Unilateral neglect, also known as hemispatial neglect, is a complex neurological condition that profoundly affects an individual’s awareness of one side of their surrounding space. Imagine if, for some unknown reason, half of your world simply ceased to exist, not visually, but in your mind’s perception. This condition is not a problem with the eyes themselves; vision remains intact. Instead, it is a disruption in how the brain processes and attends to information from that particular side of space. It is fundamentally a disorder of attention and awareness, where the brain fails to acknowledge stimuli on the affected side.
Defining Unilateral Neglect and Its Manifestations
Unilateral neglect most frequently involves a failure to respond to stimuli on the left side of space, typically following damage to the right side of the brain. Individuals with this condition behave as though the space opposite the brain lesion no longer exists, despite having no primary sensory or motor deficits. This lack of awareness can manifest in various ways, affecting different aspects of daily life.
Personal Neglect
One common manifestation is personal neglect, where individuals ignore one side of their own body. For instance, a person might only shave or apply makeup to the right side of their face. They might also not use their left arm or leg, even if those limbs are physically capable of movement, or only put clothes on one side of their body.
Peripersonal Neglect
Another form is peripersonal neglect, which involves ignoring the area within arm’s reach. An individual might only eat food from the right side of a plate, leaving the left side untouched, or consistently read only the right half of a page. This can lead to significant challenges with self-care activities and interacting with nearby objects.
Extrapersonal Neglect
Extrapersonal neglect affects the space beyond arm’s reach. Individuals might frequently bump into furniture or doorframes on their left side because they are unaware of these obstacles. They may also fail to notice people approaching them from the left, highlighting a profound lack of attention to that side of their environment.
Neurological Causes
Unilateral neglect is not a psychological issue but stems from physical damage to specific areas of the brain. The most frequent cause is a stroke, particularly one affecting the right cerebral hemisphere. Approximately 80% of patients with right hemisphere injury from an acute stroke may exhibit unilateral spatial neglect.
The brain region most commonly associated with this condition is the right parietal lobe, especially the inferior parietal cortex. This area plays a significant role in integrating sensory information and directing attention to spatial surroundings. When the right parietal lobe is damaged, the brain’s ability to process information from the left side of space is impaired, leading to the characteristic symptoms of neglect.
While stroke is the primary cause, other types of brain injury can also lead to unilateral neglect. These include traumatic brain injury (TBI), which results from external force to the head, and brain tumors that exert pressure or cause damage to the relevant neural networks. Lesions in other cortical and subcortical areas, such as the frontal lobe or basal ganglia, can also contribute by disrupting the broader brain networks involved in spatial attention.
The Diagnostic Process
Clinicians identify unilateral neglect through a combination of clinical observation and specific assessment tasks. While the behavioral manifestations of neglect can be apparent in daily activities, formal tests are used to confirm the diagnosis and assess its severity. These assessments do not merely repeat observations of symptoms but rather provide structured ways to detect the underlying attentional deficit.
Cancellation Task
One common diagnostic tool is the cancellation task, where a patient is presented with a page containing various symbols or letters and asked to cross out all instances of a specific target. Patients with unilateral neglect consistently miss targets located on the left side of the page, demonstrating their inability to attend to that space.
Line Bisection Task
Similarly, in a line bisection task, the patient is asked to mark the midpoint of horizontal lines. Those with neglect often mark the midpoint significantly to the right of the true center.
Drawing Tasks
Drawing tasks also provide clear evidence of neglect. When asked to copy a drawing, such as a flower or a clock, patients may omit or distort the left side of the image. For example, they might draw a clock with all numbers crammed onto the right side. Even when drawing from memory, the omission of the left side persists.
Therapeutic Interventions and Management Strategies
Managing unilateral neglect involves therapeutic interventions aimed at improving spatial awareness and functional independence. Rehabilitative therapies are designed to retrain the brain’s attentional systems.
Visual Scanning Training
Visual scanning training involves actively encouraging the patient to turn their head and eyes towards the neglected side, often using cues like colored lines or auditory signals to prompt attention.
Prism Adaptation Therapy
Prism adaptation therapy utilizes special glasses that shift the visual field, forcing the brain to recalibrate its spatial mapping. This can temporarily reduce the severity of neglect symptoms by encouraging the patient to attend to the neglected side.
Other Techniques
Other techniques include limb activation, where patients are encouraged to move the affected limb into the neglected space, and trunk rotation, which involves turning the body towards the neglected side to stimulate awareness.
Environmental Modifications
Beyond direct therapies, environmental modifications are practical strategies that caregivers and patients can use to manage the condition in daily life. Approaching the person from their non-neglected side can help establish communication, followed by encouragement to turn and engage with the neglected side. Placing important items, such as a remote control or a drink, within the neglected visual field can compel the patient to scan that area to retrieve them. Using bright tape or markers to highlight the left side of doorways, furniture, or eating utensils can draw attention and reduce accidents. Recovery from unilateral neglect varies among individuals and necessitates a collaborative approach involving a multidisciplinary team, including occupational therapists, physical therapists, and neuropsychologists.