Striatal dopamine transporter binding assessed by [I-123]IPT and single photon emission computed tomography in patients with early Parkinson's disease: implications for a preclinical diagnosis.
BACKGROUND
Specific binding to dopamine transporters may serve as a tool to detect early loss of nigrostriatal dopaminergic neurons in patients with Parkinson's disease.


OBJECTIVE
To determine striatal dopamine transporter binding using the cocaine analogue [I-123]N-(3-iodopropen-2-yl)-2beta-carbomethoxy-3beta-(4-chl orophenyl) tropane ([I-123]IPT) and single photon emission computed tomography.


METHODS
We studied 9 control subjects (mean age, 58 years; range, 41-69 years) and 28 patients with early Parkinson's disease (Hoehn and Yahr stages I [n = 14] and II [n = 14] [symptom duration, <5 years]; mean age, 55.5 years; range, 36-71 years). Single photon emission computed tomography was performed 90 minutes after injection of 120 to 150 MBq of radioactive [I-123]IPT.


RESULTS
Specific striatal [I-123] IPT binding (mean +/- SD) was significantly reduced in patients with early Parkinson's disease (ipsilateral striatum: 4.09+/-0.97; range, 2.46-6.40; contralateral striatum: 3.32+/-0.76; range, 1.80-5.13) compared with controls (left striatum: 7.28+/-0.94; range, 5.78-8.81; right striatum: 7.41+/-1.28; range, 5.58-9.44). IPT binding ratios (mean +/- SD) were significantly lower in patients with Hoehn and Yahr stage II (ipsilateral striatum: 3.47+/-0.75; contralateral striatum: 2.96+/-0.73) compared with those with Hoehn and Yahr stage I (ipsilateral striatum: 4.72+/-0.75; contralateral striatum: 3.69+/-0.61) (P<.001). The ipsilateral striatum of patients with Hoehn and Yahr stage I showed a significant mean+/-SD reduction of IPT binding (ipsilateral striatum: 4.72+/-0.75) compared with either right or left striatum of controls (P<.001). Only in 1 patient was IPT binding to the ipsilateral striatum (ratio, 6.40) higher than the lowest value observed in the striatum of a control subject (ratio, 5.58).


CONCLUSIONS
Use of [I-123] IPT and single photon emission computed tomography demonstrates a reduction of dopamine transporter binding in patients with early Parkinson's disease. Significantly reduced IPT binding already observed in the ipsilateral striatum of patients with Hoehn and Yahr stage I demonstrates the potential of this method to detect preclinical disease.
Schwarz
J
J
Department of Neurology, University of Ulm, Germany. johannes@cco.caltech.edu
Linke
R
R
Kerner
M
M
Mozley
P D
PD
Trenkwalder
C
C
Gasser
T
T
Tatsch
K
K
D000328:Adult; D000368:Aged; D002352:Carrier Proteins / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D050483:Dopamine Plasma Membrane Transport Proteins; D005260:Female; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D008875:Middle Aged; D017072:Neostriatum / Q000000981:diagnostic imaging / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010300:Parkinson Disease / Q000000981:diagnostic imaging* / Q000378:metabolism; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015899:Tomography, Emission-Computed, Single-Photon; D014326:Tropanes / Q000493:pharmacokinetics
D002352:Carrier Proteins; D050483:Dopamine Plasma Membrane Transport Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D019275:Radiopharmaceuticals; D014326:Tropanes; C087210:N-(3-iodopropen-1-yl)-2-carbomethoxy-3-(4-chlorophenyl)tropane; D004298:Dopamine