Spatial neglect

Abstract

The syndrome of visuospatial neglect is a common consequence of unilateral brain injury. It is most often associated with stroke and is more severe and persistent following right hemisphere damage, with reported frequencies in the acute stage of up to 80%. Neglect is primarily a disorder of attention whereby patients characteristically fail to orientate, to report or to respond to stimuli located on the contralesional side. Neglect is usually caused by large strokes in the middle cerebral artery territory and is heterogeneous, such that most patients do not manifest every feature of the syndrome. A number of treatments may improve neglect, but there is no widely accepted universal approach to therapy. Although most patients recover spontaneously, the evidence suggests that they continue to have significant cognitive impairments, particularly relating to attention.

Keywords: ATTENTION; COGNITION; NEGLECT; STROKE.

Figure 1

Demonstration of visual extinction. The patient can report the left-sided (middle panel) stimulus and the right-sided stimulus (top panel) when they are presented on their own, but reports only the rightward stimulus when both are presented together (bottom panel). Note that in the video examination the patient manifests left-sided extinction as well as a left-sided hemianopia.

Figure 2

Schematic representation of how a visual scene might appear to people with left homonymous hemianopia (middle panel) and left neglect (bottom panel). Whereas hemianopia obeys the midline and affects only the contralesional visual field, neglect affects parts of the ipsilesional field in addition to the contralesional field, such that there is a lateralised bias of attention towards the side of the lesion.

Figure 3

Star cancellation task from the behavioural inattention test. Patients are asked to find and mark all the small stars without marking the large stars or letters. Patients with severe neglect find targets only at the ipsilesional side of the array, even when they have unlimited time to complete the task. Patients with less severe neglect still tend to start on the right side of the array but may miss only a small number of contralesional targets.

Figure 4

Copying task from the behavioural inattention test. The patient tends to omit the left-sided elements of each object.

Figure 5

Disruption of attention networks in patients with spatial neglect. The dorsal attention network (DAN, in pink), critical to deploying spatial attention, includes the frontal eye fields anteriorly and the intraparietal sulcus posteriorly. The ventral attention network (VAN, in yellow), which is right-lateralised, includes the inferior frontal gyrus anteriorly and the temporoparietal junction posteriorly. The VAN is involved in sustained attention and arousal, as well as the reorienting of attention. Current accounts of the pathophysiology of neglect suggest that both these networks are disrupted in neglect, with the ventral network (including white matter connections) frequently being structurally damaged by a middle cerebral artery territory stroke, and the dorsal network often remaining structurally intact but showing disrupted function.