Interest of 123I-mIBG cardiac tomoscintigraphy coupled with myocardial perfusion in diagnosis of multiple system atrophy

Objective. - The aim of this prospective study is to assess the pertinence of using I-123-mIBG myocardial tomoscintigraphy coupled with perfusion scintigraphy as a diagnostic tool, to discriminate between multiple system atrophy (MSA) and idiopathic Parkinson's disease (PD) at first guided by clinical data and L-DOPA tests. Material and methods. - Forty patients, aged from 43 to 78 years (median 62 years) with Parkinson's syndrome were studied. Nineteen had a diagnosis of PD (criteria of brain bank) and 21 AMS (Gibbs criteria). All were given test to acute L-DOPA. Chest-centered planar imaging (128 x 128 matrix, 5 minutes of duration) is performed at 1 hour and 4 hours after injection of 220 MBq of I-123-mIBG, in addition a non-synchronised tomoscintigraphy (64 x 64 matrix, 32 images of 50 seconds, zoom 1.45) was performed after the 4th hour and 15 minutes after injection of 200 to 400 MBq of Tc-99m-tetrofosmin. Besides neurological data, the parameters retained for comparison purposes with I-123-mIBG cardiac tomoscintigraphy were patients' age, duration of disease and L-DOPA test results. Two regions of interest (ROI) identical in size and in shape are used for I-123-mIBG uptake quantifications (H/M and washout [Wo]). The first one was placed in projection of mediastinum (M) and the other one in projection of heart (H). Results. - We found an overall decreased uptake of the myocardial I-123-mIBG without perfusion abnormality in 15 of 19 patients with PD and 11 among them were L-DOPA sensitive (L-DOPA test greater than 30%). Normal tracer uptake with I-123-mIBG associated with an almost quite normal perfusion was seen in 15 of 21 patients with MSA and they were little or not L-DOPA sensitive (L-DOPA test less than 30%). Therefore, 10 discordant cases (25%) between cardiac scintigraphy and clinical evolution of disease with also discordant L-DOPA tests were observed. In the PD group, quantification of data enhanced the diagnostic decision with low heart to mediastinum ratio (HIM) (1.32 +/- 0.15 at the early stage and 1.25 +/- 0.13 at the later stage). In the MSA group, the uptake of I-123-mIBG (1.66 +/- 0.43 at the early stage and 1.72 +/- 0.42 at the later stage) was comparable to literature data, however, with significant inter-individual variations. The association of data of scintigraphy with L-DOPA test allows to improve sensitivity in 84% and specificity in 90.5%. Conclusion. - Our prospective study of 40 cases shows the relevance of cardiac sympathetic postganglionic imaging with I-123-mIBG coupled with myocardial perfusion scintigraphy to discriminate between MSA and PD with a higher sensitivity (71.4%) compared to the test with L-DOPA but a lower specificity (78.9%) than the L-DOPA. The difficulty of diagnosis is firstly linked to damage occurring to both the pre- and postganglionic sympathetic systems in patients with MSA and secondly to the integrity of the sympathetic nerve endings in patients with PD. However, the association of data of scintigraphy with L-DOPA test show a significant improvement of sensibility (84%). (C) 2010 Elsevier Masson SAS. All rights reserved.