The neuroradiological considerations about the site of lesion and pathomechanisms of aphasia caused by cerebral vascular disease were discussed. The pathophysiology is different between brain infarction and intracerebral hemorrhage. In brain infarction, embolic infarction and atherothrombotic infarction show different features.
The most common cause of aphasia is the brain infarction in the territory of the middle cerebral artery. It is considered that typical aphasic syndromes are observed in embolic occlusion. Broca's aphasia occurred with the lesion including both Broca's area and the precentral gyrus. On the other hand, the patient who has the lesion restricted to Broca's area show transcortical sensory aphasia. Broca's area is perfused by prefrontal and precentral artery, and central sulucus is the territory of central sulcus artery. Typical Wernicke's aphasia occurred in the embolic infarction of the temporal and parietal region, where is perfused the inferior group of middle cerebral artery.
Borderzone infarction, one clinical type of atherothrombotic brain infarction, may occur in the case of arteriosclerotic occlusion of large artery of brain such as internal carotid artery. Anterior type borderzone infarction will produce transcortical motor aphasia, and the case of the posterior type may present transcortical sensory aphasia. In the case on superficial borderzone infarction, the infarcted region is usually detected by CT or MRI. In the aphasic patient, however, the reduction of the cerebral flow and metabolism measured by SPECT or PET may occur more extensive than the lesion observed morphological examination. In the patient of deep borderzone infarction, severe aphasia may occur rarely. The marked reduction of cerebral blood flow and metabolism in the left cerebral hemisphere will be observed in these cases.
Brain bleeding in the basal ganglia is called putaminal hemorrhage. Aphasia can occur in the patient with putaminal hemorrhage when mass effects due to hematoma or brain edema influence to the language area of the dominant hemisphere.
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