potential role of anti-GAD antibodies in abnormal eye movements.
Glutamic acid decarboxylase (GAD) catalyzes the conversion of glutamic acid to gamma-aminobutyric acid (GABA). Autoantibodies directed against GAD (antiGAD-Ab) have been described in patients with insulin-dependent diabetes mellitus, stiff-man syndrome, and in a few patients with progressive cerebellar ataxia. The presence of these autoantibodies suggests an autoimmune pathophysiological mechanism for the neurological manifestations in these disorders. However, the exact role of antiGAD-Ab and GABAergic neurotransmission in the pathogenesis of the neurological manifestations, particularly in progressive cerebellar ataxia, is not fully understood. The cases of two patients with subacute cerebellar ataxia associated with antiGAD-Ab presenting with abnormal eye movements are reported. One patient presented a periodic alternating nystagmus (PAN), whereas the other presented a downbeat nystagmus (DBN) and slow vertical saccades. The potential role of antiGAD-Ab and the resultant GABAergic neurotransmission deficit in oculomotor manifestations is discussed.
Aged↗
Pulse-synchronous eye oscillations revealing bone superior canal dehiscence.
Superior canal dehiscence syndrome is a newly recognized syndrome characterized by vertigo and nystagmus induced by sound (Tullio phenomenon) or changes of middle ear (Hennebert sign) or intracranial pressure. We report on a patient with bilateral superior canal dehiscence syndrome who presented with unusual manifestations including pulse-synchronous vertical pendular nystagmus and Valsalva-induced, up and counterclockwise-beating jerk nystagmus. These unusual symptoms may be a clue to a better understanding of the pathophysiology of superior canal dehiscence syndrome. Abnormal communication between the inner ears and the intracranial space may explain the vertical pendular and pulse-synchronous nystagmus, modulated by increased intracranial pressure.
Adult↗
Ocular scanning and perceptual size distortion in hemispatial neglect: effects of prism adaptation and sequential stimulus presentation.
When asked to compare two lateralized shapes for horizontal size, neglect patients often indicate the left stimulus to be smaller. Gainotti and Tiacci (1971) hypothesized that this phenomenon might be related to a rightward bias in the patients' gaze. This study aimed to assess the relation between this size underestimation and oculomotor asymmetries. Eye movements were recorded while three neglect patients judged the horizontal extent of two rectangles. Two experimental manipulations were performed to increase the likelihood of symmetrical scanning of the stimulus display. The first manipulation entailed a sequential, rather than simultaneous presentation of the two rectangles. The second required adaptation to rightward displacing prisms, which is known to reduce many manifestations of neglect. All patients consistently underestimated the left rectangle, but the pattern of verbal responses and eye movements suggested different underlying causes. These include a distortion of space perception without ocular asymmetry, a failure to view the full leftward extent of the left stimulus, and a high-level response bias. Sequential presentation of the rectangles and prism adaptation reduced ocular asymmetries without affecting size underestimation. Overall, the results suggest that leftward size underestimation in neglect can arise for a number of different reasons. Incomplete leftward scanning may perhaps be sufficient to induce perceptual size distortion, but it is not a necessary prerequisite.
Adaptation, Physiological↗
After-effects of visuo-manual adaptation to prisms on body posture in normal subjects.
Postural equilibrium is known to be controlled by sensorimotor reflexes and automatic control loops but also depends on high-level body representation in space, probably implicating the right temporoparietal cortex. Indeed, short-term prism adaptation to a 10 degrees rightward visual shift has been shown to reduce predominant postural imbalance in patients with right hemisphere damage, as it did for neglect symptoms. These effects are likely to be explained by a high level effect of prism adaptation on body and space representation, rather than by a sensorimotor effect. Cognitive after-effects of prism adaptation to a leftward visual shift, suggesting neglect-like symptoms, have also recently been shown in normal subjects on line bisection tasks. In the present study, we investigated the effect of wedge prism adaptation on postural control in normal subjects. Two groups of seven healthy subjects were either adapted to a leftward or a rightward visual shift. Results showed that our procedure induced changes in lateral postural control in normal subjects. Furthermore, this lateral postural after-effect was dependent on direction of prism adaptation. Indeed, only adaptation to a leftward visual shift induced significant rightward postural bias in normal subjects. The rightward postural lateral displacement was negatively correlated with the visual vertical. Both transfer and direction specific effect of visuo-manual adaptation to prisms on postural control suggest that effects of adaptation act more on high-level postural control linked to body representation in space or at least reveal close interaction between sensorimotor plasticity and body representation.
Adolescent↗
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.
Adult↗
A lesion of the posterior parietal cortex disrupts on-line adjustments during aiming movements.
It is long known that the posterior parietal cortex (PPC) is critically involved in goal-directed movements. Nevertheless, there are still some controversies about its specific functions. Although most published studies have emphasised the role of PPC in sensorimotor planning processes, it has been recently suggested that PPC can also participate to on-line movement control. We studied kinematics of hand movements in a patient with a bilateral PPC lesion who exhibited no deficit in planning of her grasping movements in central vision. She was instructed to reach and grasp a cylinder presented at different locations and her motor performance was compared to that of four healthy control subjects. To address on-line control specifically, the cylinder was quickly and unexpectedly jumped, on a few trials, at movement onset, to a new location some 10 degrees (of apparent visual angle) from the original location. The patient could easily grasp stationary objects seen in foveal vision, exhibiting the same kinematic pattern as controls. Therefore, she could plan movements accurately. In response to the object jump, unlike the controls, the patient was unable to amend her ongoing movement. In this situation, she completed two distinct movements, a first one toward the initial object location and a second one toward the final object location. These results support the hypothesis that beyond a role in movement planning, PPC plays a major role in the on-line control of reach-to-grasp movements.
Adult↗