Technetium HMPAO SPECT study in dementia with Lewy bodies, Alzheimer's disease and idiopathic Parkinson's disease.

UNLABELLED: The aim of this study was to compare the regional cerebral blood flow measurements studied by SPECT in dementia with Lewy bodies (DLB) and Alzheimer's disease (AD) to determine the contribution of SPECT to the differential diagnosis of these two diseases. METHODS: SPECT analysis with 99mTc-hexamethyl propyleneamine oxime (HMPAO) was performed in 20 patients with probable DLB, 20 patients with probable AD and 20 patients with idiopathic Parkinson's disease (IPD). Ten pairs of regions of interest were analyzed. Tracer uptake was expressed as a corticocerebellar activity ratio. RESULTS: Compared with IPD, in the DLB group there was a global decrease of HMPAO uptake in cortical regions of interest except in the posterior frontal and occipital regions; in the AD group there was limited left temporal and parietal hypoperfusion. In the DLB group, frontal HMPAO uptake was significantly lower than in the AD group. Two predictive scores were established by a factorial discriminant analysis from six left cortical indices (medial frontal, lateral frontal, posterior frontal, temporoparietal, parietal and parietooccipital) and the Mini-Mental State Examination, which correctly classified 53 of 60 patients (88%) (DLB, 18 of 20; AD, 16 of 20; IPD, 19 of 20). CONCLUSION: These findings indicate the presence of diffuse cortical abnormalities in DLB and suggest that SPECT may be useful in discriminating in vivo DLB from AD, revealing mainly frontal hypoperfusion in the former group. We estimate that SPECT study increases the possibility of separating DLB and AD because both disorders share different patterns of cerebral blood flow abnormality.

[Importance of cerebral tomoscintigraphy using technetium-labeled sestamibi in the differential diagnosis of current tumor vs. radiation necrosis in subtentorial glial tumors in the adult]. / Intérêt de la tomoscintigraphie cérébrale au Sestamibi marqué au technétium dans le diagnostic différentiel récidive tumorale-radionécrose des tumeurs gliales sus-tentorielles de l'adulte.

CT scan and MR imaging are not always reliable in the differential diagnosis between radionecrosis and recurrence of brain tumor. We describe the results of a prospective study using 99mTc Sestamibi. 22 patients were included. The histology of the tumor was astrocytoma (grade 2-4) oligodendroglioma (grade 2-3) or mixed (grade 2-3). SPECT was performed using a Tomomatic 564, 1 h after the injection i.v. of 370 MBq of 99mTc Sestamibi. Ten slices parallel to the orbitomeatal plane were obtained. Two index were calculated i) CI: ratio of the mean counts in the lesion to the mean counts in the contralateral choroid plexus and ii) MI: ratio of the mean counts in the lesion to the contralateral mirror area. The results were compared to stereotactic biopsies or to clinical course at 6 months. Twelve patients out of 22 showed an increased uptake of the tracer and 11/12 presented with a recurrence. In 10 patients without fixation, 4 were false negative. The sensitivity for the detection of tumor recurrence was 73% and specificity was 85%. The positive predictive value was 91% and the negative predictive value was 60%. The use of a cut-off value superior to 2 for MI and superior to 0.5 for CI appears to be a good criterion for helping the diagnosis of relapse according to the analysis of Receiver Operating Characteristic curves (ROC). A positive SPECT was conclusive for the diagnosis of recurrence but a negative SPECT did not allow to assess the absence of recurrence. Limits of methods have to be stressed and searched for a better understanding of false negatives.