Left sided neglect, also known as hemispatial neglect or unilateral neglect, is a neurological condition affecting a person’s attention and awareness of one side of space. Individuals with this condition struggle to notice, process, or respond to stimuli on the affected side, most commonly the left. This is not a problem with vision itself, but rather with the brain’s ability to process and attend to information from that side of space.
Understanding Left Sided Neglect
People with left sided neglect can physically see, hear, and feel on their left side, but their brain “ignores” or fails to attend to stimuli presented there. This differs from blindness (hemianopia), where there is a genuine loss of vision due to damage to visual pathways. Individuals with hemianopia are typically aware of their visual deficit and may compensate, whereas those with neglect often remain unaware of their problem. This condition leads to a range of challenges in daily life, as the individual acts as if the left side of their world simply does not exist.
Neurological Basis
Left sided neglect most commonly results from brain injury, with stroke being a frequent cause. Traumatic brain injury and brain tumors can also lead to this condition. The brain region most often implicated is the right parietal lobe, particularly the posterior parietal cortex and the temporo-parietal junction. This is because the right hemisphere plays a significant role in attending to both the left and right sides of space, while the left hemisphere primarily attends to the right side. Damage to the right parietal lobe can therefore severely impair attention to the left side, as the left hemisphere cannot fully compensate. While right-sided neglect can occur from left hemisphere damage, it is far less common and often less severe due to the redundant processing of right-sided space by both hemispheres.
Recognizing the Manifestations
Left sided neglect can manifest in various ways, impacting a person’s daily life:
Reading: Individuals may ignore the left side of a page, starting to read sentences mid-way.
Eating: They might only eat food on the right side of their plate, missing items on the left.
Dressing and Grooming: Individuals may only dress or shave one side of their body, such as only putting their right arm through a shirt sleeve or combing the right side of their hair.
Navigation: They may frequently bump into objects or door frames on their left side, unaware of obstacles.
Social Interactions: They might ignore people or objects positioned on their left, even when spoken to directly.
Anosognosia: In severe instances, a person may deny their own left arm or leg belongs to them, referring to it as someone else’s limb. This lack of awareness of their deficit is a common aspect of the condition.
Assessment and Therapeutic Approaches
Healthcare professionals diagnose left sided neglect through careful observation of a person’s behavior and specific neuropsychological tests. Common assessment tools include:
Line Bisection Test: Individuals are asked to mark the center of a horizontal line; those with neglect often deviate their mark significantly to the right.
Cancellation Tasks: These involve crossing out specific symbols or letters on a page, revealing neglect as individuals tend to miss items on the left side.
Drawing Tasks: Asking a person to draw a clock often shows all numbers clustered on the right side of the clock face or only one half of the object drawn.
Catherine Bergego Scale (CBS): A functional checklist used to assess how neglect impacts daily activities.
Therapeutic interventions aim to improve awareness and attention to the neglected side. These include:
Visual Scanning Training: Individuals are taught to systematically move their eyes and head towards the left, often using cues like a bright line on the left side of a page.
Limb Activation: Encouraging movement or sensation on the neglected left limb to increase awareness.
Prism Adaptation Therapy: Uses special glasses that shift the visual field, forcing the brain to re-calibrate its spatial awareness.
Constraint-Induced Movement Therapy: Typically used for motor recovery, it can be adapted by restraining the unaffected right arm to encourage use and awareness of the left side.
Environmental Modifications: Placing frequently used objects on the person’s left side to promote engagement with the neglected space.
Occupational therapists, physical therapists, and speech-language pathologists play a significant role in designing and implementing these rehabilitation strategies, providing guidance and support to help individuals adapt and improve.