Traubner P

Stroke risk factors and development of collateral flow in carotid occlusive disease

Background and purpose – Blood flow through collateral vessels compensates for reduced blood flow through stenotic or occluded extracranial carotid arteries. Previous studies have shown that extent of collateral flow influences likelihood of stroke and its outcome. Here we analyzed the relationship between stroke risk factors (hypertension, coronary artery disease, diabetes mellitus, tobacco smoking and hypercholesterolemia) and number of patent intracranial collaterals detected by transcranial Doppler ultrasonography. Subjects and methods – We studied 182 patients with various degrees of angiography proven unilateral stenosis of the internal carotid artery. Contribution of the anterior and posterior communicating arteries to the perfusion of the cerebral hemisphere on the side of the stenosis or occlusion was evaluated by a series of compression tests performed during continuous insonation of the middle cerebral artery. The number of detected collateral vessels was correlated with analyzed stroke risk factors. Results – Subjects with stenosis more than 75% or occlusion of the internal carotid artery had a higher frequency of two major intracranial collateral vessels (P0.01 and P0.001, respectively). Hypertensive patients with stenosis more than 75% or total carotid occlusion were more likely to have only a single collateral vessel than patients without hypertension (P0.01 and P0.05, respectively). Other risk factors did not influence the patency of preformed collateral vessels. Conclusions – Hypertension hindered the development of preformed intracranial collateral vessels in our patients with carotid occlusive disease.

Blood flow velocities in basilar artery during rotation of the head

The authors measured blood flow velocities with transcranial Doppler ultrasonography in the basilar artery after extreme rotations of the head. Studied subjects were divided in two groups according to the degree of asymmetry of the vertebral artery lumens. Rotation of the head caused significant reduction of the mean flow velocity in the basilar artery in the subjects with asymmetry of the vertebral arteries of more than 75%. The decline occurred only after the rotation ipsilaterally to the hypoplastic vertebral artery. This study confirms the importance of the collateral flow in the compensation of dynamic compression of the vertebral artery.

Short-term prognosis of stroke due to occlusion of internal carotid artery based on transcranial Doppler ultrasonography.

Background and Purpose The clinical course of stroke due to occlusion of the internal carotid artery is influenced by amount of collateral flow. We measured mean frequency shifts in the middle cerebral artery by transcranial Doppler ultrasonography to determine its prognostic value. Methods Patients with proven extracranial occlusion of the internal carotid artery and ipsilateral hemispheral stroke were enrolled in our study. We performed transcranial Doppler ultrasonography on 31 patients within 48 hours after the stroke onset and followed up 25 patients in 28 days. At the same time, neurological examination with quantification of neurological deficit was done. We correlated values of flow frequency shifts on the side of stroke with degree of neurological deficit at the onset and at 28 days as well as the degree of clinical improvement and the value of frequency shifts. Results We found a negative correlation between blood flow frequency shifts in the middle cerebral artery and degree of neurological deficit at the onset (Spearman rank correlation coefficient, −0.567; p<0.001). We also found a positive correlation between the change of the neurological deficit during follow-up and frequency shifts at the onset (Spearman rank coefficient, 0.548; p<0.05). Conclusions Diminished blood flow velocity (mean frequency shift) in the area of stroke is a negative prognostic factor for the degree of neurological deficit at the onset and a negative prognostic factor for possible improvement. Knowledge of hemodynamic conditions in the stroke area may help to improve therapeutic decisions.

THE RELATION OF GEOGRAPHICAL AND METEOROLOGICAL FACTORS TO THE OCCURRENCE OF MULTIPLE SCLEROSIS IN CZECHOSLOVAKIA

In Czechoslovakia a part of the territory situated between 48–49°. No latitude, with about 1.4 million inhabitants, was studied as to the prevalence of multiple sclerosis. The territory studied was divided into a part having a yearly mean temperature of 10° C and an altitude of 0–137 m and another part with a yearly mean temperature of 8° C and an altitude of 145–500 m. The prevalence of multiple sclerosis in both geographical territories was compared. Moreover, the seasonal incidence of multiple sclerosis was investigated and the incidence of the disease in the warmer (April‐September) and the colder (October‐March) halves of the year was compared. The prevalence was significantly higher in the region having a lower mean temperature and a greater altitude. This relation was more conspicuous when the place of birth rather than the place of residence was taken into account. No significant difference was found for frequency of onset of the disease between the warmer and the colder part of the year.