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)
Stroke: middle cerebral artery, right hemisphere
Hemineglect: unaware of space and body. patient may deny anosognosia.
Anosognosia: unawareness of dramatic impairment like paralysis/blindness.
Stroke: middle cerebral artery, left hemisphere
Aphasias: speaking gets messed up.
Broca’s - motor problem. comprehension is good.
Wernicke’s - cognitive problem. speaking is easy buy nonsense words come out.
Ischemic stroke:
Oxygen supply is cut off by a clot. Most common type of stroke.
Stroke: anterior cerebral artery
Contralateral hemiparesis and hemisensory loss (leg/foot, paracentral lobule)
If in frontal lobe, personality change.
Stroke: posterior cerebral artery, occipital
Hemianopsia - loss of half of visual field
Visual agnosia - no comprehension of objects in visual field. an associative problem.
Stroke: posterior cerebral artery, temporal
Memory impairment.
Prosopagnosia:
Damage to inferior temporal cortex. Most commonly caused by PCA stroke.
Define: stroke
Death/dysfunction of brain tissue due to vascular disease
Define: occlusion
Closure of blood vessel (atherosclerosis/thrombosis)
Define: hemorrhage
Bleeding from a vessel (hypertension/aneurysm)
Intraparenchymal - within the brain
Extraparenchymal - at brain surface
Define: hematoma
Accumulation of blood, which then clots
Define: embolus
Something that is carried from one place and gets stuck in another
Define: embolisom
Embolus obstructs an artery
Define: aneurysm
Swelling of arterial wall
Define: ischemia
Insufficiency of blood supply
Define: infarction
Neuronal death
Venous drainage of cerebral hemispheres: superficial veins
Drain into superior sagittal sinus and cavernous sinus. Superior sagittal sinus drains into two transverse sinuses, which lead to the sigmoid sinus, which connects to the jugular vein.
Venous drainage of cerebral hemispheres: deep veins
Drain into the great vein of Galen.
