Crossed cerebellar diaschisis accompanied by hemiataxia: a PET study.

To study crossed cerebellar diaschisis (CCD), cerebellar blood flow and oxygen metabolism were measured with positron emission tomography (PET) in 12 patients who showed a minimal degree of hemiparesis due to single unilateral supratentorial lesion. Six patients presenting with mild to moderate cerebellar type hemiataxia showed CCD, that is, decreased blood flow and oxygen metabolism in the cerebellar hemisphere contralateral to the side of supratentorial lesion. Hemiataxia and reduced cerebellar blood flow and metabolism occurred in the ipsilateral side. Lesions were located in the thalamus in four patients and the parietal lobe and internal capsule in one each. The other six patients did not exhibit ataxia, and oxygen metabolism was not reduced in the contralateral cerebellar hemisphere. In two of these cases, however, reduced cerebellar perfusion was observed in the contralateral cerebellar hemisphere. These findings indicate that CCD occurs with hemiataxia and suggest that it results not only from disruption of the corticopontocerebellar pathway but also of the dentatorubrothalamic pathway. CCD associated with hemiataxia, demonstrated in patients with thalamic lesions, was presumed to result from retrograde deactivation of the cerebellar hemisphere via the dentatorubrothalamic pathway.