SSEPs

Question 1

Name the muscle activated with stim of the MN at the wrist

Answer 1

Thenar muscle group-Abductor pollicis brevis

Question 2

Name the muscle activated with stim of the UN at the wrist

Answer 2

Hypothenar group-abductor digiti minimi

Question 3

After stimulation of the median nerve at the wrist, which root entry zones are activated in the brachial plexus?

Answer 3

Median C5-T1
Ulnar C8-T1
Radial C5-T1

Question 4

What most influences the degree of pain in the waking patient?

Answer 4

intensity of stim, duration of the stim, and density of the current (size of electrode)

Question 5

Current density

Answer 5

Small stimulator (needles)=largest current density=most painful

Large stimulator (stickies)=smallest current density=least painful

Question 6

Define orthodromic

Answer 6

The direction a signal normally travels (SSEPs up, tcMEPs down)

Question 7

Define antidromic

Answer 7

The direction opposite to which a signal normally travels

Question 8

What happens when stim is reduced?

Answer 8

Amplitude ONLY decreases

Most pronounced in EP and PF

Question 9

What happens when pt gets cold?

Answer 9

Latency decreases, amplitude stays the same

Question 10

What happens during ischemia (positional, BP cuff, weighting of the head, taping of the shoulders)?

Answer 10

Both latency and amplitude decrease

Question 11

What is the function of EP/PF according to the guidelines?

Answer 11

To verify adequate stimulation

Question 12

What type of montage is best for recording subcortical or far field responses?

Answer 12

Referential

Question 13

What type of montage is best for recording cortical responses?

Answer 13

Bipolar

*bipolar montages result in cancellation of subcortical or far field potentials

Question 14

Which peak is most susceptible to anesth?

Answer 14

N20-also varies in latency with the level of alertness of pt

Question 15

What does EP to N20 define

Answer 15

the conduction time between the brachial plexus and the primary sensory cortex AKA central conduction

Question 16

What does EP latency define?

Answer 16

Peripheral conduction

Question 17

What does EP to P14 define?

Answer 17

The conduction time between the brachial plexus and the lower brainstem (central conduction)

Question 18

What does P14 to N20 define?

Answer 18

The conduction time between the lower brainstem and the cortex (central conduction)

Question 19

What does N13 to N20 define?

Answer 19

Central conduction time and central conduction velocity

Question 20

Define lumbar potential

Answer 20

Stationary/nonpropagated potential reflecting mainly postsynaptic activity in the lumbar cord FROM internuncial neurons

Question 21

What does stimulation of the PTN twitch?

Answer 21

plantar flexion of the great toe or cupping of the sole of the foot- AH activated (L4-S3)

Question 22

What does stimulation of the peroneal nerve twitch?

Answer 22

Plantar eversion of the foot-peroneus longus and peroneus brevis activated (L4-S3)

Question 23

What metal is best for epidural spine electrodes?

Answer 23

Platinum iridium-guards against neurotoxicity

Alternate electrodes are stainless steel or platinum

Question 24

What is the most common technical problem with epidural electrodes?

Answer 24

Shunting from fluid over the electrode

Question 25

Whats the best stimulator for SSEPs?

Answer 25

Constant current

Question 26

Whats the best stimulator for EMG?

Answer 26

Monopolar, constant current

Question 27

Whats the best stimulator for EMG cranial nerve?

Answer 27

Bipolar, constant current