Results confirm the high-pass filter model of cerebral autoregulation: Normal subjects showed predicted positive phase shift angles between CBFV and ABP oscillations. Patients with expected autoregulatory disturbances showed significant decreases in phase shift angles. Close correlations existed between autoregulation and CO2-induced vasomotor reactivity.

The relationship between spontaneous oscillations in cerebral blood flow velocity (CBFV) and arterial blood pressure (ABP) was analysed in normal subjects in order to evaluate whether these relationships provide information about cerebral autoregulation. CBFV was measured using transcranial Doppler sonography and continuous ABP and heart rate using Finapres in 50 volunteers. Measurements were made over 5 min in a supine position and 6 min in a tilted position. Coefficients of variation were calculated using power- and cross-spectral analysis in order to quantify amplitudes within two frequency ranges: 3-9 cycles per min (cpm) (M-waves); and 9-20 cpm (R-waves). Correlations, coherence values, phase angle shifts and gains were also computed between corresponding waves in CBFV and in ABP. A clear correlation was seen for M-waves and R-waves between CBFV and ABP and coherence values were large enough to calculate phase angle shifts and gains. Phase angles for M-waves were larger and gains lower than was the case for R-waves, either tilted or supine. These data are consistent with a highpass filter model of cerebral autoregulation. Relatively high CBFV/ABP gain values (between 1.4 and 2.0) suggest that the principle of frequency-dependent vascular input impedances has to be considered in addition to autoregulatory feedback mechanisms. Spontaneous ABP oscillations in the M-wave and R-wave ranges may serve as a basis for continuous autoregulation monitoring.

Livedo is a cutaneous sign of striking violaceous netlike patterned erythema of the skin. This dermatological phenomenon is of special interest in the differential diagnosis in neurological patients. In 1907 Ehrmann distinguished two different patterns of livedo: the pathological livedo racemosa and the physiological livedo reticularis. Despite important clinical differences, in the English language literature the heading livedo reticularis is still used for all types of livedo. A literature review about the spectrum of differential diagnosis in patients with livedo reticularis (especially cutis marmorata and amantadine-induced livedo reticularis) and livedo racemosa (especially Sneddon's syndrome, Divry-van Bogaert syndrome, systemic lupus erythematosus, antiphospholipid antibody syndrome, polyarteritis nodosa, cholesterol embolization syndrome, livedoid vasculopathy and haematological diseases) is provided.

We compared results from non-invasive autonomic testing [sympathetic skin responses (SSR), heart beat variation during deep breathing, and orthostatic manoeuvre with transcranial Doppler monitoring in 22 patients] with motor and somatosensory evoked potentials (MEP and SEP) in 30 unselected patients with multiple sclerosis. We found a similarly high yield of pathological results for SSR, MEP and SEP (66.7%, 65.5%, and 69%, respectively). When analysed for each limb (n = 120), SSR were highly correlated with MEP and SEP (for both P < 0.001). Heart beat variation was reduced in only 3 patients. In 4 of 22 patients orthostatic manoeuvre induced a pathological decrease in cerebral blood flow velocity despite normal systemic blood pressure being maintained. We conclude that SSR may be a useful additional diagnostic tool in patients with multiple sclerosis. Cerebral dysautoregulation is a rather frequent finding, although its significance is not known.

No abstract