|Year : 2022 | Volume
| Issue : 1 | Page : 55-60
A study of type of aphasia in cortical and subcortical strokes
Zulkifli Misri1, Amruta A Jhawar2, Jayashree Bhat3, Berton Craig Monteiro4, Safwan Ahmed5
1 Department of Neurology, Kasturba Medical College, MAHE, Mangalore, Karnataka, India
2 Department of Neurology, Prime Hospital, Jalgaon, Maharashtra, India
3 Department of Speech and Language Therapy, Kasturba Medical College, MAHE, Mangalore, India
4 Department of Radiodiagnosis, Father Muller Medical College, Mangalore, Karnataka, India
5 Department of Neurology, Father Muller Medical College, Mangalore, Karnataka, India
|Date of Submission||30-Jun-2021|
|Date of Acceptance||28-Sep-2021|
|Date of Web Publication||22-Apr-2022|
Department of Neurology, Father Muller Medical College, Mangalore, Karnataka
Source of Support: None, Conflict of Interest: None
Context: In the elderly stroke or stroke-related injury often results in cortical dysfunction termed as aphasia. This affects language usage and multiple aspects of communication. Comparative studies between cortical and subcortical lesions in aphasia are lacking. Aim: To study the type of aphasia in cortical and subcortical strokes. Settings and Design: Prospective observational. Subjects and Methods: Subjects with cortical and subcortical strokes of the dominant cerebral hemisphere were included in the study and divided into various aphasia types. Bedside language tests and distribution according to educational qualifications were performed. The subjects were assessed for aphasia scores and its association was performed with other baseline characteristics. Statistical Analysis Used: Data was expressed as a percentage and mean ± standard deviation. Kolmogorov-Smirnov analysis and Fischer's exact test or Chi-square test were used. Results: Significant difference was noted between the type of aphasia and age group in study subjects (P < 0.001). A severe form of language dysfunction like global aphasia was noted in subjects with a comparatively low level of education, with subcortical bleed, or those with left perisylvian infarcts. Subjects with diabetes and dyslipidemia had a higher risk of developing anomic aphasia (P = 0.02). Conclusions: This study showed the type of aphasia in subjects with cortical and subcortical strokes and it revealed that age at onset, level of education, and site of the lesion were associated with the outcome of patients of aphasia.
Keywords: Aphasia, cortical stroke, language test, stroke lesions, stroke, subcortical stroke
|How to cite this article:|
Misri Z, Jhawar AA, Bhat J, Monteiro BC, Ahmed S. A study of type of aphasia in cortical and subcortical strokes. J Sci Soc 2022;49:55-60
| Introduction|| |
Aphasia mostly seen in the elderly affects the production or comprehension of speech and thus the ability to read and write; is mostly due to injury resulting from stroke. The severity can be from mild to severe and affect a single aspect of communication or multiple. As on date the worldwide prevalence of stroke ranges from 46 to 73 per 1000 persons for persons aged 65 years or more. This number is likely to increase in the coming years due to the aging of the population. Approximately 30% of stroke survivors are observed to have aphasia in the acute phase of stroke, affecting their daily communication and quality of life.
Traditionally aphasia is defined as cortical dysfunction. However, previous studies have reported the occurrence of aphasia in isolated subcortical brain lesions.,, Overall severity is found to be associated with extensive cortical network damage involving the dorsal and ventral stream. Since aphasia involves varying degrees of impairment in communication functioning, even relatively smaller strokes affecting the cortical language network are likely to cause aphasia persisting beyond the subacute stage. Subcortical aphasia on the other hand can be a result of lesions in basal ganglia, white matter, or thalamus. It is characterized by partial or total loss of the ability to verbally communicate.
A difference between cortical and subcortical aphasia and its underlying pathophysiological mechanisms has been controversial. Though ther are studies on subcortical aphasias, comparisons between clinical characteristics of patients with the two lesion types are lacking. Thence we designed this study to characterize aphasia in cortical and subcortical stroke and associate them with lesions as seen on computed tomography/magnetic resonance imaging scan findings.
| Subjects and Methods|| |
This prospective observational study was conducted in Kasturba Medical College Hospital, Dr. B. R. Ambedkar Circle, Mangalore between May 2017 and May 2020 after obtaining ethical clearance. Data was collected from all subjects presented with acute stroke with aphasia. Subjects having cortical and subcortical strokes of the dominant cerebral hemisphere including subcortical bleeds with no prestroke dementia were included. Patients with Glasgow coma scale of <10, or with any lesion present in the right hemisphere, tumors, head injuries or any developmental dyslexia or preexisting psychiatric disorders or metabolic encephalopathies were excluded from the study.
All the subjects involved in the study were literate and could read at least one language. The subjects were divided into various types of aphasias as described in Bradley's Neurology in clinical practice by Adden Brooke's cognitive examination and simple bedside language assessment test. They were divided into age groups according to Erik Erikson's 8 stages of Psychosocial Development. Distribution into various education group levels was performed as defined by the International Standard Classification of education. The risk factors were chosen as per the suggestions given in Bradley's Neurology in Clinical Practice and associated with different types of aphasia. The subjects underwent adequate, structured linguistic rehabilitation. The subjects were assessed for aphasia scores within 24 h of reporting to the hospital and at discharge by Adden Brooke's cognitive examination and bedside language assessment test. The types of aphasia wer correlated with the age of onset, education levels, and site of the lesion. Aphasia scores on admission and at discharge were compared with the age at onset, education level, and site of the lesion.
Data were expressed as a percentage and mean ± standard deviation. Kolmogorov-Smirnov analysis was performed for checking the linearity of the data. Fischer's exact test or Chi-square test was used to analyze the significance of the difference between frequency distribution of the data. P < 0.05 was considered statistically significant. SPSS© for windows™ versus 17, IBM™ Corp NY and Microsoft excel™ 2007, Microsoft® Inc USA was used to perform the statistical analysis.
| Results|| |
[Table 1] shows general characteristics of study subjects presenting with different type of aphasia. Anomic aphasia, Broca's aphasia, and Global aphasia were observed more in patients of 41–65 years age group. Wernicke's aphasia was higher in age group of 66–80 years. Type of aphasia correlation with age group was found to be statistically significant (P < 0.001). No observable trend was associated with the gender of patients regarding different types of aphasia. Superior middle cerebral artery (MCA) territory infarcts were commonly associated with Broca's aphasia and this association was statistically significant (P < 0.01). Inferior division of MCA territory was commonly associated with anomic aphasia (P < 0.001). Left Perisylvian infarcts were found to be significantly associated with global aphasia (P < 0.001). Sub cortical infarcts were found to be associated with Broca's aphasia in anterior lesions while Global and Wernicke's aphasia in the posterior lesion (P < 0.001). Subcortical bleeds on the other hand were found to be associated\ with Broca's and Global aphasia (P < 0.04). Patients with diabetes mellitus in this study mainly had anomic aphasia (P = 0.02). Out of 11 patients with Global aphasia 10 had hypertension. However, this association was not statistically significant (P 0.17).Patients who had prior cerebrovascular accidents mainly had Global aphasia (P < 0.001). Anomic aphasia mainly occurred in patients who had dyslipidemia as a concomitant risk factor. However this association was statistically not significant (P = 0.11).
|Table 1: General characteristics of study subjects presenting with different type of aphasia|
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[Table 2] shows association of education level with improvement in different language assessment scores. For all the types of aphasia, it was observed that subjects with higher education levels showed better language assessment score (P < 0.01) when at discharge scores were compared to their respective admission scores.
|Table 2: Association of education level with improvement in different language assessment scores|
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[Table 3] shows that language assessment scores improved irrespective of the age or type of aphasia.
|Table 3: Association of age group with improvement in different language assessment scores|
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[Table 4] depicts association of site of lesion with improvement in different language assessment scores. It was observed that subjects improved irrespective of the site of the lesion.
|Table 4: Association of site of lesion with improvement in different language assessment scores|
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| Discussion|| |
In the present study, Broca's aphasia was the commonest (42%) form of aphasia. In contrast, Eslinger et al. observed global aphasia to be the commonest (32%) form of aphasia in the Copenhagen aphasia study. Type of aphasia was compared with the age of the patients and observations were compared with other studies. The observations in the study of Eslinger and Damasio indicated that Broca's and conduction aphasia occurred more frequently at younger ages than Wernicke's and global aphasia. Although Wernicke's aphasia composed the oldest group, they were not different from global aphasia. These results are largely in agreement with those of Obler et al., who suggested that although any type of aphasia may be found at virtually any age, a young stroke patient has a higher chance of developing Broca's or conduction aphasia than Wernicke's, global or transcortical sensory aphasia. Our observations were similar to the observations of the above studies.
Several hypotheses have been formulated for the association of age with type of aphasia. There might be some neuropathological variation associated with increasing age, such that the preferred locus of infarction would shift to posterior brain sites. Consequently, younger patients would demonstrate a higher incidence of relatively anterior strokes and older patients would exhibit predominantly posterior strokes. There might be changes in cerebral blood flow associated with aging, predisposing different brain areas to stroke. The higher incidence of Wernicke's aphasia in older patients might be related to the cumulative effects of mental decline associated with aging and insult to language areas of the brain, regardless of its anatomical locus. There might be continuous, age-related changes in the neurophysiological mechanisms sub-serving language functions, such that regardless of lesion location certain aphasia types might become more prevalent with age. Older patients might not recover from comprehension defects as readily as younger patients, thereby leading to a prevalence of Wernicke's aphasia. Hence, our findings could be explained based on this hypothesis inspiring the clinicians to initiate the linguistic rehabilitation at the earliest.
Anomic aphasia was mainly found in patients with the inferior division of MCA territory infarct and this association was statistically highly significant (P < 0.001). In a study, Kertesz et al. reported that poor recovery in comprehension abilities was associated with larger lesions involving the supramarginal gyrus, angular gyri and superior temporal area, while sparing of the superior temporal and middle temporal gyri was associated with good recovery of auditory comprehension in 22 individuals studied with Wernicke's aphasia. These observations were similar to our findings. Global aphasia was mainly found in patients with left perisylvian infarct and this association was statistically highly significant (P < 0.001). Pai et al. reported that Global aphasia usually occurs after large perisylvian lesions in the left MCA territory. The finding supports the observations of our study.
Subcortical infarcts were further classified into anterior i.e., caudate/striatocapsular infarct and posterior i.e., thalamic infarct. Sub cortical infarcts were mainly associated with Broca's aphasia in anterior lesions while Global and Wernicke's aphasia in the posterior lesion, and this association was statistically highly significant (P < 0.001). Alexander, et al., suggested that the basal ganglia are not involved in language, but that certain deep white matter pathways may be important. Crosson suggested that the thalamus, in addition to being involved in basal ganglia regulatory activity, was involved in semantic feedback between language formulation and language decoding centers., Both the studies endorse the association of basal ganglia and thalamus with aphasia as reported in our study.
Out of 126 patients studied, 45 had diabetes mellitus as a concomitant risk factor with stroke. If a causative association exists, its mechanisms are probably to involve cerebral microvascular complications of diabetes in conjunction with the complex neurophysiology of language function. Occlusion of small paramedian penetrating arteries causes small infarcts in the cerebral white matter which is often not overtly symptomatic but may nevertheless reduce the cerebral reserve for adequate language function. Diabetes mellitus was found to be a significant predictor of aphasia after a first-ever clinically identified stroke as reported by Kyrozis et al. in a study. We are not aware of any previous studies directly demonstrating an association of type of poststroke aphasia with diabetes mellitus. Hence in the present study most of the findings are essentially in line with previous observations, the association of type of poststroke aphasia with diabetes is of particular interest, because it has been relatively unexplored and its further study may offer insights into both diabetic cerebrovascular pathology and cerebral organization of language functions. Hence, this association we consider as a pioneer study and will be useful for encouraging preventive measures for diaberes. Global aphasia was mainly found in patients who had history of prior cerebrovascular accident and this association was statistically highly significant (P < 0.001). Any study showing this association was not recovered, hence considering our study, as a preliminary work, these results will encourage further research attempts. We do not dispute the influence that these factors have on recovery, but we argue that variability in the recovery from aphasia is tremendous and that when it comes to predicting recovery for a single specific patient, not enough is known about the pathophysiological mechanisms underpinning recovery and about the vagaries of inter-individual variations considering the risk factors.
Our study showed favorable outcome of aphasia rehabilitation in patients who had an education level of graduation than primary and secondary level groups which is similar to a study done by Nakagawa et al. who reported that among the 121 patients, 30 were university graduates and the remaining 91 were high school graduates. The improvement of comprehension underlies the improvement of other language components, e.g., speech, during recovery from aphasia, suggesting that baseline semantic function might also affect aphasia outcome as baseline comprehension of ideograms had the highest absolute t value (3.18). Nevertheless, our study indirectly encourages in improving the awareness regarding role of education level in for a favorable outcome.
It was observed that favorable outcome of aphasia rehabilitation scores in patients of middle adulthood age group which was similar to the study performed by Nakagawa et al. The average age at onset was 54.4 ± 11.9 years, and patients fell into the following age ranges: <40 years, 10%; 40–49, 19%; 50–59, 35%; 60–69, 27%; and ≥70, 9%, and results indicate that younger age at onset correlates with a better aphasia outcome. Hence, this observation confirms the notion that younger individuals have greater potential for significant recovery from aphasia and suggests that linguistic rehabilitation should be a high priority for patients.
The present study demonstrates the outcome of various type of aphasia in a specific site and type of lesion. Anomic Aphasia showed improvement in the inferior division of MCA territory infarct, Broca's Aphasia showed improvement in superior division of MCA territory infarct and subcortical infarct than subcortical bleed; Global Aphasia showed better outcome in left perisylvian infarct than superior MCA territory and subcortical bleed. Wernicke's Aphasia showed better improvement in the inferior division of MCA territory infarct than left perisylvian infarct. Nakagawa et al. studied the relationship between lesions in Wernicke's area and the linguistic components and suggested that oral reading of phonograms might be partly related to the function of Wernicke's area, whereas comprehension of ideograms has been associated with the left posteroinferior temporal cortex which concluded that long-term aphasia outcome can be predicted by a lesion in the left superior temporal gyrus including Wernicke's area. As the observations in our study show the association of outcome with the specific site of lesion, we hope that these results will encourage further attempts to characterize lesion-site-dependent treatment effects and to distinguish predictable variance from noise in this area, and that further results like this will drive the development of a more personalized medicine for stroke survivors with aphasia.
The observations in our study were strengthened by previous studies as well. Nakagawa et al. reported that long-term aphasia outcome for patients who received adequate linguistic rehabilitation for at least 2 years can be predicted by age at onset, lesion in the left superior temporal gyrus including Wernicke's area, and baseline linguistic abilities. Wilson et al. reported that overall language function typically improves substantially and steadily during the first 2 weeks after stroke, on a 10-point scale, overall language function improved by a mean of 1.07 points per week. Hence, considering our study as preliminary, the observations revealed a significant improvement in aphasia outcome in association with the indices included in the study, developing a platform for more research in this perspective and motivating the clinicians to individualize the treatment and boost linguistic rehabilitation at the earliest.
The study is a small-scale study and may require larger studies to confirm the findings. The observations revealed a significant improvement in aphasia outcome in association with the indices like age at onset, education level, and site of lesion, we recommend, more research in this perspective and to individualize the treatment for a better outcome.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]