Crossed aphasia in a patient with congenital lesion in the right hemisphere

Background: Described over 100 years ago by Bramwell (1899) as an example of atypical cerebral dominance, crossed aphasia is a clinical condition where a lesion in the right hemisphere in a right-handed person leads to aphasia. Occurring worldwide only in a few cases, it is not known what initially leads to the ontogenetic lateralisation of language to the right brain. However, we know that certain kinds of pre-existing congenital lesions in the brain, in utero or post-partum, can usually impact the language lateralisation such that it develops in the opposite hemisphere. Aims: We present neurolinguistic data from a right-handed patient with crossed aphasia, who had an atypical subcortical crossed aphasia marked with a fractionated lateralisation of functions. Early in her life she had an unsuspected, pre-existing congenital (subcortical AVM) abnormality in the right hemisphere. Methods Procedures: Clinical data in this single-participant study was obtained from a 20-year-old female who was seen for an evaluation of her residual language functions at a university speech and hearing clinic after her ruptured right subcortical AVM. The participant was reassessed 5 years after the first examination and also received treatment for impaired verbal output. Data taken from two diagnostic evaluations are compared and discussed. Outcomes Results: The patient's language nonetheless lateralised to the right hemisphere without any obvious consequence of the subcortical AVM. This would not be puzzling since a silently sitting AVM itself may not generally interfere with lateralisation. However our participant exhibited an atypical allocation of functions. The left hemisphere appeared to have lost its dominance for speech to the right hemisphere, while it nevertheless maintained the limb praxis control, since the participant was right-handed from the outset. Interestingly the right hemispheric inherent visuospatial functions remained unimpaired, while its paralinguistic functions were impaired to a certain extent. Conclusions: We present evidence of an atypical language-cognitive lateralisation in crossed aphasia in a participant with a congenital (subcortical AVM) abnormality in the right hemisphere. We discuss the mechanisms that might have contributed to the atypical allocation of the functions.