Abstract
BackgroundParkinson's disease (PD) is the second most common neurodegenerative disorder. As there is no definitive diagnostic test, its diagnosis is based on clinical criteria. Recently transcranial duplex scanning (TCD) of the substantia nigra in the brainstem has been proposed as an instrument to diagnose PD. We and others have found that TCD scanning of substantia nigra duplex is a relatively accurate diagnostic instrument in patients with parkinsonian symptoms. However, all studies on TCD so far have involved well-defined, later-stage PD patients, which will obviously lead to an overestimate of the diagnostic accuracy of TCD.We have therefore set out to conduct a prospective study testing the diagnostic accuracy of TCD in patients with a parkinsonism of unclear origin.Methods/DesignWe will enrol 250 consecutive patients, who are referred to neurology outpatient clinics of two teaching hospitals, for analysis of clinically unclear parkinsonism. Patients, whose parkinsonism is clearly diagnosable at the first visit, will be excluded from the study. All patients will undergo a TCD of the substantia nigra. As a surrogate gold standard we will use the consensus clinical diagnosis reached by two independent, blinded, movement disorder specialist neurologists after 2 years follow-up. At the time of TCD, patients will also undergo a SPECT scan of the brain.DiscussionAs this prospective trial enrols only patients with an early-stage parkinsonism, it will yield data on the diagnostic accuracy of TCD that is relevant to daily clinical practice: The neurologist needs a diagnostic tool that provides additional information in patients with a clinically indefinable parkinsonian syndrome. The above described observational longitudinal study was designed to explicitly study this aspect in the diagnostic process.Trial registration(ITRSCC) NCT00368199
Highlights
Parkinson's disease (PD) is the second most common neurodegenerative disorder
As this prospective trial enrols only patients with an early-stage parkinsonism, it will yield data on the diagnostic accuracy of transcranial duplex scanning (TCD) that is relevant to daily clinical practice: The neurologist needs a diagnostic tool that provides additional information in patients with a clinically indefinable parkinsonian syndrome
In a pilot study with 45 patients with PD or APS who underwent Single Photon Emission Computer Tomography (SPECT) and TCD we found a positive predictive value of 95% of an abnormal TCD for an abnormal FP-CIT SPECT scan [30]
Summary
The hitherto published literature on TCD in parkinsonian syndromes are cross-sectional studies on clinically welldefined patient populations [20,21,22,23,24,25,26,27,28,29,30,45]. The treating neurologist wants a diagnostic tool that provides additional information in patients with a clinically indefinable parkinsonian syndrome. The use of SPECT scans in the diagnostic work-up of parkinsonian patients is still debated, it is widely used [8,19,46]. We feel that this will add to the clinical relevancy of our study results. PD, Parkinson's disease; MSA, multiple system atrophy; PSP, progressive supranuclear palsy; VP, vascular parkinsonism; DIP, drug induced parkinsonism; ET, essential tremor; SPECT, Single Photon Emission Computer Tomography; PET, Positron Emission Tomography; FP-CIT, 123I-ioflupane; TCD, transcranial duplex scanning; SN, substantia nigra; RN, Raphe nuclei; UPDRS, United Parkinson's Disease Rating Scale
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