OLFACTORY FUNCTION IN ATYPICAL PARKINSONIAN SYNDROMES

Introduction - Olfaction is markedly impaired in patients with idiopat hic Parkinson's disease (IPD). This deficit contrasts with reports of preserved or only mildly reduced olfaction in patients with atypical p arkinsonism. However, the sensitivity and specificity of olfactory fun ction testing in the differential diagnosis of parkinsonian syndromes has not been studied. In addition, olfactory function in patients with corticobasal degeneration (CBD) is unknown. Material and methods - Us ing the University of Pennsylvania Smell Identification Test (UPSIT) w ith a test score ranging from 0 to 40 we studied olfactory function in patients with IPD as well as other parkinsonian syndromes including C BD and progressive supranuclear palsy (PSP). Results - UPSIT scores in 118 patients with IPD, 29 with MSA, 15 with PSP, and 7 patients with CBD, as well. as in 123 healthy control subjects revealed a marked imp airment in the IPD group in contrast to mild impairment in MSA patient s and normal olfaction in PSP and CBD patients. An UPSIT score of 25/4 0 was associated with a sensitivity of 77% and a specificity of 85% in differentiating IPD from atypical parkinsonism. Conclusions - These r esults indicate that olfactory function is differentially impaired or preserved in distinct parkinsonian syndromes and that it might also ha ve some value as a diagnostic pointer. Thus, preserved or mildly impai red olfactory function in a parkinsonian patient is more likely to be related to atypical parkinsonism such as MSA, PSP or CBD, whereas mark edly reduced olfaction is more suggestive of IPD.