The cerebellar cognitive affective syndrome: clinical correlations of the dysmetria of thought hypothesis

The description of deficits in higher order behaviors in patients with focal cerebellar lesions has provided pivotal clinical corroboration of a cerebellar role in cognition and emotion. This paper reviews the principal observations of the cerebellar cognitive affective syndrome (CCAS) of Schmahmann & Sherman (1998) in both adults and children, namely deficits in executive, visual-spatial, linguistic and affective behaviors. Postoperative mutism and personality changes that characterize the posterior fossa syndrome, other reports describing an association between cerebellar abnormalities and intellectual deficits and psychotic behaviors, and reports of cerebellar pathology in traditionally psychiatric diseases including schizophrenia and autism are discussed. These higher order cognitive/emotional/psychotic deficits are considered to be clinical manifestations of the dysmetria of thought hypothesis (Schmahmann, 1991) that addresses the fundamental contribution of the cerebellum to nervous system function.