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Meninges and CSF
BRS flashcards
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Medical
Professional
01/13/2013

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Term
Meninges
Definition

three C.T. membranes that cover spinal cord and brain.

consists of: pia mater and arachnoid and dura mater (pachymeninx)

 

Term
Pia Mater
Definition
  • delicate
  • highly vascular 
  • covers surface of brain and spinal cord 
  • connected to arachnoid by trabeculae

forms:

denticulate ligaments

filum terminale  

Term
Denticulate ligament
Definition

two lateral flatteend bands of pial tissue

adheres with dura mater w/ 21 attachments 

Term
Filum Terminale
Definition

nonneural band of tissue 

condensation of pia mater

extends from conus medullaris to end of dural sac and fuses with it

Term

Arachnoid 

Definition
  • delicate
  • non-vascular C.T.
  • b/w dura and pia

forms:

a. arachnoid granulations/arachnoid villi

b. subarachnoid space  

Term
Dura Mater
Definition
  • outer layer of meninges 
  • dense C.T.

forms:

a. falx cerebri

b. tentorium cerebelli

c. diaphragma sellae

d. dural sinuses

Term
Supratentorial dura innervation
Definition
trigeminal nerve 
Term
Posterior fossa innervation
Definition

vagal nerve

upper spinal nerve

Term
Falx Cerebri
Definition
  • b/w cerebral hemispheres in long. cerebral fissures
  • contains: superior and inferior sagittal sinuses b/w its two layers 
Term
Tentorium Cerebelli
Definition
  • separates: posterior cranial fossa from middle cranial fossa
  • separates: temporal and occipital lobes from cerebellum and infratentorial brainstem

contains:

a. tentorial incisure

Term
tentorial incisure
Definition

notch through which brainstem passes 

present in tentorium cerebelli

 

Term
Diaphragma sellae
Definition
  • roof of hypophyseal fossa
  • contains: aperture through which hypophyseal stalk (infundibulum) passes
Term
Dural Sinuses
Definition
[image]
Term
Meningeal Spaces
Definition
  • Spinal Epidural Space
  • Cranial Epidural Space
  • Subdural Space
  • Subarachnoid Space
  • Subarachnoid Cisterns

a. Cerebellopontine angle cistern

b. Cerebrellomedullary cistern (cisterna magna)

c. Ambient cistern

d. Superior cistern

Term
Spinal Epidural Space
Definition
  • b/w dura and vertebral periosteum
  • contains:

a. loose areolar tissure

b. venous plexuses 

c. lymphatics

  • injected w/ local anethetic to produce paravertebral nerve block
Term
Cranial Epidural Space
Definition
  • potential space b/w periosteal and meningeal layers of dura
  • contains:

a. meningeal a.
b. meningeal v. 

Term
Subdural Space
Definition

a. space b/w dura and arachnoid

b. intracranially transmits superior cerebral v. to venous lacunae of superior sagittal sinus

c. lateration of these "bridging veins" → subdural hemorrhage (hematoma)

Term
Subarachnoid Space
Definition
  • b/w pia and arachnoid
  • contains: CSF
  • surrounds entire brain + spinal cord
  • entends below conus medullaris → S2--lumbar cistern


Term
Subarachnoid Cisterns
Definition
  • dilations of subarachnoid space
  • contains CSF
  • named after structures over which they lie, i.e. pontine, chiasmatic, and interpeduncular cistersn
  • 4 types:

a. cerebellopontine angle cistern

b. cerebellomedullary cistern (cisterna magna)

c. ambient cistern

d. superior cistern

Term
Cerebellopontine angle cistern
Definition
  • receives CSF from 4th ventricle via lateral foramina of Luschka 
  • contains: facial nerve (CN VII) + vestibulocochlear n. (CN VIII)
Term
Cerebellomedullary cistern (cisterna magna)
Definition
  • in midline b/w cerebellum and medulla
  • receives CSF from 4th ventricle via median formaen of Magendie
  • tapped for CSF (suboccipital tap)
Term
Ambient Cistern
Definition
  • interconnects superior and interpenduncular cisterns
  • contains: trochlear nerve (CN IV)
Term
Superior Cistern
Definition
  • overlies midbrain tectum
Term
Meningiomas
Definition
  • benign
  • slow-growing 
  • well-demarcated tumors
  • arise from meningotheal arachnoid cells
  • 20%--primary intracranial tumors
  • 25%--spinal tumors
  • most frequently found in: anterior cranial fossa (parasagittal 25%, convexity 20%, basal 40%)
  • histologically characterized by: whorling pattern and calcified psammoma bodies
  • enlarge slowly
  • create cavity in adjacent brain
  • occurence: adult (20-60 yrs)
  • most often in women (60%)
Term
Ventricles
Definition
  • lined by ependyma
  • contain: choroid plexus, which produces CSF @ rate of 500 ml/day
  • communicate w/ subarachnoid space via 3 foramina in 4th ventricle
  • consists of: 4 fluid-filled communicating cavities w/in brain 
Term
4th Ventricle
Definition
  • two ventricles
  • located w/in cerebral hemispheres
  • communicate w/ 3rd ventricle via interventricular foramina of Monro
  • consists of 5 parts:

a. frontal (anterior) horn

b. body

c. temporal (inferior) horn

d. occipital (posterior) horn

e. trigone (atrium) 

Term
Frontal (anterior) horn--lateral ventricle
Definition
  • w/in frontal lobe
  • lateral walls are formed by head of caudate nucleus
  • lacks choroid plexus 
Term
body--lateral ventricle
Definition
  • w/in medial portion of frontal and parietal lobes
  • contains choroid plexus
  • communicates via interventricular foramen of Monro w/ 3rd ventricle
Term
Temporal (inferior) horn
Definition
  • w/in medial part of temporal lobe
  • has choroid plexus
Term
Occipital (posterior) horn
Definition
  • w/in parietal and occipital lobe
  • lacks choroid plexus 
Term
Trigone (atrium):
Definition
  • @ the junction of body, occipital horn, and temporal horn of lateral ventricle
  • contains: glomus 
Term
Glomus
Definition
  • found w/in trigone
  • large tuft of choroid plexus
  • calcified in adults 
  • visible on x-ray films and computed tomography (CT)
Term
3rd Ventricle
Definition
  • slitlike vertical midline cavity of diencephalon
  • communicated w/ lateral ventricles via interventricular foramina of Monro + 4th ventricle via cerebral aqueduct
  • contains: pair of choroid plexuses in its roof 
Term
Cerebral aqueduct (aqueduct of Sylvius)
Definition
  • w/in midbrain
  • connects 3rd ventricle w/ 4th ventricle
  • lacks choroid plexus
  • blockage → hydrocephalus (aqueductal stenosis)
Term
4th ventricle
Definition
  • b/w cerebellum and brainstem
  • contains: pair of choroid plexus in caudal roof
  • expresses CSF into subarachnoid space via two lateral foramina of Luschka and single medial foramen of Magendie 
Term
CSF
Definition
  • clear, colorless, acellular fluid
  • found in: subarachnoid space + ventricles 
Term
CSF formation
Definition
  • produced by choroid plexus 
  • rate: 500 ml/day
  • total CSF volume = 140 ml
Term
CSF Function
Definition
  • supports and cushions CNS against concussive injury
  • transports hormones + hormone-releasing factors
  • removes metabolic waste products through absorption
Term
Arachnoid Villi
Definition
  • site of greatest absorption 
Term
CSF circulation
Definition
  • flows from ventricles via 3 foramina of 4th ventricle → subarachnoid space and over the convexity of hemisphere → superior sagittal sinus → venous circulation
Term
CSF composition
Definition
  • no more than 5 lymphocytes/µl
  • sterile--usually
  • normal values

a. pH: 7.35

b. Specific gravity: 1.007

c. Glucose: 66% of plasma glucose

d. Total protein: < 45 mg/dl in lumbar cistern

Term
Normal pressure-CSF
Definition
  • 80-180 mm of water (CSF) in lumbar subarachnoid space when pt is in a lateral recumbent (decubitus) position 
Term
Hydrocephalus
Definition
  • dilation of cerebral ventricles
  • caused by blockage of CSF pathways
  • characterized by: excessive accumulation of CSF in cerebral ventricles or subarachnoid space
Term
5 types of Hydrocephalus:
Definition
  • noncommunicating hydrocephalus
  • communicating
  • normal-presure 
  • hydrocephalus ex vacuo
  • pseudotumor cerebri (benign intracranial hypertension)
Term
Noncommunicating hydrocephalus
Definition
  • due to obstruction w/in ventricles
  • i.e. congential aqueductal stenosis
Term
Communicating Hydrocephalus
Definition
  • due to blockage w/in subarachnoid space 
  • i.e. adhesions after meningitis
Term
Normal-pressure hydrocephalus
Definition
  • CSF is not absorbed by arachnoid villi
  • secondary to post-traumatic meningeal hemorrhage
  • clinically characterized by: triad of progressive dementia, ataxic gait, urinary incontinence (wacky, wobbly, and wet)
Term
Hydrocephalus ex vacuo
Definition
  • loss of cells in caudate nucleus 
  • i.e. Huntington disease
Term
Pseudotumor cerebri (benign intracranial hypertension)
Definition
  • increased resistance to CSF outlfow @ arachnoid villi
  • characterized by: 

a. papilledema w/o mass

b. elevated CSF pressure

c. deteriorating vision

  • ventricles may be slit-like
  • occurs in obese young women
Term
Meningitis (pl. meningitides)
Definition
  • inflammation of pia-arachnoid of brain, spinal cord or both
  • types:

a. bacterial (pyogenic)

b. viral (lymphocytic)

 

Term
Bacterial (pyogenic) meningitis
Definition
  • common in children under 5 yrs (>70% of all cases)
  • clinical characterization:

a. fever

b. headache

c. nuchal rigidity w/ kernig sign

  • result in cranial n. palsies (CN III, IV, VI, VIII) and hydrocephalus
Term
Common etiologic agents--bacterial meningitis
Definition
  • newborn: <1 month

cause: group B streptococci (S. agalactiae) + E. coli

immunization against Haemophilus influenzae has significantly reduced this type of meningitis

  • older infants and young children: 1 month- 9 yrs

frequent cause: S. pneumoniae + Neisseria meningitidis

  • older adults: 

cause: S. pneumoniae

Term
CSF findings in bacterial meningitis
Definition
  • numerous neutrophils
  • decreased glucose level
  • elevated protein level
Term
Viral (lymphocytic) meningitis
Definition
  • also known as: aspectic meningitis
  • characterized by:

a. fever

b. headache

c. nuchal rigidity w/ Kernig sign

 

Term
Virus causing viral meningitis:
Definition
  • Mumps virus
  • Enteric cytopathic human orphan (ECHO) viruses
  • Coxsackie virus
  • Epstein-Barr
  • Herpes simplex virus (type 2)
Term
CSF findings from viral meningitis:
Definition
  • numerous lymphocytes
  • normal glucose
  • normal to slightly increased protein
Term
3 froms of herniation in brain:
Definition
  • transtentorial (uncal)
  • transforminal (tonsillar)
  • subfalcial
Term
Transtentorial (uncal) herniation:
Definition
brain protrudes through tentorial incisure
Term
Transforaminal (tonsillar) herniation
Definition
brainstem and cerebellum protrudes through foramen magnum
Term
Subfalcial herniation
Definition
herniation below falx cerebri
Term
Circumventricular Organs
Definition
  • chemosensitive zones
  • monitor concentrations of circulating hormones in blood + CSF
  • located in periphery of 3rd ventricle
  • area prostrema--found in floor of 4th ventricle
  • highly vascularized w/ fenestrated capillaries
  • no blood-brain barrier (subcommissural organ--exception)
  • includes:

a. organum vasculosum of lamina terminalis

b. median eminence of tuber cinereum

c. subfornical organ

d. subcommisural organ

e. pineal body

f. area postrema

Term
Organum Vasculosum of lamina terminalis
Definition
  • vascular outlet for LH releasing hormone + somatostatin
Term
Median eminence of tuber cinereum
Definition
  • contains neurons that release and inhibit hormones into hypophyseal portal system
Term
Subfornical organ
Definition
  • located on inferior surface of fornix @ level of interventircular foramen of Monro
  • contains neurons that project to supraoptic nuclei + organum vasculosum
  • central receptor site for angiotensin II
Term
Subcommissural organ
Definition
  • below the posterior commisure @ junction of 3rd vent + cerebral aqueduct
  • composed of:

a. specialized ependymal cells

b. glial elements

c. capillary bed--contains nonfenestrated endothelial cells

Term
Pineal Body
Definition
  • contains: 

a. calcareous granules--in brain sand/acervulus

i. seen on x-ray film + C.T. 

ii. occur after 16 yrs of age

b. pinealocytes--epiphyseal cells 

i. highly vascular w/ fenestrated capillaries

  • derived from: diencephalon
  • innervated solely via postganglionic fibers from superior cervical ganglion of ANS
  • synthesizes: serotonin + melatonin. 
  • antigonadotrophic function
  • pinealosomes--found in dorsal midbrain syndrome
Term
Area Postrema
Definition
  • two small subependymal oval areas on either side of 4th ventricle rostral to obex
  • contains modified neurons + astrocytes-like cells surrounded by fenestrated capillaries
  • chemoreceptor zone--triggers vomiting in response to circulating emetic substances
  • role in food intake + cardiovascular regulation
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