Ipsilesional Deviation Research Articles

J.L. Prévost, Eye Deviation, and Early Steps in Space Lateralization: "Looking At or Away".

Conjugate deviation of the eyes toward side of lesion was recognized over a century ago as a manifestation accompanying hemiplegia, usually of apoplectic origin. While working on the services of Alfred Vulpian and Jean-Martin Charcot, Jean-Louis Prévost sparked international interest in the neurologic sign later named after him. His 1868 thesis represents the first systematic case series of patients with this ocular sign, observed in conjunction with head rotation toward the nonparalyzed side, which he called conjugate deviation (CD) of the eyes. Within a decade, it was uniformly reported in both French and English medical literature. Ipsilesional deviation was the rule for cortical or subcortical paralytic lesions. Contralesional deviation, more rarely seen, signaled lesions of lower brain regions, particularly pontine, or indicated irritative, excitatory effects (as in Jacksonian epilepsy). The sign was recognized to be a valuable diagnostic aid in unilateral cerebral lesions. Centralized control of CD by specific cerebral sites, such as frontal, or occipital, or oculomotor centers, was explored, along with the complex relationship with hemineglect, which interestingly was reported only several decades later. The discovery of intricate oculomotor interconnections and self-space relationships, which play an essential role in CD, owes much to Prévost and his followers.

Conjugate Eye Deviation in Unilateral Lateral Medullary Infarction.

Background and PurposeThe initial diagnosis of medullary infarction can be challenging since CT and even MRI results in the very acute phase are often negative.MethodsA retrospective, observer-blinded study of horizontal conjugate eye deviation was performed in 1) 50 consecutive patients [age 58±15 years (mean±SD), 74% male, National Institutes of Health Stroke Scale 2±1] with acute unilateral lateral medullary infarction as seen in MRI (infarction group), 2) 54 patients with transient brainstem symptoms [transient ischemic attack of brainstem (TIA) group; age 69±16 years, 59% male], and 3) 53 patients (age 59±20 years, 49% male) with diagnoses other than stroke (control group).ResultsConjugate eye deviation was found in all patients in the infarction group [n=47 (94%) with ipsilesional deviation and n=3 (6%) with contralesional deviation] compared to 41% (n=22) in the brainstem TIA group and 15% (n=8) in the control group (p<0.0001). Within all groups mean deviation and range were similar for both sides (to the right vs. to the left side 26.6°±12.3 vs. 26.1°±12.3 in the infarction group, 10.5°±5.8 vs. 8.4°±6.3 in the brainstem TIA group and 4.5°±3.2 vs. 7.5°±3.2 in the control group). The extent of eye deviation was significantly greater in the infarction group (p<0.05).ConclusionsAll patients with MRI-demonstrated unilateral medullary infarction showed conjugate eye deviation. Therefore, conjugate eye deviation in patients with suspected acute lateral medullary infarction is a helpful sensitive sign for supporting the diagnosis, particularly if the deviation is >20°.

Contraversive neglect? A modulation of visuospatial neglect in association with contraversive pushing.

Contraversive pushing (CP) is a neurologic disorder characterized by a lateral postural imbalance. Pusher patients actively push toward their contralesional side due to a misperception of the body's orientation in relation to gravity. Although not every patient with CP suffers from spatial neglect (SN), both phenomena are highly correlated in right-hemispheric patients. The present study investigates whether peripersonal visuospatial functioning differs in neglect patients with versus without CP (NP+ vs. NP- patients). Eighteen right-hemispheric stroke patients with SN were included, of which 17 in a double-blind case-control study and 1 single case with posterior pushing to supplement the discourse. A computer-based visuospatial navigation task, in which lateralized deviation can freely emerge, was used to quantify visuospatial behavior. In addition, visuospatial orienting was monitored using line bisection. Significant intergroup differences were found. The NP+ patients demonstrated a smaller ipsilesional navigational deviation and more cross-over (contralesional instead of ipsilesional deviation) in long line bisection. As such, they demonstrated a contraversive (contralesionally directed) shift in comparison with the NP- patients. These findings highlight the similarity between 2 systems of space representation. They are consistent with a coherence between the neural processing system that mainly provides for postural control, and the one responsible for nonpredominantly postural, visuospatial behavior.

Hemianopia and Neglect Influence on Straight-Ahead Perception

In spatial neglect, the pathological ipsilesional deviation of the subjective straight ahead (SSA) received both ‘translational’ and ‘rotational’ interpretations. Furthermore, hemianopia per se could also influence straight-ahead (SA) perception. Here, we aimed at disentangling the relative effects of neglect and hemianopia on the SSA by using a method analyzing translation and rotation in parallel. We included patients with a right hemisphere stroke. Ten had neglect and hemianopia, 6 neglect only, 3 hemianopia only, and 12 neither one nor the other. 15 were controls. Participants had to adjust a bar, movable in translation and rotation, SA of the navel, in darkness. Patients with spatial neglect showed systematic rightward translation, greater when hemianoptic. The rotation component appeared more variable and was influenced by the presence of a visual field defect, as most of the patients with hemianopia showed an anticlockwise rotation and most of the patients without hemianopia a clockwise rotation. Non-neglect patients and control subjects demonstrated a fair performance level. In conclusion, both neglect and hemianopia resulted in a translation error of the SSA to the ipsilesional side. In neglect patients, additional hemianopia resulted in a counterclockwise rotation. Furthermore, rotation and translation errors appeared dissociated, suggesting a different coding of these dimensions by the right posterior hemisphere.

The line bisection task in the acute stage of hemianopia and neglect

The line bisection task is a common clinical bedside tool for the assessment of spatial neglect and homonymous hemianopia (HH). While neglect patients show an ipsilesional deviation, hemianopic patients are usually known to displace their midline contralesionally towards the scotoma. Evidence for the “hemianopic line bisection error (LBE)“ came from hemianopic patients in a chronic stage of brain damage (mostly occipital stroke). As it seems to represent a compensatory shift of attention the LBE may be absent in the acute stage. If so, is the line bisection task a reliable bedside tool to distinguish hemianopia from hemineglect in the acute stage of stroke?

How body position changes visual vertical perception after unilateral vestibular loss

Visual vertical perception, posture and equilibrium are impaired in patients with a unilateral vestibular loss. The present study was designed to investigate whether body position (standing upright, sitting on a chair and lying supine) influences the visual vertical perception in Menière's patients tested before and after a unilateral vestibular neurotomy. Data were compared with sex- and age-matched healthy participants. During the first postoperative month the body position strongly influences the visual vertical perception. The ipsilesional deviation of the visual vertical judgment gradually increased from standing upright to sitting and to lying supine. The present data indicate that visual vertical perception improves when postural control is more demanding. This suggests that postural balance is a key reference for vertical perception, at least up to one month after vestibular loss.

Line bisection as an early method to assess homonymous hemianopia

Horizontal line bisection task is a common clinical task well known to most neuropsychologists. Typically, patients with visuospatial neglect show a reliable ipsilesional deviation in the bisection of long lines. Less well known in the English literature is the typical line bisection error observed in hemianopic patients who show the opposite deviation. In fact, this contralesional deviation in bisection was well known in the old German scientific literature. In 1894, more than 110 years ago, the German physician Dr. D. Axenfeld published a short case report about line bisection as a “simple method to diagnose hemianopia”. His paper is one (if not the first) historical report, describing the “typical hemianopic line bisection error”. At the time of its publication, it was a very popular paper in the German scientific community frequently cited by subsequent researchers. Between 1900 and 1920, Axenfeld's observation motivated several further studies using bisection by well-known researchers such as Best, Liepmann, Wilbrand, Poppelreuter and Fuchs. Surprisingly, most of today's clinical and cognitive studies use experimental modifications of line bisection in neglect patients and healthy subjects, often without realizing that this task was originally devised for the assessment of hemianopic patients. Consequently, the hemianopic line bisection error was “neglected” for many decades until its recent “rediscovery”. The present paper has three aims. First, Axenfeld's classical report is translated. Second, interpretations arising from early bisection studies (around 1900–1930) in hemianopic patients are summarized and framed within contemporary science. Finally, we attempt to explain why this formerly well-known clinical phenomenon was forgotten later for nearly a century.

Clinical Use of Subjective Visual Horizontal and Vertical in Patients of Unilateral Vestibular Neuritis

Subjective visual horizontal (SVH) and subjective visual vertical (SVV) used to assess otolith dysfunction and ipsilesional deviation of SVV and SVH in unilateral vestibular dysfunction is well known. The goal of this study was to investigate the clinical use of SVH/SVV and a dizziness scale in the clinical setting of acute unilateral vestibular neuritis. Thirty-five patients with unilateral vestibular neuritis were investigated. Every patient was diagnosed by physical examination and electronystagmography. Subjective visual horizontal and SVV were assessed during the acute or subacute period; the Dizziness Handicap Inventory (DHI) and Vestibular Disorder Activities of Daily Living Scale (VADL) were used for a self-dizziness scale at the same time. All patients underwent rehabilitation therapy. Subjective visual horizontal/SVV and DHI/VADL were assessed again approximately 4 weeks later. Postrehabilitation SVH/SVV and DHI/VADL data were compared with initial data. Dizziness Handicap Inventory and VADL were improved after 4 weeks of rehabilitation, and the deviation toward ipsilesional side SVH and SVV was also improved. These results demonstrate that SVH and SVV correlated with clinical dizziness symptoms in patients with acute unilateral vestibular neuritis. Therefore, SVH and SVV would be useful tools for the evaluation of clinical manifestations of unilateral vestibular neuritis.

Causes of cross-over in unilateral neglect: between-group comparisons, within-patient dissociations and eye movements

Patients with left unilateral neglect bisect long horizontal lines to the right of the true centre. However, when given short lines, many of the same patients mark the midpoint to the left of the true centre, towards the otherwise neglected space. This paradoxical phenomenon has been termed 'cross-over' and is difficult to explain based on current accounts of the neglect syndrome. To explore the causes of cross-over, in a first study we evaluated bisection of 20, 100 and 200 mm horizontal lines in groups of unilateral brain-damaged patients with neglect and hemianopia, with neglect and no hemianopia, with hemianopia and no neglect and without neglect or hemianopia. Cross-over of 20 mm lines was found only in neglect patients with hemianopia. To ascertain further the influence of visual field defects on cross-over, in a second study we compared the performance of two right-brain-damaged patients with contralesional neglect and inferior quadrantanopia with that of a patient with inferior quadrantanopia and no neglect. Patients bisected lines oriented so as to cross or uncross the blind quadrant of the visual field. When short 20 mm lines crossed the blind quadrant, neglect patients showed cross-over; when the same lines crossed the seeing quadrants cross-over was absent. These findings were confirmed by the examination of a neglect patient with sparing of the central 5 degrees of the contralesional left visual hemifield in the right eye and no sparing in the left eye. In monocular viewing, cross-over was present when 20 mm lines were bisected with the left eye and absent when bisected with the right eye. Recording of eye movements showed that at the moment of bisection left eye fixations shifted towards the contralesional line endpoint whereas right eye fixations remained anchored to the centre of the line. With long lines, both eyes deviated ipsilesionally. These results show that in neglect patients ipsilesional deviation in the bisection of long lines turns into apparently paradoxical contralesional bisection of short ones only when these cross a retinotopically blind sector of the neglected space. Cross-over seems to depend on the small spatial effects produced by reflexive contralesional gaze shifts allowing eccentric fixations with the seeing hemifield. During the bisection of long lines, these effects are cancelled out by the strong attentional deviation induced by the marked extension of the ipsilesional line segment. This explanation establishes coherence between cross-over and current accounts of the neglect syndrome.

Straight-Ahead Pointing Correlates with Long-Line Bisection in Neglect Patients

The spatial bias of neglect patients has been assumed to result from the alteration of a body-centred representation which underlies actions within personal and extra-personal spaces. This deficit seems to correspond to the ipsilesional deviation of the subjective straight-ahead (SSA), often described in neglect patients. However, several recent studies have failed to show significant correlations between the SSA deviation and performance in standard visuo-spatial tests of neglect. Since methodological choices could explain these negative results, the present study re-investigated the question. SSA, assessed by manual pointing, was anchored by instructions to a precise median body part. A body-centred line bisection task was also carried out, during the same session and in similar experimental conditions. Sixteen right brain-damaged patients with (n=8) or without (n=8) neglect, and 8 control subjects free of any neurological problem were included. Taken as a group, the neglect group stood out from the others in both tasks. Moreover, in neglect patients only, SSA position significantly correlated with bisection error for long lines, even if dissociations between SSA shift and bisection error were found in two cases. Results are discussed with regard to the nature of the tasks proposed in the different studies and to methodological aspects that could at least partly explain the aforementioned failures.

Dissociation of hemi-spatial and hemi-motor impairments in a unilateral primate model of Parkinson’s disease

Monkeys with unilateral lesions of nigrostriatal dopamine projections were tested on a series of spatial tasks. One task, in which monkeys were required to use one or the other arm to retrieve food rewards from different positions, allowed separate assessment of the use of each arm in each hemi-space in order to distinguish hemi-spatial and hemi-motor impairments. The lesioned monkeys exhibited a persistent neglect of contralesional space when using either arm which could be dissociated from a motor impairment in the contralesional arm alone. Another task allowed free use of either arm across peri-personal space and demonstrated an ipsilesional bias in the monkeys’ self-determined attention (orientation) to a task which they were trying to perform. It is argued that the tendency for monkeys with this lesion to rotate ipsilesionally is due to an ipsilesional deviation of the ‘centre of interest’ (determined by telencephalic circuitry) relative to ‘straight ahead’ (determined by brainstem circuitry). The dopamine projections may contribute to cortico-subcortical circuits which determine the spatial layout of mental representation, attention and intention. The results in this primate model of unilateral Parkinson’s disease (PD) support the view that patients with left-sided Parkinsonian symptoms exhibit a unilateral deficit in spatial mental representation as well as their well-recognised motor symptoms. Patients with bilateral Parkinson’s symptoms may exhibit bilateral deficits in mental representation.

Vestibulo-ocular and optokinetic impairments in left unilateral neglect

Right brain damaged patients affected by left unilateral neglect (N+) typically fail to explore the contralesional space. For the first time, this study investigates the dynamic and spatial features of the horizontal vestibular–ocular response (VOR), the optokinetic response (OKR) and the VOR–OKR interaction in six N+ and in five right brain damaged patients without neglect (N−). No lateral asymmetry of the gain (i.e. eye velocity to head velocity ratio) of VOR slow phases was found in either group. In the VOR, N+ had higher frequency of slow-rightward/fast-leftward phases and higher contralesional shift of the beating field (i.e. orbital position of fast phases). In the VOR–OKR, there was an increase of gain in both lateral directions and in both groups even though in N−, there was a lower phase shift between eye and head velocity. In contrast to the VOR, in the VOR–OKR, N+ had higher frequency of slow-leftward/fast-rightward phases. The VOR–OKR interaction also introduced an ipsilesional shift of the beating field in both N+ and N−. In the OKR, N+ showed a drop in the velocity, amplitude and frequency of slow-rightward/fast-leftward phases. These findings potentially suggest that each hemisphere modulates VOR with contralaterally directed slow phases and OKR with ipsilaterally directed slow phases. This organisation could facilitate maintenance or fast recovery of combined VOR + OKR after unilateral brain damage. The same findings suggest that by inducing slow-leftward phases, vestibular and optokinetic stimulation improve left side neglect through the activation of different hemispheric pathways. No ipsilesional deviation of the subjective “straight ahead” was found in N+. These results show that chronic unilateral neglect can be dissociated both from deficits of ipsilesionally directed VOR and from ipsilesional deviation of the subjective midsagittal plane of the body.

Position of the egocentric reference and performance in line bisection and subjective vertical estimation tasks

Egocentric body coordinates such as the sagittal midline have been proposed to act as a reference for ballistic movements in extracorporeal space. Symmetrical functioning of the multiple neural structures processing sensory information would account for the normal sagittal position of the egocentric reference. According to this hypothesis a unilateral parietal lesion would induce a ipsilesional deviation which would prevent neglect patients from responding to stimuli that occur on that side. In this line of reasoning, an experimental manipulation of the position of the egocentric reference by way of a postural perturbation should have an effect on visuospatial tasks performance in normal subjects. Seventeen right-handed subjects were submitted in the dark to two visuomotor tasks: the adjustment of a luminescent rod to the vertical and the bisection of a luminescent line, either with the trunk and the head aligned at 0 degrees or with a 30 degrees trunk rotation to the right or to the left. Results revealed no significant effect of trunk rotation on the performance in both tasks. We discuss these findings and their implication for the understanding of the neglect syndrome.

Auditory neglect and right parietal cortex

Many patients who have suffered right hemisphere stroke seem initially unresponsive to voices and environmental noises that emanate from their left (Heilman and Valenstein, 1972). The question of whether more subtle deficits might persist post-acutely, and whether, like visuospatial neglect, they really are more common after right than left hemisphere damage, has been comparatively little studied. Until fairly recently, auditory neglect was the poor relation of visual neglect. In part, this is because there are no auditory analogues of simple search tasks such as target cancellation, or of drawing or copying. Auditory bisection performance, where the subject is required to point to a position in space midway between two sound sources, has been reported (Ruff et al ., 1981): patients with right parietal lesions were less accurate than those with any other lesion site in terms of absolute error, but did not show a specific bias to the right. In terms of testing at the bedside, many examiners look for auditory extinction in a rough and ready fashion by clicking their fingers or jangling keys simultaneously on either side of the patient's head. The auditory subjective straight ahead (SSA) can also be tested without elaborate apparatus. When more sophisticated methods are used (e.g. presentation over headphones of stimuli with interaural and monaural cues to sound location in virtual space), the SSA is frequently found to show a large ipsilesional deviation in patients with left visual neglect after right parietal damage. It is important …

Contrasting spatial hearing deficits in hemianopia and spatial neglect

Spatial hearing deficits have been described in widely differing pathologies, including bilateral temporal or unilateral parietal lesions, hemispherectomy, spatial neglect and right-sided cortical lesions without neglect. However, the topography of spatial hearing deficits after cortical lesions is only poorly understood, unlike that of vision and touch. We investigated the auditory subjective straight ahead (SSA) with a new technique of binaural sound source simulation using broad-band single pulses which were filtered with head-related transfer functions and delivered with a 5 degree resolution over headphones in front space. Normal subjects showed quite accurate judgments of the SSA, with a small but significant shift to the left of centre (-1.7 degrees) in the horizontal plane. Hemineglect without a scotoma, produced a large ipsilesional deviation of the auditory SSA (+22 degrees), while two hemianopic subjects, both without neglect, showed the opposite deviation of their perceived auditory SSA towards their contralesional, blind hemifield (+10 vs -28 degrees). Two control patients with unilateral lesions, both without neglect and without hemianopia, produced normal judgments of their auditory SSA (-3.0 degrees, +3.8 degrees). These results suggest at least two contrasting influences on directional spatial hearing after unilateral cortical lesions: hemianopia vs hemispatial neglect. The results are interpreted in favour of multisensory convergence of visual and auditory information in directional spatial hearing.

Position of the Egocentric Reference and Directional Arm Movements in Right-Brain-Damaged Patients

We asked 12 right-brain-damaged patients (6 with left neglect signs and 6 without left neglect signs) to perform a straight ahead pointing task and a visual detection task with lateralized motor response, in order to investigate the relationship between the position of the egocentric reference and response time and accuracy in producing lateralized arm movements. Results showed that there was no correlation between the position of the egocentric reference and neglect signs, nor between the position of the egocentric reference and the latencies to direct a motor response toward either side of space. These findings were interpreted within the context of egocentric hypotheses of neglect. In particular, it was suggested that attentional or intentional neglect signs cannot be considered as a direct consequence of an ipsilesional deviation of the egocentric reference.

In search of biased egocentric reference frames in neglect

The present study was aimed at assessing, by means of visual as well as proprioceptive-kinaesthetic straight-ahead tasks, the possible causal role of the ipsilesional deviation of the egocentric reference frame in determining neglect syndrome. The hypothesis, originally proposed by Ventre et al. [3], that an alteration of the representation of body-centred space can be a cause of asymmetrical spatial behaviour in humans has been recently revived by Karnath and co-workers [24]. The results of the present study seem to challenge the view that a systematic ipsilesional displacement of the egocentric reference is the crucial mechanism responsible for unilateral visual neglect. Under visual conditions, in which patients were required to stop a moving spot as it crossed their perceived midline, the ipsilesional deviation of the egocentric reference frame was dependent upon the direction of visual scanning. Right to left visual scanning direction produced a rightward displacement of the egocentric reference. In contrast, left to right visual scanning direction allowed neglect patients to correctly locate their perceived egocentre with an accuracy which did not differ from controls. The notion that the effect of a deviation of the egocentric reference frame is actually dependent on a bias in the visual scanning orienting response was also confirmed in the proprioceptive straight-ahead pointing tasks, in which the patients were blindfolded and therefore no visual information was available. In these conditions, in which patients were required to judge the subjective midline by using head, trunk and shoulder co-ordinate systems, the displacement of the subjective egocentric midline was not present.

Patterns of dissociation between left hemineglect and deviation of the egocentric reference

Sixteen control subjects and six right brain-damaged patients with left hemiparesis (three showing signs of left unilateral neglect, three with no signs of neglect) performed a straight-ahead pointing task with their right hand while blindfolded. The aim was to test the hypothesis that the egocentric reference shows significant ipsilesional deviation in left neglect patients. We found no correlation between the position of the egocentric reference and the presence of neglect signs. Neglect patients, like non-neglect patients, showed leftware, rightward or no significant deviation when pointing straight ahead. Results are discussed with reference to egocentric hypotheses of neglect and experimental remission of neglect.