The reversed clock drawing test phenomenon in Alzheimer's disease: A perfusion SPECT study.

ABSTRACT

AIM: To unveil a brain single photon emission computed tomography (SPECT) pattern in Alzheimer's disease (AD) patients, showing a reversed clock drawing test (CDT) phenomenon. PATIENTS AND METHODS: Among 1,005 consecutive subjects, 9 AD patients who drew a reversed CDT (AD-R) underwent SPECT, which was analysed (SPM2) versus a group of 10 AD patients performing the CDT correctly (AD+) and versus 15 controls (CTR). Brain SPECT in 11 AD patients who mistook the CDT in a common way (AD-) was compared with AD+ and CTR groups. RESULTS: Relative hypoperfusion was found in AD-R versus CTR in right medial frontal, parahippocampal and subcallosal gyri, and in left insula and superior temporal gyrus. Hypoperfusion was found in AD-R versus AD+ in the right uncus, superior temporal and parahippocampal gyri. In the AD- versus CTR comparison, hypoperfusion was found in left hippocampus, parahippocampal gyrus and superior parietal lobule. In AD-R versus AD+ and CTR merged together, the analysis showed hypoperfusion in the right parahippocampus, medial frontal gyrus, superior temporal gyrus and uncus, in the left insula and superior temporal gyrus. CONCLUSION: Fronto-temporal dysfunction, especially in the right hemisphere, plays a role in the reversed CDT phenomenon in AD patients, whereas matched AD patients mistaking the CDT in a common way show left posterior temporo-parietal hypoperfusion.