Brain Protection (01/27/2021) PDF

(008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 OUTLINE I. BRAIN PROTECTION...

(008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 OUTLINE I. BRAIN PROTECTION a. Dura Mater A. MENINGES - 2 layers of fibrous connective tissue 1. 3 Layers of Meninges Periosteal layer (endosteal) - attached to bone a. Dura mater Meningeal layer (dura mater proper) - proper brain covering b. Arachnoid mater c. Pia mater - dural partitions subdivide cranial cavity & limit movement of brain: 2. Potential Intermeningeal Spaces a. Falx cerebri (sickle-shaped fold) 3. Basic Differences of Intracranial Injuries - In longitudinal fissure; attaches to crista galli of ethmoid B. CEREBROSPINAL FLUID bone 1. CSF Production - largest dural fold and separates the two cerebral 2. Ventricles hemispheres at midline. 3. CSF pathway b. Falx cerebelli (small, sickle-shaped fold) a. Hydrocephalus - Runs vertically along vermis of cerebellum C. BLOOD BRAIN BARRIER - separates the two cerebellar hemispheres. II. INPUTS FROM THE MENINGES AND DURAL c. Tentorium cerebelli (crescent-shaped fold) VENOUS SINUSES VIDEO - Sheet in transverse fissure between cerebrum & A. PARTS OF MENINGES cerebellum B. DURAL VENOUS SINUSES - is continuous with the falx cerebri and separates the cerebrum from the cerebellum. III. INPUTS FROM THE VENTRICULAR SYSTEM OF THE BRAIN VIDEO A. VENTRICLES B. CEREBROSPINAL FLUID (CSF) IV. INPUTS FROM THE BLOOD SUPPLY TO THE BRAIN VIDEO A. INTERNAL CAROTID ARTERY (ICA) B. VERTEBROBASILAR ARTERY C. CIRCLE OF WILLIS V. TEST YOUR KNOWLEDGE VI. REFERENCES I. BRAIN PROTECTION Figure 2. The dural partitions 1. Meninges: Covers the brain 2. Cerebrospinal fluid: Cushions the brain b. Arachnoid mater 3. Blood brain barrier: Prevents chemicals and toxins from entering delicate, impermeable membrane covering the brain and lying the brain between the pia mater internally and the dura mater externally It is separated from the dura by a potential space, the subdural A. MENINGES space, filled by a film of fluid. The brain in the skull is surrounded by three protective membranes or it is separated from the pia by the subarachnoid space, which meninges: the dura mater, the arachnoid mater, and the pia mater. is filled with CSF. Deep to arachnoid is subarachnoid space 1. 3 layers of Meninges: o Filled with CSF a. Dura mater o blood vessels run through (susceptible to tearing) b. Arachnoid mater Superiorly, forms arachnoid villi: CSF valves c. Pia mater o Allow draining into dural blood sinuses o Reabsorption of CSF c. Pia mater The pia mater is a vascular membrane that closely invests the brain, covering the gyri and descending into the deepest sulci. The cerebral arteries entering the substance of the brain carry a sheath of pia with them. The pia mater forms the tela choroidea of the roof of the third and fourth ventricles of the brain, and it fuses with the ependyma to form the choroid plexuses in the lateral, third, and fourth ventricles of the brain. Delicate, clings to brain following convolutions. Figure 1. The three layers of meninges Compared with the Dura and arachnoid which only cover brain loosely Page 1 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 2. Potential Intermeningeal Spaces b. Subdural Hematoma Figure 6. Sample subdural hematoma Figure 3. The potential intermeningeal spaces Epidural: Between Inner skull and Dura mater B. CEREBROSPINAL FUID Subdural: Between Dura and Arachnoid Mater Subarachnoid: Between Arachnoid and Pia mater Made in choroid plexuses (roofs of ventricles) Intracerebral: within the brain Filtration of plasma from capillaries through ependymal cells (electrolytes, glucose) 500 ml/d; total volume 100-160 ml at a time 3. Basic Differences of Intracranial Injuries Cushions and nourishes brain CSF Pressure = intracranial pressure Assayed in diagnosing meningitis, bleeds, MS Hydrocephalus: excessive accumulation Figure 7. The cerebrospinal fluid. Figure 4. The location of epidural, subdural, and intracerebral 1. CSF Production hematomas. Choroid plexus (Main CSF Production) a. Epidural Hematoma Interstitial space Ependymal lining Dura of the nerve root sleeve (Spine) Property Pediatric Adult (Newborn) Total volume 5 150 (50%) intracranial. 50% spinal Formation rate 25 ml/day 0.3-0.35 ml/min (450- 750ml/day) Table 1. CSF Production Note: CSF turnover 3x/day Figure 5. Sample epidural hematoma. Page 2 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 2. Ventricles Central cavities Filled with CSF (cerebrospinal fluid) Lined by ependymal cells (these cells lining the choroid plexus) Choroid Plexus: Production of CSF (Cerebrospinal Fluid ) Continuous with each other and central canal of spinal cord Figure 10. The ventricles CSF REABSORPTION: Subarachnoid space (Arachnoid granulation) Figure 11. The CSF reabsorption a. Hydrocephalus: Pathology in the CSF pathway Figures 8-9. The ventricles and its components 3. Take note: CSF pathway - Production in the Choroid plexus of the lateral ventricles→ foramen of Monroe → third ventricle cerebral aquaduct → 4th ventricle foramina of luschka and magendie → subarachnoid space → arachnoid granulations that drain into the Dural Venous Sinuses to be recirculated again Figure 12. An image showing a child with hydrocephalus. The rest will be drained into the central canal of the spinal cord. Page 3 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 Types of Hydrocephalus Communicating: Non-obstructive HCP. -Impaired CSF reabsorption in the subarachnoid space (Arachnoid granulations) Non-Communicating: - Obstruction within the ventricular system. Figure 14. An image showing a normal CT-scan. Communicating Hydrocephalus Enlargement of lateral, 3rd, and 4th ventricles Note sulcal effacement, temp horns, rounded 3rd, and enlarged 4th Figure 13. An image showing the causes of hydrocephalus. Figure 13. An image showing the ventricles and components. Figure 15. An image showing a CT-scan with hydrocephalus case. Page 4 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 CSF circulation: through ventricles, median and lateral apertures, CSF: subarachnoid space, arachnoid villi, and into the blood of the superior -Made in choroid plexus sagittal sinus -Drained through arachnoid villus Ventricle Cannula (narrow tube) inserted into ventricle (cavity) of the brain to drain CSF Pressure valve (adjusts fluid drainage to keep a consistent level of fluid pressure in the brain) Drainage tube passes under the skin and continues into the abdomen (belly) Cannula (narrow tube) inserted into a ventricle (cavity) of the brain to Figures 16-18. Images showing the CSF circulation. drain CSF Page 5 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 C. BLOOD BRAIN BARRIER (BBB) Tight junctions between endothelial cells of brain capillaries, instead of the usual permeability. Formed by astrocytes. Highly selective transport mechanisms Allows nutrients, O2, CO2 allows uncharged and lipid soluble molecules; allows alcohol, nicotine, and some drugs including anesthetics. Prevents lipophilic neurotoxins, bacteria Figure 20. Image showing Blood Brain Barrier. Figure 19. Actual photos from Dr. Viado. Figure 21. Image showing the lobes of the brain. Page 6 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 Figure 22. Image showing the respective functions of each lobe of the brain. Figure 24. Brain, sagittal sec, medial view 1. Cerebral hemisphere 2. Corpus callosum 3. Thalamus 4. Midbrain 5. Pons 6. Cerebellum 7. Medulla oblongata Figure 23. Pons & Cerebellum, sagittal section, medial view 1. Midbrain 2. Cerebellum 3. Pons 4. Medulla oblongata 5. Inferior colliculus 6. Superior medullary velum 7. Fourth ventricle Page 7 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 SUPPLEMENTAL NOTES: The brain is supplied by the two internal carotid and the two vertebral arteries that lie within cerebrospinal fluid of the subarachnoid space. The internal carotid begins at the bifurcation of the common carotid in the neck, where it possesses a local dilation called the carotid sinus. The internal carotid enters the cranial cavity through the carotid canal of the temporal bone. The internal carotid terminates as the anterior and middle cerebral arteries after giving off ophthalmic and posterior communicating arteries. The two vertebral arteries enter the cranial cavity through the foramen magnum after ascending through the transverse foramina of the cervical vertebrae. A. PARTS OF MENINGES The cranial portion of the vertebral artery gives off the posterior spinal, anterior spinal, posterior inferior cerebellar, medullary, and meningeal arteries. 1. Dura mater The vertebral arteries merge to form the basilar artery on the Periosteal layer and meningeal layer anterior surface of the pons. Dural septae The basilar artery branches into pontine, labyrinthine, anterior Inferior cerebellar, superior cerebellar, and posterior Dural venous sinuses cerebral arteries. 2. Arachnoid mater The circle of Willis is formed by the anastomosis between Subarachnoid space the two internal carotid and vertebral blood supplies by Arachnoid granulations (villi) communication of the anterior cerebral and anterior 3. Pia mater communicating arteries, internal carotid arteries, posterior communicating and posterior cerebral arteries, and the basilar artery. The corpus striatum and Internal capsule are supplied by the medial and lateral striate branches of the middle cerebral artery. The thalamus Is supplied by branches of the posterior communicating, basilar, and posterior cerebral arteries. The midbrain is supplied by the posterior cerebral, superior cerebellar, and basilar arteries. The pons is supplied by the basilar, anterior inferior, and superior cerebellar arteries. The medulla oblongata ls supplied by the vertebral, anterior and posterior spinal, posterior inferior cerebellar, and basilar arteries. The cerebellum is supplied by the superior cerebellar, anterior inferior cerebellar, and posterior inferior cerebellar Parts of meninges: arteries. 1. Dura mater II. INPUTS FROM THE MENINGES AND DURAL VENOUS SINUSES VIDEO What: …are the meninges …. Are the dural venous sinuses …Is the deal with the cerebral circulation Anatomy: 1. Layers of the scalp 2. Skull bones 3. Meninges 4. Brain Page 8 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 Periosteal layer and meningeal layer Most superficial layer of the meninges L. Dura “tough” L. mater “mother” Consist of 2 layers: o Periosteal layer: lines internal surface of skull; ends at the foramen magnum o Meningeal layer: continuous with the brain and spinal cord Vertical and separates cerebral hemispheres within longitudinal cerebral fissure Dural septae 2 dural layers are bound together and only separate when forming dural septae and dural venous sinuses o Periosteal layer o Meningeal layer Restrict displacement of the brain (much like a seat belt) o Falx cerebri o Falx= L. “Sickle” Tentorium cerebelli Horizontal and separates the occipital lobes and cerebellum Page 9 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 Falx cerebelli Dural venous sinuses (DVS) are similar to veins in that it contains venous blood and are lined with endothelium Located between cerebellar lobes But DVS are not similar to vein in that they lack valves and they lack tunica media Basically, Dura mater; dense connective tissue line with endothelium that’s where DVS is. B. DURAL VENOUS SINUSES Venous channels located between the periosteal and meningeal layers of dura mater Dural venous sinuses (DVS) a) Cavernous sinus Located on each side of the sella turcica (pituitary gland) CNN III, IV, V-1 and V-2 course through lateral wall CNN VI and ICA (Internal carotid artery) course through the middle Receive blood from cerebral, diploic and emissary veins Page 10 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 2. Arachnoid mater Middle layer of the meninges; drapes over brain and spinal cord Arachnoid= L. “spider-like” mater= L. “mother” Communicates with the facial vein and pterygoid plexus of veins in addition to draining into the sigmoid sinus All DVS’s ultimately drain into the Internal Jugular Vein (IJV) Subarachnoid space – is filled with CSF, which surrounds the brain and spinal cord Arachnoid granulations (villi)- CSF drains from subarachnoid space into the sup sagittal sinus Page 11 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 III. INPUTS FROM THE VENTRICULAR SYSTEM OF THE BRAIN VIDEO What …are the ventricles of the brain? …is CSF, where is it produced and where does if flow? A. VENTRICLES 1. Lateral ventricles 2. 3rd ventricle 3. 4th ventricle 3. Pia mater Pia L. “soft” mater L. “mother” They are called soft because they are composed of Loose connective Tissue Deepest layer of the meninges; intimately associated with brain and spinal cord Ventricles: 1. Lateral ventricles Paired, C-shaped chambers in each cerebral hemisphere Largest of the ventricles Below the corpus callosum 2. Interventricular foramen (of Monroe) Communication between the lateral ventricles and 3rd ventricle Page 12 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 3. 3rd ventricle Midline, narrow space between the L and R diencephalon B. CEREBROSPINAL FLUID (CSF) 4. Cerebral aqueduct Aka: Mesencephalic aqueduct / Aqueduct of Sylvius Cerebrospinal fluid (CSF): Located in the midbrain Chroroid plexus Connects the 3rd and 4th ventricles o Produces CSF (enables CNS to float) o Located in each ventricle 5. 4th ventricle Located between the pons/ medulla and cerebellum Ventricular System Flow starts at CSF from the choroid plexus from the lateral ventricles Flows into Inter-ventricular (IV) foramen Joins with the CSF of the 3rd Ventricles choroid plexuses flow down to the cerebral aqueduct Join from the CSF produce from the 4th ventricles choroid plexus Page 13 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 4th Ventricle Median Aperture (median apeture of magendie) Note: Lateral Aperture (lateral apeture of luschka) CSF come from Choroid plexus Subarachnoid space flows also at SPINAL CORD Note: this two apertures (opening) were to communicating with the CSF drain into the blood thru at superior sagital sinus thru CSF from the 4th ventricles to the Subarachnoid space arachnoid granulation Subarachnoid space - CSF from Subarachnoid space flows around the outside of the brain until it reach the arachnoid granulation. Arachnoid granulation – filtering plasma from up, filtering CSF from the subarachnoid space into the dura venous Volume of CSF in Adults = 150ml sinus and enters in the superior sagittal sinus o CSF is replaced every 8 Hours o About 500ml is formed each day o CSF cushions and gives buoyancy to the brain and spinal cord Page 14 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 A. INTERNAL CAROTID ARTERY (ICA) IV. INPUTS FROM THE BLOOD SUPPLY TO THE BRAIN VIDEO BRAIN is supplied by 2 Arteries: 1. Internal carotid artery (ICA) 2. Vertebrobasilar artery Bifurcates into internal and external carotid artery on a lateral view. Internal carotid artery ascends up and goes up on the base of the skull (carotid canal) Page 15 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 Parts of Internal Carotid: Cervical-carotid artery is on the neck, on the cervical region. Cerebral-is the part where all branches of internal carotid comes of. Petrous- carotid artery going from the base of the skull and carotid artery in the middle cranial fossa between the the two is the internal carotid artery of petrous part. Cavernous Branches of Internal Carotid: is the part that is in the cavernous sinus a. Ophthalmic artery - goes to the eyes the only artery that is inside of a vein. *Central Artery-supplies the the retina of the eyes If its occluded because of diabetes or clot, blindness will occur. Page 16 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 b. Posterior communicating artery d. Anterior communicating artery-connecting the two anterior Connects the post cerebral artery and ICA cerebral artery (ACA) e. Middle Cerebral Artery (MCA) - located at the middle of cerebrum Connects anterior and posterior circulation on one side Distribution- Lateral aspect of cerebral hemispheres (except superior front/parietal and inferior temporal lobes) c. Anterior Cerebral Artery (ACA)-supplies the front of the cerebrum Distribution- Medial aspect of cerebral hemisphere back to B. VERTEBROBASILAR ARTERY parietal lobe. Page 17 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 b. Anterior spinal artery-supplies the front of the spinal cord. c. Basilar artery-comes from two vertebral artery to become basal artery that course vertically along the pons between the pons and clivus of the scalp. consist of the Vertebral arteries and Basilar artery Vertebral arteries - arises from the subclavian artery and ascend up to neck thru the transverse foramina of the cervical vertebrae through the foramen magnun and into the skull. Then, vertebral artery traverse with foramen magnum and fuses with the other vertebral artery and becomes basal artery. C. CIRCLE OF WILLIS Branches: Branches: a. Posterior inferior cerebellar artery (PICA)-supplies the bottom a. Anterior inferior cerebellar artery (AICA)-supplies the front and back of the cerebellum bottom of the cerebellum. Page 18 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 b. Superior cerebellar artery - supplies the top of the cerebellum. Collateral circulation between the 2 ICA’s and Vertebrobasilar arteries Name after the anatomist THOMAS WILLIS (1621-1675) and numbered the Cranial nerves (CN). He is also the one who termed Diabetes Mellitus. c. Posterior cerebellar artery-supplies the back of the cerebrum Provides redundancy and permits circulation should a part of the circle be occluded. *CN III - is in between the posterior cerebral artery and superior cerebellar artery. Forms around the optic chiasm and pituitary gland if there are varying aneurysm to the both it can pulls off the CN III and leads to eye deficit. Distribution- Occipital Lobe (vissual cortex), temporal Lobe(post-med/inf) Page 19 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 V. TEST YOURSELF 10. Shunts CSF from ventricle to abdomen A. Ventriculoatrial shunting 1. True or False B. Ventriculoperitoneal Shunting Blood Brain Barrier prevents the passage of the large hydrophobic C. Ventriculopleural neurotoxins and pathogens like bacteria. D. Third ventriculostomy 2. What is the major contributor of CSF production? 11. It prevents chemicals and toxins from entering the brain A. Dura of the nerve A. Meninges B. Ependymal lining B. Cerebrospinal fluid C. Interstitial space C. Blood Brain Barrier D. Choroid Plexus D. Dural venous sinuses 3. This is due to increased CSF production but impaired 12.The following statements concern the ventricular system: reabsorption. A. The fourth ventricle has a rectangular-shaped floor. A. Meningitis B. The pineal body is suspended from the roof of the fourth B. Aneurysm ventricle. C. Hydrocephalus C. The nerve centers controlling the heart rate and blood pressure lie beneath the floor of the third ventricle. 4. Runs vertically along vermis of cerebellum. D. The choroid plexus of the lateral ventricle projects into the A. Falx cerebri cavity on its medial side through the choroidal fissure. B. Falx cerebelli C. Tentorium cerebelli 13. The following statements concern the blood—brain barrier D. Tentorium cerebri (BBB): A. It protects the brain from toxic compounds of low molecular 5. This serves as roof of ventricles. weight. (b) It is present in the pineal gland. A. Corpus callosum B. The endothelial cells of the blood capillaries are B. Superior sagittal sinus nonfenestrated. C. Choroid plexus C. The endothelial cells of the blood capillaries are held D. Third ventricle together by localized tight junctions. D. L—Dopa has difficulty passing through it in the treatment of 6. The following nerves are sensory to the dura mater: Parkinson disease. A. Oculomotor nerve B. Trochlear nerve C. Sixth cervical spinal nerve A 58-year-old man, while eating his evening meal, suddenly D. Trigeminal nerve complained of a severe headache. Moments later, he slumped E. Hypoglossal nerve forward and lost consciousness. 7. The following structure limits rotatory movements of the brain 14. On being admitted to the hospital, the examining physician within the skull: could have found the following physical signs except: A. Tentorium cerebelli A. He was in a deep coma, and his breathing was deep and B. Diaphragma sellae slow. C. Falx cerebri B. The patient’s head was turned to the left. D. Dorsum sellae C. The muscle tone of the limbs was less on the right side than on the left. 8. True or False D. The right abdominal reflexes were absent, and there was a Midbrain surrounds the third ventricle. positive Babinski response on the left side. 9. It separates supratentorial from infratentorial compartment. 15. Three days later, the patient regained consciousness, and the A. Falx cerebri following additional signs could have become apparent except: B. Falx cerebelli A. The right arm and, to a lesser extent, the right leg were C. Tentorium cerebelli paralyzed. D. Tentorium cerebri B. Movements of the left arm and leg and the left side of the face were normal. Page 20 of 21 CMED 1B  (008) BRAIN PROTECTION DR. A. VIADO | 01/27/2021 C. The upper and lower parts of the right side of his face were paralyzed. D. The patient had difficulty in swallowing. ANSWERS: 1. False. It should be hydrophilic 2. D. Choroid Plexus 3. C. Hydrocephalus 4. B. Falx cerebelli 5. C. Choroid plexus 6. D is correct. The trigeminal nerve is an important sensory nerve to the dura mater within the skull. 7. C is correct. The falx cerebri limits rotatory movements of the brain within the skull. 8. False. Diencephalon 9. C. Tentorium Cerebelli 10. B. Ventriculoperitoneal Shunting 11. C. Blood Brain Barrier 12. D is correct. The choroid plexus of the lateral ventricle projects into the cavity on its medial side through the choroidal fissure. 13. C is correct. The endothelial cells of the blood capillaries in the BBB are non fenestrated. 14. D is the exception. A positive Babinski sign was present on the right side. 15. C is the exception. The muscles of the upper part of the face on the right side are not affected by a lesion involving the upper motor neurons on the left side of the brain. This is due to the fact that the part of the facial nucleus of the seventh cranial nerve that controls the muscles of the upper part of the face receives corticonuclear fibers from both cerebral hemispheres. VI. REFERENCES PDF – Dr. Allan Viado Ph.D., S.R. (2018). Snell’s Clinical Neuroanatomy (8th ed.). LWW Videos – Dr. Allan Viado Page 21 of 21 CMED 1B