n.73 – CARDIAC ADRENERGIC DENERVATION ON TWO SEQUENTIAL 123I-MIBG MYOCARDIAL SCAN IN A CASE OF UNCERTAIN PARKINSONISM



Abstract

BACKGROUND-AIM
We report the case of a 73 year-old man who underwent a 99mTc-ECD brain perfusion SPECT for the onset of a memory deficit described as an attentive deficit associated with difficulties in driving, apathy, asthenia, sleepiness. The patient was depressed and under treatment with Duloxetin and did’nt suffer from diabetes, cardiac diseases or rhythm disturbances.
METHODS AND RESULTS
A neuropsycological examination evidenced minor depression, attentive disturbances with memory preservation. Brain 99mTc-ECD was unremarkable while a brain Magnetic Resonance (MRI) revealed chronic vascular alterations. Two years later, patient experimented an extrapiramidal syndrome (ES) characterized by bilateral asymmetric tremor of upper limbs more predominant on the right side and bradykinesia. He started L-Dopa without any subjective improvement. Four years after the first neurological evaluation, patient referred again to our Department in the suspicion of a parkinsonian syndrome.
We performed a brain scan with 123I-Ioflupane revealing a bilateral asymmetric uptake reduction more prominent on left putamen indicative of the presence of a degenerative disease. A second 123I-MIBG scan was still unremarkable. Six years after the first assessment, patient was clinically revaluated with a diagnosis of akinetic rigid Parkinson’s disease (PD) and introduced dopamine agonists again without significant response. A second brain MRI showed no differences. Because of the unresponsiveness to therapy, patient performed a 18F-FDG PET/CT in the suspicion of an atypical parkinsonian syndrome (APS). Findings were unremarkable without areas of hypometabolism. A second 123I-MIBG scan demonstrated a markedly decrease of cardiac sympathetic innervation. In our case, we had a disagreement among diagnostic criteria: at the beginning a negative 123I-MIBG scan and the unresponsiveness to L-DOPA were more consistent with an APS while the positivity of 123I-Ioflupane SPECT, the negative 99mTc-ECD SPECT and results of clinical evaluation were more consistent of PD. On the contrary, at the last evaluation all instrumental techniques were consistent with a diagnosis of PD. Reasons reducing the sensitivity of 123I-MIBG scan at the onset of the ES could be genetic factors such as an altered response to L-DOPA due to polymorphisms of the dopa-decarboxylase (DDC) gene promoter or the presence of PARK2 with a homozygous exon deletion, an early stage clinically defined as Hoehn-Yahr (H-Y) stage I.
CONCLUSION
In our case PARK2 was hardly acceptable as an explanation because of the old age at onset; clinical symptoms did not significantly differ throughout the evaluations leading to a clinical definition of the same H-Y stage independent from MIBG results. It may be hypothesized that a still unclear genetic modification could be responsible both for unresponsiveness to therapy and negative result at the first 123I-MIBG scan. Up to now no genetic modifications could be found in our patient who is still on active follow-up. A pathological examination could clarify a possible reason for these controversial results.

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