Neuromonitoring

Question 1

What is the purpose of intraoperative evoked potentials?

Answer 1

To monitor neural pathways to avoid iatrogenic injury to the nervous system

Question 2

What are SEPs?

Answer 2

Sensory evoked Potentials

Evaluate integrity of ASCENDING sensory tracts

Question 3

What are MEPs

Answer 3

Motor evoked potentials

Evaluate integrity of DESCENDING motor pathways

Question 4

T or F: Anesthetics modify cortical EP’s more than brainstem EP’s

Answer 4

T

Bolusing IV infusions or abrupt changes in MAC’s can be detrimental, esp during critical portions of a procedure

Question 5

T or F: It is possible to completely eliminate EP’s by high concentrations of volatiles

Answer 5

T

Question 6

Which of the inhaled anesthetics influence EP’s more?

Answer 6

Enflurane and Isoflurane > Sevo/Des

Question 7

Describe the effects of nitrous on EP’s

Answer 7

NO nitrous during EP monitoring = profound depressant effects on SSEP’s when combined with volatile agents

Question 8

Which of the IV anesthetic agents actually increase amplitude of EP’s?

Answer 8

Ketamine

Etomidate

Question 9

T or F: MEP’s are exquisitely sensitive to anesthetics, especially inhalational agents

Answer 9

T

Question 10

What is the rate of normal brain perfusion?

Answer 10

50cc/100g/min

Question 11

What is the rate of brain perfusion at which cellular damage occurs?

Answer 11

12cc/100mg/min

Question 12

What is the effect of volatile anesthetics on the latency and amplitude of SEP’s?

Answer 12

Prolong latency

Reduce amplitude

Question 13

List indications for an EEG

Answer 13

Craniotomy
Carotid endarterectomy
CP bypass 
Extra/intracranial bypass
Pharmacologic depression of brain for cerebral protection

Question 14

What is the function of the BIS monitor?

Answer 14

Used to measure (crudely) the depth of hypnosis under anesthesia
> 80 = emergency
40-80 = adequate hypnosis without possible recall

Question 15

T or F: The BIS monitor is useful for detecting regional ischemia

Answer 15

F

Question 16

What are three subdivisions of SEP’s

Answer 16

SSEP: Somatosensory EP’s
AEP: auditory EP’s
VEP: visual EP’s

Question 17

What’s the difference between SEP’s and EEG?

Answer 17

EEG monitors cortex only

Question 18

What is the purpose of AEP’s?

Answer 18

Monitor integrity of CNVIII during resection of acoustic neuromas.
AEP’s are resistant to the effects of anesthetic agents so there are no special anesthetic requirements during these procedures

Question 19

What is the most common form of neuromonitoring?

Answer 19

SSEP.

Recorded in response to stimulation of a cranial or peripheral sensory nerve.

Question 20

Indications for MEP’s

Answer 20

When common SSEP’s fall short of adequate monitoring and for specific situations where pure motor function needs to be monitored.

Mainly monitors motor neuron output.