Cortical metabolic 18F-FDG PET assessment and striatal dopamine transporter SPECT imaging in suspected early neurodegenerative disorders with uncertain movement and cognitive symptoms

Aim/Introduction: Neurodegenerative diseases are generally
classifed basing on cognitive (CS) or motor (MS) symptoms;
however, in some cases both symptom simultaneous presence
especially in disease early phase makes diferential diagnosis
uncertain and difcult. We evaluated whether 18F-FDG PET cortical
metabolism study combined with striatal dopamine-transporter
123I-Iofupane SPECT might support clinical diagnosis in patients
with these two disorders uncertain symptoms. Materials and
Methods: We retrospectively studied 45 consecutive patients who
referred recent appearance of both CS and MS symptoms, but with
uncertain clinical neurological exam, doubtful neuropsychological
tests and aspecifc magnetic resonance imaging. Within three
weeks, all patients underwent both PET and SPECT, according to
International Guidelines. PET and SPECT images were evaluated
both qualitatively (QL) and quantitatively (QN), the latter using two
dedicated software that consider age-matched normal controls and
provide z score (-2.0) parameter and binding potential (BP) cut of
value (3.3) for PET and SPECT, respectively. A clinical follow up of 12-
18 months confrmed diagnosis. Results: At PET QL analysis, 34/45
cases had diferent areas of cortical hypometabolism, while 11/45
showed normal metabolism; at PET QN analysis, 38/45 cases had
pathological z score in diferent cortical areas and the remaining
7/45 cases confrmed normal z score values. At SPECT QL analysis,
19/45 patients showed mild to severe striatal 123I-Iofupane uptake
reduction, while 26/45 cases had normal uptake. At SPECT QN
analysis, 23/45 cases (fve of these normal at QL) evidenced low BP
values while the other 22/45 cases had normal values. Associating
QL and QN analyses of the two procedures, in 16/45 patients
both PET and SPECT were pathological as from dopaminergic and
cognitive associated diseases; 7/45 cases with normal PET and
pathological SPECT were considered as MS without CS. The 15/45
cases with pathological PET and normal SPECT were classifed as
CS without MS. In the remaining 7/45 cases with normal PET and
SPECT both MS and CS were excluded. Conclusion: 18F-FDG PET and 123I-Iofupane SPECT combined use proved useful to discriminate
CS and MS disorders in early stage also achieving to identify
and characterize the patients with the two neurodegenerativeassociated disorders (35.5%). This performance permitted a better
appropriate patient management and a suitable therapy. The two
procedures could exclude both diseases in some cases avoiding
unnecessary treatments. PET and SPECT QN analyses gave better
results than traditional QL analysis suggesting its wider use even
more when QL is inconclusive for the diagnosis.