Cerebellar lesion studies of cognitive function in children and adolescents - limitations and negative findings.

An increasing number of human lesion and functional brain imaging studies appear to support the hypothesis that the cerebellum contributes to a wide range of non-motor functions, including attention, language and visuospatial functions. Various abnormalities have been reported in standard neuropsychological tests in children and adolescents who have been treated for cerebellar tumors. This review focuses on limitations of lesion studies and negative findings in children and adolescents with focal cerebellar lesions. Frequently cited early findings have not been replicated in later studies or have been explained by motor components of the tasks. Such discrepancies may relate to a number of methodological problems. In addition to impaired motor function, it is unclear to what extent deficits in neuropsychological tests are caused by unspecific effects such as increased intracranial pressure and depression. Effects of extracerebellar lesions are frequently not considered. Although a role of the cerebellum in specific aspects of non-motor functions seems obvious it is still an open question which cognitive functions are involved, why and to what extent. It is a matter of ongoing discussion whether or not cognitive dysfunction belongs to the symptoms of cerebellar disease. Overall, disorders appear to be mild and far less frequent than disorders observed following lesions of cerebral areas. The aim of the review is to demonstrate that many findings frequently cited to support cerebellar involvement in cognition are insufficient to prove the hypothesis. There is ongoing need of well-controlled lesion studies, which show that disorders are due to cerebellar lesions independent of motor dysfunction and other confounding factors.