Lecture 1 Flashcards
Layers of meninges:
Outside stuff Dura mater > Periosteal > Meningeal Arachnoid mater Subarachnoid space Pia mater
Outside stuff:
Skin, connective tissue, periosteum
Dura mater:
Thick, impermeable outermost layer. Two layers (periosteal, meningeal); layers are closely united except at venous sinuses.
Arachnoid mater:
Impermeable middle layer. Loosely associated with the dura mater.
Subarachnoid space:
Filled with CSF. Holds cerebral arteries.
Pia mater:
Delicate, permeable innermost layer. Rests on the surface of the brain and follows its folds.
Vascularized - arteries are sheathed by the pia as they enter the parenchyma (brain proper). The pia is lost as the arteries become capillaries.
Pia fuses with ependyma to form choroid plexus.
Periosteal layer of the dura:
Tightly attached to skull. Continuous with the periosteum (outside of skull). Not continuous with spinal cord dura.
Meningeal layer of the dura:
Penentrates spaces in cerebral hemispheres. Continuous with spinal cord dura and epineurium of cranial nerves.
Venous sinuses:
Large, low-pressure blood vessels for return of cerebral venous blood.
Falx cerebri:
Sickle-shaped fold separating the cerebral hemispheres. Superior sagittal sinus, inferior sagittal sinus, transverse/straight sinus.
Tentorium cerebelli:
Fits between cerebellum and occipital lobes. Separates posterior cranial fossa from the rest of the cranial vault. Transverse/straight sinus.
Function of partitions in the meningeal layer:
Both stabilize the brain during de/acceleration.
Epidural space and hemorrhage/hematoma: (what is it? why does it happen? symptoms?)
Potential space between skull and dura.
Usually caused by rupture of the middle meningeal artery during head trauma.
Initially no symptoms (lucid interval). Within hours, the hematoma compresses the brain, ICP increases; herniation and death will occur unless surgery is performed.
Subdural space and hemorrhage/hematoma: (what is it? why does it happen?)
Potential space between dura and arachnoid mater.
Usually caused by the rupturing of the bridging veins that pass through en route to dural sinuses.
Which is worse, epidural or subdural space?
Subdural is worse because the arachnoid mater is weaker than the dura mater.
Different severities of subdural hematoma:
Acute: high velocity impact, hyperdense.
Chronic: old people (seen when the brain atrophies and has room to wiggle around, making bridging veins more susceptible to injury), brain accommodates over time. Isodense (1-2 weeks), hypodense (3-4 weeks).
Aneurysm:
Hemorrhage in subdural space.
Trabeculae:
Delicate threads attaching the arachnoid to the pia.
Arachnoid granulations:
Site where CSF diffuses into venous sinuses.
Headaches: pain
Trigeminal nerve - pain from dura above tentorium (forehead, face)
First three cervical nerves - pain from dura below tentorium (back of head, neck)
Headaches: causes
Space-occupying legions: raised ICP causes irritation and stretching of dura.
Migraines: activation of trigeminal nerves.
Meningitis: global pain caused by inflammation of meninges.
Meningiomas: tumours in the meninges
Hangover: involves direct toxic effect on meninges.
Vascular system: territories of blood supply
Anterior circulation: internal carotid artery
Posterior circulation: basilar arter and vertebral arteries (2)
The two circulations differentiate at the aorta.
Circle of willis:
Place where vessels split/come together. Allows for overlapping blood supply.
Stroke: middle cerebral artery
Contralateral hemiparesis and hemisensory loss (face/arm)
