Crossed cerebellar diaschisis in patients with brain stem infarction

This report concerns the development of crossed cerebellar diaschisis (CCD), the presence or absence of cerebellar symptoms and the respective MRI findings in patients with brain stem infarction. SPECT and MRI were performed on 32 cases of unilateral brain stem infarction during a 3.5 year period between January 1989 and June 1992. The mean age of the patients was 67.1 years; 18 were males and 14, females. In 3 cases the main lesions were in the midbrain, in 24 in the pons and in the remaining 5 cases in the bulb. The main instruments used were Hitachi MRP-20 for MRI, permanent magnet 0.2 T and Hitachi SPECT 2000H-40 for SPECT. For CCD, the regions of interest (7 x 7 pixels) were set in the cerebellar hemispheres according to the SPECT findings by intravenous injection of 123I-IMP and the calculations were made according to this formula: asymmetry index=2 x |R-L|/(R+L) x 100%. The asymmetry index in the normal controls was 1.8±1.5%, mean +2SD and higher values were considered as CCD (+). CCD was found in 5 cases (asymmetry index: 15.6%). By the site of the lesions, they were in the pontine basis in 4 cases (16.7%) and the tegmentum of the midbrain in 1 (33.3%). CCD was not found in bulbar infarction. The asymmetry index value in the CCD patients tended to be high during the chronic stage. Thus, the values were 6.4±4.5% in the acute stage within 1 week after onset, and 13.6±4.6% during the chronic stage after 1 month or more. The MRI findings suggested impairment of the corticopontocerebellar pathway in 4 patients in whom CCD was found and of the dentatorubrothalamocortical pathway in the remaining case. Evident cerebellar symptoms were noted in 1 case of mesencephalic infarction, but not in 3 of the 4 other cases. Other neurological symptoms precluded judgement in 1 case. Depending on the site of the localized lesion, CCD could occur even in cases of brain stem infarction, and in some patients be accompanied by cerebellar symptoms. (author)