Investigators from Massachusetts General Hospital, Boston, and centers in Frankfurt, Germany, examined 22 patients with the classic phenotype of ataxia-telangiectasia for neurocognitive features, and compared patients with early stage cerebellar disease (group AT-I) versus those with late stage cerebrocerebellar disease (group AT-II). Group AT-I patients scored low average compared with standard norms on all tests and were significantly impaired compared with healthy controls for verbal IQ, vocabulary and comprehension, processing speed, visuospatial processing, and working memory. Group AT-II patients scored below average on all tests for attention, working memory, and abstract reasoning. Comprehension scores were lower for patients in AT-II than in AT-I, whereas vocabulary scores showed no difference between groups. Cognitive impairments in ataxia-telangiectasia present early, coinciding with cerebellar pathology and are characteristic of the cerebellar cognitive affective syndrome. Cognitive impairments worsen in later stages of ataxia-telangiectasia, and correlate with development of supratentorial, noncerebellar pathology. 
COMMENTARY. The cerebellar cognitive affective syndrome (CCAS) associated with acquired cerebellar lesions is characterized by cognitive impairment, disorders of executive and visuospatial function, and expressive language and affective disorders. The behavioral developmental profile of patients with congenital cerebellar malformations is variable but similar to the CCAS. Malformations affecting the cerebellar vermis induce affective and social disorders, evolving to an autistic symptomatology, whereas malformations of cerebellar hemispheres are associated with selective neuropsychological deficits involving executive functions and visuospatial and linguistic abilities . Patients with ataxia-telangiectasia, a neurodegenerative disorder, display a cerebellar motor phenotype during their first to third year of life and later, with involvement of noncerebellar or cerebrocerebellar circuits, the progression of cognitive and behavioral disorders is apparent. Functional neuroimaging studies during the phase of mutism following posterior fossa tumor resection show SPECT perfusion deficits in the supratentorial areas subserving language dynamics, syntax, naming, executive functioning, affective regulation, and behavior. The clinical remission of mutism parallels improvement of frontal perfusion deficits. A theory of cerebello-cerebral diaschisis is proposed, reflecting the impact of a cerebellar lesion on supratentorial cognitive and affective functions .