Correlati di neuroimaging funzionale dell'aprassia nelle demenze neurodegenerative

Aim. High order control of movements and gestures is attributed to a cortico-subcortical network involving the fronto-parietal cortex and connections, and the striatum. Damage within the basal ganglia would be neither necessary nor sufficient to cause clinically evident apraxia, but would add to praxis errors caused by fronto-parietal dysfunction. While the cortical component of the praxis network has been repeatedly investigated, this is the first study directly exploring the contribution of the striatum: we correlated dopaminergic uptake measured with 123-ioflupane Single Photon Emission Tomography (SPET) and PET FDG cerebral metabolism with severity of ideomotor apraxia in Cortico-Basal Syndrome (CBS). Patients and methods. Patients were evaluated with De Renzi’s Test for Ideomotor Apraxia, which allows to score separately movements performed with hand and fingers or with arm and hand, and meaningful and meaningless gestures. Both upper limbs were assessed. Occipital-striatum ratios of dopaminergic uptake were measured semiquantitatively for left and right caudate and putamen. Partial correlation analysis between apraxia scores and SPET parameters was conducted using Unified Parkinson’s Disease Rating Scale III, MMSE scores, disease duration and age as covariates. Bonferroni correction for multiple comparisons was applied. PET FDG uptake was quantified using SPM software. Results. Eleven patients diagnosed with CBS according to recent standardised criteria were included into the study. They were eight women and three men with a mean age of 70.3 years +7.8, a mean disease duration of 28.2 months +14.6, and a MMSE score of 19.7 +4.1 on average. Partial correlation analysis after Bonferroni correction showed a statistically significant relationship between reduced dopaminergic uptake in the left striatum (caudate and putamen) and poor performance of gestures with the left fingers. A correlation was demonstrated between a cluster of reduced metabolism at PET FDG in the frontal left hemisphere and right apraxia scores in the CBS subjects. Discussion. Even if confirmation in a larger sample is needed, our findings confirm a cortical involvement in the praxis network and support a role of the basal ganglia on praxis dysfunction in subjects with CBS. Conclusions. In CBS, damage to the basal ganglia is not only responsible for extrapyramidal signs and symptoms, but also contributes to the development of ideomotor apraxia.