Evaluation of cerebral vasomotor reactivity in Parkinson's disease: is there any association with orthostatic hypotension?

Cerebral vasomotor reactivity in neurodegenerative diseases

Small-caliber cerebral vessels change their diameters in response to alterations of key metabolite concentrations such as carbon dioxide or oxygen. This phenomenon, termed the cerebral vasomotor reactivity (CVMR), is the basis for blood flow regulation in the brain in accordance with its metabolic status. Typically, CVMR is determined as the amount of change in cerebral blood flow in response to a vasodilating stimulus, which can be measured by various neuroimaging methods or by transcranial Doppler. It has been shown that CVMR is impaired in cerebrovascular diseases, but there is also evidence of a similar dysfunction in neurodegenerative disorders. Here, we review studies that have investigated CVMR in the common neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and multiple sclerosis. Moreover, we discuss potential neurodegenerative mechanisms responsible for the impairment of CVMR.

Abnormal Cerebrovascular Reactivity in Patients with Parkinson's Disease

Background. Orthostatic hypotension (OH) is an important nonmotor manifestation of Parkinson's disease (PD). Changes in cerebrovascular reactivity may contribute to this manifestation and can be monitored using transcranial Doppler. Objective. To identify possible changes in cerebrovascular reactivity in patients with OH. Methods. Twenty-two individuals were selected and divided into three groups: with and without OH and controls. Transcranial Doppler was used to assess basal mean blood flow velocity, postapnea mean blood flow velocity, percentage increase in mean blood flow velocity, and cerebrovascular reactivity as measured by the breath-holding index. Results. PD patients had lower values of basal velocity (p = 0.019), postapnea velocity (p = 0.0015), percentage increase in velocity (p = 0.039), and breath-holding index (p = 0.04) than the controls. Patients with OH had higher values of basal velocity (p = 0.09) and postapnea velocity (p = 0.19) but lower values of percentage increase in velocity (p = 0.22) and breath-holding index (p = 0.32) than patients without OH. Conclusions. PD patients present with abnormalities in a compensatory mechanism that regulates cerebral blood flow. OH could be an indicator of these abnormalities.

Orthostatic hypotension in patients with Parkinson's disease and atypical parkinsonism

Orthostatic hypotension (OH) is one of the commonly occurring nonmotor symptoms in patients with idiopathic Parkinson's disease (IPD) and atypical parkinsonism (AP). We aimed to review current evidences on epidemiology, diagnosis, treatment, and prognosis of OH in patients with IPD and AP. Major electronic medical databases were assessed including PubMed/MEDLINE and Embase up to February 2013. English-written original or review articles with keywords such as "Parkinson's disease," "atypical parkinsonism," and "orthostatic hypotension" were searched for relevant evidences. We addressed different issues such as OH definition, epidemiologic characteristics, pathophysiology, testing and diagnosis, risk factors for symptomatic OH, OH as an early sign of IPD, prognosis, and treatment options of OH in parkinsonian syndromes. Symptomatic OH is present in up to 30% of IPD, 80% of multiple system atrophy (MSA), and 27% of other AP patients. OH may herald the onset of PD before cardinal motor symptoms and our review emphasises the importance of its timely diagnosis (even as one preclinical marker) and multifactorial treatment, starting with patient education and lifestyle approach. Advancing age, male sex, disease severity, and duration and subtype of motor symptoms are predisposing factors. OH increases the risk of falls, which affects the quality of life in PD patients.

Subthalamic stimulation improves the cerebral hemodynamic response to the cold pressure test in patients with Parkinson's disease

PURPOSE

Disturbances of the autonomic nervous system are common in patients with Parkinson's disease (PD) but the effect of deep brain stimulation of the subthalamic nucleus on cerebrovascular reactivity is not entirely known.

METHODS

Seven patients in an advanced stage of the disease and seven healthy age-matched controls participated in the study, which took place after one night of drug withdrawal. Cerebral blood flow velocity was continuously monitored on both sides with transcranial Doppler ultrasound, and cerebrovascular reactivity (CR) was evaluated with the cold pressure test. The measurements were repeated and compared during the stimulation-on and -off phases.

RESULTS

The PD patients had significantly higher CR values in the stimulation-on than -off conditions (15.1% ± 6.9 versus 9.4% ± 6.2; p = 0.03). CR values were higher in controls than in patients in the stimulation-off condition (20.4% ± 12.5 versus 9.4% ± 6.2; p = 0.007) without a significant difference with the stimulation-on phase.

CONCLUSIONS

CR, evaluated by the response to the cold pressure test, is impaired in patients with advanced PD and improved by subthalamic nucleus.