Levodopa does not change cerebral vasoreactivity in Parkinson's disease

Abstract

The aim of this work was to study cerebral vasoreactivity to hypercapnia in Parkinson's disease (PD) before and after levodopa administration. The prospective study was conducted in 20 patients presenting with PD, using 3T blood oxygenation level-dependent (BOLD) functional MRI (fMRI) covering the whole brain. The hypercapnic stimulus was block-designed using carbogen inhalation, a gas mixture of 7% CO2 and 93% O2, before (OFF) and 60 minutes after administration of a suprathreshold (120%) therapeutic L-dopa dose (ON). Ten age-matched controls were enrolled for between-group comparisons. Analyses were conducted with a random effects model and corrected for multiple comparisons. No adverse reaction to the hypercapnic stimulus was reported. However, 10 patients and 2 controls were excluded because of incomplete protocol realization, inappropriate hypercapnic stimulus, or excessive movements, leaving 10 patients and 8 controls for further analyses. The hypercapnic stimulus increased whole-brain BOLD signal of 1.48% ± 0.06% (mean ± standard error) in controls, 1.59% ± 0.05% in patients OFF, and 1.62% ± 0.09% in patients ON. Regions of interest analyses showed a signal increase in gray matter of 2.60% ± 0.16% in controls, 2.89% ± 0.21% in patients OFF, and 2.87% ± 0.12% in patients ON. No global or regional significant difference was detected, when comparing patients OFF and ON L-dopa, or between patients and controls. Contrary to Alzheimer's disease, the vasoreactivity to hypercapnia was normal in PD before and after L-dopa administration, compared to controls. This negative result is an important finding, especially for neuroscientists using fMRI to investigate motricity and cognition, discarding a significant confounding effect.

Is cerebral vasomotor reactivity impaired in Parkinson disease?

“…To date there have been five studies investigating VMR in IPD [12][13][14][15][16]. Of these five studies, only one study found IPD participants to have impaired VMR in comparison to age-matched HC [16], two studies failed to include a comparative HC group [14,15], whilst the latest studies using novel MRI techniques concurred with the findings of our study [12][13].…”

BOLD fMRI of cerebrovascular reactivity in the middle cerebral artery territory: A 100 volunteers’ study

“…No adverse effects of the hypercapnic challenge were detected, confirming that BOLD fMRI of CVR to hypercapnia is a safe method, which is feasible in clinical practice [4,7,8,20,26,29,[32][33][34]. These results are expected to facilitate the detection of patients at risk of hemodynamical stroke events downstream a severe MCA stenosis.…”

“…Data from one hundred non-smoking right-handed volunteers (41 females, 47.52 ± 21.58 years) were gathered from previous studies [4,7,29] performed in Grenoble Hospital, which were approved by the local University Hospital Ethics Committee. All participants gave their informed consent according to the Declaration of Helsinki.…”

“…For this reason, we conducted a retrospective study on data collected in previous studies among 100 volunteers free from extra or intracranial arterial stenosis [4,7,29]. We had two objectives.…”

Magnetic Resonance Techniques Applied to the Diagnosis and Treatment of Parkinson’s Disease

“…The limitation of these investigations lies in the fact that they are focused on a hypercapnic model. Similar vasoreactivity to hypercapnia for patients with and without levodopa treatment has been observed ( 19 ).…”