Olfaction in patients with suspected parkinsonism and scans without evidence of dopaminergic deficit (SWEDDs)

Abstract

CONCLUSIONS: In a patient with suspected PD, a high PD probability on smell testing favours the diagnosis of PD, and a low PD probability strengthens the indication for dopamine transporter imaging.

Neuroimaging in Parkinson's Disease

“…While this may indeed be the case, it appears to be an incomplete explanation. Many of the subjects with SWEDD appear to have dystonic tremor which can superficially look very much like early, tremor-predominant PD, [90] but unlike PD, olfaction is preserved, [91] the tremor is not re-emergent on assuming a new posture, and there is no true decrement in the amplitude of repetitive movements [92]. People with SWEDD do not have a convincing response to dopaminergic therapy and do not show the PDRP on glucose PET [93].…”

Premotor Symptoms and Early Diagnosis of Parkinson's Disease

“…Therefore, this nonmotor finding may be used as a premotor test to identify an at-risk group for PD, but it is certainly not diagnostic. The finding of hyposmia differentiates PD from some other parkinsonian disorders such as progressive supranuclear palsy [14] and vascular parkinsonism [15], and normal olfaction is found in most studies of essential tremor [16][17][18][19].…”

Dopamine transporter imaging in clinically unclear cases of parkinsonism and the importance of Scans Without Evidence of Dopaminergic Deficit (SWEDDs)

“…The use of the "Sniffin' Sticks" odor-identification test resulted in a sensitivity of 88.2 and 63.2% with a specificity of 85.7 and 78.6% for early-onset and late-onset PD, respectively 19 . When the University of Pennsylvania Smell Identification Test (UPSIT) was used in 21 patients with SWEDDs, their scores were significantly higher (better) than those of the PD group and did not differ from control, ET or dystonia groups 16 . A low score would indicate a high probability of PD (accuracy of 97%) and higher UPSIT scores encourage the search for alternative diagnoses.…”

“…Hyposmia occurs in 80-100% of cases of PD 16,17 and it may represents an initial symptom of the disease process 6,18 . The use of the "Sniffin' Sticks" odor-identification test resulted in a sensitivity of 88.2 and 63.2% with a specificity of 85.7 and 78.6% for early-onset and late-onset PD, respectively 19 .…”