Unit 5: Tutoring Flashcards
Layers Protecting the Brain
SCALP
- Skin
- subcutaneous Connective tissue
- galea Aponeurotica
- Loose areolar connective tissue
- Pericraneium (periosteum)
Meninges
“PAD” the brain
- Pia Mater
- Arachnoid Mater
- Dura Mater
Dura Mater
-Outermost
-Thickest/Toughest Membrane
-Means “Tough Mother”
-Peforated for cranial Nerves/Blood Vessels
Two Layers
-Periosteal: External
-Meningeal: Internal
Dural Inflodings
-Falx Cerebri
-Tentorium Cerebelli
(Both made from meningeal layer)
Falx Cerebri
Fold that extends into the longitudinal fissure (separates R/L hemispheres)
Tentorium Cereeblli
(in the back) fold that divides the occipital lobe from the cerebellum (separates cerebral hemispheres)
-Tentorial Notch: Opening in tentorium that the midbrain passes through
Separation of the dura layers
Dural Venous SInuses which mainly drain blood via the sigmoid sinus into the internal jugular vein
These folds can cause damage to the brain during high velocity impact
Falx Cerebri: Damage to the Corpus Callosum
Tentorium Cerebelli: Damage to midbrain, vessels, CN3
Epidural Space
- Epi= Above (btw skull and dura)
- Contains: Middle Meningeal Artery
- If ruptured: Epidural Hematoma (result of temporal bone fracture)
Epidural Hematoma
- Result of temporal bone fracture
- Initially asymptomatic but within hours: Increased ICP, herniation, death
Middle Meningeal Artery (Epidural Space)
-Branches odd the external carotid artery
Enters space through the foramen spinosum
-Supplies the dura
Subdural Space
- Sub=Below (btw dura and arachnoid)
- Contains: Bridging veins (susceptible to shearing forces bc brain moves; crescent shaped
- Bridging Veins: Cross the subdural space and drain into venous sinuses
- If ruptured: Subdural hematoma
Subdural Hematoma
-Chronic (elderly, shrinking brain) and acute (high velocity impacts/trauma)
Arachnoid Mater
- Delicate membrane lying between pia (internally) and dura (externally)
- Adheres to dura mater
- Arachnoid granulations
- Impermeable (doesn’t allow fluid to pass)
- Perforated to allow CN & BV to pass-through
Arachnoid Granulations
Serve as one way valve to the dural sinus
Subarachnoid Space
- Between the Arachnoid and Pia Mater
- Has trabeculae that suspend the brain
- CSF Circulation
- Contains major arteries of the brain
Subarachnoid Hemorrhage
-Buildup of blood into the CSF
-Cause severe headaches
Hemorrhages can be:
-Traumatic: Ruptured vessels that bleed in the space (more common, no vasospasm seen)
-Non-traumatic: (spintaneous) Arterial aneurysm that bleeds in the space
Non-Tramatic Subarachnoid Hemorrhage
- Spontaneous
- Arterial aneurysm that bleeds in the space
- A-comm=30%, P-comm= 25%, MCA= 20%
- Atroveneous malformation 4-5% of cases
- Sudden headache
- Delayed cerebral vasospasm: arteries realize they’re bleeding and constrict too much leading to ishemic stroke (if not monitored could lead to infarct)
Pia Mater
- Thinnest/most delicate
- Highly vascular; impermeable
- Adheres to brain tissue (contours of the brain)/spinal cord
- Extends out from spinal cord to help anchor it to the dura by dentate ligaments
What can happen when we get hemorrhages in the brain?
Herniations
Herniation
When mass effect is severe enough to push intracranial strictures from one compartment to another Types: -Subfalcine Herniation -Central Herniation -Transtentorial Herniation -Tonsillar Herniation
Subfalcine Herniation
Cingulate gyrus gets pushed under the falx cerebri
-Usually from unilateral pressure
Central Herniation
Central downward displacement of the brainstem
Uncal Transtentorial Herniation
Medial aspect of the temporal lobe (uncus) is pushed inferiorly against tentorium cerebelli
Tonsillar Herniation
Cerebellar tonsils get pushed down into foramen magnum
-Life threatening because it compresses the brainstem (regulates respirations and BP)
Ventricles
- 2 Lateral Ventricles: Telencephalon
- 1 Third Ventricle: Diencephalon
- Cerebral Aqueduct: Mesencephalon
- 1 Fourth Ventricle: Metencephalon/Myelencephalon
Chroid Plexus/CSF Production
- Occurs in the choroid plexus of each ventricle
- Made of ependymal cells and choroid epithelial cells which produce CSF (constantly!)
- Create a pressure gradient (80-180mm of water = normal)
- Cilia assist in circulating CSF
CSF Normal Values
- Normal Volume: 150cc; 20cc/hour; about 500cc/day
- Infant 10-100mm of water
- Normal Adult: 80-180mm of water
- Obese Adult: up to 280mm of water
- Appearance: Sparkling clear; not cloudy or colored with abnormal cells
CSF Functions
- Buoyancy
- Cushioning
- Cleaning
- Ionic Balance
CSF Flow
- Choroid Plexus
- Lateral Ventricles
- Interventricular Foramen (aka Foramen of Monroe)
- 3rd Ventricle
- Cerebral Aqueduct
- 4th Ventricle
- Foramen of Luschka/Magendie
- Spinal Cord
- Subarachnoid Space
- Arachnoid Granulations (reabsorbed through these)
- VDural enous Sinus
CSF diffuses through _____ & is reabsorbed into the _____?
- Arachnoid Granulations
- Venous System
The veins of the brain empty into…
Sinuses
Sinuses
-Formed by the 2 layers of the dura
-No halves in sunuses
-Drainage occurs from the superior sagittal sinus into the transverse sinuses and sigmoid sinus
-Major sinuses that feed into the internal Jugular Vein
Superior:
-Confluence SInus
-Superior Sagittal Sinus
-Transverse Sinus
-Sigmoid Sinus
-Cavernous Sinus
Deep
-Vein of Galen
-Straight Sinus
Sigmoid Sinus
Exits skull through jugular foramen
Superior Sagittal Sinus (superior)
Big one on top
Inferior Sagittal SInus (superior)
Runs along the bottom edge of the falx cerebri heading back towards the tentorium cerebelli where it becomes the straight sinus and joins with the superior sagittal sinus
Confluence of the Sinuses (SIS) (superior)
AKA: Torcular Herophili
- Area where the superior & inferior sagittal, occipital & straight sinusus comverge and are drained by the transverse sinus
- At the confluence, they head down the sigmoid sinus then into the IJV
Cavernous Sinus (superior)
-Sits on the sella turcica of the skull
-ICA runs through here
-Uses the Superior Petrosal & inferior petrosal sinuses to drain into the transverse sinus
Surrounds the:
-Pituitary gland
-CN 3, 4, 5, &6
An abnormality in venous return can compress the CN’s or IC artery
Straight Sinus (deep)
Formed by the inferior sagittal sinus and the vein of galen
Sagittal SInus Thrombosis
Obstruction of venous drainage which causes an increase in ICP
- Common after birth
- Brain decreases BP which decreases cerebral perfusion and can lead to an infarct
- Delta sign: Superior sagittal sinus will be black on scans
Foramen of Monro (interventicular foramen)
-Connects lateral ventricles to the 3rd ventricle
Cerebral Aqueduct
Connects 3rd and 4th ventricles; Travels through midbrain
Foramen of Magendie
Connects 4th ventricle medially to the SC
-Magendie=Medial
Foramen of Luschka
Connects 4th ventricle laterally to the SC
-Luschka=Lateral
Increased ICP (Disorders of CSF System)
-Can occur with any increase in size of any structure
Symptoms
-Headache
-Nasea
-Bradycardia
-Hypertension
-Loss of Consciousness
-Papilledema (optic disk pushed forward, CN2)
-Cushings Triad: HTN, Bradycardia, irregular respirations
(minto compenation can be made by body decreasing CSG andd blood volume without much rise in ICP)
Increased ICP Treatment
- Elevating bed to 30° to promote drainage
- Medications
- Shunts: Placed in lateral ventricle
- Hemicarniectomy: Removal of 1/2 the skyll overlying mass lesion to allow for surgery
- Craniotomy: Drill holes in the skull then saw the piece of skull off (bone flap) to allow the brain to swell and perform procedure (bone flap stored in storage or patients abdominal wall unil replaced)
- Lumbar Puncture: allows to check CSF
Hydrocephalus (Disorders of CSF System)
-Dialation/ Enlargement of the ventricled due to accumulation of fluid in the brain
Causes
-Blocked CSF circulation
-Impeded CSF absorption
-Too much production
Result:
-Ventricles push (pressure on corticobulbar & corticospinal tracts causing increased spacity/weakness