[Value of single photon emission computed tomography in the characterization of fronto-temporal dementia subtypes]

DFT (fronto-temporal dementia) was diagnosed in 33 patients (17 males and 16 females), mean age 74.9 years, using the criteria from Neary et al. (1998). The severity of the disease was evaluated based on the presence or absence of 4 clinical groups of signs (behavioral, affective, neurological signs and language) allowing the calculation of a global clinical ratio on 20. A CT-scan and a Single Photon Emission Computed Tomography (SPECT) scan using Tc99m-ECD with quantification of brain perfusion were then performed. This study confirmed the classical clinical forms of DFT: a psycho-affective form (21%), where negative symptoms are predominant, and a behavioral disinhibited form (9%). Most of our cases (40%) corresponded to a global form. Finally we also identified a fourth clinical form: cognitive form because of predominance of language disturbances (30%). Concerning SPECT, we found 4 topographic forms: frontal global (46%), frontal superior (24%), frontal inferior (15%) and frontal unilateral (12%). In the frontal inferior form, behavioral disturbances were correlated to the intensity of frontal inferior hypoperfusion, corresponding to an orbito-frontal dysfunction. In the frontal superior form, psycho-affective disturbances (apathy) were correlated with frontal superior hypoperfusion (anterior cingulum and superior dorso-lateral cortex). Finally, in global and frontal inferior SPECT forms, language disturbances were correlated with a frontal inferior hypoperfusion (prefrontal and inferior left frontal cortex).