Left Posterior Cerebral Artery Infarction Research Articles

Neuropathology of a remarkable case of memory impairment informs human memory

Kent Cochrane (K.C.) has been investigated by researchers for nearly three decades after intracranial trauma from a motorcycle accident at age 30 resulted in a striking profile of amnesia. K.C. suffered severe anterograde amnesia in both verbal and non-verbal domains which was accompanied by selective retrograde amnesia for personal events experienced prior to the time of his injury (episodic memory), with relative preservation of memory for personal and world facts (semantic memory), and of implicit memory. This pattern of spared and impaired memory extended to spatial memory for large-scale environments and beyond memory to future imagining and decision-making. Post-mortem brain findings at age 62 included moderate diffuse atrophy, left orbitofrontal contusion, left posterior cerebral artery infarct, and left anterior frontal watershed infarct. Notably, there was severe neuronal loss and gliosis of the hippocampi bilaterally. The left hippocampus was severely affected anteriorly and posteriorly, but CA2, CA4, and the dentate gyrus (DG) were focally spared. There was associated degeneration of the left fornix. The right hippocampus showed near complete destruction anteriorly, with relative preservation posteriorly, mainly of CA4 and DG. Bilateral parahippocampal gyri and left anterior thalamus also showed neuron loss and gliosis. There was no evidence of co-existing neurodegenerative phenomena on beta-amyloid, phosphorylated tau, or TDP-43 immunostaining. The extent of damage to medial temporal lobe structures is in keeping with K.C.'s profound anterograde and retrograde amnesia, with the exception of the unexpected finding of preserved CA2/CA4 and DG. K.C.'s case demonstrates that relatively clean functional dissociations are still possible following widespread brain damage, with structurally compromised brain regions unlikely to be critical to cognitive functions found to be intact. In this way, the findings presented here add to K.C.'s significant contributions to our understanding of clinical-anatomical relationships in memory.

Left atrial myxoma causing posterior cerebral artery infarct-a case report

A 34-year-old female patient presented with a history of sudden loss of vision in right eye. On neurological examination, she was having visual agnosia in right eye. MRI was performed which revealed left posterior cerebral artery infarct. Trans thoracic echocardiography was performed. This showed a large left atrial myxoma. Patient underwent resection and had an uneventful postoperative course. This case report showed the importance of cardiac source of emboli in patients presenting as acute stroke. Performing echocardiography and diagnosing and treating cardiac source of emboli could prevent further complications.

The Medial Temporal Lobe Supports Conceptual Implicit Memory

The medial temporal lobe (MTL) is generally thought to be critical for explicit, but not implicit, memory. Here, we demonstrate that the perirhinal cortex (PRc), within the MTL, plays a role in conceptually-driven implicit memory. Amnesic patients with MTL lesions that converged on the left PRc exhibited deficits on two conceptual implicit tasks (i.e., exemplar generation and semantic decision). A separate functional magnetic resonance imaging (fMRI) study in healthy subjects indicated that PRc activation during encoding of words was predictive of subsequent exemplar generation. Moreover, across subjects, the magnitude of the fMRI and behavioral conceptual priming effects were directly related. Additionally, the PRc region implicated in the fMRI study was the same region of maximal lesion overlap in the patients with impaired conceptual priming. These patient and imaging results converge to suggest that the PRc plays a critical role in conceptual implicit memory, and possibly conceptual processing in general.

Incidental Detection of Previously Undiagnosed Primary Breast Carcinoma With a Gallium-67 Scan Performed for Evaluation of Occult Infection

A 63-year-old female patient with a recent left posterior cerebral artery infarction and pyelonephritis presented with persistent fevers despite adequate intravenous antibiotic therapy. Whole-body gallium-67 scintigraphy was performed to evaluate for occult infection. Tracer accumulated bilaterally in the kidneys consistent with the previously diagnosed pyelonephritis. Relatively intense uptake was also noted in the area of a known occipitoparietal infarct. Incidentally noted was an abnormal focus of increased tracer uptake in the retroareolar region of the right breast. Subsequent guided core biopsy of the right breast mass demonstrated a previously undiagnosed invasive ductal carcinoma.

Deafferentation–disconnection neglect induced by posterior cerebral artery infarction

To investigate patients with posterior cerebral artery (PCA) infarctions to learn whether hemispatial neglect is more frequent and severe after right than left PCA infarction; whether visual field defects (VFDs) influence the presence or severity of hemispatial neglect; and the anatomic loci of lesions that are associated with hemispatial neglect. The authors recruited 45 patients with PCA infarction that involved only the occipital lobe or the occipital lobe plus other areas served by the PCA. All subjects received seven neglect tests within 2 months after onset. Overall, the frequency of hemispatial neglect was 42.2%. The frequency did not significantly differ between the right (48.0%) and left (35.0%) PCA groups, but the severity of hemispatial neglect was significantly greater in the right group. VFD alone did not influence the frequency or severity of neglect after controlling other variables. Isolated occipital lesions were rarely associated with hemispatial neglect, and it was only the occipital plus splenial lesion that significantly influenced the frequency and severity of neglect. This study suggests that after excluding such confounding factors as aphasia or hemiplegia, neglect frequency does not differ between the right and left posterior cerebral artery (PCA) groups, but the severity of neglect is greater after right PCA infarctions; even in the acute stage of PCA infarction; visual field defect from an isolated occipital lesion does not cause hemispatial neglect; and the injury to both the occipital lobe and the splenium of the corpus callosum is important for producing hemispatial neglect with PCA infarction.

左後大脳動脈梗塞例における失読の研究 仮名失読／漢字失読／視覚失語の障害水準について

左後大脳動脈領域の脳梗塞で視覚失語を呈した症例における読みの能力を検討した。漢字，仮名ともに音読はほとんど不能であったが，漢字と絵カードとの matching が比較的良好であった。 (1) 文字の正誤判断， (2) 文字分類テストの成績は良好で，漢字,.仮名ともに文字形態記憶は保たれていた。 (3) 仮名文字列の lexical decision はまったく不能で，仮名文字列を全体として意味的処理を行う経路は障害されていると考えられた。(4) 漢字の odd word out test, (5) 漢字の分類テスト，(6) 漢字の連想テストの結果から，漢字の表す意味のカテゴリーや漢字同士の連合的および統合的関係の把握は良好であると考えられた。(7) 漢字の pointing では，選択枝が同一のカテゴリーに属する場合には成績が不良で，意味的に近縁な漢字の判別には障害があると考えられた。 以上の結果を，純粋失読における音読と読解の解離や視覚失語の視覚性呼称障害の成立機序との関連において考察した。

Loss of visual imagery and loss of visual knowledge—A case study

As a sequel of a left posterior cerebral artery infarction a patient had severely defective mental imagery of shapes and colours of objects. Imagery of faces, letters, and topological relationships was preserved. The impairment of imagery of object colours was associated with colour agnosia and colour anomia. For colours, there was no difference between performance on tasks calling for imagery of object colours and tasks affording a distinction between correctly and incorrectly coloured objects. For shapes of objects, imagery appeared to be below the level of the patient's knowledge about the visual appearance of objects as manifested by the ability to identity objects and to distinguish correctly from incorrectly drawn pictures. The apparently selective image generation deficit for shapes of objects could be a sequel of loss of knowledge about visual attributes of objects, if superior performance on shape recognition tasks was afforded by perceptual entry level representation which enable a rapid identification of objects but are inaccessible to introspective consciousness.

Outcome of neonatal strokes.

We examined the clinical outcome of 17 children, 1 to 11 years of age, who experienced major cerebral artery infarctions (strokes) as neonates. Nine of the 17 children had left middle cerebral artery (MCA) infarctions, five had right MCA infarctions, two had bilateral MCA infarctions, and one had a left posterior cerebral artery infarction. Fourteen of the 17 children developed seizures as neonates. Most of these children who developed seizures were neurologically abnormal as neonates, became seizure free and neurologically normal early in the first year of life, and their anticonvulsant therapies were discontinued. After a seizure-free period of one to eight years, three of the 14 patients again required anticonvulsant therapy for seizure control. Two of the 16 surviving children continue to be severely handicapped while 11 of the 16 are making apparently normal developmental progress. One of the two children presently attending school has cognitive deficits appropriate to the site affected by the original infarction. Most children with neonatally diagnosed strokes appear to have a good short-term outcome, but later onset of seizures and subsequent recognition of cognitive deficits may not be uncommon.

A case study of mental imagery deficit

We describe a patient with a deficit in imagery ability, following a left posterior cerebral artery infarction and possible anoxic episode. This deficit was inferred from the patient's performance on several tasks, including one in which normal adults are known to rely on imagery and two that tested imagery nonverbally, allowing us to examine the possibility of a language-imagery disconnection. In addition, we queried the patient on some cognitive capacities related to visual imagery: dreaming, geographical knowledge, and introspection regarding visual and auditory imagery. Hypotheses concerning the critical lesion site and underlying cognitive mechanism of image generation deficits are discussed in relation to this and other recent cases of impaired imagery ability with intact recognition ability, and the relevance of this deficit to the “imagery debate” is discussed.