Posterior Cortical Lesions Research Articles

Posterior Reversible Encephalopathy Syndrome Induced by an Acute Postinfectious Glomerulonephritis.

Posterior reversible encephalopathy (PRES) is a rare but a serious disease that affects the central nervous system. PRES is responsible for various but nonspecific neurological symptoms, including confusion, coma, and seizures as well as visual disturbances. Diagnosis is made using cerebral MRI which typically shows at the early stage, bilateral symmetrical parietooccipital hyperintensities on T2 and fluid-attenuated inversion recovery (FLAIR) sequences. Case study. In this article, we base our research on a case study that includes, as a population sample, a 9-year-old boy who suffers from an acute postinfectious glomerulonephritis and arterial hypertension. Two days before diagnosis, he developed confusion with generalized tonic-clonic attacks. His blood pressure was 180/80 mmHg. A cerebral computed tomography made in emergency showed cerebral edema. It was supplemented by magnetic resonance imaging which revealed cortical and posterior cortical lesions which appear as hypointense on T1 and hyperintense on T2 and Flair. An MRI control was performed 40 days later which shows a clear improvement of the occipital lesions. PRES is a radioclinical syndrome characterized by the association of variable neurological signs which reversibility is conditioned by the early diagnosis and the correction of the contributing factors.

Hallucinatory Palinopsia in COVID-19-Induced Posterior Reversible Encephalopathy Syndrome.

Hallucinatory Palinopsia in COVID-19-Induced Posterior Reversible Encephalopathy Syndrome.

Executive dysfunction contributes to verbal encoding and retrieval deficits in posterior cortical atrophy

Posterior Cortical Atrophy (PCA) is a neurodegenerative syndrome that typically presents with predominant visual and spatial impairments. The early diagnostic criteria specify a relative sparing of functioning in other cognitive domains, including executive functions, language, and episodic memory, yet little is known of the cognitive profile of PCA as the disease progresses. Studies of healthy adults and other posterior cortical lesion patients implicate posterior parietal and temporal regions in executive functions of working memory and verbal fluency, both of which may impact episodic memory. Relatively little has been reported about these cognitive functions in PCA, and to our knowledge there has not yet been a study of the impact of such deficits on memory function in PCA. We sought to examine PCA patients' performance on tests of executive function and the associations to verbal episodic memory encoding, storage, and delayed recall. Nineteen individuals with PCA underwent neuropsychological and neuroimaging evaluations as part of a comprehensive clinical assessment. We developed a novel consensus rating method—the Neuropsychological Assessment Rating (NAR) scale—to grade the severity of test performance impairments in selected cognitive domains and subdomains. Hypothesis-driven analyses demonstrated relative deficits in working memory and lexical-semantic retrieval. Preliminary analyses suggested associations between both deficits and atrophy in the left-hemisphere inferior parietal lobule. These executive deficits were also associated with impairments in verbal encoding and delayed recall, but not with recognition discriminability. We conclude that deficits in verbal executive functions impact verbal episodic memory in PCA. Our findings also support theories emphasizing the role of the posterior parietal cortex in supporting executive and lexical-semantic contributions to verbal episodic memory.

Supra-Tentorial Cortical Ependymoma in an Adult: Case Report and Review of the Literature

Supratentorial cortical ependymoma is a rare primary brain tumor in adults. Only 50 cases are reported in the literature including pediatric and adult patients. We report a 30-year-old male with sensory-type seizures who was found to have a right posterior frontal cortical lesion with large cystic component. The lesion was resected completely and histopathology and immunohistochemistry examinations confirmed anaplastic ependymoma WHO grade III. The patient received radiotherapy treatment post-surgery, and he was tumor free one year after treatment.

Characteristics of Chinese-English bilingual dyslexia in right occipito-temporal lesion

Current literature suggests that right hemisphere lesions produce predominant spatial-related dyslexic error in English speakers. However, little is known regarding such lesions in Chinese speakers. In this paper, we describe the dyslexic characteristics of a Chinese-English bilingual patient with a right posterior cortical lesion. He was found to have profound spatial-related errors during his English word reading, in both real and non-words. During Chinese word reading, there was significantly less error compared to English, probably due to the ideographic nature of the Chinese language. He was also found to commit phonological-like visual errors in English, characterized by error responses that were visually similar to the actual word. There was no significant difference in visual errors during English word reading compared with Chinese. In general, our patient’s performance in both languages appears to be consistent with the current literature on right posterior hemisphere lesions. Additionally, his performance also likely suggests that the right posterior cortical region participates in the visual analysis of orthographical word representation, both in ideographical and alphabetic languages, at least from a bilingual perspective. Future studies should further examine the role of the right posterior region in initial visual analysis of both languages.

REHABILITATION OF PATIENTS WITH SPEECH DISORDERS OCCURRING FROM POSTERIOR CORTICAL LESIONS

Актуальность. Накопившиеся в последнее время научные данные о механизмах компенсации у больных с последствиями нарушения мозгового кровообращения позволяют пересмотреть традиционные методики восстановления афазии.

Right posterior cortical functions in a tumour patient series

It is standardly believed that the localisation of cognitive function by means of impairments arising from cortical tumour is not possible as the functional defects that result are mild and unspecific. These assumptions were not supported in an investigation of four processes generally sensitive to right posterior cortical lesions, when patients with parieto-occipital lesions were compared with prefrontal ones. In three of the tests loading on the individual processes – Reaching Accuracy, Star Cancellation, Fragmented Letters and Cube Analysis – parieto-occipital impairments were found in the basic groups analysis and this was so in the right-hemisphere group. More critically, in these tests Lesion Behaviour Mapping showed the critical lesion site for the tests to have relatively little overlap with those of the other tests, indicating that the cognitive effects were not widespread and diffuse. In addition, in three of the tests the critical lesion sites fitted localisations arrived from other procedures. Patients with high-grade tumours performed considerably worse than those with low-grade tumours in only two of the tests (Star Cancellation, Cube Analysis) particularly in the right parieto-occipital group. In three (Reaching Accuracy, Star Cancellation, Cube Analysis) there was a deterioration with the operation specifically in the low-grade tumour patients. It is suggested that a tumour patient series may provide converging evidence for the localisation of a function initially obtained by some other procedure.

Burkitt lymphoma presenting as posterior reversible encephalopathy syndrome secondary to hypercalcaemia

A 50-year-old Caucasian female presented with fever and increasingly obtunded. Physical examination showed normal blood pressure and no focal neurological signs. There was no organomegaly or lymphadenopathy. A full blood count showed: haemoglobin 86 g/l, white cells 9AE9 · 10/l (with 6% blasts) and platelets 114 · 10/l. A coagulation screen showed evidence of disseminated intravascular coagulopathy. Biochemistry tests revealed hypercalcaemia with a calcium of 3AE91 mmol/l and increased ionized calcium to 2AE05 mmol/l, in association with raised lactate dehydrogenase to 345 iu/l but normal alkaline phosphatase level. The serum free kappa light chain level was increased to 33AE6 mg/l (reference interval: 3AE3–19AE4 mg/l) and there was generalized immunoparesis. Bone marrow aspiration showed hypercellular particles packed with 76% blasts (left upper panel). The blast cells were mostly medium sized showing round nuclei, dispersed chromatin, multiple small nucleoli and scanty basophilic cytoplasm that was sometimes vacuolated. Trephine biopsy showed hyperplastic marrow that was diffusely replaced by a monotonous population of medium-sized blasts with frequent mitotic figures. Blast cell immunophenotyping by flow cytometry supplemented by immunohistochemistry demonstrated clonal B-cells (CD19 CD20 CD22 CD79a surface IgM) that expressed CD10 and BCL2, but were negative for terminal deoxynucleotidyltransferase and BCL6. The Ki-67 labelling index was virtually 100%. Interphase FISH on bone marrow blasts showed MYC gene rearrangement (left lower panel) as detected by a dual colour break-apart probe (Abbott Molecular, IL, USA) but negative for IGH/MYC fusion, consistent with MYC translocation other than classical t(8;14). The IGH/BCL2 fusion was negative. The diagnosis was Burkitt lymphoma. Magnetic resonance imaging (MRI) of the brain showed symmetrical posterior cortical and subcortical lesions in axial (right upper panel) and coronal (right lower panel) sections. The cerebrospinal fluid was unremarkable. The patient was started on haemodialysis for acute renal failure (creatinine 463 lmol/l) and the calcium level was normalized after institution of cytotoxic therapy. A repeat MRI scan after treatment showed complete resolution of the brain lesion. The neurological diagnosis was posterior reversible encephalopathy syndrome (PRES) secondary to severe hypercalcaemia. The patient returned to her native country for further management. This case illustrated the uncommon presenting feature of PRES due to hypercalcaemia in Burkitt lymphoma.

Lesion characteristics related to treatment improvement in object and action naming for patients with chronic aphasia

Few studies have examined the relationship between degree of lesion in various locations and improvement during treatment in stroke patients with chronic aphasia. The main purpose of this study was to determine whether the degree of lesion in specific brain regions was related to magnitude of improvement over the course of object and action naming treatments. Participants and methodsFifteen left hemisphere stroke patients with aphasia participated in treatments for object and/or action naming. Two raters assessed extent of lesion in 18 left hemisphere cortical and subcortical regions of interest (ROIs) on CT or MRI scans. Correlations were calculated between composite basal ganglia, anterior cortical, and posterior cortical lesion ratings, on the one hand, and both pretreatment scores and treatment change for both object and action naming, on the other hand. ResultsUnexpectedly, greater anterior cortical lesion extent was highly correlated with better object and action naming scores prior to treatment and with greater improvement during treatment when partial correlations controlled for total basal ganglia lesion extent (r ranging from .730 to .858). Greater total basal ganglia lesion extent was highly correlated with worse object and action naming scores prior to treatment and with less improvement during treatment when partial correlations controlled for total anterior lesion extent (r ranging from −.623 to −.785). Correlations between degree of posterior cortical lesion and naming indices generally were not significant. No consistent differences were found between the correlations of ROI lesion ratings with object naming versus action naming scores. ConclusionLarge anterior cortical lesions and intactness of the basal ganglia may both contribute to more efficient reorganization of language functions.

Memory and psychomotor impairment following high-dose interferon treatment in amyotrophic lateral sclerosis.

Patients with amyotrophic lateral sclerosis were treated with high-dose intravenous infusion of human leukocyte interferon for six days. Neuropsychological examinations were carried out before, during and after the treatment. Marked reversible dysfunction was detected in immediate memory functions, coordination of hand movements, and drawing. Motor perseveration, micrographia, and slowing of behaviour were also observed. Changes appeared four to 12 days after start of treatment, with the peak on days six to eight. Recovery was almost complete by day 15. Intellectual ability, as measured by three WAIS subtests, praxis of hand movements, visuognostic functions, speech, reading, writing, and calculation remained essentially unaffected. The profile of the neuropsychological deficits observed, the absence of defects typical of focal posterior cortical lesions, the simultaneously slowed electroencephalographic activity with frontal accentuation, and the increased central conduction times of brain stem auditory evoked potentials suggest frontobasal involvement.

Functional MRI of the primary somatosensory cortex in extinction to simultaneous bilateral tactile stimuli due to right temporal lobe stroke

Patients with right posterior temporoparietal cortical lesions often exhibit extinction to tactile double simultaneous stimuli (EDSS). It is not known whether sensory unawareness-extinction results from suppression of sensory input into the somatosensory cortex (SI), inhibition of SI, or interference which prevents SI output from activating and being fully processed by association areas. A patient with EDSS due to a right temporal stroke sparing SI and posterior parietal cortex and eight age-matched healthy controls were studied with fMRI during tactile stimulation. The volume of activation of SI during tactile stimulation of the right hand, the left hand and both hands was measured and the patient's volume of activation was compared to that of the control subjects in each of these stimulus conditions. Although the patient demonstrated behavioral EDSS, during fMRI the patient's activation of SI on both sides was within the range of the control participants' volumes of activation. These findings suggest that EDSS in patients with a right temporal lobe stroke results from processing abnormalities that occur after these afferent tactile stimuli are processed by SI.

Impaired orienting of attention in left unilateral neglect: A componential analysis.

Twenty-six patients suffering from damage to the right side of the brain, 19 of whom exhibited signs of left neglect, as well as 32 matched controls, ran 3 spatial cuing tasks. Patients were also tested with 2 cancellation tests, a line-bisection test, the copy of a complex drawing, and a visual extinction procedure. Results first showed correlations between extinction and cancellation tests performance on one hand, and between line bisection and copy on the other hand. Second, results demonstrated that an engagement deficit toward contralesional targets appeared to be the most striking feature of neglect, and the engagement score was correlated with the cancellation score and extinction. Most patients with neglect also presented a deficit in disengagement, a deficit of inhibition of return, and probably a deficit of alertness. Deficits in engagement and in disengagement, as well as poor scores in cancellation tests, seemed to be related with posterior cortical and subcortical lesions. Most important, even if an endogenous deficit (frequently related with a thalamic lesion) could aggravate the neglect behavior, neglect syndrome was mainly explained by a deficit of exogenous attention.

Interaction between Cortical Control of Vestibular Function and Spatial Representation in Man

An asymmetry of the vestibulo-ocular reflex is observed after unilateral posterior cortical lesions in human. The co-occurrence of vestibular deficits and visuo-spatial disorders suggests a functional link between the representation and update of space and the integration of vestibular information in the occipito-parieto-temporal cortex of the right hemisphere.

Unconditioned stimulus pathways to the amygdala: effects of posterior thalamic and cortical lesions on fear conditioning

Plasticity in the lateral nucleus of the amygdala is thought to be critical for the acquisition of Pavlovian fear conditioning. The pathways that transmit auditory conditioned stimulus information originate in auditory processing regions of the thalamus and cortex, but the pathways mediating transmission of unconditioned stimuli to the amygdala are poorly understood. Recent studies suggest that somatosensory (footshock) unconditioned stimulus information is also relayed in parallel to the lateral nucleus of the amygdala from the thalamus (the posterior intralaminar thalamic complex, PIT) and the cortex (parietal insular cortex). In the present study we reexamined this issue. Our results showed that bilateral electrolytic lesions of the PIT alone blocked fear conditioning, whereas bilateral excitotoxic PIT lesions had no effect. These electrolytic PIT lesions did not affect fear conditioning using a loud noise as unconditioned stimulus, defining the effects of PIT lesions as a disruption of somatosensory as opposed to auditory processing. Finally, we performed combined bilateral excitotoxic lesions of the PIT nuclei and electrolytic lesions of the parietal insular cortex. These, like excitotoxic lesions of PIT alone, had no effect on the acquisition of fear conditioning. Thus, somatosensory regions of the thalamus and cortex may well be important routes of unconditioned stimulus transmission to the amygdala in fear conditioning, but information about the unconditioned somatosensory stimulus is also transmitted from other sources that send fibers through, but do not form essential synapses in, the thalamus en route to the amygdala.

Cortical involvement in temporal reproduction: evidence for differential roles of the hemispheres

Only few studies have addressed temporal processing for durations longer than 1 s, and even fewer studies have investigated cortical involvement in time perception, in particular temporal production and reproduction. The present study investigated temporal reproduction in healthy control subjects and patients with anterior or posterior cortical lesions in the left or right hemisphere, or with subcortical left-hemispheric lesions. The paradigm involved presentation of either auditory or visual stimuli of 10 different standard intervals ranging from 1 to 5.5 seconds duration. Participants were required to reproduce the duration of a stimulus. Our results show that: (1) temporal reproduction across this temporal range can be better described with two separate linear regressions (bilinear approach) than with one single linear regression, thus contrasting the scalar timing concept; (2) that patients can, regardless of the hemisphere lesioned, perform reproductions of durations smaller than 2–3 s with reasonable accuracy; and (3) that patients with right-hemispheric lesions appear to be impaired in reproductions of stimuli longer than 2–3 s. Since attention appeared not to be impaired in the patients tested, the findings suggest that the integrity of the right hemisphere seems to be critical for temporal reproduction of intervals longer than 2–3 s.

The automatic updating of egocentric spatial relationships and its impairment due to right posterior cortical lesions

The non-visual updating of body-centred spatial relationships was investigated in an experiment in which blindfolded patients had to point to previously seen targets after a body rotation in the absence of vision. Patients with lesions to the right dorsal (RD) area were impaired at updating their positions relative to non-RD patients and normal subjects: they tended to underestimate systematically the angle through which they had turned. The results are interpreted in terms of impoverished locomotor input and/or systematically biased processing or locomotor proprioception in the RD patients, which prevented accurate tracking of changes in egocentric spatial relationships.

Hippocampal modulation of cingulo-thalamic neuronal activity and discriminative avoidance learning in rabbits.

Two experiments assessed the effects of 1) combined subicular complex and posterior cingulate cortical lesions on training-induced neuronal activity (TIA) in the anterior ventral (AV) and medial dorsal (MD) thalamic nuclei; 2) hippocampal (Ammon's horn and dentate gyrus) lesions on TIA in cingulate cortex and in the AV and MD thalamic nuclei. The rabbits acquired a conditioned avoidance response (CR), stepping in an activity wheel upon hearing a 0.5-s tone (CS+), in order to prevent a foot-shock scheduled 5 s after tone onset. No response was required after a different, safety-predictive tone (CS-). In experiment 1 the combined subicular and cingulate cortical lesions enhanced thalamic TIA during acquisition and increased CR incidence in the first session of acquisition. These results confirmed the hypothesis that subicular and cingulate cortical efferents are not essential for thalamic TIA or for avoidance learning. Hippocampal lesions (experiment 2) also enhanced thalamic TIA. However, unlike subicular lesions, hippocampal lesions enhanced posterior cingulate cortical TIA as well, especially during extinction training. Hippocampal lesions did not affect CR performance. The results suggested that subicular excitatory efferents are responsible for incrementing cingulate cortical TIA, which is viewed as subserving associative attention. Activity from hippocampus downregulates the cue-elicited neuronal activity of the cingulo-thalamic circuits by suppressing the excitatory influence of the subiculum. The hippocampal influence reduces cingulo-thalamic cue-elicited activation in particular circumstances, such as the onset of CR extinction, when an expected reinforcer is omitted.

General discussion

L. Weiskrantz ( Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, U. K.). I have tried to link what we have heard from experimental studies in humans with what we have heard from experimental studies in monkeys concerning functions of the prefrontal cortex. The obvious difference is that in my experience, patients with posterior cortical lesions are often those with shortterm memory deficits (such as patient KF), whereas you have to work very hard with frontal lobe lesioned patients to see profound impairments of that kind. This provides an obvious contrast with experimental studies in monkeys which suggest a role for the prefrontal cortex in just such simple short-term or working memory processes. I was wondering if any of the speakers would care to comment on this rather obvious distinction between human and monkey work that has been presented so far?

Does monocular viewing improve target detection in hemispatial neglect?

Experimental animals with large posterior-cortical lesions develop disturbances of visual perception and visually-guided behavior in the contralateral space, resembling the syndrome of unilateral spatial neglect (USN) in humans. The visuo-motor performance in the ignored space is recovered some time following additional lesion inflicted to the contralesional superior colliculus (SC) or section of the intercollicular pathways. Based on the model that explains this recovery by disinhibition of the ipsilesional SC (the 'Sprague effect') Posner and Rafal [37] proposed that ipsilesional monocular occlusion could possibly reduce the 'tone' of contralesional collicular neurons thereby removing an important contributor of hemineglect. A group of twenty-six right-hemisphere-damaged patients with USN was given a cancellation task under binocular and monocular (left and right) viewing conditions. Thirteen patients showed amelioration of left hemineglect in conditions of left-monocular viewing, as compared to the baseline binocular state. Although this result superficially resembles the Sprague effect, two patients benefited from right-monocular viewing whereas eleven patients showed no significant change in either right or left viewing conditions. The possible role of structures mediating interocular differences in target detection in cases of right hemisphere damage is discussed. It is suggested that even if the Sprague effect contributes to the salubrious influence of monocular viewing it is hardly the single factor involved.

Is there a place for ipsilesional eye patching in neglect rehabilitation?

Neglect behavior of experimental animals with unilateral posterior cortical lesions improves with the placement of a second lesion in the contralesional superior colliculus or in the intercollicular commissure. Given that the retinotectal fibers are mainly crossed, it has been speculated that ipsilesional eye patching, by depriving the contralesional superior colliculus of its main facilitatory visual input, might achieve similar results, and thus be used as a remediation maneuver in patients with neglect. From six patients with severe persistent neglect, only one showed an unequivocal beneficial effect from ipsilesional eye patching. We discuss the factors which possibly underlie success and failure with this procedure, and the place for it in neglect rehabilitation.