8/23 Ventricles and Meninges - Glendinning Flashcards Preview

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Flashcards in 8/23 Ventricles and Meninges - Glendinning Deck (27):
1

cerebrospinal fluid

 

properties/volume

functions

clear, colorless liquid (140mL)

replaced 2-3x/day

 

fx:

  • buoyancy, protection against sudden movements
  • maintenance of intracranial pressure
  • controls ECF of brain
  • some antibacterial props

2

choroid plexus

tissue within brain ventricles that produces CSF

also forms blood-CSF barrier

 

  • ependymal cells with adherent jx line ventricles : allow free movement of CSF into brain
  • at choroid plexus, ependymal cells form tight jx → create choroid epithelium : blood-CSF barrier
    • choroid epithelium has active transport, ion exchange mechs to determine flow of molecules
    • implication : need active transport in order to make it from blood into the CSF!
  • choroidal caps (in subarachnoid space) are fenestrated with no tight jx

 

lateral ventricles in cerebral hemispheres → intervertebral foramen of Monroe → 3rd ventricle in diencephalon → cerebral aqueduct in midbrain/mesencephalon → 4th ventricle in pons/medulla

3

blood brain barrier

formed by capillary endothelium and astroyte foot processes

fx: 

  • control ionic environment : neurotrans
  • protects brain from toxins
  • prevents drugs from enetering brain
  • contains transporters for critical molecules (glucose, proteins)

BBB may be disrupted by infections, tumors, trauma → "vasogenic edema"

4

circumventricular organs

regions where BBB is interrupted → enables brain to respond to changes in blood chemistry

5

2 barriers between blood and brain

1. blood-CSF barrier

  • formed by choroid epithelium

2. blood-brain barrier

  • formed by capillary endothelium

6

CSF flow from ventricles to subarachnoid space

 

how does CSF get from ventricles to venous sinuses? (pathway)

how specifically does CSF get from subarachnoid space into sinuses?

4th ventricle → foramen of Magendie (median) and Luschka (lateral x2) → subarachnoid space around brain and spinal cord → arachnoid granulations → venous sinuses

 

arachnoid villae : smal evaginations of arachnoid into sinus

  • large villi = arachnoid granulations
  • giant vacuoles engulf CSF materials

7

meninges

  • dura, 2 layers : periosteal, meningeal
  • arachnoid
  • pia

dural layers : pachymeninges

arachnoid/pia : leptomeninges

8

cisterns

 

what is a cistern?

what are the main cisterns of the brain?

pools of enlarged areas of subarachnoid space

 

1. interpeduncular cistern

2. cisterna magna

3. prepontine cistern

4. quadrigeminal cistern

 

also ambient cistern, lumbar cistern

9

lumbar puncture

 

where?

whats teh point?

when should you use

L3-L4 in adults, L4-L5 in children

contraindicated if there's increased intracranial pressure!

  • if there's pressure on the brain and you pull fluid from below → tentorial/cerebellar herniation risk

 

CSF pressure should be measured, should be < 20cm water

 

 

use in order to...

1. look out for:

  • subarachnoid hemmorhage : blood
  • infections ex. meningitis : high protein, high WBC, low glucose
  • Guillan Barre : high protein, NL cell count
  • MS : 70% of patients with high IgG, oligoclonal bands

2. push drugs into system

10

dura

arachnoid

pia

 

brain vs spinal cord

DURA

in brain, dura has 2 layers

  • periosteal and meningeal (split to form sinuses)

in spinal cord, dura has 1 layer

  • periosteum is a separate thing from the dura mater
  • in between...epidural space!

ARACHNOID

in brain : arachnoid trabeculae and many cisterns

in spinal cord : fewer trabeculae  and 1 cistern

PIA

spinal cord - forms denticular ligaments, filum terminale

11

dural folds

folds of inner dural layer between brain regions → create compartments in cranial cavity

 

1. falx cerebri : between cerebral hemispheres (longitudinal fissure)

2. falx cerebelli : between two hemispheres of cerebellum

3. tentorium cerebelli : between posterior cerebral hemispheres and cerebellum

4. diaphragm sellae : circular fold beneath the brain that covers teh sella turcica

12

trauma to the head

 

what should you be on the lookout for?

middle meningeal artery bleeding!

 

epidural hematoma: between skull and dura

subdural hematoma: between dural and arachnoid

13

epidural hematoma

causes:

  • trauma to skull → usually middle meningeal artery
  • also sinuses (15%)

lens shaped structure on MRI

often period of lucidity before severe symptoms (from brain herniation)

 

14

subdural hematoma

often due to tears in bridging veins

  • sometimes during rapid accelerations

symptoms may progress over longer periods

 

crescent shaped 

15

subarachnoid hemorrhage

usually secondary to trauma

can also be "non traumatic" from bleeding from an AV malformation or ruptured aneurysm

 

classic presentation: sudden-onset, severe headache (due to blood irritating meninges)

  • why? meninges are full of pain receptors! (in contrast, brain does not have sensory receptors!)

16

non-traumatic subarachnoid hemorrhage

burst aneurysm is cause of 80%

  • aneurysm forms when vessel wall is weakened and burst under conditions of increased pressure
  • most aneurysms occur in anterior circulation (internal carotid artery -supplied)
    • most common MEN: anterior commmunicating a
    • most common WOMEN: posterio communicating a

17

increased intracranial pressure

 

causes

1. tumor

2. hemorrhage

3. abscess

4. edema

5. hydrocephalus

6. infections

18

sx of incr intracranial pressure

  1. headache
  2. alt mental status
  3. nausea/vomiting
  4. eyes appearing to look downwards
  5. papilledema (swelling of optic papilla)
  6. visual loss
  7. diplopia (double vision)
  8. Cushing's triad: HTN, bradycardia, irreg resp (brainstem)
  9. kids - skull can expand

19

types of brain herniation

1. subfalcine : under falx cerebri

  • subdural hematoma → cingulate gyrus herniates below falx cerebri

2. transtentorial and central herniation : through tentorial notch

  • tumor in temporal lobe → temp lobe herniates through tentorial notch
  • aka uncal herniation

3. tonsillar herniation : through foramen magnum

  • cerebellar tumor → cerebellum herniates through foramen magnum

 

 

20

hydrocephalus

 

what it is

causes

"water in the head"

condition of excess CSF

 

1. excess production : choroid plexus tumors

2. obstructed flow (in ventricles or subarachnoid space - tumors, malformations, hemorrhage)

3. decreased reabsorption via arachnoid granulations

21

communicating vs noncommunicating hydrocephalus

communicating : lateral ventricles communicate with subarachnoid space

ex. prob within choroid plexus

 

non-communicating : flow obstructed WITHIN ventricular system

22

sx of hydrocephalus

decreased cognitive fx

neck pain

vomiting (esp in morning)

blurred vision (papilledema)

drowsines

failure of upward gaze

23

hydrocephalus : small children and infants

 

sx

signs: rapid head growth, bulding fontanelle, dilated scalp veins

symptoms : poor feeding, irritability, vomiting, lethargy, downward eyes

24

chiari malformations I-IV

congenital hindbrain anatomic anomalies (cerebellum, brainstem, or craniocervical jx)

  • result in downward displacement of cerebellum
  • tonsils can herniate through foramen magnum

 

sx usually in adults caused by...

1. compression of medulla and upper spinal cord

2. compression of cerebellum

3. disruption of CSF flow through foramen magnum

→→→ produce hydrocephalus

 

25

Chiari I

most common

  • oftentimes due to cyst in middle of spinal cord

1. cerebellar tonsils below foramen magnum

2. syringomyelia

3. compression of brainstem

 

most common symptoms:

  • headache (due to incr ICP)
  • ataxia (cerebellar dysfx)
  • impaired movement (brainstem compression)

26

Chiari II

less common

can cause significant herniation through foramen magnum → aqueductal stenosis and hydrocephalus, usually with meningomyocele

27

Normal Pressure Hydrocephalus

elderly patients

  • cause not entirely understood...maybe impaired reabs from meningitis/subarachnoid hem?

CLASSIC TRIAD

1. gait disturbance

2. dementia

3. urinary incontinence (urgency, freq, diminished awareness of need to urinate)

 

NO HEADACHE bc no incr ICP! normal pressure

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