Patients with focal cerebellar lesions due to tumor or hematoma were evaluated by a neuropsychological test battery, neurological examination and MRI, and cognitive function was correlated with location of the lesions in a study of 21 adult patients at the Department of Neurosurgery, Christian Albrechts Universitat, Kiel, Germany. Compared to matched controls, patients showed deficits in general memory, delayed recall, and visual memory, but not in verbal memory; and deficits in executive function and in attentional processes such as working memory and divided attention. Patients with right-sided cerebellar hemisphere lesions were more impaired than those with left-sided lesions, and their deficits were verbal whereas those with left-sided lesions were more often non-verbal and spatial. The connection of the right cerebellum to the left cerebral hemisphere, which is dominant for language and right hand movements, explains the greater impairment of function with right-sided lesions. Motor impairments were not correlated with cognitive deficits. Cerebellar lesions lead to a “dysmetria of thought.” [1]

COMMENT. The study confirms that cognitive functions are impaired after cerebellar lesions, and particularly right-sided hemisphere lesions. In accordance with the earlier work of Courchesne E and Allen G [2], cerebellar damage does not eliminate function but impairs the performance. The cognitive impairments are not explained by a dysmetria of motor performance but rather a “dysmetria of thought” (authors’ term).