Treatment of bacterial meningitis is through antibiotics, but viral meningitis cannot be treated with antibiotics because viruses do not respond to that type of drug. Fortunately, the viral forms are milder. In other tissues, water and small molecules are filtered through capillaries as the major contributor to the interstitial fluid.
In the brain, CSF is produced in special structures to perfuse through the nervous tissue of the CNS and is continuous with the interstitial fluid. Specifically, CSF circulates to remove metabolic wastes from the interstitial fluids of nervous tissues and return them to the blood stream. The ventricles are the open spaces within the brain where CSF circulates. In some of these spaces, CSF is produced by filtering of the blood that is performed by a specialized membrane known as a choroid plexus.
The CSF circulates through all of the ventricles to eventually emerge into the subarachnoid space where it will be reabsorbed into the blood. There are four ventricles within the brain, all of which developed from the original hollow space within the neural tube, the central canal. The first two are named the lateral ventricles and are deep within the cerebrum.
These ventricles are connected to the third ventricle by two openings called the interventricular foramina. The third ventricle is the space between the left and right sides of the diencephalon, which opens into the cerebral aqueduct that passes through the midbrain.
The aqueduct opens into the fourth ventricle , which is the space between the cerebellum and the pons and upper medulla Figure 4. Figure 4. Cerebrospinal Fluid Circulation. The choroid plexus in the four ventricles produce CSF, which is circulated through the ventricular system and then enters the subarachnoid space through the median and lateral apertures. The CSF is then reabsorbed into the blood at the arachnoid granulations, where the arachnoid membrane emerges into the dural sinuses.
As the telencephalon enlarges and grows into the cranial cavity, it is limited by the space within the skull. The telencephalon is the most anterior region of what was the neural tube, but cannot grow past the limit of the frontal bone of the skull. Because the cerebrum fits into this space, it takes on a C-shaped formation, through the frontal, parietal, occipital, and finally temporal regions.
The space within the telencephalon is stretched into this same C-shape. The two ventricles are in the left and right sides, and were at one time referred to as the first and second ventricles. The interventricular foramina connect the frontal region of the lateral ventricles with the third ventricle. The third ventricle is the space bounded by the medial walls of the hypothalamus and thalamus. The two thalami touch in the center in most brains as the massa intermedia, which is surrounded by the third ventricle.
The cerebral aqueduct opens just inferior to the epithalamus and passes through the midbrain. The tectum and tegmentum of the midbrain are the roof and floor of the cerebral aqueduct, respectively. The aqueduct opens up into the fourth ventricle. The floor of the fourth ventricle is the dorsal surface of the pons and upper medulla that gray matter making a continuation of the tegmentum of the midbrain. The fourth ventricle then narrows into the central canal of the spinal cord.
The ventricular system opens up to the subarachnoid space from the fourth ventricle. The single median aperture and the pair of lateral apertures connect to the subarachnoid space so that CSF can flow through the ventricles and around the outside of the CNS. Cerebrospinal fluid is produced within the ventricles by a type of specialized membrane called a choroid plexus.
Ependymal cells one of the types of glial cells described in the introduction to the nervous system surround blood capillaries and filter the blood to make CSF.
The fluid is a clear solution with a limited amount of the constituents of blood. It is essentially water, small molecules, and electrolytes. Oxygen and carbon dioxide are dissolved into the CSF, as they are in blood, and can diffuse between the fluid and the nervous tissue.
The choroid plexuses are found in all four ventricles. Observed in dissection, they appear as soft, fuzzy structures that may still be pink, depending on how well the circulatory system is cleared in preparation of the tissue.
The CSF is produced from components extracted from the blood, so its flow out of the ventricles is tied to the pulse of cardiovascular circulation. From the lateral ventricles, the CSF flows into the third ventricle, where more CSF is produced, and then through the cerebral aqueduct into the fourth ventricle where even more CSF is produced. A very small amount of CSF is filtered at any one of the plexuses, for a total of about milliliters daily, but it is continuously made and pulses through the ventricular system, keeping the fluid moving.
From the fourth ventricle, CSF can continue down the central canal of the spinal cord, but this is essentially a cul-de-sac, so more of the fluid leaves the ventricular system and moves into the subarachnoid space through the median and lateral apertures.
The supply of blood to the brain is crucial to its ability to perform many functions. Without a steady supply of oxygen, and to a lesser extent glucose, the nervous tissue in the brain cannot keep up its extensive electrical activity. These nutrients get into the brain through the blood, and if blood flow is interrupted, neurological function is compromised. The common name for a disruption of blood supply to the brain is a stroke.
It is caused by a blockage to an artery in the brain. The blockage is from some type of embolus: a blood clot, a fat embolus, or an air bubble. When the blood cannot travel through the artery, the surrounding tissue that is deprived starves and dies.
Strokes will often result in the loss of very specific functions. A stroke in the lateral medulla, for example, can cause a loss in the ability to swallow.
Sometimes, seemingly unrelated functions will be lost because they are dependent on structures in the same region. Along with the swallowing in the previous example, a stroke in that region could affect sensory functions from the face or extremities because important white matter pathways also pass through the lateral medulla. Loss of blood flow to specific regions of the cortex can lead to the loss of specific higher functions, from the ability to recognize faces to the ability to move a particular region of the body.
Many aneurysms also occur within the circle of Willis, although the risk of rupture may be less than it would be in smaller arteries. A subarachnoid hemorrhage occurs when blood leaks into the space between two membranes surrounding the brain. Issues with blood vessels can cause the….
Stroke blocks the blood supply to the brain and can be life threatening. Learn more about strokes, including the types, symptoms, and how treat and…. Strokes are the fifth-leading cause of death in the U. Men tend to be younger than women when they have strokes, and some symptoms are more common…. When they rupture, they can cause a stroke. Learn about their symptoms…. What are the causes and risk factors of an ascending aortic aneurysm? What are the different types, how is it diagnosed and can it be prevented?
What is the circle of Willis? Medically reviewed by Seunggu Han, M. What it is Function Structural differences Associated conditions Summary The circle of Willis is a junction of several important arteries at the bottom part of the brain. What is it? Share on Pinterest. Structural differences. Associated conditions. Exposure to air pollutants may amplify risk for depression in healthy individuals. Costs associated with obesity may account for 3. Related Coverage.
What to know about subarachnoid hemorrhage. Medically reviewed by Seunggu Han, MD. Warning signs of stroke in men. What to know about brain aneurysms. Ascending aortic aneurysm: What you need to know. Thus, this systematic review and meta-analysis aimed to determine the pooled measure association between the anatomical variations of the COW and ischemic stroke using the available studies.
The reporting of the current systematic review and meta-analysis followed the preferred reporting items for systematic reviews and meta-analysis statements Additional file 1 [ 33 ]. In this review, assessing the association between COW and ischemic stroke was the primary outcome. Vessels in COW were defined as a patent, occlude, anomaly, incompleteness, or variation by using an imaging technique. Besides, reference lists of identified studies were navigated for the presence of additional studies.
The primary search was conducted in the PubMed database. The inclusion criteria for this review were studies published in the English language and carried out in any country. Published or unpublished full studies that reported a measure of association between the variation anomaly, hypoplasia, or absent vessels in COW and ischemic stroke were included.
When the information needed to consider eligibility was missing, animal-based experimental studies, cadaveric studies, and the study that did not report a direct association was excluded. In this review, the study quality was evaluated using the Newcastle—Ottawa Quality Assessment Scale for case—control and cohort studies Additional file 2 [ 34 ].
This quality assessment scale has three sections: the first focuses on selection , the second comparability , and the third section exposures, the outcome for cohort study.
Disagreements between reviewers were solved by taking the average score of the two reviewers. In the end, we considered good quality if the study scored six and above points on all quality assessment items. All essential data were extracted using a standardized data abstraction template.
After the removal of duplicate articles, all eligible studies were screened based on title and abstract for possible inclusion. Full-text articles were screened and reviewed for the entirety to identify the final inclusion. Qualitative and quantitative data were extracted by two reviewers MO and AM from selected studies using a predetermined data collection template.
Interestingly, publication year, main author, sample size, response rate, age of participants, study country, study design, duration of the study, sex of participants, the site of COW, imaging technique, branches of COW, the measure of association odds ratio with its confidence interval , and other risk factors of ischemic stroke were included in the data abstraction template.
The data were extracted in Microsoft Excel logarithm of the odds ratio and standard error of the logarithm of the odds ratio for each study was calculated and exported into STATA for further analysis. The heterogeneity across studies was assessed by using the Cochrane Q test statistic chi-square statistic with k-1 degree of freedom, P-values , and I 2 I-Squared test statistic.
Therefore, the fixed-effect model was applied to estimate the pooled effect of the measure of association between COW and ischemic stroke [ 36 ]. Visually, we used the Galbraith plot and Forest plot to assess the presence of heterogeneity across studies. Meta-cumulative of the measure of association between COW and ischemic stroke was presented.
In all cases, a P-value of less than or equal to 0. Significant publication bias was considered if a P-value became less than or equal to 0. A total of articles were initially retrieved on the association between COW and ischemic stroke, of which thirty-four were excluded due to duplicated articles. Of sixty-eight articles, thirty-three articles were excluded after reviewing their titles and abstracts, it was non-essential.
All included studies were prospective cohort and case—control study design, two prospective cohort, and four case—control studies [ 17 , 38 , 39 , 40 , 41 , 42 ].
The lowest and highest mean age of the respondents was 36 years and The studies included participants, ranging from to [ 41 , 42 ]. The largest study was carried out in Netherland. From all studies, two conducted in Netherland [ 40 , 41 ], one in Taiwan [ 38 ], one in the United States [ 39 ], one in Poland [ 17 ], and one in Albania [ 42 ]. The total number of participants included in this study were participants Table 1.
By using the Newcastle—Ottawa Quality Assessment Scale criteria, the quality score of the included studies was ranged between six-point and nine-points. All studies scored above six points. Therefore, no studies were included that had poor quality in this review. Hypertension was the most common comorbid condition across the studies, followed by diabetes mellitus, smoking, coronary artery disease, and hyperlipidemia.
The mean age of ischemic stroke patients was significantly higher than the control groups [ 42 ] Table 3. In this meta-analysis, six original studies, participants were involved to estimate the pooled effect measure between COW and ischemic stroke. Therefore, the pooled odds ratio was 1. As a result, the fixed-effect model was used to estimate the pooled effect of the measure of association between COW and ischemic stroke. The participants with variation, incompleteness, or hypoplasia in any part of the circle of Willis were 1.
Forest plot of the pooled measure of association between the circle Willis and ischemic stroke, The Galbraith plot also visualized all studies based on their country and it indicated that there is no variability between the studies as studies are located within its confidence interval limits Fig. The Galbraith plot provided a graphical display of the amount of heterogeneity from a meta-analysis.
This plot displayed the coefficient over the standard error of the coefficient is plotted against the inverse of the standard error, known as the study precision. The position of each study country on the horizontal axis indicated the weight allocated to it in a meta-analysis while the position on the vertical axis gave the contribution of each study to the Q statistic for heterogeneity.
Galbraith plot showing the variability of individual measure of association between the circle Willis and ischemic stroke by study country, This study describes the cumulative effect of the association between COW and ischemic stroke from to The significance of the association was increased successively from each year Fig. Meta-cumulative of the measure of association between the circle Willis and ischemic stroke by study country, The statistically non-significant association between variation in PcomA and ischemic stroke was observed [pooled OR: 1.
The respondents who had hypoplasia or incomplete PcomA were 1. Forest plot of the pooled measure of association between hypoplasia of posterior communicating artery and ischemic stroke, The association between variation like incompleteness in AcomA and ischemic stroke was estimated and the statistically non-significant positive association was detected [pooled OR: 1.
The participants who had variation incompleteness in AcomA were 1. Forest plot of the pooled measure of association between variation in anterior communicating artery and ischemic stroke, The Galbraith plot visual display showed that the non-variability between studies Fig.
Galbraith plot that shows the variability in measure of association between variation in anterior communicating artery and ischemic stroke, This systematic review and meta-analysis were employed to determine the association between the variation of COW and ischemic stroke. Stroke is one of the leading causes of death and disability in the United States. The American Heart Association and American Stroke Association estimated the number of new strokes that occurred each year has become increasing [ 10 ].
It may not be different in this regard in developing countries too. Even though there are some studies done in some countries that provide data on the association between COW and ischemic stroke, very few of these gave a direct measure association with dichotomous outcomes including cases and controls or exposed and unexposed, which allow comparability between the studies. The data in this review provide estimates of the variational impact of COW on ischemic stroke in different countries of the world.
In this systematic review and meta-analysis, a total participants were included to estimate the pooled measure of association. In most studies, hypertension was the most common comorbid condition in groups, followed by diabetes mellitus, smoking, hyperlipidemia, and coronary artery disease [ 17 , 38 , 40 , 41 , 42 , 44 ]. This review showed there was no heterogeneity across the studies. A fixed-effect model estimated that the participants with variation, incompleteness, or hypoplasia in any part of the circle of Willis were 1.
This finding is in agreement with the reviews conducted by the American Heart Association [ 45 , 46 ], having internal carotid artery stenosis may predispose to the development of ischemic stroke. The time trend of the significance and the association increases over time due to the accumulative effect of studies over the successive year.
The pooled effect of the measure of association was relatively free from the publication bias. In this review, we tried to associate COW variants and ischemic stroke.
The PcomA is a principal collateral circulation pathway and the source of numerous penetrating arteries that supply the ventrolateral and dorsomedial thalamic nuclei, as well as the lateral aspect of the thalamic pole, cerebral peduncle, tuber cinereum, and mammillary bodies. PcomA hypoplasia is a congenital variant of the COW characterized by a narrow, underdeveloped PcomA with restricted blood flow [ 38 ]. As reviewed articles have shown, the PcomA hypoplasia is associated with the risk of ischemic stroke, even in the absence of ICA occlusion.
The most common ischemic event, in those who had PcomA hypoplasia, was ipsilateral thalamic lacunar infarctions with or without occipital lobe involvement [ 38 ]. On the other hand, an incomplete anterior COW combined with an incomplete posterior COW is associated with anterior circulation stroke. An incomplete anterior COW and a one-sided or two-sided incomplete posterior COW are positively associated with anterior circulation stroke [ 41 ]. The variations of COW are clinically important.
It plays an important role in cerebral hemodynamics and collateral anastomotic network. Therefore, individuals who have effective collateral circulations are less at risk of developing ischemic stroke than those with ineffective collateral circulations [ 23 , 24 , 25 , 26 , 28 , 29 ]. This review provided cumulative evidence on qualitative and quantitative data between the variation in the circle of Willis and ischemic stroke; give a better understanding between the nature of the circle of Wills and the development of the disease.
The review limitation was the consideration of studies published in English. Besides, this meta-analysis represented only the studies from the six countries. This systematic review and meta-analysis showed that there was a non-significant positive association between the variation of the circle of Willis and ischemic stroke. Therefore, the authors recommend that, special awareness creation for the people to focus on primary prevention by undergoing early screening about the status of circle Willis through imaging technique.
By doing so, the stroke-prone individuals will be identified and targeted for particular interventions. Prevention remains the cornerstone of therapy for these devastating diseases. Baburao P, Kardile B, et al. Anatomical variation in anterior communicating artery.
J Clin Diagn Res. Google Scholar. Karatas A, et al. Assessment of the circle of Willis with cranial tomography angiography. Med Sci Monitor. Article Google Scholar. Paul S, Mishra S. Variations of the anterior cerebral artery in human cadavers: a dissection study. J Anat Soc India. Clinically oriented Anatomy, Head, the brain. Lippincott Williams Wikins Philadelphia.
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