In vivo SPECT imaging of muscarinic acetylcholine receptors using (R,R) 123I-QNB in dementia with Lewy bodies and Parkinson's disease dementia.
BACKGROUND
Alterations in cholinergic function have been reported to be associated with dementia. The aim of this study was to investigate differences in the distribution of muscarinic acetylcholine receptors (mAChRs) using (R,R) 123I-iodo-quinuclidinyl-benzilate (QNB) and single photon emission computed tomography (SPECT) in dementia with Lewy bodies (DLB), Parkinson's disease dementia (PDD) and age-matched controls. 123I-QNB binding was also compared to the corresponding cerebral perfusion changes in the same subjects.


METHODS
63 subjects (24 controls, 14 DLB, 25 PDD) underwent 123I-QNB and perfusion 99mTc-exametazine SPECT scanning. Image analysis, using statistical parametric mapping (SPM99), involved spatial normalisation of each image to a customised template, followed by smoothing and intensity normalisation of each image to its corresponding mean whole brain uptake. Group effects and correlations were assessed using two sample t tests and linear regression respectively.


RESULTS
Relative to controls, significant elevation of 123I-QNB binding was apparent in the right occipital lobe in DLB and right and left occipital lobes in PDD (height threshold p<or=0.001 uncorrected). PDD also showed significant loss in uptake in frontal regions and temporal lobes bilaterally that was not present in DLB. These patterns appeared to be independent of any corresponding rCBF changes.


CONCLUSIONS
Significant elevation of mAChRs in the occipital lobe was associated with DLB and PDD. This may relate to the visual disturbances that are prevalent in these disorders. Further studies are required in order to establish the role of mAChRs in visual function.
Colloby
Sean J
SJ
Institute for Ageing and Health, Newcastle University, Wolfson Research Centre, Newcastle General Hospital, Westgate Road, Newcastle upon Tyne NE4 6BE, UK. s.j.colloby@ncl.ac.uk
Pakrasi
Sanjeet
S
Firbank
Michael J
MJ
Perry
Elaine K
EK
Piggott
Margaret A
MA
Owens
Jonathan
J
Wyper
David J
DJ
McKeith
Ian G
IG
Burn
David J
DJ
Williams
E David
ED
O'Brien
John T
JT
D000368:Aged; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007457:Iodine Radioisotopes; D020961:Lewy Body Disease / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000000981:diagnostic imaging*; D011813:Quinuclidinyl Benzilate / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D012016:Reference Values; D013667:Technetium; D015899:Tomography, Emission-Computed, Single-Photon
D007457:Iodine Radioisotopes; D011813:Quinuclidinyl Benzilate; D013667:Technetium; C040062:3-quinuclidinyl-4-iodobenzilate