Can Lesions in the Right Basal Ganglia Cause Aphasia? Crossed Aphasia in a Right-Handed Patient.

Background: Aphasia is a common neurocognitive disorder caused by impaired speech and language, with stroke being the most frequent cause. The neuroanatomical mechanism underlying this condition is not yet fully understood.

Case description: This case describes a 74-year-old Caucasian woman admitted with a clinical picture of right total anterior circulation infarct (TACI) and aphasia, scoring 17 on the National Institutes of Health Stroke Scale. Neuroimaging showed a large cortico-subcortical frontotemporoparietal and insular infarct involving the basal ganglia of the right hemisphere and bilateral focal atherosclerotic stenosis on the M1 segment of the middle cerebral artery. There was no left hemispheric lesion or abnormal electric activity on the electroencephalogram. A formal evaluation was compatible with transcortical motor aphasia. The aetiological study revealed atrial fibrillation, and the case was admitted as an ischaemic stroke of undetermined aetiology with two possible causes - intracranial atherosclerotic stenosis or atrial fibrillation.

Conclusion: Our patient fulfilled all the formal criteria for crossed aphasia in dextral (CAD): aphasia, a lesion in the right hemisphere coupled with the structural integrity of the left hemisphere, an established preference for right-hand use without a familial history of left-handedness individuals, and an absence of brain damage in childhood. Our patient's case adds to the evidence that deep structures - alone or in combination with cortical structures - are primarily affected in CAD.

Learning points: The diagnostic criteria for crossed aphasia in dextral (CAD) are derived from clinical case studies and include aphasia, a lesion in the right hemisphere, a strong preference for using the right hand, the structural integrity of the left hemisphere and no history of brain damage during childhood.The right lentiform nucleus was found to be the most frequent anatomical substrate involved in CAD patients, consistent with our case description.Our patient experienced transcortical motor aphasia due to a stroke in the right hemisphere, adding to the evidence that in CAD patients, deep structures are primarily affected. In contrast, in left hemispheric lesions, cortical structures seem to be the main culprits.