Neuroanatomic correlation of the post-stroke aphasias studied with imaging

Stroke is the leading cause of disability in many countries. Aphasia is a common sign of stroke that is observed in about one-third of stroke patients and contributes to disease morbidity. However, the relationship between anatomy and different forms of aphasia remains poorly understood. We intend to study the characteristics of aphasia in the acute stage of stroke and to identify neuroanatomical correlates using MRI.

Lesion sites were selected from 1198 patients with cerebral infarction, who were hospitalized in the stroke unit of our hospital between March 2002 and March 2006. We enrolled 325 patients who fulfilled our criteria. All patients received an MRI examination within 1 week after admission and were evaluated with the Western battery aphasia (WAB) test, in order to determine what type of aphasia they had. The severity of their language deficit was further classified using the Boston diagnostic aphasia examination (BDAE) severity grading standard.

Among 1198 cases, five cases with Broca's areas and four cases with Wernicke's areas lesions on MRI works were free of language deficits. Within the 325 patients who demonstrated clinical signs of aphasia, the results of WAB showed that there were 83 Broca' aphasia cases, 48 Wernicke's aphasia cases, 12 conduction aphasia cases, 36 transcortical motor aphasia cases, 17 transcortical sensory aphasia cases, 19 transcortical mixed aphasia cases, 58 global aphasia cases and 52 anomic aphasia cases. Two hundred and eighty-eight cases were located within classical language centers while 37 cases were located at other sites. In 325 aphasia patients with grade criteria of BDAE of grades 0, 1, 2, 3 or 4, there were 84, 79, 77, 63 and 22 cases respectively. Many of cases with grades 0 and 1 were distributed within classical language centers.

This study showed that it is possible to draw a neuroanatomical map of aphasia that encompasses the 95% of aphasia cases. It also demonstrates that the main determinant of aphasic disorders is the neuroanatomical location of the lesion. Furthermore, this study shows that most lesion locations associated with specific aphasic disorders fit classical data associated with previous aphasia research. More importantly, the language disorders of patients whose lesions were located at classical language centers were more serious. Consequently, this paper demonstrates the power of MRI in prognosticating the potential for a patient to recover from aphasia due to stroke.