Abstract

Background
A lthough the transcranial D oppler (TCD) has been used to detect cerebrovascular hemodynamic changes in m igraine patients, the interpretation is limited. Reportedly, the TCD w aveform shows low dimensional chaotic patterns in normal conditions. The purpose of this study is to evaluate the changes of nonlinear parameters of the TCD w aveforms in m igraine patients.
Methods
W e m easured the TCD w aveforms in the middle cerebral artery (MCA) and analyzed the m aximum blood flow velocities. The phase trajectories w ere reconstructed and draw n in a three-dimensional phase portrait. The values of conventional and nonlinear analysis (correlation dimension, D2; the largest Lyapunov exponent, LLE) w ere compared betw een tw o groups.
Results
C erebral blood flow velocities of the left M CA w ere higher in m igraine patients (p<0.05). N onlinear analysis of the TCD time series showed dynamical chaos based on the fractal dimension of the TCD signal and the positive Lyapunov exponents in both groups. The value of D 2 of right M CA w aveform w as decreased in m igraine patients (p<0.05). The D 2 of left M CA w as not different (p>0.05). The LLE did not show any significant trend.
Conclusion
The variability of the TCD signal is not due to a random process but due to a low dynamical chaos. The change of D 2 in m igraine patients seems to be related to changes in compliance and vascular tone, w hich are known to influence the TCD w aveform profoundly. Korean Journal of Headache 7(1):46-49, 2006