Objective: To evaluate CVR in people with PD (pwPD) and its acute modulation after Levodopa administration.

Background: Parkinson’s disease (PD) is associated with neurovascular unit dysfunction and reduced cerebrovascular reactivity (CVR) [1]. Levodopa may modulate cerebral hemodynamics through direct vascular effects; however, its acute impact on CVR remains unclear [2].

Method: Twenty pwPD with Hoehn & Yahr scale <4 were enrolled. CVR was assessed using transcranial Doppler with Breath-Holding Index (BHI) at the bilateral middle cerebral arteries in OFF state (≥12 h wash-out) and ON state (1 h after usual Levodopa dose). Sixteen patients completed Doppler assessment. Clinical (MDS-UPDRS part III), autonomic (SCOPA-AUT, orthostatic blood pressure testing), and cognitive evaluations (MoCA, Stroop, verbal fluency) were performed. Patients with significant cerebrovascular stenosis, MMSE<18, and incomplete clinical records were excluded.

Results: Mean BHI in pwPD was reduced compared with normative values (0.757 ± 0.266 vs 1.29 ± 0.31). BHI showed a trend toward a reduction in ON compared with OFF (p = 0.054). In the ON condition, BHI was significantly lower in the contralateral of the more affected motor side (p = 0.035), and within the more affected side, BHI was higher in OFF than in ON (p = 0.030). Basal flow velocities and pulsatility index did not differ significantly between OFF and ON states. ΔBHI correlated inversely with OFF BHI (r = −0.668, p = 0.003). Four patients presented neurogenic orthostatic hypotension, without significant differences in BHI. Levodopa significantly improved UPDRS-III scores (p < 0.001) and Stroop interference performance (p = 0.016), without increasing CVR.

Conclusion: PwPD exhibit reduced cerebrovascular reactivity. Acute Levodopa administration does not enhance hypercapnic vasodilatory reserve and may compress CVR, particularly in the more affected hemisphere, consistent with a vascular “ceiling effect”. Further studies are needed to clarify the longitudinal impact of dopaminergic therapy and the potential role of CVR as a non invasive potential biomarker of neurovascular dysfunction.

References: 1. Brisson, Rodrigo Tavares et al. “Ultrasonographic Changes in Brain Hemodynamics in Patients with Parkinson’s Disease and Risk Factors for Cerebrovascular Disease: A Pilot Study.” Parkinson’s disease vol. 2021 1713496. 5 Oct. 2021, doi:10.1155/2021/1713496
2. Yong, Seok Woo et al. “The effect of levodopa treatment on cerebral hemodynamics in patients with Parkinson’s disease: serial transcranial Doppler studies.” Parkinsonism & related disorders vol. 16,3 (2010): 225-7. doi:10.1016/j.parkreldis.2009.09.003

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cerebrovascular-reactivity-in-parkinsons-disease-acute-effects-of-levodopa-assessed-by-transcranial-doppler/