Modification of low-frequency spontaneous oscillations in blood flow velocity in large- and small-artery disease.

During a 30-minute period, the blood flow velocity of both middle cerebral arteries (MCAs) was measured bilaterally in 27 patients with obstructive carotid disease (n = 18, large-artery disease) or subcortical vascular encephalopathy (n = 9, small-artery disease) and in control subjects of similar age and sex distribution (n = 14). To identify low-frequency spontaneous oscillations (LFSOs), MCA envelope curves were Fourier transformed with filter application to select low-frequency spectra (0.01-0.05, 0.05-0.15, 0.15-0.50 Hz). To measure the extent of LFSO amplitudes, a coefficient of variation (CoV) was calculated. In addition, a coefficient of correlation (CoC) was calculated to assess LFSO bilateral synchronicity. Normal ranges for CoV (mean = 5.38 +/- 1.82%) and CoC (mean = 0.91 +/- 0.06) were established in control subjects. In patients with large-artery disease, a significant CoV reduction was observed ipsilateral to the carotid lesion (CoV mean = 3.91 +/- 1.10%; p < 0.05, Wilcoxon's test) with a contralateral compensatory increase (CoV mean = 5.68 +/- 1.79%). In addition, a significant desynchronization of LFSOs was found in patients with large-artery disease (CoC = 0.39 +/- 0.35, p < 0.05). This was less obvious in patients with small-artery disease, who demonstrated a marked bilateral reduction of LFSO activity (CoV mean = 3.60 +/- 0.71%, p < 0.05) and CoC values.(ABSTRACT TRUNCATED AT 250 WORDS)