NEURO1A-LC13-MENINGES.pdf

OUTLINE I. MENINGES II. DURA MATER III. ARACHNOID MATER IV. PIA MATER V. CLINICAL CORRELATES I. MENINGES - Protective membranes that surround the brain and the spin...

OUTLINE I. MENINGES II. DURA MATER III. ARACHNOID MATER IV. PIA MATER V. CLINICAL CORRELATES I. MENINGES - Protective membranes that surround the brain and the spinal cord plastic-like - Composed of o Dura mater o Arachnoid mater o Pia mater II. DURA MATER Figure 3. Meningeal Layer - Outermost of the three meninges - Two layers of dura mater Parts of Dura Mater o Endosteal layer - closely apposed the bone; just follows where the bone 1. Falx Cerebri goes Fold of dura mater that lies in the midline between the two ○ Meningeal layer - more inner layer; associated with other meninges like cerebral hemispheres arachnoid mater; go inward Anterior end is attached to the internal frontal crest and the crista - Closely united except along certain lines where they separate to form galli venous sinuses (venous sinus - confluence of the brain) Posterior part blends in the midline with the upper surface of the tentorium cerebelli (it is what divide the cerebrum to the cerebellum) Superior sagittal sinus runs in its upper fixed margin (part of venous system) Inferior sagittal sinus runs in its lower concave free margin (part of venous system) Straight sinus runs along its attachment to the tentorium cerebelli 2. Tentorium Cerebelli Crescent-shaped fold of dura mater that roofs over the posterior cranial fossa Covers the upper surface of the cerebellum and supports the occipital lobes of the cerebral hemispheres Superior petrosal sinus runs along its attachment to the petrous bone Transverse sinus runs along its attachment to the occipital bone 3. Falx Cerebelli Small sickle-shaped fold of dura mater attached to the Figure 1. Layers of Dura Mater (red arrow: endosteal layer, green arrow: meningeal layer) internal occipital crest, projects forward between two cerebellar hemispheres. Contains the occipital sinus on its posterior margin Figure 2. Endosteal layer Figure 4. Falx cerebri, Tentorium cerebelli, Falx cerebelli Page 1 of 7 [NEUROSCIENCE 1A] 1.13 MENINGES – Dr. Vida Margaret Andal 4. Diaphragma Sellae Small, circular fold of dura that forms the roof for the sella turcica Has a small opening on its center for passage of the pituitary stalk Figure 7. Foramen spinosum Anterior branch roughly corresponds to the precentral gyrus Posterior branch curves backward Implicated in epidural hematoma - commonly seen in head trauma e.g. vehicular crashes it is superficial and a big artery that’s why it can easily be Figure 5. Diaphragma sellae severed by trauma Blood Supply of Dura Mater (has a lot of blood supply since it is found anywhere in the brain) 1. Middle meningeal artery - main artery Arises from the external carotid artery to internal maxillary artery Figure 8. Anterior branches of meningeal artery Figure 6. External carotid artery to Middle meningeal artery Other arteries: Internal carotid artery Enters the skull via the foramen spinosum then lies between the Maxillary artery endosteal and meningeal layer of the dura (epidural space) Ascending pharyngeal artery Vertebral artery Occipital artery 2. Middle meningeal veins Middle meningeal veins lie in the endosteal layer of the dura Follow the branches of the middle meningeal a. and drains into the pterygoid venus plexus or the sphenoparietal sinus. Page 2 of 7 [NEUROSCIENCE 1A] 1.12 HYPOTHALAMUS – Dr. Vida Margaret Andal - Connected to the pia by delicate fibrous tissue (web-like structures seen in Figure 11) Figure 11. Arachnoid mater Figure 9. Middle meningeal veins - In certain areas, the arachnoid projects into the venous sinuses to form arachnoid villi (projections). 3. Dural venous sinuses ○ Sites where CSF diffuses into the bloodstream. Receive (1) unoxygenated blood from the brain through the ○ Most numerous along the superior sagittal sinus - Arachnoid granulations = aggregations of arachnoid villi cerebral veins and (2) cerebrospinal fluid from the subarachnoid space through the arachnoid villi Ultimately drain into the internal jugular vein before it gets returned to the lungs to be oxygenated Veins are lined by endothelium and their walls are thick but are devoid of muscular tissue Valveless a. Superior sagittal sinus b. Transverse sinus c. Confluence of sinuses d. Occipital sinus e. Inferior sagittal sinus f. Straight sinus g. Cavernous sinus h. Superior petrosal sinuses i. Inferior petrosal sinus j. Sigmoid sinus Figure 12. Arachnoid projection forming arachnoid villi IV. PIA MATER - Innermost layer; hard to separate gray mater with pia mater in gross anatomy - Vascular membrane covered by flattened mesothelial cells - Closely invests the brain surface, covering the gyri and descending into the deepest sulci - Extends out over the cranial nerves and fuses with their epineurium. Figure 10. Dural venous sinuses III. ARACHNOID MATER - Lies between the pia mater and dura mater - Separated from the dura mater by the subdural space below the dura - Separated from the inner pia mater by the subarachnoid space, which is filled with cerebrospinal fluid (CSF) ○ Space where cerebral arteries, veins and cranial nerves pass through ○ Extends around the optic nerve as far as the eyeball. Page 3 of 7 [NEUROSCIENCE 1A] 1.12 HYPOTHALAMUS – Dr. Vida Margaret Andal Figure 15. Middle meningeal artery Figure 13. Pia mater Lentiform-shaped (look like a lens, has concave surface) Mostly due to traumatic mechanisms of head injury such as motor vehicle collisions, physical assaults or accidental falls V. CLINICAL CORRELATES Higher incidence in males, adolescents and younger adults With advancing age, the dura becomes more adherent to the overlying bone so chances of epidural hemorrhage is lower since it is already closely apposed to the underlying bone Non-traumatic causes: ○ Infection/abscess ○ Coagulopathy ○ Hemorrhagic tumors on that specific space ○ Vascular malformations (dural AV fistula) Figure 14. Meningeal Hemorrhages 1. Epidural Hemorrhage found in layers of dura and even between the dura and skull Extra-axial (most external) collection of blood within the potential Figure 16. Epidural hemorrhage space between the endosteal and meningeal layers of the dura *In CT scan, bleeding/hemorrhage appears dense or white. Confined by the lateral sutures (where the dura inserts), has clear distinct borders Non-surgical if Most common artery to be damaged: anterior division of the middle ○ Hematoma volume less than 30ml meningeal artery ○ Clot diameter of < 15mm Pterion - most common site severed middle meningeal artery ○ Midline shift < 5mm (if there’s a shift in the structures of one hemisphere to another hemisphere) ○ GCS > 8 with no focal neurologic symptoms Repeat neuroimaging within 6-8hrs following brain injury to observe if after 6-8 hours, you still have the same scenario Requires prompt (within 1-2 hours of presentation) surgical intervention (craniotomy and hematoma evacuation) if: Hematoma volume greater than 30ml regardless of GCS GCS < 9 with pupillary abnormalities Midline shift >5mm 2. Subdural Hemorrhage Page 4 of 7 [NEUROSCIENCE 1A] 1.12 HYPOTHALAMUS – Dr. Vida Margaret Andal Collection of blood in the subdural space (between dura mater ○ Neonates: Traumatic birth and use of extraction devices (like and arachnoid mater, not go into the sulci) forceps) Caused by rupture of the bridging veins that connect the ○