The physiological and clinical significance of nonlinear TCD waveform analysis in occlusive cerebrovascular disease.
In order to compare the results of nonlinear analysis of hemodynamically compromised and noncompromised cerebral circulations we measured consecutive transcranial Doppler (TCD) waveforms of fourteen patients with a unilateral or bilateral occlusion of the internal carotid artery. The cerebral vasomotor reactivity (VMR) to acetazolamide in both middle cerebral artery (MCA) territories was established by using TCD. Conventional TCD data and nonlinear TCD analysis of data were compared. Nonlinear analysis of the TCD time series suggested dynamical chaos based on the fractal dimension of the TCD curve and the positive Lyapunov exponents in the compromised and noncompromised MCA territories. In the areas with the compromised circulation the positive Lyapunov exponents were significantly lower compared to the noncompromised side and in some cases with a negative VMR, the Lyapunov exponent was almost zero. The latter is suggestive for periodic behavior of the impaired cerebral circulation instead of the dynamical chaos which is found under normal conditions. The TCD time series of a hemodynamic compromised cerebral territory not only shows phenomena related to a decreased perfusion pressure (such as a 'damped waveform') but also phenomena which are related to a more prominent periodicity. We speculate that conventional and nonlinear TCD analysis could be used to determine the VMR.
Visée
H F
HF
Department of Neurology and Clinical Neurophysiology, Leyenburg Hospital, The Hague, The Netherlands.
Keunen
R W
RW
Pijlman
H C
HC
Vliegen
J H
JH
Tavy
D L
DL
Stam
K J
KJ
Giller
C A
CA
D000368:Aged; D000369:Aged, 80 and over; D001157:Arterial Occlusive Diseases / Q000000981:diagnostic imaging*; D002560:Cerebrovascular Circulation; D002561:Cerebrovascular Disorders / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017711:Nonlinear Dynamics; D017585:Ultrasonography, Doppler, Transcranial