Cranium, Ventricles, & Meninges

cranium

bony framework of the head that protects the head and houses special sensory organs

neurocranium

houses the brain, meninges, supporting vasculature, and cranial nerve nuclei and associated fibers until they exit

"cranial vault"

calvaria

roof of the neurocranium

cranial base

floor of the neurocranium

- frontal

- ethmoid

- sphenoid

- occipital

- temporal (2)

- parietal (2)

what bones make up the neurocranium (6)?

viscerocranium

forms the anterior part of the cranium and consists of bones surrounding the mouth, nose, and most of the orbits

- mandible

- ethmoid

- vomer

- maxilla (2)

- inferior nasal conchae (2)

- zygomatic (2)

- palatine (2)

- nasal (2)

- lacrimal (2)

what bones make up the viscerocranium (9)?

coronal suture

sagittal suture

lambdoid suture

squamous suture

suture

interlocking line of union between bones

cranial fossa

three paired, tiered depressions (anterior, middle, posterior) on the internal base of the skull that cradle and protect the brain

anterior cranial fossa

part of the cranial fossa that contains openings for olfactory and ethmoidal structures & supports the frontal lobes

middle cranial fossa

part of the cranial fossa that is the major passageway for cranial nerves 2-6, and houses the temporal lobes & pituitary gland

posterior cranial fossa

part of the cranial fossa that is a major passageway for cranial nerves 7-12, and houses the cerebellum, pons, medulla, and the fourth ventricle

1. ethmoid

2. frontal

3. lesser wing of sphenoid

what 3 bones make up the anterior cranial fossa?

foramen cecum

hole that is typically closed, but may transmit the emissary vein

cribiform foramina

hole that transmits olfactory nerve filaments

ethmoidal foramina

hole that transmits ethmoidal nerves, arteries, and vessels

sella turcica

region of the middle cranial fossa that houses the pituitary gland

1. sphenoid (body/greater/lesser wings)

2. temporal bone (squamous & petrous)

what 2 bones make up the middle cranial fossa?

optic canal

hole that transmits the optic nerve (CN II) & the opthalmic artery

superior orbital fissure

opening that transmits cranial nerves III, IV, V1 and VI, and the superior opthalmic vein

foramen rotundum

hole that transmits the maxillary nerve (CN V2)

foramen ovale

hole that transmits the mandibular nerve (CN V3) and the accessory meningeal artery

foramen spinosum

hole that transmits the middle meningeal artery and vein

1. occipital

2. temporal (petrous part)

3. sphenoid (posterior)

what 3 bones make up the posterior cranial fossa?

foramen magnum

large opening at the based of the skull that transmits the spinal cord, vertebral arteries, and spinal accessory nerve (CN XI)

internal acoustic meatus

passage for facial (VII) and vestibulocochlear (CN VIII) nerves

jugular foramen

opening that transmits the internal jugular vein and cranial nerves IX, X, and XI

hypoglossal canal

hole that transmits the hypoglossal nerve (CN XII)

cervicomedullary junction

transition between the medulla oblongata and upper cervical spinal cord (C1-C2) that is located at the level of the foramen magnum

*houses ascending/descending tracts (decussation) and nuclei that influence breathing, CV control, and CN 9-12

*orange line on picture

1. skin

2. connective tissue

3. aponeurosis

4. loose connective tissue

5. pericranium

5 layers of the scalp?

1. dura mater

2. arachnoid mater

3. pia mater

3 meninge layers?

dura mater

dense, tough, outermost meningeal layer that adheres to the inner surface of the skull

*provides mechanical protection & stabilizes brain

1. periosteal layer

2. meningeal layer

2 layers of the cranial dura mater?

periosteal layer

outer layer of dura mater that is attached to the skull

meningeal layer

inner layer of the dura mater that contains the falx cerebri and tentorium cerebelli

"true dura"

falx cerebri

sickle-shaped meningeal fold of the dura mater that lies between L & R cerebral hemispheres

*sup. sagittal sinus along superior margin

*inf. sagittal sinus along inferior margin

ethmoid, internal occipital protuberance

the falx cerebri runs from the ____ bone to the ______ _____ _____

tentorium cerbelli

horizontal meningeal fold of the dura mater that separates the cerebellum from the occipital lobe

*contains passage for brainstem (tentorial notch)

dural venous sinuses

large veins in the dura mater that drain venous blood and CSF from the vein

*superior & inferior sagittal

*transverse & sigmoid

epidural space

potential space between the inner surface of the skull and the dura mater

*contains meningeal arteries, veins, and nerves

*ARTERIAL injury

epidural space, middle meningeal

______ _____ is the common site for epidural hematomas and is commonly associated with ____ _____ artery

epidural hematoma

presentation of what cranial disorder?

brief loss of consciousness → lucid interval (short period of restored consciousness & mental clarity) → rapid decline → death (if no immediate treatment)

subdural space

potential space between dura mater and arachnoid mater that contains a thin film of fluid

*VENOUS injury

subdural hematoma

venous bleeding under the dura mater that presents with delayed or gradual symptoms and is often common in adults that take anticoagulants

subdural hematoma

presentation of what cranial disorder?

- headache

- confusion

- weakness

- gait changes

arachnoid mater

middle meningeal layer between the dura mater and pia mater that has a thin, avascular membrane resembling a spider

*protective barrier around brain

subarachnoid space

space between the arachnoid mater and pia mater that is filled with CSF

*contains major cerebral arteries and veins

*CSF cushions the brain and spinal cord, nutrient delivery, and waste removal

arachnoid granulations

extensions of the arachnoid mater that allow excess CSF to be absorbed by the dural venous sinuses

*↓ fluid build up

subarachnoid hemorrhage

bleeding into the subarachnoid space that disrupts CSF flow and can lead to ↑ intracranial pressure

subarachnoid hemorrhage

presentation of what cranial disorder?

- headache

- sensitivity to light (photophobia)

- neurological deficits

pia mater

thin, delicate, innermost meningeal layer that provides structural support to neural tissue and contributes to the blood brain barrier

pia mater injury

commonly seen in meningitis or inflammatory conditions, and may affect cortical function seen in surface-level brain injuries (TBI, infection)

CSF, ependymal cells

ventricles of the brain are filled with _____ and are lined by _____

lateral ventricles

set of paired ventricles lying within the cerebral hemispheres that contain the choroid plexus for CSF production

*largest

choroid plexus, ependymal cells

the _____ _____ in the lateral ventricles produce CSF, and _____ ______ distribute CSF

third ventricle

the ventricle located between thalami and are close to autonomic centers & hypothalamus

interventricular foramen

the lateral ventricles and third ventricle are connected by what structure?

cerebral aqueduct

structure that connects the third and fourth ventricles, and is located at the midbrain

*vulnerable to obstruction due to narrow nature

*common cause of non-communicating hydrocephalus

fourth ventricle

the ventricle located between the cerebellum and brainstem, connecting to the subarachnoid space via lateral foramina of Luschka and medial foramina of Megendie for CSF distribution

*connects spinal cord to central canal

cerebrospinal fluid (CSF)

clear fluid surrounding the brain and spinal cord that is essential for CNS protection and homeostasis

*total volume ~ 150 mL

* ~ 500 mL produced daily

CSF

5 functions of what structure?

1. cushion & protect brain and spinal cord

2. reduce brain weight (buoyancy)

3. deliver nutrients and remove waste

4. regulate intracranial pressure

5. provide stable chemical environment for neurons

CSF impairments

presentation of what impairment/issues with what cranial structure?

- balance

- gait

- cognition

- hydrocephalus

cisterns

enlarged spaces within the subarachnoid space that act as reservoirs facilitating CSF circulation

cisterna magna

cistern found between the cerebellum and medulla

interpeduncular cistern

cistern found at the base of the midbrain

suprasellar (chiasmatic) cistern

cistern that surrounds the optic chiasm

quadrigeminal cistern

cistern posterior to the midbrain

pontine cistern

cistern anterior to the pons

basal

subarachnoid hemorrhage often accumulates in _____ cisterns

blood brain barrier

protective separation between blood and CNS tissue that regulates what substances enter the brain and spinal cord

*capillary endothelial cells, basement membrane, astrocyte end-feet, pericytes

*infection control!

1. oxygen

2. carbon dioxide

3. lipid-soluble substances

3 substances that can cross the BBB?

glucose, amino acids

the blood brain barrier allows substances through, which are transported by _____ and _____

blood brain barrier (BBB)

presentation of what impairment/issues with what cranial structure?

- spasticity

- fatigue

- immune cell infiltration

- infection

- increased cytokines

- cerebral edema

blood-CSF barrier

barrier regulating exchange between blood and CSF, overall maintaining a stable chemical environment for the CNS

*located at choroid plexus (lateral, third, fourth ventricles)

*vascular tissue, fenestrated capillaries, epithelial cell layer

choroid plexus, brain capillary

the blood CSF barrier is contained within the _____ _____ epithelium, and the blood brain barrier is contained within the ____ ____ endothelium

sodium, chloride, water

transporters of CSF (ependymal cells) regulate _____, ______, and _____ movement

neonates

barrier immaturity within ______ increases vulnerability to infection (pia mater)

older age

_____ may reduce barrier efficiency and commonly contributes to neurological risks

5-15

normal intracranial pressure (ICP) is around _____ to _____ mmHg in adults

monro-kellie doctrine

states that due to rigidity of the cranium.... brain tissue, blood, and CSF share a fixed cranial volume

1. TBI

2. intracranial hemorrhage

3. edema

4. hydrocephalus

5. tumors

6. impaired venous drainage

6 common causes of increased ICP?

elevated ICP

presentation of what impairment/issues with what cranial structure?

- headache

- nausea/vomiting

- altered consciousness

- pupillary changes

- cushing's triad (HTN, bradycardic, irregular respiration)

cushing's triad

three classic signs—bradycardia, hypertension, and bradypnea—seen with increased ICP

1. valsalva

2. excessive exertion

3. improper positioning

what 3 things should be avoided when working with a pt that has increased ICP?

brain herniation

displacement of brain tissue to due increased ICP

subfalcine (cingulate) herniation

herniation of the brain where the medial frontal lobe shifts under the falx cerebri

transtentorial (uncal) herniation

herniation of the brain where the temporal lobe shifts through the tentorial notch

*1 on diagram

tonsillar herniation

herniation of the brain where cerebellar tonsils descend through the foramen magnum

central herniation

herniation of the brain where there is downward displacement of the brainstem

brain herniation

presentation of what impairment/issues with what cranial structure?

- altered consciousness

- pupillary asymmetry or non-reactive pupils

- abnormal posture

- respiratory and CV instability

intracranial hemorrhage (ICH)

bleeding within the skull that leads to increased ICP and reduced cerebral perfusion

*traumatic or spontaneous

*major cause for neurologic morbidity and mortality

epidural hemorrhage

arterial bleeding between the skull and dura

*middle meningeal artery affected

subdural hemorrhage

venous bleeding between the dura and arachnoid

*due to rupture of bridging veins

intracerebral hemorrhage

bleeding within the brain tissue

ICH

presentation of what impairment/issues with what cranial structure?

- headache

- nausea/vomiting

- altered consciousness

- weakness

- speech or vision deficits

- seizures

- rapid neurological decline

hydrocephalus

excess CSF causing ventricular enlargement