Bilateral neglect after bihemispheric strokes

Case Report: SMART ANTON: Anton-Babinski Syndrome in Stroke-Like Migraine Attacks (SMART) After Radiation Therapy: Two Rare Syndromes, One Case

Introduction

We describe the case of a 57-years-old patient who presented an Anton-Babinski syndrome in the context of a stroke-like migraine attack after radiation therapy (SMART).

Case Report

The patient was brought to the emergency room following a sudden loss of vision in the context of a pre-existing left-sided hemianopia after excision of a right occipital astrocytoma followed by radio-chemotherapy 35 years prior to his admission in our services. At admittance, he also presented hyperthermia, hypertension, and a GCS of 7. The MRI showed a leptomeningeal enhancement in the left temporal, parietal, and occipital lobes. After exclusion of other differential diagnoses, we diagnosed a cortical blindness in the context of a SMART syndrome affecting the left hemisphere. While the symptoms improved under corticosteroid therapy, the patient successively presented an Anton-Babinski syndrome, a Riddoch syndrome and a visual associative agnosia before finally regaining his usual sight.

Discussion

This is, to our knowledge, the first report of an Anton-Babinski syndrome in the context of a SMART syndrome. A dual etiology is mandatory for cortical blindness in SMART syndrome since the latter affects only one hemisphere. A SMART syndrome affecting the contralateral hemisphere in respect to the radiation site seems to be uncommon, which makes this case even more exceptional.

Development and evaluation of a new instrument to measure visual exploration behavior

Effective visual exploration is required for many activities of daily living and instruments to assess visual exploration are important for the evaluation of the visual and the oculomotor system. In this article, the development of a new instrument to measure central and peripheral target recognition is described. The measurement setup consists of a hemispherical projection which allows presenting images over a large area of ± 90° horizontal and vertical angle. In a feasibility study with 14 younger (21-49 years) and 12 older (50-78 years) test persons, 132 targets and 24 distractors were presented within naturalistic color photographs of everyday scenes at 10°, 30°, and 50° eccentricity. After the experiment, both younger and older participants reported in a questionnaire that the task is easy to understand, fun and that it measures a competence that is relevant for activities of daily living. A main result of the pilot study was that younger participants recognized more targets with smaller reaction times than older participants. The group differences were most pronounced for peripheral target detection. This test is feasible and appropriate to assess the functional field of view in younger and older adults.

Model approach to neurological variants of visuo-spatial neglect

Neglect is a neurological disorder of spatial attention with reduced awareness of visual stimuli in the hemifield contralateral to an acute temporo-parietal lesion mainly of the right hemisphere. There is a close association of multisensory orientation centers (MSO) and vestibular tonus imbalance. A lesion of the dominant right MSO causes a left-sided neglect due to a lack of ipsilateral activation of the visual cortex, which is further enhanced by increasing inhibition from the contralateral visual cortex. The nondominant MSO in the left hemisphere might be involved in the manifestation of the less frequent and more transient right-sided neglect and in the plastic mechanisms of gradual recovery from left-sided neglect or extinction. There is evidence that a vestibular tonus inbalance due to peripheral or central vestibular pathway lesions may also induce a neglect. In a first model approach using an attractor network and assuming that there is only one MSO in the right hemisphere, it is possible to simulate attentional shifts into a visual hemifield and to induce a neglect. The neural network model consists of four layers of neurons: retina, MSO, visual cortex V1, and superior colliculus. The superior colliculus layer is modeled as a recurrent attractor network with one inhibitory interneuron and synaptic weights chosen to implement a winner-take-all network that centers the hill of activity on the strongest input. We are well aware of the simplifications used in the conceptual drawings and the computational model, but nevertheless hope that they will serve as an inspiration for further modeling and clinical studies.