Cranium, Ventricles and Meninges Flashcards Preview

DPT 736 Neuroanatomy > Cranium, Ventricles and Meninges > Flashcards

Flashcards in Cranium, Ventricles and Meninges Deck (33)
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Cranial Vault

-brain encased in protective layers that cushion it from trauma
-SCALP: Skin, subcutaneous Connective tissue, galea Aponeurotica, Loose areolar connective tissue, Pericardium (periosteum)



-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


Potential Spaces of Meninges

-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


Dura Mater

-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)


Arachnoid Mater

-soft,translucent membrane
-separated from dura by narrow subdural space
-CSF percolates over surface of brain


Pia Mater

-microscopically thin, delicate and highly vascular membrane
-adheres closely to surface of brain and into sulci and over gyri


Epidural Space

-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


Epidural Hematomas

-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


Subdural Space

-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


Subdural Hematoma

-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


Subarachnoid Space

-CSF filled space between arachnoid and pia
-major arteries of brain travel within this space (ACA, MCA, PCA)
-actual space


Subarachnoid Hematoma

-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


Intracerebral Hematoma

-bleeding in brain as a result of trauma, contusion, and/or tearing



-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


Ventricular System

-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


Lateral Ventricles

-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


3rd Ventricle

-diencephalon (thalamus and hypothalamus form walls)
-interventricular foramen (foramen of monro)
-cerebral aqueduct-communicates to 4th ventricle and travels through midbrain


4th ventricle

-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



-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


Circulation of CSF

-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


CSF Examination

-usually obtained from lumbar subarachnoid space via spinal tap
-usually L34 or L45 interspaces
-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



-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


Blood Brain Barrier

-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


Blood-CSF Barrier

-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


Disruptions to Blood Brain Barrier

-brain tumors
-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


Elevated ICP

-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


Symptoms of Elevated ICF

-altered mental status
-nausea and vomiting
-papilledema (engorgement and elevation of optic disc)
-visual loss
-cushing's triad: HTN, bradycardia, and irregular respirations --> pressing on brainstem


Brain Herniations

-mass effect severe enough to push structures from one area to another


Head Trauma

-concussion-reversible impairment of neurologic function for a period of hours or minutes following head injury
-CT and MRI are normal
-clinical features...
-"seeing stars"
-can lead to increased ICP


Corticomedullary Junction

-where spinal cord meats brainstem at medulla
-happens at the foramen magnum of skull