Cranium, Ventricles and Meninges Flashcards
1
Q
Cranial Vault
A
- brain encased in protective layers that cushion it from trauma
- SCALP: Skin, subcutaneous Connective tissue, galea Aponeurotica, Loose areolar connective tissue, Pericardium (periosteum)
2
Q
Fossae
A
- ridges of bone separate base of cranial cavity into compartments
- anterior fossa: frontal lobe, lesser wing of sphenoid separates from middle fossa
- middle fossa: temporal lobe, petrous ridge of temporal bone
- posterior fossa: cerebellum and brainstem
3
Q
Potential Spaces of Meninges
A
- epidural space: dura-skull interface
- subdural space: dura-arachnoid interface
- sub-arachnoid space: arachnoid-pia interface, contains CSF (protects brain, circulates throughout brain and spinal cord, helps maintain ICP) space extends to 2nd sacral segment
- spaces: layers are touching each other and should fluid get in a space will form
4
Q
Dura Mater
A
- tough, fibrous membrane
- periosteal layer: inner surface of skull (outer layer)
- meningeal layer (inner layer-divides in between hemispheres to become –> falx cerebri-interhemispheric fissure; tentorium cerebelli-horizontal shelf between inferior portion of posterior cerebrum and dorsal portion of cerebellum, midbrain passes through tentorial notch=tent over cerebellum and separates it from occipital lobe
- structures above tentorial notch=supratentorial (occipital lobe)
- structures below tentorial notch=infratentorial (cerebellum)
5
Q
Arachnoid Mater
A
- soft,translucent membrane
- separated from dura by narrow subdural space
- CSF percolates over surface of brain
6
Q
Pia Mater
A
- microscopically thin, delicate and highly vascular membrane
- adheres closely to surface of brain and into sulci and over gyri
7
Q
Epidural Space
A
- potential space between skull inner surface and dura
- middle meningeal artery enters foramen spinosum and runs in epidural space: branch of external carotid, supplies dura
8
Q
Epidural Hematomas
A
- tearing of middle meningeal artery
- causes increased ICP
- requires neurological intervention
- usually caused by head trauma or fracture to temporal bone
- lots of bleeding that’s typically faster
- biconvex shape-bleed into space that tends to stop at sutures
- usually no symptoms right away until pressure builds up –> increased volume –> increased ICP –> compression/herniation –> death
9
Q
Subdural Space
A
- between inner layer of dura and loosely adherent arachnoid
- bridging veins in here: drain cerebral hemispheres and pass blood thru dural venous sinuses, sigmoid sinuses, internal jugular veins
10
Q
Subdural Hematoma
A
- tearing of veins in subdural space as they pass from brain to venous sinus
- may be rapid or slow developing
- venous so makes it a slower bleed
- often looks like a crescent shape on CT but not as bright
- Tx: shunts
11
Q
Subarachnoid Space
A
- CSF filled space between arachnoid and pia
- major arteries of brain travel within this space (ACA, MCA, PCA)
- actual space
12
Q
Subarachnoid Hematoma
A
- sub-arachnoid hemorrhage into space often due to saccular (berry) aneurysms…sub-arachnoid HA
- most common in circle of willis (ant communicating and posterior communicating branches)
- diffuse bleeding thinner and ruptures over larger area because it’s an actual space
13
Q
Intracerebral Hematoma
A
-bleeding in brain as a result of trauma, contusion, and/or tearing
14
Q
Meningitis
A
- viral or bacterial
- viral=normally mild
- bacterial=more serious, may lead to damage of brain and cranial nerves
- headache, photophobia, and vomiting
- febrile, purulent
- neck stiffness
- may cause death due to increased ICP and brain displacement
15
Q
Ventricular System
A
- neural tube forms cavities within brain called ventricles
- contain CSF which is produced by choroid plexus inside the ventricles
- brain=elaborate interconnecting ventricular system
- lateral ventricles (one inside each hemisphere)
- 3rd ventricle (diencephalon)
- 4th ventricle (surrounded by pons, medulla, and cerebellum)
- spinal cord-central canal
- brain folds around neural tube when developing and space left behind becomes the ventricles
16
Q
Lateral Ventricles
A
- also called 1st and 2nd
- have extensions or horns that extend in direction where they’re located
- interventricularforamen of monro
- large, C-shaped, located within cerebrum: anterior horn (frontal) begin anterior to foramen of monro, body, posterior horn (occipital), inferior horn (temporal)
- extends into each of the lobes
17
Q
3rd Ventricle
A
- diencephalon (thalamus and hypothalamus form walls)
- interventricular foramen (foramen of monro)
- cerebral aqueduct-communicates to 4th ventricle and travels through midbrain
18
Q
4th ventricle
A
- dorsal surface of brain stem just anterior to cerebellum
- roof of 4th formed by cerebellum and floor by pons and medulla
- cerebral aqueduct (junction to 4th ventricle)
- drained by medial opening=foramen of magendie and laterally there are two foramen of luschka
- these then drain into subarachnoid space
- lateral canal of spinal cord is open in embryos but is close din adults
19
Q
CSF
A
- produced by choroid plexus: located in lateral, 3rd and 4th ventricles
- colorless fluid with little protein or cells
- 150 cc (produced continuously, enough to fill ventricles several times a day
- about 500 cc/day is produced
20
Q
Circulation of CSF
A
- lateral ventricles then through interventricular foramen to 3rd ventricle
- 3rd ventricle then through cerebral aqueduct to 4th ventricle
- 4th ventricle to subarachnoid space
- CSF leaves ventricular system through foramina in 4th ventricle
- percolates around brain
- reabsorbed by arachnoid granulations
- into dural sinuses
- back to bloodstream
21
Q
CSF Examination
A
- usually obtained from lumbar subarachnoid space via spinal tap
- usually L34 or L45 interspaces
- indications…
- suspected infection
- diagnosis of subarachnoid hemorrhage
- chemical and immunologic profiles to aid in diagnosis of disorders
- cytologic examination when carcinomatous meningitis is suspected
- manometric pressure
22
Q
Hydrocephalus
A
- buildup of fluid in cavities (ventricles) deep within brain
- excess fluid increases size of ventricles and puts pressure on brain
- can occur at any age but is common among infants and older adults
- surgical treatment can restore and maintain normal CSF levels in brain
- variety of interventions often required to manage symptoms or functional impairments resulting from hydrocephalus
23
Q
Blood Brain Barrier
A
- capillary walls of endothelial cells in most of body separated by fenestrations allowing free passage of fluids and molecules
- in brain the capillary endothelial cells linked by tight junctions
- substances leaving or entering brain must travel through endothelial cells via cellular transport
- protects brain from chemical fluctuations in body
- barbiturates can enter; HTN can also cause junctions to be looser and less effective
24
Q
Blood-CSF Barrier
A
- similar to blood brain barrier
- between choroid plexus and CSF
- capillaries of choroid plexus are permeable but choroid epithelial cells form a barrier between blood and CSF
25
Q
Disruptions to Blood Brain Barrier
A
- brain tumors
- infections
- trauma
- HTN
- can allow fluids into interstitial space
- in certain brain regions called circumventricular organs, BBB is disrupted to allow brain to respond to changes in chemistry and secrete modulatory neuropeptides into bloodstream
26
Q
Elevated ICP
A
- contents of intercranial space are confined: blood, brain, CSF
- when there is a space-occupying mass, something must leave skull to accommodate
- smaller lesions can be accommodated but larger ones will cause ICP to rise leading to herniation and death of tissues
27
Q
Symptoms of Elevated ICF
A
- headache
- altered mental status
- nausea and vomiting
- papilledema (engorgement and elevation of optic disc)
- visual loss
- diplopia
- cushing’s triad: HTN, bradycardia, and irregular respirations –> pressing on brainstem
28
Q
Brain Herniations
A
-mass effect severe enough to push structures from one area to another
29
Q
Head Trauma
A
- concussion-reversible impairment of neurologic function for a period of hours or minutes following head injury
- CT and MRI are normal
- clinical features…
- LOC
- “seeing stars”
- headache
- dizziness
- nausea
- vomiting
- can lead to increased ICP
30
Q
Corticomedullary Junction
A
- where spinal cord meats brainstem at medulla
- happens at the foramen magnum of skull
31
Q
Meningioma
A
- tumor in meninges or space between meninges
- compressesnervous tissues and may cause a shift in them toward midline
32
Q
CSF Cistern in Subarachnoid Space
A
- CSF collection sites
- where arachnoid space widens to hold CSF
- Prepontine cistern: in front of pons
- cisterna magna: largest and below cerebellum
- lumbar cistern: where cauda equina is; lumbar punctures happen here
33
Q
Circumventricular Organs
A
- organum vasculosum: keeps fluid balance
- neurohypophysis: maintains blood and releases hormones
- pineal: use of melatonin for sleep
- area postrema: vomiting center-detects toxins and expels them
