Multiple system atrophy and progressive supranuclear palsy. Diminished striatal D2 dopamine receptor activity demonstrated by 123I-IBZM single photon emission computed tomography
E. van Royen, N. F. Verhoeff, J. D. Speelman, E. C. Wolters, M. A. Kuiper and A. G. Janssen
Department of Nuclear Medicine, Academic Medical Centre, University of Amsterdam, The Netherlands.
OBJECTIVE--To measure D2 dopamine receptors in the striatum in patients
with multiple system atrophy and progressive supranuclear palsy by I
3-iodo-6-methoxybenzamide labeled with iodine I 123 (123I-IBZM) single
photon emission computed tomography and differentiate them from control
subjects. DESIGN--Survey with the following as retrospective criterion
standards: (1) parkinsonism, (2) negative apomorphine test, and (3) no or
only slight reaction to dopaminergic medication. SETTING--Ambulatory or
hospitalized care in an academic referral center. PATIENTS AND CONTROL
SUBJECTS--Twenty-one patients with parkinsonism not responding to
dopaminergic medication (17 with multiple system atrophy and four with
progressive supranuclear palsy) and 21 control subjects without
parkinsonism. INTERVENTION--In vivo imaging by single photon emission
computed tomography using the D2 dopamine receptor specific radioligand
123I-IBZM. MAIN OUTCOME MEASURE--Striatum/occipital cortex ratio of count
rate density as semiquantitative measurement for striatal D2 dopamine
receptor density. RESULTS--A highly significant loss of striatal uptake of
123I-IBZM was observed in the patients in comparison to the control
subjects with little or no overlap between values. CONCLUSIONS--The
hypothesized loss of D2 receptors in multiple system atrophy has been
confirmed. Use of 123I-IBZM single photon emission computed tomography may
be a cost-effective alternative to positron emission tomography in the
differential diagnosis of parkinsonism and in the selection of patients for
dopaminergic therapy.
