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Atherosclerosis is the leading cause of death in economically developed countries. The arteries most frequently affected are the aorta, coronary and cerebral arteries. Atherosclerosis only affects large and medium calibre arteries of the general circulation. The lesion involves the arterial intima. The two lesions usually described are lipid striae and atheromatous plaques. The lesions are heterogeneous and it is difficult to correlate them to each other. Atheromatous plaque may be complicated by several types of independent or combined lesions: stenosis of the arterial lumen, haemorrhage into the plaque, ulceration or calcification of the plaque, organisation of a thrombus, aneurysm formation. Lesions predominantly affect the extracranial arteries at the carotid bifurcation and the origin of the vertebral arteries and the cerebral arteries at the origin and termination of the internal carotid artery, the basilar trunk and carotid bulb. The causes of this disease are unknown at the present time. Only the risk factors can be controlled. Pathogenic hypotheses are still highly controversial.

By means of transcranial Doppler (TCD), the author reports intracranial haemodynamic consequences of 57 stenosis or occlusions of the internal carotid artery (ICA), 13 dissections and 44 atheromatous lesions, in 50 patients 32 of whom having had angiography. If a stenosis is significant, the curve of the middle cerebral artery (MCA) becomes dampened and PTI (Pulsatility Transmission Index) diminishes. In this series, the association MCA curve dampened and PTI lower than 0.90 is the evidence of a more than 90% stenosis, except in 2 atheromatous and symptomatic occlusions. No precise explanation for these exceptions is given by literature. An ICA stenosis has also an influence on communicating arteries. In this study, collateralisation by the circle of Willis exists in 14% of 50-75% stenosis, 72.7% of 75-90% stenosis and 100% of more than 90% stenosis. It can depend on anterior communicating artery (ACoA) alone, posterior communicating artery (PCoA) alone or both. Detailed study of the 3 groups leads to the hypothesis of a hierarchy in the function of the communicating arteries, ACoA having the priority.

The most important aspects of normal and pathological brain ageing are considered from a structural, cellular, hemodynamical, chemical and clinical point of view. It seems admitted that cerebral blood flow and cerebral consumption for oxygen decrease with age but when severe health criteria are used to select normal old subjects, no significant differences exist between normal young and optimally healthy elderly. The question arises whether the blood flow reductions are responsible for the alterations in metabolism, or whether it is simply an autoregulatory response to the lesser metabolic demands of the tissue. The part of cerebral arteriosclerosis is questioned on cerebral flow drop accompanying clinical signs in senile mental impairment. Among some cardiovascular risk factors, hypertension seems to play a leading part in acute and chronic neurological diseases associated with age and with certain types of senile dementia (multi-infarct). However in all other cases, hypertension and cerebral vascular insufficiency, for all that this syndrome exists, seem to have been overestimated to explain chronic senile brain deterioration.

The validity of transcranial Doppler (tD) was evaluated for the identification of stenoses of the middle cerebral artery (MCA). Twenty patients with atheromatous stenosis of the proximal MCA of more than 30% (3 of these cases with stenosis of more that 75%) had repeated transcranial Doppler between 1975 and 1987 and conventional angiography. No patient had carotid stenosis nor embolus-producing cardiopathy. Ten patients had had infarcts or transient ischemic attacks (symptomatic group). Ten patients were asymptomatic (asymptomatic group). Cerebral infarcts in the MCA territory occurred in 1 patient of each group and 1 additional patient in each group had an infarct in another territory. Follow-up was possible in 15 patients. The stenosis remained unchanged in 14, occlusion occurred in 1. The results of transcranial Doppler were compared to those of angiograms in this series and in an additional series of 40 patients who had had a normal angiogram. Sensitivity of transcranial Doppler was 60% (75% when stenosis was over 50%). Specificity was 95%. Comparison with angiography findings showed, among causes of failure of tD, analysis of the artery over too short a segment or kinked artery of very long stenoses, or too decreased blood flow. The failure rate of tD due to failure of bone penetration by ultrasounds was 5%. This new reproducible, non-invasive method appears to be able to detect MCA stenoses of 50% or more and help in follow-up.