Aktuelle Neurologie 2008; 35 - P547
DOI: 10.1055/s-0028-1086801

Myocardial meta-iodobenzylguanidin SPECT: a useful clinical tool?

I Froehlich 1, W Pilloy 1, M Vaillant 1, N Diederich 1
  • 1Luxemburg, LUX

Purpose: To evaluate the diagnostic usefulness of myocardial Metaiodbenzylguanidin SPECT (MIBG-SPECT) in patients with different parkinsonian syndromes (PS).

Background: The cardiac uptake of MIBG-SPECT is reduced in idiopathic Parkinson's disease (IPD), Lewy Body dementia (LBD) and idiopathic REM sleep behaviour disorder (iRBD). It is normal in PS related to tauopathies and in other dementia disorders.

Methods: The concordance of MIBG diagnosis (MD) and clinical diagnosis (CD) was evaluated in different clinical set-ups. CD was based on established guidelines and reassessed at the last follow up visit. MD was based on the delayed heart/mediastinum (HM) ratio. Based on literature a unique cut off of 1.6 was chosen, with values below considered to be abnormal. The following clinical set-ups were retrospectively analyzed.

  • Set-up A: differentiation between IPD and other PS or essential tremor.

  • Set-up B: differentiation between LBD and other dementia disorders.

  • Set-up C: prognostic evaluation of iRBD.

We analyzed 50 consecutive patients: 24 men and 26 women; mean age 65; range 38–87. All patients were maintained on their antiparkinsonian or antihypertensive medications. The follow-up period after the SPECT exam was 2.72 years (range: 0.16–13)

Results: In set-up A 38 patients were analyzed; in set-up B 9 patients and in set-up C 2 patients. In set-up A diagnostic concordance was 64%. MIBG-SPECT suggested IPD in further 26% of patients, not confirmed by clinical follow-ups. In set-up 2 the concordance rate was 88%. In set-up 3, MIBG suggested possible progression to PD/LBD in both patients included.

Conclusion: In clinical set-ups, myocardiac MIBG-scintigraphy is of moderate diagnostic accuracy. False positive diagnostic results are possibly due to not yet recognized age-related, but PS-independent postsynaptic noradrenergic degeneration or reduced uptake caused by antihypertensive co-medications. Further investigations should include larger cohorts of presumably healthy elderly subjects and separately address the individual impact of currently used antihypertensive co-medications sustained and complete withdrawal of these medications, as presently suggested, is risky and thus hard to realize in ambulatory patients.