3. The Meninges (1).pdf

THE MENINGES DR NADINE RAMPF | PHD [email protected] LECTURE OUTLINE Overview 04 Dura mater 06 Dural reflections 08 Arachnoid mater 13 Subarachnoid cisterns 16 Pia Mater 19 Dural spaces 21 Spinal meninges...

THE MENINGES DR NADINE RAMPF | PHD [email protected] LECTURE OUTLINE Overview 04 Dura mater 06 Dural reflections 08 Arachnoid mater 13 Subarachnoid cisterns 16 Pia Mater 19 Dural spaces 21 Spinal meninges 23 Clinical correlations 27 02 OBJECTIVES Describe the location and identifying characteristics of the dura mater, arachnoid, and pia mater Identify the meningeal spaces and include a description of whether the spaces are real or potential Identify and describe the four dural reflections List the major cisterns of the subarachnoid space and describe the location of each 03 LECTURE OUTLINE Overview Dura mater Dural reflections Arachnoid mater Subarachnoid cisterns Pia Mater Dural spaces Spinal meninges Clinical correlations 04  Epicranius Pericranium Cranium Periosteal layer Dura mater Dura mater Meningeal layer Arachnoid mater Cerebrum Arachnoid mater Leptomeninges Pia mater Functions Provide a supportive framework for the cerebral and cranial vasculature Acting with cerebrospinal fluid to protect the CNS from mechanical damage 05 LECTURE OUTLINE Overview Dura mater Dural reflections Arachnoid mater Subarachnoid cisterns Pia Mater Dural spaces Spinal meninges Clinical correlations 06  DURA MATER Dural venous sinus Outermost meningeal layer Tough fibrous membrane (dense irregular connective tissue) Skin Consists of two layers: 1. Periosteal layer Bone 2. Meningeal layer Dura mater These two layers are normally closely adherent to one another but in certain regions become separated to enclose blood-filled space, the dural venous sinuses In some regions: Tightly adherent to the inner surface of the skull (e.g. cranial cavity floor and midline of the cranial roof) Separated from the skull by a narrow extradural space (e.g. frontoparietal area) Source: "Servier - Drawing Meninges - no labels" by Servier Medical Art, license: CC BY Supplied primarily by the middle meningeal artery and vein Innervated by the trigeminal nerve (V1, V2 and V3) 07 LECTURE OUTLINE Overview Dura mater Dural reflections Arachnoid mater Subarachnoid cisterns Pia Mater Dural spaces Spinal meninges Clinical correlations 08 DURAL REFLECTIONS The meningeal layer of dura mater folds inwards upon itself to form four dural reflections These reflections project into the cranial cavity, dividing it into several compartments – each of which houses a subdivision of the brain Falx cerebri Diaphragma sellae Falx cerebelli Tentorium cerebelli Source: Brain-Inter-Atlas https://sites.uclouvain.be/braininteratlas/en/chapter/meninges 09 FALX CEREBRI Vertical, midline dural reflection Extends from the cranial roof into the longitudinal fissure between the cerebral hemispheres, separating them Borders: Attached - adheres to the inner surface of the skull Free - above the corpus callosum Attachments: Anterior - attach to the bony ridge of the crista galli Posterior - internal occipital protuberance and becomes continuous with the tentorium cerebelli Houses the superior sagittal and inferior sagittal sinuses Source: Brain-Inter-Atlas https://sites.uclouvain.be/braininteratlas/en/chapter/meninges 10 TENTORIUM CEREBELLI Extends from the occipitotemporal region of the skull to lie in the transverse cerebral fissure between the posterior part of the cerebral hemispheres and cerebellum Separates the cerebrum from the cerebellum Divides the intracranial space into supratentorial and infra- tentorial compartments that contain the forebrain and hindbrain, respectively Free border (aka tentorial notch) that encircles the midbrain, as the brainstem communicates between the posterior and middle cranial fossae Becomes continuous with the falx cerebri in the midline Contains the transverse, straight and superior petrosal sinuses Source: Brain-Inter-Atlas https://sites.uclouvain.be/braininteratlas/en/chapter/meninges 11 DIAPHRAGMA SELLAE Covers the hypophyseal fossa of the sphenoid bone FALX CEREBELLI Projects from the midline of Contains a small opening for the occipital bone passage of the stalk of the Separates the right and left pituitary gland cerebellar hemispheres Houses the anterior and Houses the occipital sinus posterior intercavernous sinuses Source: Brain-Inter-Atlas https://sites.uclouvain.be/braininteratlas/en/chapter/meninges 12 LECTURE OUTLINE Overview Dura mater Dural reflections Arachnoid mater Subarachnoid cisterns Pia Mater Dural spaces Spinal meninges Clinical correlations 13  ARACHNOID MATER Middle meningeal layer Spiderweb-like, thin, translucent, collagenous, avascular Skin membrane Bone Loosely envelops the brain Dura mater The outer surface attaches to the dura mater forming a barrier that prevents the leakage of CSF into the subdural space Arachnoid trabeculae The inner surface shows thin fibrous projections called the arachnoid trabeculae that traverse the subarachnoid space and attach to the outer surface of the pia mater Due to their embryological and cellular similarities the pia Subarachnoid Arachnoid mater mater and arachnoid together are referred to as the space Source: "Servier - Drawing Meninges - no labels" by Servier Medical Art, license: CC BY leptomeninges 14 ARACHNOID GRANULATIONS aka Pacchionian bodies "Mushroom-like" protrusions of the arachnoid mater Skin Formed by evaginations of arachnoid mater through the Bone meningeal layer of dura mater Dura mater The core of each arachnoid granulation is continuous with the subarachnoid space Arachnoid trabeculae Enter the venous dural sinuses and facilitate the one-way flow of cerebrospinal fluid (CSF) from the subarachnoid space into the venous circulation Found in large numbers along the superior sagittal sinus but are associated with all dural sinuses Subarachnoid Arachnoid mater space Source: "Servier - Drawing Meninges - no labels" by Servier Medical Art, license: CC BY 15 LECTURE OUTLINE Overview Dura mater Dural reflections Arachnoid mater Subarachnoid cisterns Pia Mater Dural spaces Spinal meninges Clinical correlations 16 SUBARACHNOID CISTERNS Formed where significant depressions or fissures in the brain are spanned by the arachnoid mater There are 10 major subarachnoid cisterns: Cisterna magna (cerebellomedullary cistern) Pontine cistern Chiasmatic cistern Quadrigeminal cistern Interpeduncular cistern Ambient cistern Crural and carotid cisterns Cistern of lateral cerebral fossa (Sylvian cistern) Cerebellopontine cistern Cistern of lamina terminalis Source: https://www.uptodate.com/contents/image?imageKey=ONC%2F74410 17 SUBARACHNOID CISTERNS Superior cistern aka quadrigeminal cistern, ambient cistern or cistern of the great cerebral vein Location: Between the splenium of the corpus Inderpeduncular cistern callosum and the upper surface of the cerebellum, dorsal to the midbrain Wide and cone-shaped Extends laterally around the midbrain Occupies the interpeduncular fossa from great cerebral v. to 3rd ventricle Surrounded by the cerebral peduncles Content: Deepest between the two cerebral peduncles of Pineal gland the midbrain Trochlear n. (CN IV) Location: Great cerebral v. At the confluence of the supra- and 3rd part of post. cerebral a. + some of its infratentorial spaces between the two perforating branches temporal lobes 3rd part of sup. cerebellar a. + some of its Content: perforating branches Bifurcation of basilar a. Prox. post. cerebral a. + some of its perforating branches Prox. sup. cerebellar a. Oculomotor n. (CN III) Cisterna magna Mammillary bodies aka cerebellomedullary cistern Location: Between medulla anteriorly and cerebellum posteriorly Pontine cistern Content: Vertebral a. Location: Glossopharyngeal n. (CN IX) Anterior to pons Vagus n. (CN X) Content: Accessory n. (CN XI) Basilar a. Choroid plexus Ant. inf. cerebellar a. CSF flows into this cistern from the 4th Abducens n. (CN VI) ventricle Sup. cerebellar a. Can be tapped for CSF (suboccipital tap) Source: Coverings of the central nervous system Fig. 5.4 Crossman and Neary, Neuroanatomy: An Illustrated Colour Text 18 LECTURE OUTLINE Overview Dura mater Dural reflections Arachnoid mater Subarachnoid cisterns Pia Mater Dural spaces Spinal meninges Clinical correlations 19  PIA MATER Innermost meningeal layer Microscopically thin, delicate and highly vascular membrane Adheres to the surface of the brain, closely following its Skin contours Bone Separated from the brain by the subpial space formed by the end-feet of the astrocytes (glia limitans) Dura mater Many superficial blood vessels of the brain are related to the pia mater, some are partially embedded within its thickness, Arachnoid mater while others are suspended by the arachnoid trabeculae Functions: Physically separate the neural tissue from the blood vessels in the subarachnoid space, adding to the efficacy Source: "Servier - Drawing Meninges - no labels" by Servier Medical Art, license: CC BY of the blood-brain barrier Contributes to the degradation of the neurotransmitters, Pia mater preventing their prolonged action on the nervous tissue 20 LECTURE OUTLINE Overview Dura mater Dural reflections Arachnoid mater Subarachnoid cisterns Pia Mater Dural spaces Spinal meninges Clinical correlations 21 DURA MATER ARACHNOID MATER Epidural Space Subdural Space Subarachnoid Space Potential space Potential space Real space Located between the dura mater Located between the arachnoid Located between arachnoid mater and the bones of the cranial vault mater and dura mater and pia mater (cranial) or tissues that line the vertebral canal (spinal) Can develop as a result of Contains arachnoid trabeculae haemorrhage inducing brain Transmits cerebral veins to the trauma (e.g. subdural haematoma) Traversed by numerous arteries venous lacunae of the superior and veins sagittal sinus Contains CSF Laceration of these “bridging veins” results in extra/epidural In adult, extends below the conus haemorrhage (haematoma) medullaris to the level of the 2nd sacral vertebra as the lumber Spinal epidural space is a site of cistern applying the local epidural anaesthesia 22 LECTURE OUTLINE Overview Dura mater Dural reflections Arachnoid mater Subarachnoid cisterns Pia Mater Dural spaces Spinal meninges Clinical correlations 23 SPINAL DURA MATER Outermost meningeal layer Differs from that of the brain by having only one layer - the meningeal layer The periosteal layer is missing because the vertebral canal has a true periosteum Attachments: Superiorly: tectorial membrane and posterior longitudinal ligament Inferiorly: it extends up to S2 vertebral level, thus extending below the spinal cord termination (L1/L2) Dura mater The space between the spinal dura mater and the periosteum of the vertebral column is called the epidural space It is filled with loose connective and adipose tissues, and traversed by the anterior and posterior internal vertebral venous plexuses. Source: Brain-Inter-Atlas https://sites.uclouvain.be/braininteratlas/en/chapter/meninges 24 SPINAL ARACHNOID MATER Middle meningeal layer Continuous with arachnoid mater of the brain Arachnoid mater It lies close and beneath the spinal dura, with a narrow subdural space existing between them Spinal subarachnoid space between arachnoid and pia This space expands at the level of the conus medullaris of the spinal cord, forming the lumbar cistern The lumbar cistern: Location: Extends from L1-S2 Content: Dorsal and ventral rootlets of L2-Co spinal nerves (cauda equina) Clinically significant as it is the site of lumbar puncture Source: Brain-Inter-Atlas https://sites.uclouvain.be/braininteratlas/en/chapter/meninges 25 SPINAL PIA MATER Innermost meningeal layer Continuous with cranial pia at the level of the foramen magnum Pia mater Contains vascular plexus for the spinal cord tissue. Gives off a fibrous projection from the apex of the conus medullaris called the filum terminale Filum terminale extends ± 20 cm downwards and attaches to the periosteum of the first coccygeal vertebra Denticulate ligaments Starting from the level of the foramen magnum to the level of vertebra T12 21 pairs of ligamentous lateral projections that pass through the arachnoid and attach to the spinal dura mater Each pair is located halfway between the successive pairs of the spinal nerves Position and hold the spinal cord in place Source: Brain-Inter-Atlas https://sites.uclouvain.be/braininteratlas/en/chapter/meninges 26 LECTURE OUTLINE Overview Dura mater Dural reflections Arachnoid mater Subarachnoid cisterns Pia Mater Dural spaces Spinal meninges Clinical correlations 27 Extradural Haematoma HAEMATOMAS Haematoma = collection of blood Can cause a rapid increase in intracranial pressure Death will result if untreated Two types of haematomas involving the dura mater: Case courtesy of Dr Sandeep Bhuta, Epi/Extradural Subdural Haematoma "https://radiopaedia.org/">Radiopaedia.org From the case https://radiopaedia.org/cases/4458">rID: 4458 Arterial blood collects between the skull and periosteal layer of the dura The causative vessel is usually the middle meningeal artery, tearing as a consequence of brain trauma Subdural Venous blood collects between the dura and the arachnoid mater Results from damage to cerebral veins as they empty into the dural venous sinuses Source: Case courtesy of Dr Matt Skalski, Radiopaedia.org, rID: 21542 28 Case courtesy of Dr David Cuete https://radiopaedia.org/">Radiopaedia.org From the case https://radiopaedia.org/cases/23293">rID: 23293  MENINGITIS Inflammation of the meninges resulting from infection with viruses, bacteria, fungi and protozoa Symptoms include headache, photophobia, vomiting, fever and neck stiffness when moving head Viral meningitis is normally mild and self-limiting Bacterial and fungal meningitis leads to damage to cranial nerves and the brain itself If left untreated, proceeds to raised intracranial pressure, brain www.youtube.com/watch? v=1B2TZNkYWZU displacement and death 29  THANK YOU FOR YOUR ATTENTION Content for this lecture: Chapter 15 | Snell's Clinical Neuroanatomy, 8th Edition