Hemispatial neglect is a neurological condition where a person experiences a lack of awareness or attention to one side of their body or the space around them. This condition typically arises after brain damage, most commonly affecting the right side of the brain, which then leads to neglect of the left side of space. Individuals with this condition do not simply ignore one side; rather, they are genuinely unaware of stimuli presented in that neglected field. It is a complex challenge that affects how the brain processes and perceives information from one half of the environment.
What is Hemispatial Neglect
Hemispatial neglect is a neuropsychological condition where individuals are unaware of stimuli on the side of space opposite to brain damage, known as the contralesional side. This is not a visual impairment; rather, it’s a deficit in the brain’s attention and awareness system. The core issue lies in how the brain allocates attention and constructs a complete representation of space.
Unlike visual field cuts, where a person cannot physically see a portion of their visual field, hemispatial neglect involves a failure to pay attention to sensory input, even if the sensory organs are intact. The affected individual often believes their perception of space is complete, distinguishing this condition from simply ignoring one side. It can manifest across visual, auditory, and tactile information.
How It Manifests
Hemispatial neglect presents in various ways that can significantly impact daily activities. Individuals may consistently overlook items placed on their neglected side, such as food on one half of a plate, leading them to eat only from the other side. When reading, they might miss words or letters on the neglected side of a page, or only read half of a sentence. This lack of awareness can extend to personal care, where a person might only shave or apply makeup to one side of their face, or forget to dress one arm or leg.
Navigating through environments also becomes challenging. A person with neglect might frequently bump into objects or door frames on their neglected side because they are unaware of their presence. They may also overlook people or objects positioned on that side, making social interactions or finding things difficult. In some cases, individuals might not spontaneously move or use a limb on their neglected side, even if it is physically capable of movement.
Underlying Causes
Hemispatial neglect most commonly results from brain damage, with stroke being the most frequent cause. Approximately 80% of patients who experience a stroke in the right hemisphere of their brain develop hemispatial neglect, typically affecting awareness of the left side of space. This occurs because the right hemisphere plays a dominant role in processing spatial information and directing attention across both sides of the body and environment. Damage to specific brain regions within the right hemisphere, particularly the temporo-parietal junction and posterior parietal cortex, is strongly associated with the condition.
While stroke is the primary cause, other neurological events can also lead to hemispatial neglect. These include traumatic brain injury, brain tumors or cysts that exert pressure on attention networks, and neurodegenerative diseases like Alzheimer’s or Parkinson’s, though these are less common causes.
Diagnosis and Rehabilitation
Diagnosing hemispatial neglect involves a series of clinical assessments designed to reveal the patient’s inattention to one side of space. Common tests include the line bisection task, where patients are asked to mark the center of a line but consistently deviate towards the non-neglected side. Cancellation tasks require individuals to cross out specific targets scattered on a page, and those with neglect will often miss targets on the affected side. Drawing tests, such as asking a patient to draw a clock or a flower, can also highlight the condition, as they may only draw half of the object or place all numbers on one side of the clock face.
Rehabilitation strategies aim to improve awareness and functional independence in individuals with hemispatial neglect. Visual scanning training encourages patients to consciously turn their head and eyes towards the neglected side, helping them to explore the full visual field. Limb activation therapy involves actively moving the neglected limb to draw attention to that side of space. Prism adaptation therapy uses prism lenses to shift the visual field, encouraging the brain to recalibrate its spatial awareness. Environmental modifications, such as positioning important objects or people on the non-neglected side, can also help manage daily challenges.