Stroke lateralization and symptoms
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Stroke Lateralization: Right vs. Left Hemisphere Stroke Symptoms
Research shows that the side of the brain affected by a stroke—its lateralization—can influence both the symptoms and complications experienced by patients. In large hemisphere infarctions, right-sided strokes are more often associated with atrial fibrillation, cardio-embolism, and a higher risk of malignant brain edema and cardiovascular events during hospitalization, compared to left-sided strokes. However, the overall long-term outcomes, such as mortality and functional recovery, do not significantly differ between right and left hemisphere strokes . Similarly, in insular cortex strokes, lateralization does not appear to impact stroke recurrence, cardiovascular events, or mortality over a five-year period .
Lateral Medullary Syndrome (Wallenberg Syndrome) and Symptom Patterns
Lateral medullary syndrome (LMS), a type of posterior circulation stroke, typically presents with a distinct set of symptoms: pain and temperature loss on the same side of the face and the opposite side of the body, ataxia, vertigo, nystagmus, dysphagia, hoarseness, hiccups, and Horner’s syndrome . However, the onset and progression of these symptoms can vary. Some patients may initially present with only vertigo or dizziness, with classic symptoms developing days later, highlighting the importance of considering stroke evolution in diagnosis . Dysphagia, while common in LMS, can sometimes be the only initial symptom, which may lead to misdiagnosis or delayed care if not carefully evaluated .
Supratentorial Stroke: Vestibular Symptoms and Lateralization
In supratentorial strokes, acute vestibular symptoms such as vertigo are relatively rare (3.7% of cases) and are not strongly linked to the lateralization of the stroke. Both left and right hemisphere strokes can cause these symptoms, and there is no clear pattern of one side being more likely to produce vestibular complaints .
Cardio-Embolic Stroke: Anatomical Predictors of Lateralization
Certain anatomical and hemodynamic factors can influence whether a cardio-embolic stroke affects the left or right hemisphere. For example, a higher left internal carotid artery angle, a specific aortic arch anatomy (bovine type), and slower blood flow in the right middle cerebral artery are associated with a greater likelihood of left-sided strokes .
Visuoattentive Deficits: Lateralized and Non-Lateralized Effects
Patients with unilateral strokes can experience both lateralized (contralesional) and non-lateralized visuoattentive deficits. Right hemisphere strokes may lead to more pronounced neglect of the left visual field, but both right and left hemisphere strokes can cause general visual inattention that is not specific to one side .
Brain Activity and Hemodynamic Changes After Stroke
After a stroke, the affected hemisphere often shows higher motor cortical activity, reduced independence from the other hemisphere, and abnormal timing in blood flow responses. These changes in lateralization of brain function are linked to the severity of motor impairment and may be useful in guiding rehabilitation .
Conclusion
Stroke lateralization influences the type and severity of symptoms, especially in large hemisphere and posterior circulation strokes. While some complications and symptom patterns are more common with right or left hemisphere involvement, many outcomes and deficits can occur regardless of lateralization. Understanding these patterns is crucial for accurate diagnosis, timely treatment, and effective rehabilitation planning.
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Most relevant research papers on this topic
Lateral medullary syndrome: Case report and review of literature
Lateral medullary syndrome (LMS) is an uncommon and often underdiagnosed cause of posterior circulation stroke, resulting in symptoms such as pain, temperature deficits, and Horner's syndrome.
The Trouble with Swallowing: Dysphagia as the Presenting Symptom in Lateral Medullary Syndrome.
Emergency providers should have a high level of suspicion for lateral medullary syndrome, as dysphagia is often the presenting symptom in this rare stroke, to avoid misdiagnosis and delayed care.
Lateralization of Insular Ischemic Stroke is Not Associated With Any Stroke Clinical Outcomes: The Athens Stroke Registry.
Lateralization of insular ischemic stroke involvement is not associated with any stroke clinical outcomes.
DOI
Incidence, characteristics, and neuroanatomical substrates of vestibular symptoms in supratentorial stroke
Acute vestibular symptoms occur in 3.7% of supratentorial stroke patients and involve diffuse multisensory cortical-subcortical networks without clear lateralization.
Factors associated with the laterality of Cardio-Embolic stroke.
Higher left internal carotid angle, presence of bovine type AA, and slow right middle cerebral artery peak systolic velocity predict left stroke lateralization in cardio-embolic stroke patients.
DOI