Right Hemisphere Strokes Although strokes occur about as often on the right as on the left side of the brain, much more attention is given to left hemisphere (LH) strokes, which results in biases in stroke severity assessments and medical treatment. ... Article
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Article  |   July 12, 2016
Right Hemisphere Strokes
Author Affiliations & Notes
  • Margaret Lehman Blake
    Department of Communication Sciences & Disorders, University of Houston, Houston, TX
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  • Financial: The author has no relevant financial interests to disclose.
    Financial: The author has no relevant financial interests to disclose.×
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    Nonfinancial: The author has no relevant nonfinancial interests to disclose.×
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Special Populations / Part 2
Article   |   July 12, 2016
Right Hemisphere Strokes
Perspectives of the ASHA Special Interest Groups, July 2016, Vol. 1, 63-65. doi:10.1044/persp1.SIG2.63
History: Received February 1, 2016 , Revised May 12, 2016 , Accepted May 12, 2016
Perspectives of the ASHA Special Interest Groups, July 2016, Vol. 1, 63-65. doi:10.1044/persp1.SIG2.63
History: Received February 1, 2016; Revised May 12, 2016; Accepted May 12, 2016

Although strokes occur about as often on the right as on the left side of the brain, much more attention is given to left hemisphere (LH) strokes, which results in biases in stroke severity assessments and medical treatment.

Hemispheric strokes occur only slightly less often on the right (45%) than the left (55%) side of the brain (Foerch et al. 2005; Hedna et al., 2013). The medical community's bias to left hemisphere (LH) strokes increases immediately following the onset of the stroke.
Foerch and colleagues (2005)  reported on over 20,000 patients with stroke admitted to an acute care hospital in Germany. A LH bias was observed for ischemic but not hemorrhagic strokes, which were equally distributed in the right hemisphere (RH) and LH. Overall, the bias was reduced with larger strokes and more severe symptoms, but increased for mild strokes and with increasing age. The imbalance for transient ischemic attacks (TIAs) was the most striking; 63% of patients presenting with TIAs had LH events, while only 37% had RH TIAs.
Together, these results suggest that when there are severe symptoms, or sudden, dramatic changes such as those resulting from a hemorrhagic stroke, RH and LH events are recognized equally as often. However, symptoms of mild RH strokes, particularly TIAs, are not readily recognized. Adults with RH strokes may not present to a hospital until their stroke has extended to the point that the symptoms are severe. Those with RH TIAs rarely go to the hospital at all. The imbalance seen in older adults might indicate that RH symptoms, even though they occur rapidly with the onset of stroke, are misinterpreted as effects of normal aging. The differences have substantial consequences on medical treatment.
Given that the most effective treatment for ischemic stroke, tissue plasminogen activator (tPA), must be administered within a relatively small time window (approximately 4 hours), early identification is critical (American Stroke Association, 2013b). A variety of studies have reported that patients who arrive earlier to emergency departments (EDs) are more likely to have hemorrhagic strokes, severe symptoms, good social networks, and LH strokes (Fink et al., 2002; Foerch et al., 2005; Hedna et al., 2013; Wee & Hopman, 2005). Individuals with RH ischemic strokes are less likely to get to an ED in time to receive the best medical treatment. Perhaps as a result they are more likely to have longer hospital stays (Di Legge, Fang, Saposnik, & Hachinksi, 2005; Wee & Hopman, 2005).
Some have suggested that anosognosia, or reduced awareness of deficits, may reduce the chance that RH stroke patients themselves will recognize that something is wrong (Foerch et al., 2005). Family members or others within a patient's social network must be the ones to identify the changes. It is also likely that anosodiaphoria, or reduced concern about deficits, will decrease the chances that persons will seek help for themselves, and increase the chance that they will try to convince a family member that they are fine. The incidences of acute anosognosia and anosodiaphoria following RH stroke are unknown, as is the influence of these disorders on recognition of and early medical treatment for stroke.
In addition to the disparity in the patients who arrive at a hospital, general stroke scales are biased toward identification of LH strokes. The National Institutes of Health Stroke Scale (NIHSS; Brott et al., 1989) is widely used both in the United States and internationally. It is a 42-point scale used to assess sensory, motor, language, and cognitive function. Seven of the 42 points are specifically for language assessment, while only 2 are for neglect. In a comparison of NIHSS scores for patients with lateralized strokes (Fink et al., 2002), there was a significant, and striking difference for those with mild strokes (scores 0-5). The volume of tissue loss for mild RH strokes was more than double (8.8 cc) that of LH strokes (3.9 cc). While tissue loss was not significantly different for more severe strokes, this finding suggests that the NIHSS is not as sensitive to mild signs/symptoms resulting from RH compared to LH lesions. The Scandinavian Stroke Scale (Scandinavian Stroke Study Group, 1985) is a 58-point scale in which up to 10 points are related to aphasia, and none are related to neglect, aprosodia, or any other deficit specifically related to RH strokes.
Unilateral neglect is arguably the most recognizable disorder associated with RH stroke, and the presence of neglect with a RH stroke doubles a patient's chances of receiving tPA (Di Legge et al., 2005). Additionally, the addition of line cancellation and visuoperceptual tasks to the NIHSS increased the sensitivity to lesion size (Gottesman et al., 2010). However, estimates suggest that only 25% of patients with RH stroke initially present with neglect (Dara, Bang, Gottesman, & Hillis, 2014). Dara and colleagues (2014)  reported that the presence of neglect resulted in identification of only 63% of RH strokes, and that aprosodia was a more sensitive indicator of RH stroke in their sample.
Much work is needed to right this ship that is listing to the left. Most important is education for medical professionals and the public regarding deficits other than neglect that are indicative of RH stroke. The stroke awareness campaign to “Think FAST,” (American Stroke Association, 2013a) educating the public to look for Facial asymmetry, asymmetry in Arm strength or range of motion, Speech production or comprehension, and the idea that Time is critical, should result in identification of the majority of strokes that occur in the middle cerebral artery territory of either hemisphere because of the effects on the motor systems (face/arm asymmetries and motor speech pathways) and LH language areas (speech/language production and comprehension). Symptoms of a RH stroke that did not affect the motor system are unlikely to be detected.
Studies need to be conducted to determine how often anosognosia occurs, and whether it is related to stroke identification and early treatment. Research is also needed to identify how individuals outside the medical profession might be able to recognize signs of neglect. Additionally, the stroke scales need to be revised to include tests of other RH deficits, such as aprosodia, that would increase the chances of identifying strokes on the “nondominant” side of the brain.
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