Spatial neglect is a complex neurological condition where an individual loses awareness of one side of their body or the space around them, despite having intact vision and sensation. It is not an issue with the eyes themselves, but rather a disorder of attention, where the brain fails to process information from the affected side. This condition can significantly impact daily life, as individuals may genuinely be unaware of things on the neglected side and often do not recognize their deficit without prompting.
What is Spatial Neglect?
Spatial neglect is a behavioral syndrome that typically arises after a brain injury, characterized by a failure to orient, respond, or report stimuli on the side of space opposite to the brain lesion. This means that if the brain injury is on the right side, the individual will neglect the left side of their space, and vice versa. The “space” that is neglected can include areas within arm’s reach (peripersonal space), beyond arm’s reach (extrapersonal space), or even within the individual’s mental imagery.
The manifestations of spatial neglect can be quite varied and impact many aspects of daily life. For instance, a person with spatial neglect might only eat food from one half of their plate, leaving the other side untouched, or they might only shave or apply makeup to one side of their face. They may bump into objects or overlook people on their neglected side, or forget to put one arm into a shirt sleeve when dressing. Reading can also be affected, with individuals only reading one side of a book or page. These behaviors occur because the brain is simply not registering the presence of stimuli on the affected side.
Why Spatial Neglect Occurs
Spatial neglect commonly results from damage to specific brain regions, most often the right cerebral hemisphere, particularly the right posterior parietal cortex. Damage to other regions such as the frontal lobe or subcortical structures like the basal ganglia, thalamus, and cingulate cortex can also lead to neglect. The right hemisphere plays a dominant role in attentional processes, explaining why right-sided brain damage often leads to more severe and persistent neglect of the left side of space.
The most frequent cause of spatial neglect is a stroke, especially those affecting the right middle cerebral artery territory. Up to 82% of patients in the acute stage following a right hemisphere stroke may experience spatial neglect. Other causes include traumatic brain injury, brain tumors, and neurodegenerative diseases. Damage to these brain areas disrupts the neural networks responsible for spatial attention, leading to an abnormal bias in attention towards the side of the brain injury.
Identifying Spatial Neglect
Healthcare professionals employ various methods to identify spatial neglect, often combining observation of daily behaviors with specific standardized tests. Family members or caregivers often provide the initial observations of behavioral changes, as individuals with spatial neglect are frequently unaware of their deficits. These observations might include difficulties with dressing, grooming, or navigating their environment.
Specific assessment tasks help to confirm and characterize the presence of spatial neglect. The line bisection test involves asking patients to mark the perceived middle of horizontal lines; individuals with left-sided neglect often mark the line shifted towards the right. Cancellation tasks, such as the Bells test or Letter cancellation, require patients to find and cross out specific targets scattered among distractors on a page; patients with neglect tend to miss targets on the affected side. Drawing tasks, where patients are asked to copy a picture or draw an object from memory like a clock or house, can also reveal neglect if they omit details on one side of the drawing. Cancellation tests are considered more effective tools for detecting spatial neglect.
Approaches to Recovery and Adaptation
Rehabilitation for spatial neglect focuses on strategies aimed at improving awareness and function in daily life. Visual scanning training is a common approach, where patients are systematically guided to explore the neglected side of space through tasks like scanning pictures, copying, or reading. Therapists may use cues or provide feedback to help patients actively engage with the neglected side.
Prism adaptation involves wearing special glasses that shift the visual field, forcing the brain to recalibrate its spatial perception. Patients wearing these prisms typically point to targets that are shifted to the right (for left-sided neglect) and, upon removal of the prisms, show a temporary reduction in their neglect symptoms. This approach can lead to improvements in everyday activities.
Limb activation therapy involves engaging the limb on the neglected side, such as moving the affected arm, to draw attention to that side of space. Environmental modifications also play a role, which can involve placing frequently used objects on the non-neglected side initially, then gradually moving them towards the neglected side to encourage engagement.
Occupational therapists and physical therapists are instrumental in implementing these strategies, tailoring interventions to individual needs and focusing on functional tasks. They help individuals with spatial neglect regain independence. While many patients show some spontaneous recovery, a proportion may experience persistent deficits. Compensatory strategies, alongside therapeutic interventions, remain important for long-term adaptation and improving overall quality of life.