We report the clinical and pathological study of a patient with vascular leucoencephalopathy almost restricted to the left posterior hemisphere. A 65 year--old right handed hypertensive woman has presented with a neuropsychological symptomatology of transcortical sensorial aphasia. We discuss the following points: 1) the patient's disease must be considered as Binswanger's subcortical encephalopathy despite the asymetric topography of the lesions ; 2) particular hemodynamic cerebral factors has possibly determined the asymetric nature of the disease ; 3) a lesion of the left temporo-parieto-occipital area that was strictly sub-cortical, with complete destruction of the posterior part of the arcuate fasciculus has presented with the clinical picture of a transcortical sensorial aphasia.