Meninges, ventricles, and CSF

Unit 6

Epidural space

potential space between dura and calvaria

Subdural space

potential space in the innermost dural layer, near the dura-arachnoid interface

subarachnoid space

normally present space, CSF filled, space enlarges in cisterns

What happens if the epidural space opens up

arterial bleeding

What happens if the subdural space opens up

venous bleeding

What are the types of cerebral hemorrhages?

subdural, subarachnoid, epidural, intracerebral

Decorticate rigidity

destructive lesion of the corticospinal tracts near cerebral hemispheres

Decerebrate rigidity

lesion of the diencephalon, midbrain, vestibulospinal pathways

epidural hematoma physical features

* skull fracture
* rapid expanding with arterial blood
* torn middle meningeal artery
* dura pushed away from hematoma

subdural hematoma physical features

* slowly expanding with nexus blood
* torn bridging vein
* dura is attached, so cannot cross falx, tentorium

Shape of an epidural hematoma

local and biconvex (lemon)

Shape of subdural hematoma

diffuse and concave (banana)

What part of the brain would an epidural hematoma be located?

temporal or temporo-parietal

What part of the brain would a subdural hematoma be located?

entire brain surface

What type of consciousness can we expect with an epidural hematoma?

lucid interval

What type of consciousness can be expected with a subdural hematoma?

severe brain damage **immediately present**

Prognosis for epidural hematoma

related to pre-surgical status

Prognosis for subdural hematoma

poor

Amount of patients with epidural hematoma

0\.5% head injury patients

Amount of patients with subdural hematoma

30% head injury patients

Falx cerebri

dural folds that separate the two cerebral hemispheres

Tentorium cerebelli

dural fold between the cerebral hemispheres and the cerebellum

Diaphragm sellae

dural fold that covers the pituitary fossa and admits the infundibulum through a small perforation

Anterior attachment of falx cerebri

crista galli of ethmoid bone

Posterior attachment of falx cerebri

internal occipital protuberance

What part of the tentorium does the brainstem travel through?

tentorium notch AKA tentoria incisura

Anterior (and inferior) attachment of tentorium

petrous bone

Posterior attachment of the tentorium

occipital bone

What type of compartments does the tentorium create?

supratentorial and infratentorial compartments

contents of the supretentorial compartment

forebrain

contents of the infratentorial compartment

* brainstem and cerebellum

What fossa is the infratentorial compartment found in?

posterior fossa

What majorly supplies the dura mater

middle meningeal arter

Anterior blood supply of the dura mater

ophthalmic artery

posterior blood supple of the dura mater

branches of the occipital and vertebral artery

Venous sinuses

between cerebral hemispheres

What parts of the brain/matter do not feel pain?

brain, arachnoid mater, and pia mater

what parts of the brain are pain sensitive?

dura mater, proximal portions of blood vessels at base of brain

What CN does the cranial fossa receive sensory innervation from?

CN V - trigeminal

Where do dural nerves end?

1. near middle meningeal arteries
2. near dural sinuses

What do the dural dural nerves follow?

meningeal arteries

What happens when there is pain near the meningeal arteries

dural nerves perceive pain as localized

What happens when there is pain near the dural sinuses?

dural nerves perceive pain to the peripheral distribution of the CN V

What is the posterior fossa innervated by?

CN 2, 3, 10

What happens when there is pain by the dural arteries

pain is perceived as localized

What happens when there is pain near venous sinuses

pain is referred and perceived behind the **ear and back of neck**

Where can CN 2, 3, and 10 be found near?

1. dural arteries
2. venous sinuses

Arachnoid trabeculae

strains of CT extend to the pia mater and merge with the pia mater

Arachnoid mater

thin, a vascular membrane with few interspersed layers of cells

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semi-transparent and **cobweb-like**

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attached to the dura mater bu the **dural border cells**

Subarachnoid space

where the arachnoid mater conforms with the brain but does not dip into the sulci

Subarachnoid cisterns

areas that contain substantial CSF

What separate arachnoid cisterns from each other

arachnoid trabeculae

What separates blood and CSF in the dural sinuses?

arachnoid mater

Arachnoid villi

herniate through the wall of dural sinus

Arachnoid granulations AKA pacchonian bodies

large clusters of arachnoid villi

What parts of the mater can calcify with age?

arachnoid villi

How does the arachnoid mater have its barrier function?

its cells are connected by tight junctions

How does CSF travel through the arachnoid mater?

one-way valve-type travel

Pathway of CSF through the arachnoid mater

1. allow CSF to flow from subarachnoid space into venous space
2. CSF pressure exceeds venous pressure
3. Never flows in reverse, even if pressure gradient reverses

Pia mater

invests all external surfaces of the CNS, delicate membrane

leptomeningeal complex

the area where the arachnoid trabeculae and pia mater merge, very difficult to distinguish the 2 apart

Virchow-Robin space

each vessel enters and leaves with a sleeve of perivascular space

How is the spinal dura different from the brain dura?

1. spinal dura has no periosteal component
2. cranial epidural is a **potential space**, while the spinal dura is **actual space**

how many denticulate ligaments are there in the spine?

21

filum terminale

anchors the conus medullaris to the caudal end of the spinal dural sheath

What is the function of the denticulate ligaments?

anchor the spinal cord to the arachnoid

Lumbar cistern

where lumbar puncture can be performed, **space in subarachnoid space in the lumbar region**

opening CSF of pressure

90-180 mmH20 while laying supine and lateral

What are the constituents of CSF like

plasma

Procedures that can be performed at the lumbar cisterns?

1. lumbar puncture
2. epidural anesthesia

Where is CSF formed?

lateral portions of 3rd and 4th brain ventricles

Where does CSF emerge from after being formed?

4th brain ventricle apertures → fill subarachnoid space

What is responsible for suspending the brain?

CSF

What is CSF’s role in brain communication?

route for chemical messengers to reach brain rapidly

What are the ventricles of the brain lined with?

ependymal cells

What does the neural tube develop into?

continuous fluid-filled system of ventricles

Cavum septum pellucidum

potential space in between the brain ventricles

how do the lateral ventricles communicate with he 3rd ventricle

inter ventricular foramina of Monroe

how does the 3rd ventricle communicate with the 4th ventricle

aqueduct of sylvius

What side of the lateral ventricles would be larger in a right-handed individual?

posterior horn on LEFT side

What form the lateral ventricles?

corpus callosum and septum pellucidum

What forms the floor and medial wall of inferior horn

hippocampus

What shape do the lateral ventricles make

C-shaped

What would a blockage of the *interventricular foramen of Monroe* cause?

obstructive hydrocephalus

What part of the brain does the 3rd ventricle mostly fill?

midline of diencephalon

interthalamic adhesion

hole found in the 3rd ventricle, where the 2 thalami join each other

Where does the 3rd ventricle end anteriorly?

*lamina terminalis*, remnant of rostral neuropore

what are the recesses of the 3rd ventricle

1. supraoptic recess
2. infundibular recess
3. pineal recess
4. supra-pineal recess

Limits of the 4th ventricle

anteriorly: pons/medulla

posteriorly: cerebellum

Diamond shaped hole in 4th ventricle

rhomboid fossa

Narrow tube in 4th ventricle

lateral recess

Roof of the 4th ventricle

superior medullary velum

Where does the lateral recess of the 4th ventricle end?

flocculus of the cerebellum

Apertures of 4th ventricle

1. unpaired median aperture - foramen of Magendie
2. 2 lateral aperatures - foramina of Luschka

Total volumes of CSF in brain and spinal cord

200mL

Volume of CSF in lateral ventricles

23mL

Volume of CSF in 3rd and 4th ventricles

2mL

Volume of normal ventricular CSF

approximately 10-30mL

How much does SNS stimulation reduce CSF production by?

30%

How many times does CSF completely turnover a day?

3-4 times, actively secreted product