Prodromal parkinsonism motor changes could help early diagnosis
MedWire News: Parkinson's disease could be diagnosed at an early stage with the use of simple quantitative motor measures, suggest researchers.
They used direct assessment of motor examination before parkinsonism in patients with a rapid eye movement (REM) sleep behaviour disorder who are at increased risk for developing Parkinson's disease.
"Based on our analysis, we estimate that total UPDRS [Unified Parkinson's Disease Rating Scale] first becomes abnormal approximately 4.5 years before diagnosis," Jacques Montplaisir (Hôpital du Sacré-coeur de Montréal in Quebec, Canada) and colleagues report.
A total of 78 patients participated in the study, of whom 20 were diagnosed with parkinsonism, according to standard criteria, by a movement disorders specialist.
Motor testing carried out in the years preceding diagnosis was assessed and compared against that for healthy individuals.
Abnormal UPDRS scores were detected in the patients who developed parkinsonism about 4.5 years before diagnosis, with other quantitative motor tests deviating from normal even earlier, at 8.6 years for the Purdue Pegboard, 8.2 years for the alternate-tap, and 6.3 years for the timed up-and-go test.
The first signs of parkinsonism to develop were voice and facial akinesia, occurring approximately 9.8 years before diagnosis, followed by rigidity (4.4 years), gait abnormalities (4.4 years), and limb bradykinesia (4.2 years).
The sensitivity and specificity of the motor measures declined in line with the length of duration preceding diagnosis. However, the alternate-tap test and the Purdue Pegboard were able to predict eventual diagnosis of parkinsonism even 3 years before diagnosis, with a sensitivity and specificity of between 71% and 82%.
A UPDRS score above 4 predicted future parkinsonism at a sensitivity of 88% and a specificity of 94% at 2 years before diagnosis. Removal of action tremor scores improved the sensitivity and specificity to 94% and 97%, respectively, based on a score above 3.
The researchers note in Brain that it was difficult to distinguish between different types of parkinsonism, but they found that prodromal dementia with Lewy bodies appeared to have a slower progression than Parkinson's disease, with prodromal intervals of 6.0 versus 3.8 years.
They conclude: "Simple quantitative motor measures may be capable of reliably predicting parkinsonism, even before a clinical diagnosis can be made by experienced movement disorders neurologists."
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By Lucy Piper