Neuro Week 2

Question 1

Normal ICP measured in CSF

Answer 1

Less than 200 mm water

Question 2

Clinical presentation of increase ICP

Answer 2

headache
nausea
vomiting
decreased consciousness
papilledema (but NOT always!)

Question 3

Consequence of cerebellar tonsil herniation

Answer 3

if cerebellar tonsils go through the foramen magnum, compression of the medullary respiratory centers will results in death

Question 4

consequence of lateral brain displacement

Answer 4

if the diencephalon is also laterally displaced then that might throw off the ascending reticular activating system (thus a loss of consciousness)

Question 5

consequenceS of uncal (temporal) lobe hernation (4 of em)

Answer 5

1) unilateral compression of the “outer” fibers on the oculomotor nerve, which are parasympathetic, thus you will get ipsilateral pupillary dilation
2) Compression of midbrain cerebral peduncles results in CONTRAlateral hemiparesis/hemiplegia
3) Compression of posterior cerebral artery against free edge of tentorium results in hemorrhage of that artery producing infarction in ipsilateral occipital lobe (near calcarine fissures) resulting in homonymous hemianopsia
4) Brainstem compression can cause a SECONDARY compression of brainstem veins potentially cause a bleed known as a secondary brainstem hemorrhage aka Duret hemorrhage which can cause death
- also note that compression happens from top to bottom aka midbrain to medulla thus oculomotor changes first, then ultimately respiratory centers in medulla cause death

Question 6

Consequences of Central herniation (rostrocaudal deterioration)

-in regards to consciousness and respiratory changes

Answer 6

Can also cause duret hemorrhage

as the brainstem is also pushed rostrocaudally… consciousness levels decline from less alert to drowsy to stupor and coma (as the ARAS is streched)

characteristic respiratory change buzzowords by lesion location:

• diencephalon —> cheyne-stokes respiration
• midbrain —> central neurogenic hyperventilation
• pons —> apneustic respiration
• medulla —> ataxic respiration

Question 7

Central herniation lesions locations to cause 2 different types of rigidity

Answer 7

Decorticate rigidity (legs extended/arms flexed) with a lesions widspread throughout cerebral cortex

De”cerebrate” rigidity (legs AND arms extended) with a lesion disconnecting brainstem from cerebral hemispheres aka a rostral (upper) midbrain

Question 8

Comatose pt with small reactive pupil indicates

Answer 8

lesion in diencephalon— includes the hypothalamus which sends sympathetic fibers via sup. cervial ganglia to dilate eye… without those parasymp takes over for a smaller pupil

Question 9

comatose pt with unilateral dilated and fixed pupil

Answer 9

uncal herniation – compression of ipsilateral oculomotor nerve to press on outer-lying parasymp fibers that allow symp fibers to dominate and dilate

Question 10

comatose pt with midposition fixed lesion

Answer 10

Midbrain lesion… That way CN3 is fugged up (so no parasympathetic) AND the descending sympathetic from the hypothalamus through the midbrain are also disrupted… thus not constricted or dilated and fixed

Question 11

comatose oculocephalic reflex

Answer 11

aka “doll’s eye movements”… a positive sign indicates an intact brainstem… in a comatose pt. hold eyelids open and turn head… if the eyes stay straight ahead then that indicates a positive sign

Question 12

oculovestibular reflex in comatose pts.

Answer 12

aka caloric stimulation… place cold or warm water in an ear… COWS… the saccade will go toward the opposite if cold and to the same if warm… indicates in intact vestibulocochlear nerve (balance) and CN III and VI intact

Question 13

hydrocephalus

Answer 13

excessive accumulation of CSF within the ventricular system of the brain

Question 14

non-communicating hydrocephalus

Answer 14

obstruction to CSF flow within ventricular system or at an outlet foramina (ie aqueductal stenosis)

Question 15

communicating hydrocephalus

Answer 15

obstruction to CSF flow in the subarachnoid space after exit from the 4th ventricle. Fibrosis seals and obstructs CSF outflow from subarachnoid space back to bloodstream via arachnoid granulations (that poke through dura to gain access to blood vessels)

• causes leptomeningitis
• causes subarachnoid hemorrhage

Question 16

Type of head trauma due to linear acceleration/deceleration

Answer 16

Coup lesions (directly beneath impact location)
countrecoup (directly opposite)

Question 17

Head trauma due to rotation of brain 4 of em

Answer 17

1) shearing bridging veins (subdural hemm)
2) shearing of small vessels producing petechial intracranial or subarachnoid hemm (bloody CSF)
3) stress causing rupture or stretching of axons (diffuse axonal injury)
4) contusions – brain rubbing against sharp/rough edges of the skull

Question 18

post-traumatic epilepsy is due to what?

Answer 18

seizures induced by meningocerebral scar tissue formation post-injury

Question 19

Epidural hemorrhage

Answer 19

• MMA
• often associated with skull fracture
• typically unconscious immediately after trauma, then a lucid period, followed by coma and possibly death within 2-12 hours via brainstem compression (uncal herniation)

Question 20

Subdural hemorrhage

Answer 20

• bridging vein tear usually due to rotational movement
• often due to blunt trauma without skull fracture
• can be acute or chronic (chronic is more common in peds, elderly, alcoholics, demented)
• chronic can take weeks to months to present!

Question 21

subarachnoid hemorrhage

Answer 21

-blood in CSF usually due to cerebral contusion

Question 22

Diffuse axonal injury

Answer 22

• major cause of prolonged traumatic coma
• causes 35% of head trauma deaths
• autopsy presents a brain with NO lesions on its surface

Question 23

Wallerian Degeneration in spinal cord injury

Answer 23

• always occurs distal to site of injury…
• distal for corticospinal tract is BELOW level of spinal cord lesion
• distal for spinothalamic/dorsal columns is ABOVE level of spinal cord lesion