Answers
Andrew Schofield, Paul Schofield in The Complete SAQ Study Guide, 2019
Strokes are commonly seen in the elderly population, and are often terminal events. The risk factors for cerebrovascular disease are the same as those for cardiovascular disease, such as hypertension, diabetes, hypercholesterolaemia and smoking. Patients with atrial fibrillation are also at an increased risk of stroke due to the formation of thrombus in the left atrium and subsequent embolisation to the cerebral arteries. The arterial network in the brain is called the Circle of Willis. The anterior communicating artery links the two anterior cerebral arteries, and the posterior communicating arteries link the internal carotid arteries to the posterior cerebral arteries. This allows redistribution of blood flow within the brain if it has been compromised.
Looking at the injured brain
Ross Balchin, Rudi Coetzer, Christian Salas, Jan Webster in Addressing Brain Injury in Under-Resourced Settings, 2017
Strokes tend to occur in fairly specific brain regions. The most commonly affected areas are the three cerebral arteries that supply each hemisphere with blood. The middle cerebral artery (MCA) is commonly involved, but areas of dead tissue (known as infarcts) can also occur in the regions supplied with blood by the posterior cerebral artery (PCA) and the anterior cerebral artery (ACA). Anterior communicating artery strokes, in particular those involving aneurysms, occur in a circular vascular structure that is found at the base of the brain (known as the Circle of Willis). When these aneurysms burst, a haemorrhagic stroke occurs. The structures most commonly affected at the base of the brain are the thalamus, brainstem and basal ganglia.
Fragility
Rudi Coetzer in The Notebook of a New Clinical Neuropsychologist, 2017
As a specific example of how strokes can affect patients, I decide to look at the case of Mr Stevens again, and why his neuropsychology findings were most likely compatible with his neurological diagnosis. To understand Mr Stevens’ case, I realise I first need some very basic knowledge of the blood supply to the brain. The Circle of Willis essentially consists of the anterior communicating artery and the posterior communicating artery, supplied inferiorly (from the direction of the neck) by the two internal carotids and the basilar artery, which itself is supplied by the two vertebral arteries. This explains why humans have four big vessels in their necks, supplying the brain with blood. From the Circle of Willis, on each side (left and right) three important blood vessels travel superiorly (upwards) to irrigate relatively specific regions of the brain. These vessels are the anterior, middle and posterior cerebral arteries respectively. Another, but entirely different type of bleed for the neuropsychologist to be aware of is subarachnoid haemorrhages. These occur when there is a bleed underneath the coverings of the brain, onto the underlying cortical surface, in any area of the brain. Later on I learn from Dr Carstens that new bleeds show up as white on a CT scan because of the iron in our blood, while old strokes show up as black because of water filling the space left by dead tissue.
Beyond descriptive neurology: Broca, cerebral hemodynamics, and cortical function
Published in Journal of the History of the Neurosciences, 2018
Richard Leblanc
The evaluation of CBF in patients suffering a cerebral ischemic attack, as Broca tried to do with thermometry, is now commonplace. Cerebral angiography performed in patients who have suffered a stroke reveals the site of obstruction, the avascular central area about the Sylvian fissure, and the recruitment of collateral channels across the border zones into the penumbra. The importance of collateral channels at the base of the brain in mitigating the effect of stroke was highlighted by Charles Miller Fisher (1913–2012) in a landmark paper on carotid occlusion (1951): The anterior cerebral arteries on the two sides are connected by the anterior communicating artery, which completes the circle of Willis anteriorly. The two posterior cerebral arteries complete the circle of Willis posteriorly. The size of each of these component arteries is highly variable and determines the adequacy of collateral circulation from one side to the other, as well as between the basilar and the carotid systems. In some cases there are probably small arteries on the surfaces of the hemispheres, which provide important connections between the anterior, middle and posterior cerebral arteries. (Fisher, 1951, p. 348)
Oculomotor Nerve Palsy Associated with Duplication of Middle Cerebral Artery, Anterior Communicating Artery Aneurysm, and Parietal Meningioma
Published in Neuro-Ophthalmology, 2019
Ayman G. Elnahry, Gehad A. Elnahry
Isolated oculomotor nerve paralysis occurs most commonly due to diabetes mellitus, hypertension, neoplasia, or intracranial aneurysms, particularly a posterior communicating artery aneurysm.1,2 Anterior communicating artery aneurysms have been rarely reported to cause oculomotor nerve paralysis; however, an associated intracranial hematoma was usually present in these cases.2,3 Fetal-type posterior cerebral artery, a relatively common variant of the posterior cerebral circulation in which the posterior cerebral artery directly originates from the internal carotid artery, is another rarely reported cause of oculomotor nerve paralysis that is postulated to compress the oculomotor nerve when it becomes more tortuous with aging and atherosclerosis.4 Meningiomas have seldom been recognized as the cause of oculomotor nerve paralysis, presumably by causing cerebral oedema and increased intracranial pressure.5 Duplicate MCA is a rare variant of the cerebral circulation that has a reported prevalence of 0.2–2.9% and can be smaller or equal in size to the main MCA.6,7 It has not been previously reported to be associated with oculomotor nerve paralysis. MCA fenestration has also been very rarely reported.8 The authors suspect that the oculomotor nerve palsy in the presented case may have been caused by compression of the oculomotor nerve by the tortuous duplicate MCA on two separate occasions. This compression could have been precipitated by the other associated conditions. Intraoperative confirmation is warranted.
Adenosine-induced transient asystole to control intraoperative rupture of intracranial aneurysms: institutional experience and systematic review of the literature
Published in British Journal of Neurosurgery, 2021
Eric S. Nussbaum, Elizabeth Burke, Leslie A. Nussbaum
Ruptured cerebral aneurysms carry high rates of morbidity and mortality, causing approximately 500,000 deaths worldwide each year.1–3 Up to 40% of ruptured intracranial aneurysms may rupture intraoperatively, and few strategies have been developed that can mitigate the increased rate of treatment-related morbidity and mortality in these cases.4–6 In 2000, we reported the first case in which adenosine-induced transient asystole was utilized in the context of a ruptured aneurysm to control intraoperative bleeding.7 In that case, a complex aneurysm of the anterior communicating artery that was feeding a distal, high flow arteriovenous malformation, bled intraoperatively, and we were unable to control the bleeding using standard techniques. Intravenous adenosine administration resulted in a brief period of asystole and profound hypotension that allowed for safe dissection and clipping of the aneurysm.
Related Knowledge Centers
- Aneurysm
- Anterior Cerebral Artery
- Bitemporal Hemianopsia
- Circle of Willis
- Blood Vessel
- Brain
- Optic Chiasm
- Body
- Longitudinal Fissure
- Circle of Willis
- Visual Field