B7.056 Prework: Brain Environs

Question 1

major skull hole

Answer 1

foramen magnum- location of medullary, spinal cord junction

Question 2

skull fossae and the part of the brain within them

Answer 2

anterior fossa- inferior frontal lobe
middle fossa- inferior temporal lobes
posterior fossa- brainstem and cerebellum

Question 3

layers of meninges

Answer 3

skull
dura
-outer leaflet adherent to periosteum of skull
-inner leaflet forms tentorium and falx
arachnoid
pia
-adherent to surface of brain
-follows penetrating arteries to form perivascular space
brain

Question 4

meningeal spaces

Answer 4

epidural (between skull and dura)
subdural (between dura and arachnoid)
subarachnoid (between arachnoid and pain, contains CSF)

Question 5

what are the tentorium and falx cerebri

Answer 5

sheets made of the inner leaflet of dura

Question 6

falx

Answer 6

divides L and R hemispheres from top of brain to level of corpus callosum

Question 7

tentorium

Answer 7

divides supra and infratentorial conpartments

Question 8

components of supratentorial compartment

Answer 8

cerebral hemispheres

Question 9

components of infratentorial compartment

Answer 9

cerebellum and brainstem

within posterior fossa

Question 10

composition of normal CSF

Answer 10

125 ml
clear, colorless
pressure: 70-180 mm H2O
0-5 WBCs
protein < 45 mg%
glucose 50-75 mg%

Question 11

function of CSF

Answer 11

shock absorber
provides some nutrients
removes some waste

Question 12

structure of the ventricles

Answer 12

4 total

• 1 and 2 are lateral, C shaped and have an anterior, posterior, and inferior horn
• 1 and 2 connect with 3 via interventricular foramen
• 3 connects to 4 via cerebral aqueduct

Question 13

extra-axial CSF spaces

Answer 13

contiguous with subarachnoid space over cerebral convexity

called cisterns

Question 14

how is CSF produced

Answer 14

choroid plexus- specialized ependymal cells that produce an ultrafiltrate of plasma
located in ventricles
electrolyte comp similar to plasma
500 ml/ day produces

Question 15

CSF circulation path

Answer 15

produces in ventricles
access to extra-axial space via median aperture (foramen of Magendie) and lateral apertures (foramen of Luschka) at medulla
percolate through subarachnoid space over cerebral convexities to arachnoid granulations

Question 16

what causes CSF to flow

Answer 16

Pv&raquo_space; Psas

created gradient to drive flow

Question 17

absorption of CSF

Answer 17

via arachnoid granulations within major sinuses (sagittal and transverse)
one way bulk transport of CSF to venous system

Question 18

sagittal sinus

Answer 18

along top of falx

Question 19

transverse sinuses

Answer 19

at intersection of tentorium and skull

Question 20

major vessels of venous drainage

Answer 20

sagittal sinus
straight (rectus sinus)
transverse sinus
internal jugular

Question 21

meningeal lymphatics

Answer 21

located parallel to the dural sinuses and meningeal arteries

drain immune cells, small molecules, and excess fluid from the CNS into the deep cervical lymph nodes

Question 22

blood brain barrier

Answer 22

tight junctions of brain capillaries endothelial cells limit transfer of molecules (esp ionized molecules)

Question 23

blood CSF barrier

Answer 23

tight junctions of choroid endothelial cells limit transfer of molecules

Question 24

significance of circumventricular organs

Answer 24

locations where BBB is interrupted

Question 25

major circumventricular organs

Answer 25

pineal > melatonin release neurohypophysis/median eminence > pituitary hormone release area postrema > chemotactic trigger zone

Question 26

4 types of herniation syndromes

Answer 26

1. sub falcine 2. central 3. uncal 4. tonsillar

Question 27

sub falcine herniation

Answer 27

brain pushed under falx | ACA and RAS live here and are vulnerable

Question 28

central herniation

Answer 28

compresses midbrain | sympathetic and parasympathetic fibers affected as visualized by pupils being midrange and nonreactive

Question 29

uncal herniation

Answer 29

lateral mass puts pressure on CN III exit from midbrain | unilateral, dilated, nonreactive pupil

Question 30

tonsillar herniation

Answer 30

life ending compresses medulla breathing and heart function impaired

Question 31

broad classes of causes of meningitis

Answer 31

inflammation of the meninges - infection - neoplastic - chemical - autoimmune

Question 32

symptoms and signs of meningitis

Answer 32

``` headache photophobia, sonophobia nausea nuchal rigidity encephalopathy cranial neuropathies ischemic stokes ```

Question 33

acute bacterial meningitis CSF

Answer 33

100-5000 WBC (usually PMNs) 100-1000 protein glucose < 40

Question 34

chronic, aseptic meningitis CSF

Answer 34

10-300 WBC (usually lymphocytes) protein 50-100 normal or reduced glucose

Question 35

common causes of bacterial meningitis

Answer 35

listeria h. flu Neisseria strep pneumo

Question 36

ttx for bacterial meningitis

Answer 36

ampicillin | ceftriaxone

Question 37

non communicating hydrocephalus

Answer 37

obstruction to flow intra-axial | 4th ventricle not enlarged

Question 38

communicating hydrocephalus

Answer 38

obstruction to flow extra-axial | 4th ventricle enlarged

Question 39

syndrome of hydrocephalus

Answer 39

gait problems incontinence cognitive issues due to selective vulnerability of leg fibers, micturition center, and cingulum memory fibers near lateral ventricles

Question 40

diagnosis of hydrocephalus

Answer 40

``` triad: gait problems, incontinence, cognitive problems supportive imaging lumbar puncture -opening pressure -meningitis? ```

Question 41

normal pressure hydrocephalus

Answer 41

very chronic, communicating hydrocephalus

Question 42

hydrocephalus ex vacuo

Answer 42

enlarged ventricles secondary to atrophy no derangement in CSF flow cortical sulci also enlarged

Question 43

pseudotumor cerebri

Answer 43

idiopathic intracranial hypertension

Question 44

etiologies of pseudotumor cerebri

Answer 44

poor absorption of CSF rarely overproduction of CSF (choroid plexus papilloma) venous sinus thrombosis

Question 45

factors associated with pseudotumor cerebri

Answer 45

obesity tetracycline vit A

Question 46

symptoms and signs of pseudotumor cerebri

Answer 46

``` slowly developing headache episodic blurred vision, vision loss double vision papilledema normal head imaging ```

Question 47

treatment of pseudotumor cerebri

Answer 47

Diamox (decrease CSF production) optic nerve fenestration CSF shunt

Question 48

indication / contraindication of LP in increased ICP

Answer 48

contraindicated with focal mass lesions (increased P in once compartment compared to another) not contraindicated in patients with diffuse processes head imaging needed to exclude mass lesion

Question 49

causes of intracranial hypotension

Answer 49

``` post traumatic spontaneous -encephalocele -tarlov cyst -idiopathic ```

Question 50

symptoms and signs of intracranial hypotension

Answer 50

orthostatic headaches | low opening pressure

Question 51

treatment of intracranial hypotension

Answer 51

repair leak | blood patch