L7 Meninges25 PDF - Meninges, Ventricles & Dural Venous Sinuses

Meninges, Ventricles & Dural Venous Sinuses Supplemental Reading: Moore et al., pages: 865 - 888 1  Learning Objectives: Name the 3 meningeal coverings of the...

Meninges, Ventricles & Dural Venous Sinuses Supplemental Reading: Moore et al., pages: 865 - 888 1  Learning Objectives: Name the 3 meningeal coverings of the brain; identify the potential and actual spaces that exist between the meningeal layers at cranial levels versus spinal cord levels. Identify which meningeal space contains cerebrospinal fluid (CSF); diagram the flow of CSF from the lateral ventricles to the superior sagittal sinus. Explain the function of arachnoid granulations. What would happen if these channels were blocked? 2  Learning Objectives (continued): Name the dural partitions that extend into the cranial cavity, separating the major parts of the brain from one another. Identify the following dural venous sinuses on the cadaver: superior sagittal, inferior sagittal, straight, confluence, transverse, sigmoid, superior & inferior petrosal and cavernous. List the neurovascular structures that are contained within the cavernous sinus. What symptoms would pertain if each of these structures where damaged? Differentiate between an epidural, subdural and subarachnoid bleed. 3  Coverings of the Spinal Cord “The Meninges” Pia (Innermost) Arachnoid Dura (Outermost) 4  Spaces Between Meningeal Layers (at spinal cord levels) No space between pia & cord Subarachnoid – true space containing cerebrospinal fluid (CSF), between arachnoid & pia Subdural – potential space, between dura & arachnoid Epidural – true space, contains fat & the internal vertebral venous plexus 5 6  Dura: 1. One layer around the spinal cord 2. Two layers around the brain: a. Periosteal (periosteum) b. Meningeal (continuous through foramen magnum) 7 8  Dural “Partitions” Infoldings of the meningeal layer of dura in the cranial cavity Partitions project into spaces between various regions of the brain 9 1. Falx Cerebri: sickle-shaped partition between the cerebral hemispheres 2. Falx Cerebelli: small, sickle-shaped projection between the cerebellar hemispheres 3. Tentorium Cerebelli: horizontal projection between the occipital lobes and the cerebellum 10  Falx Cerebri Falx Cerebelli 11 Tentorium Cerebelli 12 13 Innervation of the Dura V V CN X & Cervical Nn. 1-3 14  Spaces between the Meninges at Cranial Levels Epidural: real vs. potential a. Cranial cavity: potential – can become an actual fluid-filled space due to a vascular hemorrhage (torn Middle Meningeal Artery) b. Spinal cord: real; fat & veins Subdural: no space, but “potential” 15 “Talk & Die Syndrome” - Symptoms of brain compression generally occur within 2-3 hours 16 Subdural Hematoma – is due to the rupture of the bridging cerebral veins as they pass from the brain surface into one of the venous sinuses 17  Subarachnoid space True space containing cerebrospinal fluid (CSF) (1) Produced by choroid plexus (located in the ventricles) (2) Arachnoid granulations: “Transfer” CSF to the superior sagittal sinus (venous blood) Contains cerebral arteries and veins 18  Pia mater Cerebral vein 19 Subarachnoid hemorrhage – is due to the rupture of a cerebral artery contained within the subarachnoid space (Circle of Willis) 20  Ventricles Located within the brain Filled with cerebrospinal fluid (CSF) Choroid plexus (red ‘dots’ in adjacent diagram): 1. Produces CSF 2. Located in all ventricles (but not in the cerebral aqueduct) Communicate with the subarachnoid space through foramina in the roof of the medulla: Luschka (2), Magendie (1) 21  Flow of CSF Lateral Ventricles (Cerebral Cortex) > Interventricular Foramina (of Monro) > Third Ventricle (Thalamus) > Cerebral Aqueduct (Midbrain) > Fourth Ventricle (Pons & Medulla) > Foramina of Luschka & Magendie > Subarachnoid Space > Arachnoid Granulations > Dural Venous Sinus 22 Hydrocephalus Hydrocephalus is an increase in the amount of cerebrospinal fluid. This can result from one of three things: Increased production Blockage in ventricular system Impaired absorption 23 Dural Venous Sinuses Located between the layers of dura in the cranial cavity Provide the principal blood return from the brain 24 Superior Sagittal Sinus Located along the attached margin of the falx cerebri Inferior Sagittal Sinus Located in the inferior (free) margin of the falx cerebri 25 Straight Sinus Located along the line of attachment of the falx cerebri to the tentorium cerebelli Formed when the great cerebral vein (of Galen) joins the inferior sagittal sinus Occipital Sinus Located in the attached margin of the falx cerebelli 26 Confluence of Sinuses Formed by the joining of the superior sagittal, straight and occipital sinuses * * 27 Sigmoid Sinus Follows an ‘S-shaped’ course in the posterior cranial fossa Empties through the jugular foramen into the upper end of the internal jugular vein Transverse Sinus Located within the posterior attachment of the tentorium cerebelli Drains blood from the confluence of sinuses 28  Cavernous Sinus X Located on either side of the body of the sphenoid bone Blood from the cavernous sinus enters either the superior or inferior petrosal sinuses 29  CN III Internal Carotid A. CN IV CN V1 CN V2 CN VI The facial area which can potentially drain into the cavernous sinus is the triangular area defined by the mid-line and by lines drawn from the external auditory meatus to the lateral corners of the eye and mouth (danger triangle of the face) Although this area usually drains into the facial vein, blood may go via the ophthalmic veins, to the cavernous sinus. Hence, an infection of the face may spread to this sinus and lead to damage of its contents. 30 Thanks for your time. 31