A 52-year-old woman has been under observation for a complete locked-in syndrome of vascular origin, since 1984. Her cognitive functions today are still normal. When first diagnosed, a CT-scan was made and 23 years later performed, a cerebral MRI was performed. A focal, bilateral and symmetric atrophy of the dorsomedial prefrontal gyri was clearly shown, contrasting with the non-atrophy of the precentral gyri (motor area), others prefrontal areas, frontopolar gyri and temporal cortices. Degeneration of the corticopontine projection, the first step in the corticopontocerebellar circuit, could explain this selective atrophy. This unique observation leads to the precise in vivo anatomical location of the Arnold tract.