Surgical treatment of internal carotid artery anterior wall aneurysm with extravasation during angiography--case report.
A 54-year-old female presented subarachnoid hemorrhage from an aneurysm arising from the anterior (dorsal) wall of the internal carotid artery (ICA). During four-vessel angiography, an extravasated saccular pooling of contrast medium emerged in the suprasellar area unrelated to any arterial branch. The saccular pooling was visualized in the arterial phase and cleared in the venophase during every contrast medium injection. We suspected that the extravasated pooling was surrounded by hard clot but communicated with the artery. Direct surgery was performed but major premature bleeding occurred during the microsurgical procedure. After temporary clipping, an opening of the anterior (dorsal) wall of the ICA was found without apparent aneurysm wall. The vessel wall was sutured with nylon thread. The total occlusion time of the ICA was about 50 minutes. Follow-up angiography demonstrated good patency of the ICA. About 2 years after the operation, the patient was able to walk with a stick and to communicate freely through speech, although left hemiparesis and left homonymous hemianopsia persisted. The outcome suggests our treatment strategy was not optimal, but suture of the ICA wall is one of the therapeutic choices when premature rupture occurs in the operation. (+info)
Visual perception of motion, luminance and colour in a human hemianope.
Human patients rendered cortically blind by lesions to V1 can nevertheless discriminate between visual stimuli presented to their blind fields. Experimental evidence suggests that two response modes are involved. Patients are either unaware or aware of the visual stimuli, which they are able to discriminate. However, under both conditions patients insist that they do not see. We investigate the fundamental difference between percepts derived for the normal and affected hemifield in a human hemianope with visual stimuli of which he was aware. The psychophysical experiments we employed required the patient, GY, to make comparisons between stimuli presented in his affected and normal hemifields. The subject discriminated between, and was allowed to match, the stimuli. Our study reveals that the stimulus parameters of colour and motion can be discriminated and matched between the normal and blind hemifields, whereas brightness cannot. We provide evidence for associations between the percepts of colour and motion, but a dissociation between the percepts of brightness, derived from the normal and hemianopic fields. Our results are consistent with the proposal that the perception of different stimulus attributes is expressed in activity of functionally segregated visual areas of the brain. We also believe our results explain the patient's insistence that he does not see stimuli, but can discriminate between them with awareness. (+info)
When the left brain is not right the right brain may be left: report of personal experience of occipital hemianopia.
OBJECTIVES: To make a personal report of a hemianopia due to an occipital infarct, sustained by a professor of neurology. METHODS: Verbatim observation of neurological phenomena recorded during the acute illness. RESULTS: Hemianopia, visual hallucinations, and non-occipital deficits without extraoccipital lesions on MRI, are described and discussed. CONCLUSIONS: Hemianopia, due to an occipital infarct, without alexia, is not a disability which precludes a normal professional career. Neurorehabilitation has not been necessary. (+info)
The association of visual field deficits and visuo-spatial neglect in acute right-hemisphere stroke patients.
BACKGROUND: Visuo-spatial neglect (VSN) after stroke is associated with a poor prognosis for rehabilitation. The co-existence of a visual field deficit (VFD) with VSN may be associated with impaired visuo-spatial functioning and thereby poor functional outcome. OBJECTIVE: To determine whether the presence of a VFD (i) exacerbates VSN and (ii) influences recovery of VSN. METHODS: A prospective study of consecutive acute (<7 days), right-hemisphere stroke patients who were able to undergo detailed assessment of visuo-spatial functioning and visual fields. Clinical assessment and a standardized neuropsychological test was administered by one observer, followed by independent assessment of visual fields by a second observer. Patients were followed up for 12 weeks with 4-weekly re-assessments. RESULTS: 44 consecutive patients (23 women) with a first in a lifetime, acute hemisphere stroke were recruited. Twenty had VSN and VFD, seven VSN only, one VFD only and 17 had normal visual fields and no neglect. The finding of a VFD was significantly associated with the presence of VSN (P<0.0001). Patients with both VFD and VSN had a significantly lower score on the behavioural inattention test. One month post-stroke, this difference was no longer significant. Recovery of VSN and VFD was maximal in the first month, however VSN recovery continued for up to 12 weeks. Patients with VSN and a VFD on admission had a greater mortality at 1 and 3 months. CONCLUSION: The presence of a VFD does appear to exacerbate neglect in the acute stroke patient; this effect is no longer seen after 1 month. Recovery of VSN continues independent of a VFD. Patients with neglect and a VFD have an increased mortality, probably because of greater neurological impairment. (+info)
Attention without awareness in blindsight.
The act of attending has frequently been equated with visual awareness. We examined this relationship in 'blindsight'--a condition in which the latter is absent or diminished as a result of damage to the primary visual cortex. Spatially selective visual attention is demonstrated when information that stimuli are likely to appear at a specific location enhances the speed or accuracy of detection of stimuli subsequently presented at that location. In a blindsight subject, we showed that attention can confer an advantage in processing stimuli presented at an attended location, without those stimuli entering consciousness. Attention could be directed both by symbolic cues in the subject's spared field of vision or cues presented in his blind field. Cues in his blind field were even effective in directing his attention to a second location remote from that at which the cue was presented. These indirect cues were effective whether or not they themselves elicited non-visual awareness. We concluded that the spatial selection of information by an attentional mechanism and its entry into conscious experience cannot be one and the same process. (+info)
Parietal and occipital lobe contributions to perception of straight ahead orientation.
OBJECTIVES: Several studies have investigated how peripheral stimulation affects the perception of body orientation in healthy subjects. The studies showed that opposing stimulation of two different input modalities can cancel out, leaving perception of body orientation unchanged. It was ascertained whether a comparable phenomenon could be found in brain damaged patients with two distinct disorders which individually lead to opposing shifts of the perceived midline. METHODS: The visual subjective straight ahead was measured in patients with pure neglect, pure hemianopia, or a combination of neglect and hemianopia. RESULTS: As in previous studies, patients with pure neglect displayed an ipsilesional displacement of the perceived straight ahead. Patients with pure hemianopia showed a contralesional shift. By contrast, no significant midline shift occurred in the patients with both neglect and hemianopia. CONCLUSIONS: Neglect and hemianopia interact so that opposing biases in the perception of body orientation neutralise each other. Both parietal and occipital areas seem to contribute to the perception of straight ahead body orientation and seem to have counteracting effects when lesioned in the same hemisphere. (+info)
Bitemporal pseudohemianopia related to the "tilted disk" syndrome: CT, MR, and fundoscopic findings.
We describe a case of the "tilted-disk" syndrome in a patient with a bitemporal field depression (a pseudohemianopia). CT and MR imaging showed thinning and prolapse of the nasal sectors of the posterior walls of the globes and flattening of the temporal portion of the globes. (+info)
The oculomotor distractor effect in normal and hemianopic vision.
The present study investigated the inhibitory effect of visual distractors on the latency of saccades made by hemianopic and normal human subjects. The latency of saccades made by hemianopic subjects to stimuli in their intact visual field was not affected by visual distractors presented within their hemianopic field. In contrast, the latency of saccades made by normal subjects was increased significantly under distractor conditions. The latency increase was larger for temporal than nasal distractors. The results are inconsistent with previous proposals that the crossed retinotectal pathway from the nasal hemiretina to the superior colliculus may mediate a blindsight inhibitory effect when distractors appear within a hemianopic temporal visual field. Instead, the distractor effect appears to reflect the normal processes involved in saccade target selection which may be mediated by a circuit involving both cortical and subcortical structures. (+info)