FP-CIT SPECT in clinically inconclusive Parkinsonian syndrome during amiodarone treatment: a study with follow-up

Abstract

To evaluate whether dopamine transport system imaging by FP-CIT single-photon emission computed tomography (SPECT) can be helpful to differentiate idiopathic Parkinson's disease (IPD) from secondary Parkinsonism induced by amiodarone. Twenty-two patients with Parkinsonism during amiodarone therapy were evaluated by clinical neurological examination and FP-CIT SPECT. Thereafter, amiodarone was discontinued whenever possible and antiparkinsonian treatment was modified, if required. Clinical neurological status was reevaluated within a year of the SPECT examination. At baseline, clinical neurological examination was quite similar in all patients. No clinical symptom was able to clearly orientate the diagnosis toward IPD or drug-induced Parkinsonism. Using SPECT, the number of normal and abnormal patients was evenly distributed. In the abnormal SPECT group, amiodarone was modified in seven patients of whom six improved at follow-up. Antiparkinsonian treatment had been modified in all the patients. In the four cases with no amiodarone changes, clinical improvement was noted if antiparkinsonian treatment was optimized (three patients). In the 11 normal SPECT patients, amiodarone was modified in five patients. All patients ameliorated (two) or even normalized (three). In the six patients with normal SPECT in whom amiodarone had not been modified, symptoms remained stable despite the absence of antiparkinsonian treatment. In patients treated with amiodarone, IPD is sometimes clinically difficult to differentiate from drug-induced Parkinsonism. Using FP-CIT, a normal scan suggests drug-induced Parkinsonism, hence, there is no need for antiparkinsonian treatment and all possible attempts to reduce or preferably stop amiodarone. An abnormal scan, on the other hand, indicates IPD. In this case, treating IPD seems to have more impact on motor changes than modifying the antiarrhythmic drug.