To review the status of tau protein specific PET in Parkinsonian disorders To provide a guide for future research directions for tau protein specific PET

With the development of newer tau specific radiotracers there is interest in whether 4 repeat (4R) predominant taupathies—progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) and its clinical syndrome, corticobasal syndrome—can be differentiated from idiopathic Parkinson’s disease (IPD) and multiple system atrophy (MSA) that are α-synucleinopathies.1 This has clinical implications as treatment differs – for example atypical parkinsonian disorders (CBS, PSP and MSA) do not respond to levodopa to the same magnitude as IPD.2 Studies correlating clinical features with pathological diagnosis have shown that clinical...

There are three main PET radiotracers researched currently: 18F-THK-5351, 11C-PBB3, 18F-AV-1451. Tau protein radiotracers have unique uptake distributions in Parkinsonian disorders that allow researchers todistinguish between select diseased patients and controls.3-6 PSP is the most extensively studied taupathy. Studies evaluating the use of radiotracers in diagnosing PSP have correlated the extent of disease with the uptake of radiotracers with variable results.7,8In comparing progression of symptomology of MRI and tau-PET radiotracers in PSP, MRI midbrain atrophy has been found to be superior.9Non-specific binding of radiotracers continues...

The accurate imaging of tau proteins in Parkinsonian disorders is an ongoing issue affecting the usefulness of these radiotracers in current practice. Tau protein imaging can discriminate diseased patients fromhealthy controls in some instances. The main limitations of using tau protein radiotracers are: non-specific binding, the lack of longitudinal data, heterogenous results and the lack of specificity for 4R taupathies. Current generation tau protein radiotracers are inadequate for clinical purposes and need to be refined for viability through future research.

1.Irwin DJ. Tauopathies as clinicopathological entities. Parkinsonism & related disorders. 2016;22 Suppl 1:S29-33. 2. Constantinescu R, Richard I, Kurlan R. Levodopa responsiveness in disorders with parkinsonism: A review of the literature. Movement Disorders. 2007;22(15):2141-8. 3. Alexander SK, Rittman T, Xuereb JH, Bak TH, Hodges JR, Rowe JB. Validation of the new consensus criteria for the diagnosis of corticobasal degeneration. Journal of neurology, neurosurgery, and psychiatry. 2014;85(8):925-9. 4. Alexander SK, Rittman T, Xuereb JH, Bak TH, Hodges JR, Rowe JB. Validation of the new consensus criteria...