A case of alien hand syndrome after right posterior cerebral artery territory infarction]

We report a 63-year-old right-handed man who presented an alien hand syndrome (AHS). He complained of clumsiness of his left hand and admitted to our hospital. On the first examination, he presented left homonymous hemianopia, left spatial neglect and left limb ataxia, but neither paralysis nor sensory impairment. A few days after, he complained that his left hand was controlled by someone else, and we considered this phenomenon as AHS. At that time, he lost sensation of almost all modalities including deep sensation on his left upper and lower limb. Magnetic resonance image examination was performed, and it showed acute cerebral infarction at right posterior cerebral artery territory including right thalamus (ventral posterior lateral nucleus). Generally, AHS is caused by left mediofrontal and callosal lesion (frontal type AHS), or by callosal with bilateral frontal or without frontal lesion (callosal type AHS). However, some cases were reported that they presented AHS after damage of the basal ganglia, right thalamus, right occipital or inferior parietal lobe. Some authors described this phenomenon as "sensory" or "posterior" type AHS. In such cases, included our case, we speculate that sensory impairment causes AHS. Especially in our case, AHS might be caused by not only the sensory impairment but also by left homonymous hemianopia and left spatial neglect. So, because of these symptoms, our patient could not recognize the motion of the left hand, and presented AHS. We think that this "sensory" or "posterior" type AHS should be distinguished from frontal and callosal type AHS.     

Hemispatial visual defect in Alzheimer's disease

We describe a 56-year-old woman with Alzheimer's disease with left hemispatial neglect and left homonymous hemianopsia with macular sparing considered a manifestation of Alzheimer's disease resulting from severe degenerative change in the right primary visual cortex. Hemispatial neglect normally results from brain damage to the right cerebral hemisphere. Homonymous hemianopsia is commonly the result of localized brain disease, especially cerebral infarction or hemorrhage. To our knowledge, a patient with Alzheimer's disease showing hemispatial neglect and homonymous hemianopsia with macular sparing has not previously been reported.     

Right-sided neglect following a left subcortical lesion

Unilateral spatial neglect is, in humans, typically consequent to lesions of the right hemisphere and pertains to the left hemispace. Although neglect is maximally frequent after right cortical lesions, it may also ensue from lesions confined to right subcortical structures. By contrast, hemispatial neglect consequent to left hemispheric lesions occurs less frequently. Reports of neglect following lesions to left subcortical structures are even more rare and largely anecdotal. Here we report on a right-handed man who had two successive left-sided brain lesions at an interval of 10 years from one another. The first lesion, centered upon the occipital lobe, induced a contralateral hemianopia, but no signs of hemispatial neglect; by contrast, the second lesion, a capsulo-thalamic hemorrhage, did induce a florid and persistent right-sided neglect. This finding would suggest that left subcortical structures may be important nodes in the network subserving spatial representations.     

Japanese encephalitis presenting with left hemiplegia and thalamic neglect--a case report]

This report concerns a 51-year-old right-handed man with Japanese encephalitis, showing left hemiplegia and left hemispatial neglect. On admission, he had a slight fever, mild consciousness disturbance, left hemiplegia, and left hemispatial neglect but no neck stiffness, headache nor nausea. He was treated on the basis of cerebral infarction, but his fever and consciousness disturbance worsened. We found pleocytosis (145/mm3) in the cerebrospinal fluid (CSF) and right thalamic edema on a brain CT scan obtained 4 days later. He was finally diagnosed as having Japanese encephalitis on the basis of an increase in anti-viral antibodies observed in paired CSF and serum samples. In the exacerbation phase, 123I-IMP single photon emission CT (SPECT) demonstrated a marked decrease in cerebral perfusion in the right hemisphere, while a brain MRI revealed irregular lesions localized the right thalamus (mainly posterior and medial parts), showing low intensity on T1-weighted and high intensity on T2-weighted images. In the recovery phase, asymmetrical perfusion was no longer observed on SPECT and the symptoms including the left hemispatial neglect had improved. These findings suggest that the left hemispatial neglect in this patient might been caused by the right thalamic lesion resulting in damage to the activating system of the right hemisphere. This case thus shows that acute onset of hemispatial neglect could be caused by cerebral encephalitis.     

Proximal posterior cerebral artery occlusion simulating middle cerebral artery occlusion

We describe 12 cases of acute stroke in which clinical features of proximal posterior cerebral artery occlusion simulated the clinical syndrome of middle cerebral artery occlusion. The majority of patients developed contralateral hemiparesis, homonymous hemianopia, hemispatial neglect, and sensory loss or sensory inattention. All 8 patients with dominant hemisphere lesions were aphasic. Accurate diagnosis in each case was achieved only after a head CT, showing occipital lobe, thalamic, and inferomesial temporal lobe infarction. "Cortical" signs are probably explained by thalamic involvement. Recognition of this syndrome has implications for management and prognosis.     

Crossed aphasia with left spatial neglect and visual imperception: a case report

A 64-year-old right-handed woman with no left-handers in the family developed aphasia associated with moderate left hemiparesis and dense left homonymous hemianopia following rupture of a right middle cerebral artery aneurysm and subsequent selective surgery confined to the right hemisphere. Severe left spatial neglect and constructional apraxia were also present. The patient was an achondroplasic dwarf whose previous medical and neurological history was otherwise unremarkable. Computed tomography of the brain showed a large right temporo-insulofrontoparietal lesion. Language and nonverbal cognitive functions were assessed after 2 and 6 months, and then four years later. A reportedly overall language disruption in the acute period evolved into Wernicke's aphasia and then into a mild form of conduction aphasia. The associated left spatial neglect eventually shrank to a minimum. The patient never had clinically detectable visual agnosia, but on specific tests of visual recognition and perception some impairment was found four years after onset. The left hemiparesis disappeared in time while the left hemianopia persisted. This case is a convincing example of an entirely righthanded person in whom both linguistic and visuospatial functions are represented in the right hemisphere. Received: 12 May 2002 / Accepted in revised form: 18 November 2002 Correspondence to L.A. Vignolo     

Directional hypokinesia: prolonged reaction times for leftward movements in patients with right hemisphere lesions and neglect

Patients with hemispatial neglect perform activities poorly in the hemispace contralateral to the lesion. We postulate that hemispatial neglect induced by right hemisphere lesions may be associated with a directional hypokinesia: initiation of movements toward the hemispace contralateral to the lesion is affected more than movements toward the lesion. We tested 6 patients with hemispatial neglect caused by right hemisphere damage, 7 with left hemisphere damage and no neglect, and 12 controls. Patients with left hemispatial neglect initiated responses to left hemispace more slowly than toward right hemispace.     

Impaired reading in patients with right hemianopia

A left occipital stroke may result in alexia for two reasons, which may coexist depending on the distribution of the lesion. A lesion of the left lateroventral prestriate cortex or its afferents impairs word recognition ("pure" alexia). If the left primary visual cortex or its afferents are destroyed, resulting in a complete right homonymous hemianopia, rightward saccades during text reading are disrupted ("hemianopic" alexia). By using functional imaging, we showed two separate but interdependent systems involved in reading. The first, subserving word recognition, involved the representation of foveal vision in the left and right primary visual cortex and the ventral prestriate cortex. The second system, responsible for the planning and execution of reading saccades, consisted of the representation of right parafoveal vision in the left visual cortex, the bilateral posterior parietal cortex (left > right), and the frontal eye fields (right > left). Disruption of this distributed neural system was demonstrated in patients with severe right homonymous hemianopia, commensurate with their inability to perform normal reading eye movements. Text reading, before processes involved in comprehension, requires the integration of perceptual and motor processes. We have demonstrated these distributed neural systems in normal readers and have shown how a right homonymous hemianopia disrupts the motor preparation of reading saccades during text reading.     

Right sided hemispatial neglect and bilateral cerebral lesions.

This study compared the frequency with which unilateral and bilateral cerebral disease gives rise to right sided visual hemispatial inattention. A retrospective survey identified brain injured patients for whom target omissions on visual target cancellation tasks significantly exceeded control values. Subjects consisted of 40 right handed patients referred for clinical evaluation or research study of hemispatial inattention. Right sided visual hemispatial inattention occurred with greater frequency and severity in patients with bilateral lesions than in patients with unilateral left sided or right sided lesions. All eight patients with bilateral lesions manifested right sided hemispatial inattention and failed to detect more targets overall than patients in the other two groups. Of the 13 patients with left sided lesion, seven ignored more targets on the right and six ignored more targets on the left. All but one of the 19 patients with right sided lesions ignored more targets on the left. The association of severe right sided visual hemispatial inattention with bilateral cerebral disease extends previous findings and showed that, in this sample, the most common setting for right sided hemispatial neglect occurred in patients with bilateral cerebral lesions.     

Two distinct deficits of visual tracking caused by unilateral lesions of cerebral cortex in humans

We studied horizontal visual tracking in 20 patients with unilateral cerebral lesions and in 10 age-matched control subjects. Five patients, all with posterior lesions, showed impaired smooth pursuit of predictable targets moving toward the side of the cerebral lesion. Using nonpredictable step-ramp stimuli, we identified two distinct deficits of visual tracking. The first was a unidirectional deficit of smooth pursuit, for targets moving toward the side of the lesion, in response to stimuli presented into either visual hemifield. The second deficit, identified in a sixth patient who did not show pursuit asymmetry to predictable targets, was a bidirectional inability to estimate the speed of a moving target in the visual hemifield contralateral to the side of the lesion; this caused inaccurate saccades to moving (but not stationary) targets and impaired smooth pursuit initiation. These visual tracking deficits were independent of homonymous hemianopia or hemispatial neglect. These two tracking deficits are similar to those described in rhesus monkeys with lesions of the medial superior temporal and middle temporal visual areas.     

Hemianopia, hemianesthesia, and spatial neglect: a study with evoked potentials.

We recorded somatosensory or visual evoked potentials (SEPs, VEPs) to stimuli contralateral and ipsilateral to the lesion in three right-brain-damaged patients with left spatial hemineglect and in three left-brain-damaged patients without evidence of neglect, as assessed by visual exploratory tasks. All patients had contralateral homonymous hemianopia or hemianesthesia. The three neglect patients showed normal SEPs or VEPs to stimuli delivered to the left half-field or to the left hand, without conscious perception and verbal report of the stimulation. By contrast, the three left-brain-damaged patients without neglect showed no recognizable cortical evoked response to contralateral visual or somatosensory stimuli. In all patients, the cortical evoked responses to ipsilateral stimulation were normal. In patients with spatial hemineglect, hemianopia and hemianesthesia may be manifestations of the neglect syndrome (visual and somatosensory hemi-inattention), rather than representing primary sensory deficit. Visual and somatosensory hemi-inattention may be due to defective access to the neural processes subserving conscious perception by information that has undergone early sensory processing.     

Does spatial cueing affect line bisection in chronic hemianopia?

Patients with homonymous hemianopia often show a contralesional shift towards their blind field when bisecting horizontal lines ("hemianopic line bisection error", HLBE). The reasons for this spatial bias are not well understood and debated. Cueing of spatial attention modulates line bisection significantly in patients with visuospatial neglect. Moreover, recent evidence showed that attention training significantly improves deficits of visual search in hemianopia. Here, we tested in 20 patients with chronic homonymous hemianopia (10 left-sided, 10 right-sided) without visual neglect, 10 healthy control subjects, 10 neurological control patients, and 3 patients with left visuospatial neglect and leftsided hemianopia whether spatial cueing influences the HLBE. Subjects indicated verbally the midpoint of horizontal lines in a computerized line bisection task under four experimental cue positions (cue far left, mid-left, mid-right or far-right within the horizontal line). All 20 hemianopic patients showed the typical HLBE towards their blind field, while the two control samples showed only a small but significant leftward shift (pseudoneglect). None of the 4 cueing manipulations had a significant effect on the HLBE in the hemianopic patients. Moreover, no differential effects of cueing on line bisection results were obtained when analyzed in lesion subgroups of hemianopic patients with circumscribed occipital lesions (N=8) as contrasted with patients having more extended (occipito-temporal or temporal) lesions (N=12). This null-effect contrasts with marked cueing effects observed in 3 neglect patients with left hemianopia in the same tasks, showing the principal efficacy of our cueing manipulation. These results argue against attentional explanations of the HLBE.     

Eye-movement patterns do not mediate size distortion effects in hemispatial neglect: looking without seeing

Over the last decade a range of studies have shown that some patients with hemispatial neglect subjectively underestimate the size of objects presented in their contralesional hemispace. Recently, it has been suggested that the effect is simply due to either hemianopia [Brain 124 (2001) 527], or the combination of neglect and hemianopia [Neurology 52 (1999) 1845]. In the current study we asked right hemisphere lesioned patients with and without neglect and hemianopia as well as healthy controls to judge either two horizontal or vertical lines presented simultaneously in right and left hemispace and monitored their eye movements. Three out of the six patients showed the predicted size distortion effect for horizontal lines. We found no evidence that the effect was mediated by eye movements. The two neglect patients who showed the strongest left side underestimation showed symmetrical (left, right) scanning of the lines both in terms of number of fixations and fixation time, yet they still failed to judge the relative size veridically. In addition, we did not find strong evidence for a link with hemianopia. We therefore propose that the effect reflects a computational/representational failure of processing for horizontal extent.     

Opticosensory ataxia and alien hand syndrome after posterior cerebral artery territory infarction

A right-handed woman developed left homonymous hemianopia and left hemianesthesia from infarction due to right posterior cerebral artery occlusion. Ataxia of the left arm and leg was severe and was not improved by vision. The patient often interpreted spontaneous movements of the left arm as alien in origin. The ataxia may have been caused by a combination of sensory ataxia, resulting from right thalamic infarction, and crossed-optic ataxia, resulting from posterior disconnection of the hemispheres due to right temporo-occipital infarction. This opticosensory ataxia was associated with a new form of "alien hand" syndrome.     

Mechanisms underlying hemispatial neglect.

If patients with left-sided hemispatial neglect bisect lines incorrectly because hemianopia or sensory hemiinattention prevents them from seeing how far the line extends to the left, a strategy that ensures their seeing the left side of the line in their normal field should improve performance. If patients have hemispatial hypokinesia, moving the line toward the normal half of body space should improve performance. Six patients with left-sided neglect from right hemisphere infarctions were required to identify a letter at either the right or the left end of a line before bisecting that line. The task was given with the lines placed at either the right, the center, or the left of the body midline. Performance in trials when subjects were required to look to the left before bisecting a line did not differ from when they were required to look right. Performance was significantly better when the line was placed to the right side of the body than to the left. These observations support the hypothesis that patients with hemispatial neglect have hemispatial hypokinesia. An alternative hypothesis is that these subjects had a hemispatial memory defect. Although they saw the left side of the line in their normal field, they were incapable of forming a stable trace and performed as if they did not see the left side of the line.     

Visual search training for a case of homonymous field defect with multiple visual dysfunctions]

A 72-year-old right handed man developed right homonymous hemianopia without macular sparing, left homonymous lower quadranopia with macular sparing, cerebral amblyopia, cerebral achromatopsia, impaired form vision, and mild right hemispatial neglect, after multiple cerebral infarctions, involving bilateral occipital cortices. His intelligence and memory were deteriorated moderately. He failed to notice objects located in the affected visual field, because of his severely impaired visual search. When ordinary lighting was used, he showed severe right-sided omissions on the line cancellation test. However, omissions were less marked under the brighter lighting. By using a modified method of Kerkhoff and Vianen (1994), he was trained to make saccadic eye movements toward affected regions to find a target and to search and point at targets arranged randomly. As the sensitivity for contrast of isoluminante red and green stimuli was preserved well at high spatial frequencies despite the decreaced contrast sensitivity for brightness, we used green targets as the training stimuli. After the training, search field and pointing range that could be covered by the patient increased in size for both green and white targets, and daily activities improved. Moreover, after the training, he no longer showed discrepancy in line cancellation performances between ordinary and brighter lighting conditions. In the follow up period, the search field and the performance on the line cancellation test were maintained, while the performance of pointing targets array declined. The family members complained of mild re-deterioration of daily activities. Then, the training for searching and pointing re-introduced at home. After the training, his pointing performance and daily activities, evaluated by questionnaires to his family members, improved again. In conclusion, it was suggested that disordered visual search after a homonymous field defect can be treated effectively, even if multiple visual dysfunctions were associated.     

Disentangling neglect and hemianopia.

In this paper we report findings which question the diagnosis of a hemianopia in B.Q., a 66-year-old lady who shows unilateral spatial neglect following a lesion to the right parietal lobe. The presence of a hemianopia has been indicated following two independent assessments of B.Q.'s visual fields. We examined B.Q.'s performance on a visuo-spatial task in which single or double stimuli were displayed left and right of a central fixation point. B.Q. failed to report left stimuli when the fixation point was continuously displayed (OVERLAP CONDITION). This performance is consistent with the suggestion of a left hemianopia as indicated by perimetric field testing. In a further condition the fixation point was extinguished prior to stimuli onset (GAP CONDITION). B.Q. consistently responded to left stimuli in the gap condition and also showed improved performance to right stimuli. Eye movements were recorded on a separate testing session, in which B.Q. showed a normal saccadic response to left targets in the gap condition, but not during the overlap condition. These results suggest that B.Q.'s failure to report left stimuli during field plotting is due to her neglecting left stimuli and not because she has a visual field defect. By using a testing procedure which reduces the severity of neglect B.Q. is able to respond to left stimuli. Reducing the severity of B.Q.'s neglect also abolishes the apparent hemianopia. Standard field plotting techniques which use a consistently displayed fixation point may not be appropriate for the testing of neglect patients' visual fields.     

Crossed aphasia: description of a case

We describe a new case of crossed aphasia in a right-handed patient with a right hemispheric lesion. A right-handed man, 76 year-old, developed a sudden left hemiparesis with sensitive impairment and mutism. He has neither family history of left handeness or ambidexterity or vascular risk factors. CT cerebral scan showed a large infarct of the middle cerebral artery on the right side, with haemorrhagic suffusion. Cerebral MRI and EEG-cartography confirmed the indemnity of the left hemisphere. Aphasia studies confirmed a mutism with spared verbal comprehension, but alexia was present. A year later, left hemiparesis was recovered but aphasia remained. Crossed aphasia is rarely seen. It is caused by a right hemispheric lesion in right-handed subjects. Fluency is most commonly impaired. At onset, mutism is the common symptom, which evolves to expressive aphasia. Several hypothesis have been raised about the possible mechanisms involved. The few number of PET or SPECT studies performed in these patients have disclosed extensive areas of hypometabolism in the right hemisphere, that exceed the size of the image observed with CT scan or MRI.     

Impaired size processing for single objects after hemispatial neglect.

Some patients with hemispatial neglect show deficits in horizontal size perception. Most previous studies investigating this effect required the relative comparison of two horizontal stimuli. We examined whether the effect would also be present for single stimuli which would reflect an impairment in the computation of absolute horizontal length. Ten neglect patients, five with and five without hemianopia, and two control groups were asked to verbally judge the length of horizontal lines varying in length (3, 3.5, 4 inches) and spatial location (extreme left to extreme right). Three of the ten neglect patients judged a single object on the left as significantly smaller than a single object on the right, thus demonstrating a size processing deficit. This deficit was unrelated to hemianopia.     

Hemispatial visual inattention masquerading as hemianopia

The defect occurring when a patient fails to report a visual stimulus presented in a visual half-field may be attributed to hemianopia (deafferentation) caused by a geniculocalcarine lesion. However, failure to report a stimulus presented in a visual field may also be caused by hemispatial visual inattention. We report a patient with right thalamic and temporo-occipital lesions who had a left visual field defect when her eyes were directed either straight ahead (midsagittal plane) or toward left hemispace. However, this visual field defect abated when her eyes were directed to right hemispace, suggesting that the patient had hemispatial visual inattention rather than hemianopia.