Brain 123I-ioflupane SPECT and 18F-FDG PET combined use in movement and cognitive associated diseases of recent appearance

Background-Aim: 123I-Ioflupane SPECT (SPECT) represents a useful tool in the diagnosis of movement disorders (MD) with basal ganglia dopaminergic damage as Parkinson’s disease (PD) while 18FFDG PET (PET) defines metabolic impairment in cognitive disorders (CD) as Alzheimer’s disease (AD) and other dementias. Since an association of MD with CD has been reported in some cases, we evaluated whether the combined use of SPECT and PET might be useful in the patients affected by both these conditions. Methods: We investigated 41 consecutive patients with recent appearance of clinical symptoms suspect for MD and CD with doubtful signs at neurological examination and neuropsychological tests and aspecific data at magnetic resonance imaging. According to the international guidelines, within 3 weeks the patients were also submitted to both SPECT and PET. In the two procedures, the images were evaluated both qualitatively (QL) and quantitatively (QN), the latter using a dedicated software that compares each patient with age matched normal control groups (cut-off value of 3.3 and Z core of - 2.0 for SPECT and PET, respectively). Results: At SPECT, QL analysis evidenced tracer reduction uptake in basal ganglia of 18/41 patients, mild in four and severe in 14, while the uptake was normal in the remaining 23/41 cases. QN analysis evidenced uptake reduction in 20/41 cases (two of these normal at QL) and normal values in the other 21 patients. At PET, QL analysis showed different patterns of cortical hypometabolism in 33/41 patients and was normal in the remaining 8/41 cases; QN evidenced pathological values in 34/41 cases and normal values in the remaining 7/41 patients. The combining use of the two procedures, evidenced pathological SPECT and PET in 15/41 (36.6%) patients, considered with associated dopaminergic and cognitive diseases. SPECT was pathological and PET was normal in 5/41 (12.2%) cases who were classified as MD without CD. SPECT was normal and PET pathological in 19/41 (46.3%) cases who were classified as affected by CD without MD. Both SPECT and PET were normal in 2/41 (4.9%) cases, thus excluding MD and CD. QN analysis of SPECT and PET showed better performance than QL analysis. Conclusions: In this study, the combined use of 123I-Ioflupane SPECT and 18F-FDG PET has led to a more appropriate disease diagnosis and characterization, and an adequate treatment and correct management of patients affected by associated MD and CD of recent appearance. In particular, the use of QN analysis in both SPECT and PET proved a useful complementary tool to the conventional QL analysis, especially when the latter is inconclusive. A wider use of these combined procedures is suggested even more when the other exams are not decisive for the diagnosis.