Myocardial Scintigraphy in Parkinsonian Disorders

Parkinson’s disease (PD) is a relatively common neurological disorder in the elderly. However, only 76% of patients considered clinically to have PD are confirmed to have PD after postmortem examination (Hughes et al., 1993). The most common atypical form of parkinsonism is multiple system atrophy (MSA) (Hughes et al., 1994). MSA is clinically characterized by a combination of parkinsonian, autonomic, pyramidal and/or cerebellar symptoms and signs. The differential diagnosis of disorders with parkinsonism is very important because prognosis and treatment options differ substantially (Wenning et al., 1997). However, although the diagnoses of PD and MSA are based on current clinical criteria (Gelb et al., 1999; Gilman et al., 1999), they continue to lack sufficient specificity (Hughes et al., 1992; Litvan et al., 1997), particularly early in the disease course (Osaki et al., 2002). Extrapyramidal signs in dementia with Lewy bodies (DLB) resemble those seen in PD, although less rest tremor and left/right asymmetry, but more severe rigidity, favors a diagnosis of DLB. The subtle differences in the nature of extrapyramidal signs between DLB and PD may be of limited help in clinically differentiating the two disorders. This is particularly true in the early disease stages because the sensitivity of the clinical diagnosis of DLB based on the consensus criteria of the DLB International Workshop was 0.22 compared with 0.83 based on a neuropathological diagnosis (McKeith et al., 1996). The clinical features of PD and autosomal recessive juvenile parkinsonism (AR-JP) are also similar. Thus, it may be difficult to differentiate these two disorders. Neuropathological studies in AR-JP have revealed selective degeneration with gliosis of the pigmented neurons of the substantia nigra and locus ceruleus, but generally no Lewy bodies (Takahashi et al., 1994; Mori et al., 1998; Paviour et al., 2004), suggesting that the pathological findings and disease process of AR-JP differ from those of PD. Metaiodobenzylguanidine (MIBG) is a physiological analogue of noradrenaline (norepinephrine) (Wieland et al., 1981) and 123I-MIBG myocardial scintigraphy has been used to evaluate postganglionic cardiac sympathetic innervation in parkinsonian disorders (Braune et al., 1999; Orimo et al., 1999; Druschky et al., 2000; Taki et al., 2000; Suzuki et al., 2005). 123I-MIBG myocardial scintigraphy can be performed safely and is clinically used to estimate local myocardial sympathetic nerve damage in PD (Braune et al., 1998; Orimo et al., 1999; Takatsu et al., 2000a). Myocardial innervation imaging using 123I-MIBG has also