Q&A Flashcards Part 1

Active electrode is usually placed placed on the scalp behind _____ for lower limb SSEP.

Vertex (Cz)

Warning criteria for SSEP?

10% latency increase

Central conduction time for median nerve is calculated between which peaks?

P14-N20

Peripheral conduction time for median nerve is between which peaks?

EP-P14

Central conduction time for PTN is calculated between which peaks?

LP-P37

Peripheral conduction time for PTN is calculated between which peaks?

PF-LP

SSEP isn't recordable when perfusion drops below

15cc/min/100 grams of tissue

Normal amplitude of SSEP responses from the scalp is approximately

.1uv to 10uv

If there is sudden loss of ipsilateral Erb's point and contralateral N20 response, what is the first step for troubleshooting?

Check arm positioning

Latency/amplitude changes in SSEP responses can result from:

Anesthesia, hypothermia, surgical manipulation, technical failure

Where is the P14 from?

Caudal medial lemniscus

N34 subcortical response is a near-field or far-field response?

Far field.

LP is a stationary (non-propagated) potential.

True

The most reliable criteria for SSEP abnormality is:

Missing obligate waveforms or increased interpeak latencies.

N18 subcortical response is a near field or far field response?

Far field.

After stimulation of the median nerve at the wrist, the response recorded at the Erb's point consists of:

Orthodromic Sensory.

Anti-dromic Motor Action Potentials.

Obligate waves of the median nerve are:

N9, N13, P14, N18, N20.

Obligate waves of the PTN are:

PF, LP, P31, N34, P37

What is the location of injury if there is loss of cortical responses but intact EP responses?

Brainstem / Thalamus

Which of the following sensations are not transferred via dorsals column?

Temperature

What is the blood supply of cortical responses elicited by MN stim?

MCA

Ohm's law is mathematically expressed as

V=IR

Good insulating materials that inhibit the current flow are:

Glass, rubber, wood

Maximum allowable chassis leakage current?

Less than 300uA with ground open

What is the maximum allowable leakage current through patient leads to ground with 120vac applied?

10uA RMS

In order to minimize filter-induced phase shift, the ratio of high-to-low frequency filter should be at least

100:1

A large current passing from an external surface to another is known as

Macroshock

A very low current as small as 10 microvolts that can be lethal to the patient if it passes through the heart is known as

Microshock

A band-stop filter is known as

60hz notch filter

What is the electrical line frequency in the OR in the USA?

60hz

ISI of a 40hz stim will be

25ms

Unequal electrode impedances may result in

More noise

Electrical charge stored by capacitor is known as

Capacitance

Opposition to change in current flow is known as

Inductance

Subdural electrodes made of platinum have what advantage?

Inert, stability during stim and MRI capable

True or False: Impedances of subdermal needle electrodes are usually higher than scalp

True

Cortical grid is made of what metal?

Platinum

What is the electrical frequency of the OR in europe?

50hz

ECochG conists of what responses?

Cochlear Microphonic

Summating Potential

Auditory Nerve CMAP

Bandpass filter sittings for BAEP?

10-30Hz

2500-3000Hz

Filter roll-off for BAEP should not exceed what values for LFF and HFF?

12db/octave for LFF

24db/octave for HFF

How many trials should be averaged for BAEP recordings?

1000-4000

Most prominent component of ECochG arises from

Auditory nerve fibers

First component of a BAEP arises where?

Auditory nerve

ECoG recording is done by placing a cotton wick electrode at which structure?

Tympanic Membrane and/or external auditory meatus

What happens if the ear canal is full of water?

Delays in IPL

In BAER, wave 1 can be lost due to what?

Bone drilling

TIVA is abbreviation for

Total Intravenous Anesthesia

Which TIVA agent cause an increase in amplitude fo SSEP/MEPs?

Ketamine and Etomidate

If a patient has hemaotocrit between 10-15%, SSEP waveforms will

Increase in latency and decrease in amplitude

If a patient has hemaotocrit below 10%, SSEP waveforms will

Disappear

What agent has the least affect on MEPS?

Inhalational agents

What short acting muscle agent is given during intubation?

Succinylcholine

What does pavulon (pancuronium) affect?

EMG and MEPs

Oldest NMB?

Curare

What modality benefits from NMBs?

SSEPs

True or False: Is fentanyl an opiod.

True

What is a peripheral response in SSEPs?

Erbs point, Pop Fossa

What agents affect peripheral responses?

None

What anesthetics are contraindicated when monitoring MEPs?

NMBs

True or False: Facial Nerve Monitoring was a result of of post-op facial weakness after acoustic nerve surgeries

True

Stimulating the trigeminal nerve (CN V) produces a response from:

Masseter

Intracranial stimulation of the Facial Nerve (CN 7) produces a muscle response at what latency?

7ms

EMG train activity during surgical procedures involving the Facial nerve can be caused by

Nerve traction; cold irrigation; heating of the nerve

To monitor cranial nerve XI, what muscle is it?

Trapezius

To monitor cranial nerve IV, what muscle is it?

Superior oblique

To monitor cranial nerve XII, what muscle is it?

Tongue

To monitor cranial nerve IX, what muscle is it?

Soft palate, Glossopharyngeal

What cranial nerves should be monitored for a cerebellopontine angle tumor less than 2cm?

CN VII and VIII

What type of electrode is recommended for facial nerve monitoring?

Hookwire

Compound auditory nerve action potentials can be recorded by using what type of electrode?

Cueva nerve electrode

Microvascular decompression of the cranial nerve is:

Placing a Teflon pad between an artery and a nerve to separate them.

To monitor cranial nerve V, what muscle is it?

Masseter

What modalities should be used for a vestibular schwannoma?

BAER and Facial Nerve EMG

What is the maximum intensity for direct cranial nerve stim?

1.0

EMG from CN VI can be monitored using which muscle?

Lateral rectus

What type of unpattern VEPs are there?

Flash VEP

Bandpass for VEPs?

1-100Hz

Analysis time for VEPs?

250ms or 25ms/div

True or False: VEPs are not affected by inhalational agents

False

A Mass electrical response of the retina to visual stimulation is typically recorded as:

Electroretinogram (ERG)

Main components of flash ERG are

A wave and B wave

ERG may be absent with an intact FVEP

True

What peaks are recorded for VEP?

N75, P100, N145

True or False: PVEP is affected by drowsiness

True

Wave 1 of a BAER generator is

Distal auditory nerve

Wave 2 of a BAER generator is

Proximal auditory nerve

Cochlea is separated into 3 fluid filled compartments by which membranes?

Basilar and Reissner's Membranes

A negative N20 peak is generated in response to median nerve stimulation at:

Contralateral Somatosensory Cortex

Areas of skin supplied by cutaneous branches of the spinal nerves are known as:

Dermatomes

Upper limb SSEPs are transmitted via

Fasiculus Cuneatus

Lowerlimb SSEPs are transmitted via

Fasiculus Gracilis

Median nerve is formed by the spinal roots at which level?

C5-T1

Ulnar nerve is formed by the spinal roots at which level?

C8-T1

PTN is formed by the spinal roots at which level?

L4-S3

Femoral nerve is formed by the spinal roots at which level?

L2-L4

Pudenal nerve is formed by the spinal roots at which level?

S2-S4

A response recorded by an epidural electrode due to direct activation of the corticospinal tract is known as:

D waves

A response recorded by an epidural electrode due to INDIRECT activation of the corticospinal tract is known as:

I waves

Blood supplied to the cochlea is through which artery?

Cochlear Artery