[Investigation of cerebral autoregulation in Parkinson's disease--a transcranial Doppler study]

The frequent orthostatic intolerance in Parkinson's disease could be the consequence of cardiovascular autonomic failure and/or a damaged cerebral autoregulation (AR). To clarify this question the regulation of cerebral circulation was investigated by polygraphic method.

On a tilt table simultaneous and continuous registrations were made of MCA velocity (V(MCA)) by transcranial Doppler, arterial blood pressure by non-invasive method, and end-tidal CO2, in supine and in tilted positions of 10 degrees, 30 degrees, 70 degrees grades. The cerebral autoregulation was characterized by the slope of the curve of the arterial blood pressure at the level of the Willis-circle (BP(W) as MCA perfusion pressure) plotted against the MCA velocity, achieved by linear regression (y = ax + b function, a=AR, or index of autoregulation).

The data of 17 parkinsonian patients (PP) and eight age-matched controls (C) were analyzed.

The decrease of blood pressure in parkinsonian patients was significantly lower than in the controls when supine position was restored from 70 degrees (deltaABP 70 degrees - 0 degree pp = -3.1 +/- 7.5 Hgmm; deltaABP 70 degrees - 0(C) degrees = -11.1 +/- 7.3 Hgmm; p < 0.05), which suggests a damage to the sympathetic cardiovascular system. A disturbance of the cerebral autoregulation in patients was suggested by a 'progressively decreasing MCA average velocity (V(MCA)) during graded tilt, which was significant at 70 degrees (deltaV(ACM) = 9.8 +/- 8.82% cms(-1); p(C-PP) P 0.5), and by a higher slope of pressure-velocity curve (AR(C) = 0.143 +/- .125% cms(-1)/Hgmm; AR(PP) = 0.38 +/- 0.25% cms(-1)/Hgmm; p(C-PP) < 0.05).

The results show that the cerebral blood flow of patients is more dependent on perfusion pressure compared to healthy controls. The disturbance of the sympathetic cardiovascular system and of cerebral autoregulation could be the consequence of a damage to the postganglionic structures in Parkinson's disease. These results could explain the frequent orthostatic intolerance of patients even with normal blood pressure.