Blood Pressure Variability as a Diagnostic Marker for α-Synucleinopathy in Patients With Orthostasis.

BACKGROUND: It is widely accepted that patients with α-synucleinopathy show large blood pressure (BP) variability. We aimed to investigate the diagnostic utility of ambulatory BP monitoring in detecting α-synucleinopathy in patients with orthostasis. METHODS: We prospectively recruited consecutive patients with orthostatic dizziness between December 2021 and February 2024 at the Dizziness Center of a tertiary referral-based hospital in South Korea. All patients underwent a detailed examination using Frenzel goggles and systematic extrapyramidal neurologic examination for eligibility. All patients underwent 24-hour noninvasive ambulatory BP monitoring and head-up tilt table test using a Finometer. RESULTS: Among the 223 patients, 22 (10%) were finally diagnosed with α-synucleinopathy. The diagnosis could have been made with emergence of motor symptoms 1 to 3 years after the presentation in 5 (22%) of the 22 patients. The coefficient of variance of systolic BP (SBP; P=0.023) and differences in the average systolic BP between day and night (P=0.001) were associated with α-synucleinopathy, after adjusting for other covariates. Differences in the average systolic BP between day and night yielded a sensitivity of 76.2% and specificity of 83.6% in discriminating α-synucleinopathy, with an area under the curve of 0.79 (95% CI, 0.66-0.92). The sensitivity and specificity were 77.3% and 71.6% with an area under the curve of 0.80 (95% CI, 0.70-0.90) for the coefficient of variance of systolic BP. CONCLUSIONS: Our findings implicate that ambulatory BP monitoring can help detect α-synucleinopathy in patients with orthostasis. Large BP variability and loss of circadian BP rhythm during ambulatory BP monitoring can serve as early warning signs of α-synucleinopathy, even before the prominent manifestation of motor symptoms.