A stroke occurs when the brain’s blood supply is interrupted, causing a lack of oxygen and nutrients that leads to rapid cell death. The Middle Cerebral Artery (MCA) is the largest cerebral artery, supplying blood to the vast lateral surface of the cerebrum, including the frontal, parietal, and temporal lobes. A stroke in the right MCA territory is one of the most common types of ischemic stroke, resulting in a distinct collection of cognitive and behavioral changes related to the functions governed by the right hemisphere.
Functions Controlled by the Right Hemisphere
The right hemisphere is often considered the non-dominant hemisphere for language, but it is highly specialized for complex functions. This side of the brain excels at holistic perception, processing information simultaneously to grasp the “big picture.” It is largely responsible for visual-spatial processing, including the ability to judge distances, perceive depth, and understand the relationship between objects in space.
The right hemisphere maintains a broad, sustained attention network that monitors both the left and right sides of the environment. It is specialized for directing attention, particularly toward the left side of the body and surrounding space. The comprehension of non-verbal communication, such as interpreting a speaker’s tone of voice (prosody), is also a function of the right hemisphere. Damage to this area impairs these specialized non-linguistic skills.
Primary Deficits in Attention and Spatial Awareness
The most prominent cognitive consequence of a right MCA stroke is Hemispatial Neglect, also called Unilateral Neglect. This is a profound failure to report, respond, or orient to any stimuli presented on the left side of the body or surrounding space. This deficit is an attentional problem, not a primary visual or sensory loss, meaning the eyes and sensory organs remain functional.
Patients might only draw the right half of a clock face, apply makeup only to the right side of their face, or fail to eat food on the left side of a plate. Neglect affects up to 80% of patients in the acute phase, creating safety and mobility risks. This condition reflects a disruption in the right hemisphere’s ability to attend to the entire environment, causing the patient to behave as if the left side of the world does not exist.
Another associated deficit is Anosognosia, which is an unawareness or denial of one’s neurological deficits, often a left-sided physical weakness or paralysis. The patient may genuinely believe they can move their affected limb, despite evidence to the contrary. Anosognosia results from damage to the right parietal and frontal regions involved in monitoring self-image and motor control. This lack of insight presents a major obstacle to rehabilitation and prioritizing personal safety.
Impairments in Emotion and Executive Function
A right MCA stroke frequently impairs higher-level cognitive and social processing skills that fall under executive function. Patients may exhibit poor judgment, difficulty with impulse control, and a lack of awareness of the social consequences of their actions. This can manifest as inappropriate behavior in public or a reduced ability to plan and organize multi-step tasks.
Emotional processing is also affected, leading to receptive aprosodia, which is a challenge in understanding the emotional tone of speech. The patient can comprehend the words, but they cannot interpret the underlying emotion, such as distinguishing a joke from a serious warning. This difficulty with interpreting vocal emotion can disrupt social interaction and communication.
Apathy and emotional blunting, or a flat affect, are common, where the patient shows reduced emotional expression and a reduced intensity of pleasant emotions. This emotional change, sometimes described as alexithymia, can lead to difficulty in describing personal feelings, which may be misinterpreted as depression. These deficits are linked to damage in structures like the insula, basal ganglia, and the anterior cingulate cortex.
Therapy and Management of Cognitive Changes
Rehabilitation for right MCA stroke deficits involves a specialized, interdisciplinary approach led by occupational therapists, speech-language pathologists, and neuropsychologists. For Hemispatial Neglect, the goal is to teach the patient consistent scanning strategies to compensate for the inattention. A popular technique is the “Lighthouse Strategy,” where the patient is instructed to imagine their eyes as a lighthouse beam, sweeping from the far left to the far right of their environment.
Visual scanning training is combined with physical anchors, such as a bright line or object placed on the left side of a workspace, to cue the patient to initiate their scan. Prism adaptation therapy is another technique, where specialized glasses temporarily shift the visual field to the right, forcing the brain to recalibrate and shift attention back toward the neglected left side.
Managing Anosognosia requires improving self-awareness through direct, compassionate feedback and error-awareness training. Therapists use video recordings or structured activities that demonstrate the patient’s impairment to help bridge the gap between their belief and actual function. For deficits in judgment and impulsivity, management emphasizes establishing safety routines and providing external structure, ensuring the patient practices controlled decision-making in a supervised environment.