Unit 7. Neuro

Name the four types of glial cells

Astrocytes

Ependymal

Oligodendrocytes

Microglia

What are astrocytes?

Most abundant glial cell

Regulation of metabolic environment

Repair neuron after injury

What are ependymals?

Found in roof of 3rd & 4th ventricles & spinal cord

From choroid plexus, produces CSF

What are oligodendrocytes?

Form myelin sheath in CNS

What are microglia?

Act as macrophages

Function of the frontal lobe?

Motor cortex

Function of the parietal lobe?

Somatic sensory cortex

Function of the occipital lobe?

Vision cortex

Function of the temporal lobe?

Auditory cortex & speech centers

What are two sub-areas of the temporal lobe?

Wernicke's - understanding speech

Broca's - motor control of speech

Name the 12 cranial nerves

1. Olfactory

2. Optic

3. Occulomotor

4. Trochlear

5. Trigeminal

6. Abducens

7. Facial

8. Vestibulocochlear

9. Glossopharyngeal

10. Vagus

11. Accessory

12. Hypoglossal

CN. 1

Olfactory

Sensory

Smell

CN. 2

Optic

Sensory

Vision

CN. 3

Occulomotor

Motor

Eye movement, pupil constriction

CN. 4

Trochlear

Both

Eye movement

CN. 5

Trigeminal

Both

V1 (opthalamic) - somatic sensation to face

V2 (maxillary) - somatic sensation to ant. 2/3 of tongue

V3 (mandibular) - mastication

CN. 6

Abducens

Motor

Eye movement

CN. 7

Facial

Both

Face movement (except mastication), eyelid closing, taste to ant. 2/3 of tongue

Name the branches of CN. 7

"Two Zebras Bit My Carrot"

Temporal, zygomatic, buccal, mandibular, cervical

CN. 8

Vestbulocochlear

Sensory

Hearing & balance

CN. 9

Glossopharyngeal

Both

Somatic sensation & taste to post. 1/3 of tongue

CN. 10

Vagus

Both

Swallowing

CN. 11

Accessory

Motor

Shoulder shrug

CN. 12

Hypoglossal

Motor

Tongue movement

Which cranial nerves control eye movements?

CN. 3, 4, 6

Which eye movements does CN. 4 control?

Superior oblique

Intorsion, depression

Which eye movements does CN. 6 control?

Lateral rectus

Abduction

Which cranial nerve controls all other eye movements?

CN. 3

Which CN resides in the central nervous system?

CN. 2 - all others reside in the peripheral nervous system

What is a complication of CN. 2 being in the CNS?

If you inject LA into the optic nerve when doing regional this would be a big problem

What is tic douloureux?

Trigeminal neuralgia, CN. 5, neuropathic pain in the face

What is Bell's palsy?

Injury to facial n. (CN. 7), ipsilateral facial paralysis

What is the function of CSF?

Cushions the brain, buoyancy, & delivers optimal conditions for neurological function

Where is CSF located?

Ventricles (left lateral, right lateral, 3rd, & 4th)

Cisterns

Subarachnoid space in brain & spinal cord

What regions of the brain are NOT protected by the BBB?

CRTZ, post. pituitary, pineal gland, choroid plexus, & parts of hypothalamus

What is the normal volume & specific gravity of CSF?

~150mL

1.002 - 1.009

Where & how much CSF is produced?

Produced by ependymal cells in choroid plexus at rate of 30mL/hr

What is the circulation of CSF?

"Love My 3 Silly 4 Lorn Magpies"

L&R lateral ventricles

Foramen of Monro

3rd vent

Aqueduct of Sylvius

4th vent

Foramen of Luschka

Foramen of Magendie

Where is CSF reabsorbed?

Venous circulation via the arachnoid villi in the superior sagittal sinus

What is the formula for CBF?

CBF = CPP / cerebral vascular resistance

What are the normal values for global, cortical, and subcortical flow? (mL/100g tissue/min)

Global = 45-55 (or 15% of CO)

Cortical = 75-80

Subcortical = 20

What are the 5 determinants of CBF?

1. CMRO2

2. CPP

3. Venous pressure

4. PaCO2

5. PaO2

What is the normal value for CMRO2?

3.0 - 3.9 mL/O2/100g brain tissue/min

What factors cause CMRO2 to decrease?

Hypothermia (7% per 1 degree)

Halogenated gas

Propofol

Etomidate

Barbiturates

What factors cause CMRO2 to increase?

Hyperthermia

Szrs

Ketamine

N2O

What is the formula for CPP?

CPP = MAP - ICP (or CVP, whichever is higher)

What is the normal CPP?

50-150 mmHg

What happens if CPP is too low?

CBF becomes pressure dependent

Risk of cerebral hypoperfusion

What happens if CPP is too high?

CBF becomes pressure dependent

Risk of cerebral edema and hemorrhage

4 conditions that reduce CPP d/t increased venous pressure?

Jugular compression (improper head positioning)

Increased intrathoracic pressure (coughing, PEEP)

Vena cava thrombosis

Vena cava syndrome

What is the relationship between PaCO2 and CBF?

Linear relationship & pH of CSF around arterioles controls cerebral vascular resistance

PaCO2 40 = CBF 50 mL/100g brain tissue/min

At what PaCO2 does max cerebral vasodilation occur? What about constriction?

Max dilation = 80-100

Max constriction = 25

For every 1 mmHg increase (or ↓) in PaCO2, CBF will increase (or ↓) by 1-2 mL/100g brain tissue/min

What is the relationship between CMRO2 & CBF?

General rule:

Things that increase CMRO2 cause vasodilation (↑ CBF) & opposite is true for decreased CMRO2

Halogenated gas is the exception (they reduce CMRO2 but cause vasodilation)

How do acidosis & alkalosis affect CBF?

Resp. Acidosis = ↑

Resp. Alkalosis = ↓

Met. alk/acid does. not affect CBF b/c H+ cannot pass BBB

How does PaO2 affect CBF?

PaO2 < 50-60 = vasodilation & increases CBF

> 60 = no affect

What is the normal ICP?

5-15 mmHg

> 20 = cerebral HTN

When is ICP measurement indicated?

GCS

What is the gold standard for ICP measurement?

Intraventricular catheter

S/S of intracranial HTN

HA

N/V

Papilledema (swelling of optic nerve)

Focal neuro deficits

Deceased LOC

Szrs

Coma

What is the Monroe-Kellie hypothesis?

Brain lives in a rigid box (the skull) with 3 components: brain, blood, CSF. Equilibrium must remain, if one goes up in size or volume, one or both of the others must decrease

What is Cushing's triad?

HTN

Bradycardia

Irregular respirations

What does Cushing's triad indicate?

Intracranial HTN

Name 4 areas where brain herniation can occur?

Cingulate gyrus under the flax

Contents over tentorium cerebelli

Cerebellar tonsils through foramen magnum

Through surgery site or trauma

How does hyperventilation affect CBF?

CO2 dilates cerebral vessels = ↓ cerebral vascular resistance → ↑ CBF & ↑ ICP

Hyperventilation (PaCO2 30-35) constricts the vessels → ↓ CBF & ↓ ICP

How do NTG & Nitroprusside affect ICP?

Cerebral vasodilators → ↑ CBF & ↑ ICP

How does head position affect ICP?

Head elevation > 30 degrees facilitates venous drainage

Neck flexion or extension can compress the jugular veins, reduce venous outflow & ↑ ICP

Head down ↑ ICP

How does Mannitol decrease ICP?

Increases serum osmolarity & pulls water across the BBB towards the blood stream

What problems can arise when mannitol is given?

If BBB is disrupted, mannitol enters the brain & promotes cerebral edema

Its transiently increases blood volume, which can ↑ ICP & stress the failing heart

Discuss the anterior circulation of the brain

Internal carotid arteries supply ant. circulation

Enter the skull through foramen magnum

Aorta → carotid a. → internal carotid a. → circle of willis → cerebral hemispheres

Discuss the posterior circulation of the brain

Vertebral arteries supply post. circulation

Enter skull through foramen magnum

Aorta → subclavian a. → vertebral a. → basilar a. → post. fossa structures & cervical spinal cord

Discuss the anatomy of the Circle of Willis

What population of stroke pts should be given a thrombolytic agent?

Within 4.5 hours of onset of symptoms of ischemic stroke

Should diagnose with a non-contrast CT first

What is the relationship between hyperglycemia & cerebral hypoxia?

During cerebral hypoxia, glucose is converted to lactic acid. Cerebral acidosis destroys brain tissue & associated with worse outcomes. Treat with insulin

How is transmural pressure calculated (regarding cerebral aneurysm)?

MAP - ICP (MAP is pressure pushing outwards, ICP is pressure pushing inward)

What is the most common clinical finding in a pt with a subarachnoid hemorrhage?

"Worst headache of my life"

What are other S/S?

LOC (50%)

N/V

Photophobia

Fever

Obstructive hydrocephalus

What is the most common cause of morbidity & mortality in pts with SAH?

Cerebral vasospasm

What is the incidence of cerebral vasospasm & when is it most likely to occur?

25% of pts following SAH

Most likely to occur 4-9 days following SAH

What is the treatment for cerebral vasospasm?

Triple H therapy → Hypervolemia, hypertension, and hemodilution (Hct 27-32%)

Nimodipine is the only CCB shown to reduce morbidity and mortality associated with vasospasm. It does not relieve the spasm, but instead increases collateral blood flow

During endovascular coil placement for a cerebral aneurysm, it ruptures. What is the best tx at this time?

Give protamine (1mg/100U of heparin), MAP should be lowered into low/normal range

GCS

How do you treat the pt with an intracerebral bleed who is on Warfarin?

FFP, prothrombin complex, and/or recombinant factor VIIa

(Vit. K is not best for acute reversal)

How do you treat the pt with an intracerebral bleed who is on clopidogrel?

Platelet transfusion

What are 2 common ways of reducing ICP that should specifically be avoided in the pt with TBI?

Hyperventilation

Steroids

Is N2O safe in the pt with TBI?

No

Describe Grand Mal szr

Generalized tonic-clonic

Respiratory arrest

Grand Mal tx

Acute: propofol, diazepam, thiopental

Surgical: vagal nerve stim, resection of foci

Describe Focal Cortical szr

Localized to cortical region

Can be motor or sensory

Usually no LOC

Describe Absence (Petit Mal) szr

Temporary loss of awareness (but remains awake)

More common in kids

Describe Akinetic szr

Temporary LOS & postural tone

Can result in fall = head injury

More common in kids

Describe Status Epilepticus

Szr that lasts > 30min or 2 grand mal w/o regaining consciousness in between

Respiratory arrest

Acute tx for status epilepticus

Phenobarbital

Thiopental

Phenytoin

Benzos

Propofol

GA

What is the relationship between etomidate & szrs?

Etomidate can cause myoclonus. This is not associated with ↑ EEG activity in pts that do not have epilepsy

Can be used to determine where szr foci is during mapping

Describe the patho of Alzheimer's

Development of diffuse beta amyloid-rich plaques and neurfibrillary tangles in the brain

Dysfunctional synaptic transmission

Apoptosis

What class of drugs is used to tx Alzheimer's?

Cholinesterase inhibitors (tacrine, donepezil, rivastigmine, and galantamine)

How do cholinesterase inhibitors interact with Sux?

They increase the DOA of Sux

Describe the patho of Parkinson's

Dopaminergic neurons in the basal ganglia are destroyed

What drugs increase the risk of extrapyramidal s/s in the pt with parkinson's?

Drugs that antagonize dopamine

Metoclopramide

Butyrophenones (haloperidol & droperidol)

Phenothiazines (promethazine)

What is the most common eye complication in the periop period?

Corneal abrasion

What is the most common cause of vision loss in the periop period?

Ischemic optic neuropathy