Disconnection Syndromes

Abstract Evolutionary pressures on a finite amount of cortical space led the cerebral hemispheres to evolve into subspecialised regions subserving specific functions. Impaired communication between these highly specialised brain regions gives rise to a variety of clinical syndromes known as the disconnection syndromes. While some of the original concepts proposed by the initial protagonists of the disconnection theory in the mid‐nineteenth century have been disproved, other conditions are now recognised as having a disconnectionist aetiology (e.g. autism and dyslexia). With improved neuroimaging, especially functional brain imaging, it is conceivable that the number of disorders attributable to disconnection syndromes will continue to increase. Disconnection syndromes may be under‐recognised, owing to both lack of physician knowledge of and difficulties elucidating these disorders, because of their subtle presentations (e.g.anterior callosal lesions). Key Concepts Disconnection syndromes should be considered when dealing with aphasia, alexia and agnosia and impaired hand function. Autism and dyslexia can be thought of as congenital disconnection syndromes. Presentations of disconnection syndromes may be subtle and need to be specifically examined for in order to avoid missing the diagnosis. Disconnection syndromes involve interruption of communication between highly specialised brain regions.