A study on Olfactory dysfunction in various subtypes of Parkinsonism.

Impairment of olfaction in Parkinson’s disease (PD) was first recognized in the 1970s, but it is mainly in the past decade that insights into its pathogenic basis and specificity have occurred. Various degrees of olfactory dysfunction occur in some other Parkinsonian syndromes, but a marked reduction in the sense of smell remains a highly characteristic feature of PD. The early or pre clinical detection of Parkinson’s disease is increasingly recognized as an area in which olfactory testing may be of value. Research findings have confirmed a role for olfactory testing in the differential diagnosis movement disorders, and suggest that this approach is currently underused in clinical practice. Validated test batteries are now available that may prove to be of practical use in the differential diagnosis of Parkinsonian syndromes and indeterminate tremors. Since the pioneering work of Valentin (1848), who determined the lowest concentration of an odorous gas that a subject could perceive, a plethora of nominally distinct olfactory tests has been developed, including tests of sensitivity(e.g., odor detection and recognition thresholds),discrimination, identification, memory and suprathreshold intensity. Katerina Markopoulou [et al.], Doty [et al.] &Stern et al have extensively studied olfactory functions in various types of parkinsonian patients and they have found out the usefulness of doing olfactory function tests in he diagnosis of various subtypes of parkinsonism. Doty [et al.] have developed the olfactory function test kit, the University of Pennsylvania Smell Identification Test (UPSIT) in 1988 and have researched in detail about the olfactory impairment in various neurodegenerative diseases like parkinsonism, various types of dementia and hereditary ataxias. Significant olfactory impairment is present even in early stages of idiopathic parkinsonism 1) Odour identification and odour discrimination are both impaired and odour threshold is elevated in idiopathic parkinsonism. 2) Olfactory impairment is severe in later stages of Idiopathic parkinsonism. 3) The severity of olfactory impairment is not dependent on the duration of illness but dependant on the disease stage. 4) In doubtful early clinical presentation of parkinsonism, presence of significant olfactory impairment suggests the possibility of Idiopathic parkinsonism. 5) Dopa therapy does not alter the presence or severity of olfactory impairment in various subtypes of parkinsonism. 6) In Familial parkinsonism, olfactory functions are impaired. 7) In Multi system atrophy, olfactory functions are impaired mildly in late stages of illness. In Progressive supranuclear palsy, Vascular parkinsonism, Spinocerebellar ataxia presenting with parkinsonism, olfactory functions are not impaired. 8) Olfactory function tests can be used as an easy bedside supplementary clinical tool in the diagnosis of various subtypes of parkinsonism