Homonymous defect of macular vision in ischemic stroke

Visual fields and optical coherence tomography (OCT) in neuro-ophthalmology: Structure-function correlation

Visual field (VF) testing is an essential component of the neurological examination. The differential diagnosis of VF defects depends on relating this measure of afferent visual function to the structure of the visual pathway and optical coherence tomography (OCT) is an invaluable tool for detailed structural evaluation of the optic nerve and retina. This review describes the ways in which interpretation of VF and OCT can be used together to increase the accuracy of the localization of lesions along the visual pathway. Lesions of the anterior visual pathway (originating in ganglion cells or nerve fibre layer of the retina or optic nerve) will typically produce defects that respect the horizontal midline, reflecting the arcuate path of the ganglion cell axons as they travel to the optic nerve. OCT of peripapillary retinal nerve fibre layer and ganglion cell complex (GCC) will typically demonstrate irreversible thinning in compressive and demyelinating lesions affecting anterior visual pathway. Chiasmal lesions produce highly localizable VF defects (junctional scotoma and bitemporal hemianopia) which correspond to the thinning of nasal portion of GCC. Lesions of the optic tract result in incongruous homonymous hemianopia on VF with corresponding hemianopic thinning on GCC developing within months. Lesions affecting optic radiations usually produce more congruous homonymous VF defects and can also produce homonymous thinning on GCC, however, this takes much longer to develop as trans-synaptic degeneration at the lateral geniculate body must occur.

Stable habituation deficits in the early stage of psychosis: a 2-year follow-up study

Neural habituation, the decrease in brain response to repeated stimuli, is a fundamental, highly conserved mechanism that acts as an essential filter for our complex sensory environment. Convergent evidence indicates neural habituation is disrupted in both early and chronic stages of schizophrenia, with deficits co-occurring in brain regions that show inhibitory dysfunction. As inhibitory deficits have been proposed to contribute to the onset and progression of illness, habituation may be an important treatment target. However, a crucial first step is clarifying whether habituation deficits progress with illness. In the present study, we measured neural habituation in 138 participants (70 early psychosis patients (<2 years of illness), 68 healthy controls), with 108 participants assessed longitudinally at both baseline and 2-year follow-up. At follow-up, all early psychosis patients met criteria for a schizophrenia spectrum disorder (i.e., schizophreniform disorder, schizophrenia, schizoaffective disorder). Habituation slopes (i.e., rate of fMRI signal change) to repeated images were computed for the anterior hippocampus, occipital cortex, and the fusiform face area. Habituation slopes were entered into a linear mixed model to test for effects of group and time by region. We found that early psychosis patients showed habituation deficits relative to healthy control participants across brain regions, and that these deficits were maintained, but did not worsen, over two years. These results suggest a stable period of habituation deficits in the early stage of schizophrenia.

Patterns of Cortical Visual Field Defects From Embolic Stroke Explained by the Anastomotic Organization of Vascular Microlobules

The cerebral cortex is supplied by vascular microlobules, each comprised of a half dozen penetrating arterioles that surround a central draining venule. The surface arterioles that feed the penetrating arterioles are interconnected via an extensively anastomotic plexus. Embolic occlusion of a small surface arteriole rarely produces a local infarct, because collateral blood flow is available through the vascular reticulum. Collateral flow also protects against infarct after occlusion of a single penetrating arteriole. Cortical infarction requires blockage of a major arterial trunk, with arrest of blood flow to a relatively large vascular territory. For striate cortex, the major vessels compromised by emboli are the inferior calcarine and superior calcarine arteries, as well as the distal branches of the middle cerebral artery. Their vascular territories have a fairly consistent relationship with the retinotopic map. Consequently, occlusion by emboli results in stereotypical visual field defects. The organization of the arterial supply to the occipital lobe provides an anatomical explanation for a phenomenon that has long puzzled neuro-ophthalmologists, namely, that of the myriad potential patterns of cortical visual field loss, only a few are encountered commonly from embolic cortical stroke.

BILATERAL OCCIPITAL POLE HYPERTENSIVE STROKE DIAGNOSED WITH MACULAR INTEGRITY ASSESSMENT (MAIA) MICROPERIMETRY

PURPOSE

To describe the utility of microperimetry testing in the diagnosis of a bilateral occipital stroke.

METHODS

Retrospective case report.

RESULTS

A 57-year-old male with hypertension presented with complaints of bilateral blurred central vision and bilateral hypertensive retinopathy with cotton-wool spots. Automated perimetry demonstrated a central scotoma in both eyes that did not respect the vertical midline; however, microperimetry testing revealed a bilateral homonymous hemianopia that suggested cerebrovascular disease which was subsequently confirmed with magnetic resonance imaging.

DISCUSSION

In cases of unexplained central visual loss, microperimetry testing may be a useful ancillary test for the diagnosis of cerebrovascular disease.

Spontaneous recovery and treatment effects in patients with homonymous visual field defects: a meta-analysis of existing literature in terms of the ICF framework

Homonymous visual field defects (HVFDs) are a common consequence of posterior brain injury. Most patients do not recover spontaneously and require rehabiliation. To determine whether a certain intervention may help an individual patient, it is necessary to predict the patient's level of functioning and the effect of specific training. We provide an overview of both the existing literature on HVFDs in terms of the International Classification of Functioning, Disability, and Health (ICF) components and the variables predicting the functioning of HVFD patients or the effect of treatment. We systematically analyzed 221 publications on HVFD. All variables included in these articles were classified according to the ICF, as developed by the World Health Organization, and checked for their predictive value. We found that ICF helps to clarify the scope of the existing literature and provides a framework for designing future studies, which should consider including more outcome measures related to Activities and Participation. Although several factors have been described that predict HVFD patients' level of functioning or the effects of training, additional research is necessary to identify more.

A prospective profile of visual field loss following stroke: prevalence, type, rehabilitation, and outcome

AIMS

To profile site of stroke/cerebrovascular accident, type and extent of field loss, treatment options, and outcome.

METHODS

Prospective multicentre cohort trial. Standardised referral and investigation protocol of visual parameters.

RESULTS

915 patients were recruited with a mean age of 69 years (SD 14). 479 patients (52%) had visual field loss. 51 patients (10%) had no visual symptoms. Almost half of symptomatic patients (n = 226) complained only of visual field loss: almost half (n = 226) also had reading difficulty, blurred vision, diplopia, and perceptual difficulties. 31% (n = 151) had visual field loss as their only visual impairment: 69% (n = 328) had low vision, eye movement deficits, or visual perceptual difficulties. Occipital and parietal lobe strokes most commonly caused visual field loss. Treatment options included visual search training, visual awareness, typoscopes, substitutive prisms, low vision aids, refraction, and occlusive patches. At followup 15 patients (7.5%) had full recovery, 78 (39%) had improvement, and 104 (52%) had no recovery. Two patients (1%) had further decline of visual field. Patients with visual field loss had lower quality of life scores than stroke patients without visual impairment.

CONCLUSIONS

Stroke survivors with visual field loss require assessment to accurately define type and extent of loss, diagnose coexistent visual impairments, and offer targeted treatment.

Central and Paracentral Visual Field Defects and Driving Abilities

The effect of central and paracentral visual field defects on driving abilities has until now received little attention. To date studies and surveys have concentrated on visual acuity and peripheral field loss. Here we summarise for the first time those diseases causing central visual field defects likely to be associated with binocular visual acuity adequate for driving.

Homonymous Hemianopia in Stroke

BACKGROUND

Previous reports have suggested that most cases of homonymous hemianopia (HH) are caused by occipital stroke. However, these reports have not always been supported by brain imaging.

METHODS

We reviewed the medical records of all patients seen in our unit between 1989 and 2004 who had HH documented by formal perimetry or confrontation visual fields and had undergone brain imaging. HHs were divided into those caused by stroke and by non-stroke conditions. The clinical and visual field characteristics were compared in the two groups.

RESULTS

Among 850 patients with 902 HHs, 629 (69.7%) resulted from stroke, of which 531 (84.4%) were from infarction and 98 (15.6%) from primary intraparenchymal hemorrhage. Non-stroke causes included head trauma (123), brain tumor (102), neurosurgical procedures (22), multiple sclerosis (13), and miscellaneous conditions (13). Occipital lesions most commonly resulted from stroke. The configuration of the HH did not predict where in the retrochiasmal visual pathway the responsible lesion lay.

CONCLUSIONS

Ischemic stroke causes most HHs from lesions in the occipital lobe that generally do not produce other neurologic manifestations. The configuration of the HH does not predict the location of the lesion within the retrochiasmal visual pathway.

Pediatric homonymous hemianopia

INTRODUCTION

Homonymous hemianopia is a disabling condition caused by numerous lesions affecting the retrochiasmal visual pathways. Little is known about homonymous hemianopia in childhood.

METHODS

All patients seen in the Neuro-Ophthalmology Unit at Emory University with homonymous hemianopia (confirmed by Goldmann, Humphrey, or confrontation visual fields) between 1989 and 2004 were included. Demographic characteristics, clinical features, and evolution of the visual field defects were compared between the pediatric group (18 years of age or younger) and the adult group (older than 18 years).

RESULTS

Among 852 patients with homonymous hemianopia, there were 81 children (86 homonymous hemianopias) and 771 adults (818 homonymous hemianopias). Formal visual field testing was obtained in 93% of pediatric cases and 96% of adults; a majority of patients in both groups were evaluated with Goldmann visual field testing. Demographic and visual field characteristics were similar in both groups. Significant differences were noted for the causative lesions and their location. Traumatic brain injury (34%) and tumor (27%) were the most common causes of homonymous hemianopia in the pediatric group, whereas infarction (63%), traumatic brain injury (12%), and hemorrhage (11%) were the most common causes in the adult group. Most lesions involved the optic radiations (37%), followed by the occipital lobes (26%), in the pediatric group, whereas occipital lobes (47%), followed by optic radiations (32%), were most commonly involved in adults. Approximately one third of the pediatric patients were seen in follow-up, and one third of these homonymous hemianopias spontaneously improved over the course of time. Of the 16 pediatric homonymous hemianopias evaluated within 1 month of onset of the cerebral disorder, 8 (50%) improved.

CONCLUSION

Trauma and tumors are the most common cause of homonymous hemianopia in childhood. Although spontaneous improvement can be expected in approximately one third to one half of patients within the first few months, the recognition of homonymous hemianopia frequently is delayed in this population.