Is cerebral autoregulation impaired in Parkinson's disease? A transcranial Doppler study.

Orthostatic hypotension (OH) is one of the many autonomic disturbances observed in Parkinson's disease (PD). It has been debated whether an additional impairment of cerebral autoregulation (CA) in PD patients may exacerbate the consequences of OH upon brain perfusion. We assessed CA in PD patients and the potential influence of dopaminergic agents. CA was determined by means of transcranial Doppler (TCD) monitoring of the middle cerebral artery (MCA) at rest and during a thigh cuff release test inducing a systemic blood pressure (BP) drop. Fourteen patients were investigated when taking their usual dopaminergic medication and after drug discontinuation for 12 h. A control group was composed of 11 age-matched subjects (CS). In comparison with PD patients, CS presented a significantly higher increase of the mean cerebral blood flow velocities in the MCA after the BP drop. Mean velocities were increased above the initial values in all CS, whereas a flattened curve was observed in PD patients. No significant differences could be further observed between the PD patients regarding the BP, the cerebrovascular resistance, the heart rate and the pulsatility index. These results provide evidence of an impaired cerebral autoregulation in PD patients which appears independent of dopaminergic treatment.