08 26 2014 Meninges and Ventricals Flashcards
Cerebral Spinal fluid
Clear, colorless liquid
140mL
Provides buoyancy, and protects against sudden movements.
Some antibacterial properties
Cisterns
Enlarged areas of subarachnoid space (around brain stem)
- Perimesencephalic cisterns
- Prepontine cistern
- cisterna magna
perimesencephalic cisterns
Interpeduncular cistern (ventral and abovepons)
Quadrigeminal (and ambient) cisterns (between corpus collusum and cerebellum and pons)
Prepontine cistern
ventral to pons (aka in front of pons)
Cisterna magna
below cerebellum
Why do you use a lumbar puncture?
Diagnose subarachnoid hemorrhage and meningitis or introduce drugs.
Adults: L3-L4
Children: L4-L5
What is normal pressure of CSF
< 20 cm H2O
Layers of Dura in Brain vs. spinal cord?
Brain: 2 layers
-periosteal and meningeal – split to form sinuses
Spinal cord : 1 layer – meningeal (vertebrae have their own periosteum)
Layers of Arachnoid in brain vs. spinal cord?
Brain: arachnoid trabecular and many cisterns
Spinal cord: fewer travecule and 1 cistern (lumbar cistern)
- this is where you do lumbar puncture
Layers of Pia in brain vs. spinal cord?
Spinal cord: forms denticulate ligaments and filum terminal
Denticulate Ligament of spinal cord?
anchor pia to dura (from pia to dura)
Filum Terminum of spinal cord?
anchors spinal cord to arachnoid.
Coccygeal ligament (filum terminale externum) of spinal cord?
anchors spinal cord to coccyx
What are the dural folds?
just name them
Invaginations of inner dural layer. Create the supratentorial and infratentorial spaces (in reference to tentorium)
- Flax cerebri
- Falx cerebelli
- Tentorium cerebelli
- Diaphragm sellae
Falx cerebri
in between cerebral hemispheres (in longitudinal fissure)
Falx cerebelli
separates cerebellum in right vs. left
Tentorium cerebelli
lies between the posterior cerebral hemispheres and the cerebellum
Diaphragm sellae
circular fold beneath the brain that covers the sella turcica.
posterior fossa
the cavity formed with occipital bone as base and tentorium cerebella as roof.
Contains cerebellum and brainstem
tentorial notch
hole within dural folds where the brainstem can go through
Flow of CSF
lateral ventricles — foramen of Monro–> third ventricle (diencephalon) – cerebral aqueduct (midbrain) –> 4th ventricle in pons/medulla— foramen of Magendie and Luschka –> subarachnoid space around brian and spinal cord —> arachnoid granulations —> veinous sinuses
Blood - CSF barrier
choroidal capillaries are fenestrated with no tight junctions BUT choroid epithelium (ependymal cells w/tight junctions) has the tight junctions. Therefore the choroid epithelium form the blood-CSF barrier
hydrocephales
increase volume of CSF
- overproduction (rare)
- Obstruction of flow
- decrease reabsorption via arachnoid granules
May be chronic in children
Communicating hydrocephalus
blockage of CSF reabsorption in arachnoid granules OR obstruction of flow in the subarachnoid space
Noncommunicating hydrocephalus
obstruction of flow within ventricular system
Symptoms of increased intracranial pressure
- headache
- Nausea and vomitting
- 6th Nerve palsy
- eyes appear to look downwards
- papilledema (swelling of optic papilla)
- Decreased vision/ diplopia (double vision)
- Decreased cognition
- Unsteady gait
- Cushing’s triad: hypertension, bradycardia, and irregular respirations (brainstem)
Blood brain barrier
formed by tight junctions of epithelium on capillary. The BBB may be disrupted by infections, tumor or trauma and can cause “vasogenic edema”
- shows up as breakdown of epithelium.
Circumventricular organs
parts in which the BBB is interrupted. It enables the brain to resound to changes in the blood chemistry
- Area postrema: detecting circulating toxins that cause vomiting
Epidural Hematoma
Potential space
caused by trauma (fracture of the temporal bone) that lesions middle meningeal artery.
Rapidly expanding hemorrhage
Lens- biconvex shape
Increase in pressure causes a herniation
Subdural hematoma
Potential space
rupture of bridging veins due to a high velocity impact. (acute)
Can be a chronic condition in elderly (brain shrinks which puts them at an increased risk of tearing a bridging vein.
Cresent shape
Subarachnoid hematoma
Real space – has blood vessels
- Non-traumatic
- WORST HEADACHE OF MY LIFE
- aneurysms or Arteriovenus malformations
- Traumatic
- bleeding into CSF from damaged blood vessels associated with cerebral contusions and other traumatic brain injuries
What are the two types of Aneurysms?
- Saccular/ Berry:
- balloon like
- Fusiform
-main vessel itself becomes dilated (less likely to rupture and thereofer more likely to compress something)- Posterior communicating arter –> 3rd Nerve
palsy
- Posterior communicating arter –> 3rd Nerve
where do aneurysms mostly occur? (Saccular)
- Anterior communicating artery (30%)
- Posterior communicating artery (25%)
- Middle cerebral artery (20%)
- Posterior circulation (15%)
Transtentonial Herniation and symptoms
Uncal herniation – medial temporal lobe herniates through tenurial notch.
- blown pupil – ipsilateral dilated, unresponsive pupil (CN 3)
- Hemiplegia: paralysis of half of the body
- coma
- posterior cerebral arteries may be compressed – infarction in posterior cerebral artery territory.
Central herniation
central downward displacement of the brainstem.
Mild herniation = traction on abducen’s nerve = lateral rectus (unilateral or bilateral)
Tonsillar herniation
Cerebellar tonsils move downward through foramen magnum.
- compression of medulla
- leads to respiratory arrest, blood pressure instability and death
Subfalcine herniation
unilateral mass lesions that cause cingulate gyrus (and other structures) to herniate under the flax cerebra from one side of the cranium to the other.
- may be symptomatic
- may have symptoms of increased cranial pressure
