Stroke Review (KCP PDF)

Stroke Review newer slide updated Learning outcomes 1. Describe the blood supply of the brain 2. Recognise the difference between anterior and posterior circulations 3. Describe the structure of the cerebral cortex 4. Understand the sensory...

Stroke Review newer slide updated Learning outcomes 1. Describe the blood supply of the brain 2. Recognise the difference between anterior and posterior circulations 3. Describe the structure of the cerebral cortex 4. Understand the sensory and motor functions of the cerebral cortex 5. Describe the language functions of the cerebral cortex 6. Describe the organisation of the motor and sensory pathways in the spinal cord 7. Recognise the features of Parkinson’s disease 8. Recognise presentation of a stroke and transient ischaemic attack 9. List the risk factors for a stroke 10. Outline initial investigation of a stroke 11. Describe the key features of a randomised, double blind, placebo-controlled study 12. Outline initial treatment of an acute stroke The brain Uses 20% of total energy expenditure Independent of how hard you think! Blood supply critical to deliver oxygen and nutrients Needs sleep 86 billion neurons with a quadrillion synapses ( a 1 with 15 “0”s) Movement and balance Stroke 1  Hearing, vision, touch Speech and language Emotions and mood Breathing, circulation, appetite, thirst Dreams and ideas We have a motor and a sensory cortex Stroke 2  Movement - how we interact with the world Certain parts of the body are overrepresented in the brain eg face and hands Stroke and TIA Due to interruption of blood supply to the brain Stroke 3  TIA to stroke is on a spectrum 90% of TIA resolve within 90 minutes Risk increases with age and more common in men Treatment of a stroke How do we decide how to treat a stroke? Understand brain anatomy and physiology Understand underlying pathogenesis Arteries supplying the brain Stroke 4  Arterial blood supply to the heart Stroke 5  Treatment of stroke Aspirin had been shown to be of benefit in myocardial infraction Reduces the stickiness of platelets Heparin thins blood and used to treat clots in veins How could we find out if either is beneficial in strokes? Conclusion Aspirin reduced risk of further ischaemic strokes Heparin reduced risk of further ischaemic strokes BUT increased risk of brain haemorrhage Standard treatment of stroke is oral aspirin initially + Stroke lifetime risk: 1 in 4 men, 1 in 5 women A clinical stroke is characterised by: Rapid onset focal neurological symptoms and/or signs lasting >24 hours (or leading to death) with no apparent cause other than vascular Stroke 6  Conditions that may mimic stroke: Brain tumour, brain abscess Bleed around the brain Hypoglycaemia Neurological condition affecting the brain eg multiple sclerosis epileptic seizure Modifiable risk factors for a stroke Hypertension: lower blood pressure, salt Smoking: stop smoking Hyperlipidaemia: statins, diet, exercise Diabetes melitus: weight loss, sugar content Excessive alcohol intake: decrease alcohol Atrial fibrillation: modify clotting of blood 10 factors for population attributable risk of stroke 1. Hypertension 2. Lack of Regular physical activity 3. Obesity 4. Hyper-lipidaemia 5. Smoking 6. Diet risk score 7. Cardiac causes 8. Diabetes 9. Stress, depression Treatment after an acute stroke Aspirin Blood pressure control Stroke 7  Statins for increased cholesterol Stroke unit vs conventional ward Carotid surgery for Carotid stenosis Anticoagulation for Atrial fibrillation What are the causes of stroke? Infarction (85%) Atherothromboembolism 50% Intracranial small vessel disease 25% Embolism from heart 20% Rarities 5% Haemorrhage 15% How do we decide how to treat a stroke Understand brain anatomy and physiology Understand underlying pathogenesis The brain and spinal cord are delicate and so they have two protective coverings The outer covering consists of bone: cranial bones encase the brain; vertebrae encase the spinal cord The inner covering consists of membranes known as meninges. Three distinct layers compose the meninges Dura mater the outermost, toughest and most durable layer made of thick, dense connective tissue that helps protect the brain and spinal cord Arachnoid mater Middle, web-like membrane Stroke 8  Thinner and more delicate than the dura mater Pia mater innermost layer, which is thin and tightly adheres to the surface of the brain and spinal cord, following all the contours and folds of the brain Highly vascular, meaning it has many blood vessels that provide nutrients and oxygen to the brain and spinal cord Stroke 9  The central nervous system Stroke 10  Coverings of the brain. A, Coronal (frontal) section of the superior portion of the head, as viewed from the front. Both the bony and the membranous coverings of the brain can be seen. B, Sagittal section of the skull, viewed from the left. The dura mater has been retained in this specimen to show how it lines the inner roof of the cranium and the falx cerebri extending inward. Stroke 11  Coverings of the spinal cord. The dura mater is shown in purple. Note how it extends to cover the spinal nerve roots and nerves. The arachnoid mater is highlighted in pink and the pia mater in orange. The dura mater has three important inward extensions: Falx cerebri projects downward into the longitudinal fissure to form a kind of partition between the two cerebral hemispheres Falx cerebelli sickle-shaped extension that separates the two hemispheres of the cerebllum Tentorium cerebelli Separates the cerebellum from the cerebrum. A number of spaces lie between and around the meninges. Three of the spaces are the following: Epidural space Subdural space Subarachnoid space Stroke 12  Formation of cerebrospinal fluid occurs mainly by separation of fluid from blood in the choroid plexuses Choroid plexuses are a network of capillaries that project from the pia mater into the lateral ventricles and into the roofs of the third and fourth ventricles. Stroke 13  A, The CSF produced by filtration of blood by the choroid plexus of each ventricle flows inferiorly through the lateral ventricles, interventricular foramen, third ventricle, cerebral aqueduct, fourth ventricle, and subarachnoid space and to the blood. B, Inset showing arachnoid villus, where CSF is reabsorbed into the blood of the superior sagittal sinus. C, Simplified diagram showing flow of CSF. The cerebrum consists of the right and left cerebral hemispheres The surface of the cerebrum - called the cerebral cortex - is made up of grey matter only 2 to 4 mm thick Though, cerebral cortex has 6 layers, each composed of millions of axon terminals synapsing with millions of dendrites and cell bodies of other neurones Wrinkling in the surface of the brain regions provide great advantages Stroke 14  Such folding increases the total amount of grey-matter surface area and thereby increasing the processing power of cerebrum and cerebellum Stroke 15  Beneath the cerebral cortex lies the large interior of the cerebrum It is mostly white matter made up of numerous tracts Tracts that make up the cerebrum’s internal white matter are of three types projection association commissural Stroke 16  A, Lateral perspective, showing various association fibres. B, (Coronal) perspective, showing commissural fibres that make up the corpus callosum and the projection fibres that communicate with lower regions of the nervous system. C, Magnetic resonance (MR) tractography image showing a three- dimensional view of tracts colour-coded by direction, as seen in a brain viewed from above. Note the band of fibres in the corpus callosum connecting the two cerebral hemispheres. Projection tracts are extensions of the ascending, or sensory, spinothalamic tracts and descending, or motor, corticospinal tracts Association tracts Most numerous of cerebral tracts Extend from one convolution to another in the same hemisphere Commissural tracts Extend from a point in one hemisphere to a point in the other hemisphere Compose the corpus collosum and the anterior and posterior commissures Stroke 17  A, The basal nuclei seen through the cortex of the left cerebral hemisphere. B, The basal nuclei seen in a coronal (frontal) section of the brain. The caudate nucleus, internal capsule, and lentiform nucleus constitute the corpus striatum Basal nuclei is involved in regulating voluntary motor functions, thinking and learning Cerebral plasticity - brains ability to adapt and reorganise its functions in response to injury, experience, or change over time The postcentral gyrus functions mainly as a general somatic sensory area It receives impulses from receptors activated by heat, cold and touch stimuli The precentral gyrus functions as the somatic motor area. Impulses from neurons in this area descent over motor tracts and eventually stimulate somatic effectors, the skeletal muscles The transverse gyrus of the temporal lobe serves as the primary auditory area. Stroke 18  The primary visual areas are in the occipital lobe. It is important to remember that no part of the brain functions alone. Many structures of the central nervous system must function together for any one part of the brain to function normally. The somatic senses include sensations of touch, pressure, temperature, body position, and similar perceptions that do not require complex sensory organs The special senses include vision, hearing, and other types of perception that require complex sensory organs, such as the eye and the ear Sensory fibres carrying information from receptors in specific parts of the body terminate in specific regions of the somatic sensory area Areas such as the face and hand have a proportionally larger number of sensory receptors, so their part of the somatic sensory map is larger Likewise, information regarding vision is mapped in the visual cortex, and auditory information is mapped in the primary auditory area Information sent to the primary sensory areas is in turn relayed to the various sensory association areas, as well as to other parts of the brain. There the sensory information is compared and evaluated. Eventually, the cortex integrates separate bits of information into whole perceptions The precentral gyrus constitutes the primary somatic motor area Stroke 19  A secondary motor area lies in the gyrus immediately anterior to the precentral gyrus Neurons in the premotor area just anterior to the precentral gyrus are thought to activate groups of muscles simultaneously. Consciousness depends on excitation of cortical neurons by impulses conducted to them by a network of neurons known as the reticular activating system. The reticular activating system (RAS) consists of centres in the brainstem’s reticular formation that receive impulses from the spinal cord and relay them to the thalamus and from the thalamus to all parts of the cerebral cortex Both direct spinal reticular tracts and collateral fibres from the sensory tracts (spinothalamic, lemniscal, auditory, and visual) relay impulses over the reticular activating system to the cortex Without continual excitation of cortical neurons by reticular activating impulses, an individual is unconscious and cannot be aroused Two current concepts about the reticular activating system Functions as the arousal or alerting system for the cerebral cortex Its functioning is crucial for maintaining consciousness Drugs known to depress the reticular activating system decrease alertness and induce sleep. Stroke 20  Reticular activating system (RAS). Consists of centres in the brainstem’s reticular formation plus fibres that conduct to the centres from below and fibres that conduct from the centres to widespread areas of the cerebral cortex. Functioning of the RAS is essential for regulating levels of consciousness. Emotions involve functioning of the cerebrum’s limbic system Stroke 21  Structures of the limbic system The cortex is capable of storing and retrieving both short-term and long-term memory. Short-term memory involves the storage of information over a few seconds or minutes Region Structure Function Elongated cylinder extending from the brainstem through the foramen magnum of the skull; Integration of simple, subconscious Spinal cord grey matter interior surrounded spinal reflexes; conduction of nerve by white matter; 31 pairs of impulses spinal nerves attached by dorsal and ventral nerve roots Numerous synapses and interneurons arranged into Integration of spinal reflexes and Grey matter anterior, lateral, and posterior filtering of information going to higher grey columns linked by a grey centres (as in gated pain control) commissure Myelinated nerve tracts Ascending tracts conduct sensory arranged into anterior, lateral, information to higher CNS centres; White matter and posterior white columns descending tracts conduct motor (funiculi) information from higher CNS centres Stroke 22  Extends inferiorly from diencephalon to foramen magnum of skull, where it meets the spinal cord; central grey Subconscious integration of basic Brainstem matter nuclei surrounded and vital functions connected by white matter tracts; 10 of the 12 pairs of cranial nerves attached here Inferior region of brainstem Integration of cardiac, vasomotor Medulla between the spinal cord and the (vessel muscle), respiratory, digestive oblongata pons and other reflexes Integration of numerous autonomic Intermediate region of brainstem reflexes mediated by cranial nerves V, Pons between the medulla and the VI, VII, and VIII (see Chapters 21 and midbrain 22 ) and respiration Integration of numerous cranial nerve Superior region of the brainstem reflexes, such as eye movements, Midbrain between the pons and the pupillary reflex, ear (sound muffling) diencephalon reflexes Roughly cylindrical network of Operates the reticular activating Reticular nerve pathways and centres system (RAS) that regulates state of formation extending through the brainstem consciousness and into the diencephalon Roughly spherical structure Coordinates many functions of attached at the posterior of the cerebrum, including planning and brainstem; wrinkled grey matter control of skilled movements, posture, Cerebellum cortex, branched network of balance, coordination of sensory white fibres inside (arbor vitae), information relating to body position and several small grey nuclei and movement Brain region in the central part of the brain, between the Numerous coordinating and Diencephalon cerebrum and brainstem integrating functions (midbrain); made up of various grey-matter nuclei Thalamus Large ovoid of grey matter, Crude sensations, coordination of divided into two large lateral sensory information relayed to masses connected by an cerebrum; involved in emotional intermediate mass response to sensory information; Stroke 23  involved in arousal; general processing of information to/from cerebrum Integration/coordination of many Numerous grey-matter nuclei autonomic reflexes, hormonal Hypothalamus clustered below the thalamus functions; involved in arousal, appetite, thermoregulation Single nucleus of Produces melatonin, a timekeeping Pineal gland neuroendocrine tissue posterior hormone, as part of the body’s to the thalamus biological clock Largest, most superior region of Complex processing of sensory and brain; divided into right and left Cerebrum motor information; complex hemispheres, connected by the integrative functions corpus callosum Highly wrinkled grey-matter Higher-level processing of sensory surface of the cerebrum; and motor information, including divided into five major lobes per conscious sensation and motor Cerebral cortex hemisphere; functionally control; complex integrative functions mapped based on concept of such as consciousness, language, localization memory, emotions White-matter tracts connect Conduction information between CNS various regions of the cortex Cerebral tracts areas to facilitate complex processing with each other and with inferior and integration CNS structures Integration and regulation of conscious motor control, especially Grey-matter nuclei deep in the Basal nuclei posture, walking, other repetitive cerebrum movements; possible roles in thinking and learning Stroke 24 Stroke 25 Stroke 26 Stroke 27 Stroke 28  Anterior Circulation Stroke Motor &/OR Senesory loss affecting Face Stroke 29  Arm Hand Leg Posterior Circulation Stroke Any of: Facial weakness Disorder of eye movement Contra-lateral motor / sensory loads Co-ordination loss Treatment of stroke Aspirin had been shown to be of benefit in myocardial infraction Reduces the stickiness of platelets Heparin thins blood and used to treat clots in veins How could we find out if either is beneficial in strokes? Conclusion of stroke treament Aspirin reduced risk of further ischaemic strokes Heparin reduced risk of further ischaemic strokes BUT increased risk of brain haemorrhage Stroke 30  Standard treatment of stroke is oral aspirin initially Stroke 31