Thalamic involvement in a spinocerebellar ataxia type 2 (SCA2) and a spinocerebellar ataxia type 3 (SCA3) patient, and its clinical relevance.

In spite of the considerable progress in clinical and molecular research, knowledge regarding brain damage in spinocerebellar ataxia type 2 (SCA2) and type 3 (SCA3) still is limited and the extent to which the thalamus is involved in both diseases is uncertain. Accordingly, we performed a pathoanatomical analysis on serial thick sections stained for lipofuscin granules and Nissl substance through the thalami of two genetically confirmed cases: one an SCA2 patient, the other an SCA3 patient. During this systematic study, we detected severe destruction of the reticular (RT), fasciculosus (FA), ventral anterior (VA), ventral lateral (VL), ventral posterior lateral (VPL), ventral posterior medial (VPM), cucullar (CU) and mediodorsal thalamic nuclei (MD), the lateral geniculate body (LGB) and inferior nucleus of the pulvinar (PU i) in the SCA2 case, and a severe neuronal loss in the RT, FA, VA and PU i of the SCA3 case. In the SCA2 patient, additional obvious neuronal loss was observed in all nuclei of the anterior and rostral intra laminar groups, in the lateral posterior nucleus (LP), the lateral (PU l) and the medial subnuclei of the pulvinar (PU m), whereas in the SCA3 patient only two of the nuclei that belong to the anterior thalamic group, the VL, VPL, VPM, LP, LGB, PU l and PU m, displayed marked neurodegeneration. These novel findings indicate that thalamic involvement in SCA2 and SCA3 patients has been underestimated in the past. In view of what is known about the functions of the affected thalamic nuclei, the present findings provide an appropriate pathoanatomical explanation for some of the disease-related symptoms seen in both of our and other SCA2 and SCA3 patients: gait, stance, truncal and limb ataxia, dysarthria or anarthria, falls, dysdiadochokinesia and bradykinesia, problems with writing, somatosensory deficits, saccadic dysfunctions, executive dysfunctions and abnormalities of visual evoked potentials.