13: Electrophysiology Testing Biofeedback

cell depolarization can be stimulated via?

electricity for recording

what does CNAP stand for?

compound nerve action potential

what does CMAP stand for?

compound muscle action potential

2 recording and 1 ground electrodes detect ionic changes from what?

cell depolarization

sodium rushes into nerve fibers beneath the first recording electrode and the area beneath the electrode becomes more _______

negative

sodium moves into excitable cells between the two electrodes and ionic concentrations beneath each electrode become _____

EQUAL

sodium rushes into excitable tissues beneath the second electrode, then the first electrode appears more _____

POSITIVE

benefit of using surface electrodes?

• easy to use

• patient friendly

cons of using surface electrodes?

get more interference from other excitable subcutaneous tissue

benefit of subcutaneous electrodes?

record deeper tissue, smaller areas, and more sensitive

less noise, but less comfortable

what can you record from in biofeedback?

voluntary muscle contraction

externally stimulated AP

biologic signals are in what range?

microvolt to millivolt range

(amplify small voltage to get a signal)

what electronic device increases the amplitude of voltages measured in nerve or muscle?

amplifiers

what is level detection in EMG and ENG recording?

target level the EMG activity needs to meet for signal

what are the different things that can affect amplitude regarding motor units?

number and size that are firing

frequency of firing

what are the different things that can affect amplitude regarding distance?

distance between electrodes and the muscle they’re recording

why would you want to adjust the sensitivity on devices measuring amplitude?

so that more or less of the signal registers (makes the electrodes more or less sensitive)

what is the the relationship of the actual signal recorded and the output voltage from the amplifier?

gain

f the recorded V is 1mV, and the signal is increased (by the amplifier) to 10mV

what is the gain?

10!!

purpose of gain?

to amplify every signal that is going to pick up

cuts out things that are too high or too low to be a biologic signal

what is the purpose of filtering?

cancels out the extra noise and gets ride of things that aren’t applicable

→ ex) moving wires or electrodes

nerves and muscles firing have ______ frequencies

characteristic

what is repeated stimulation of tissue with voltage measured each time?

all voltage recordings are summed, and will increase the recording of an action potential

signal averaging

what changes negative deflections to positive?

→ adds all the AP values together

rectification

what is the summation of a rectified signal?

integration

CNAP and CMAP have characteristic _____, _____, and ______

shape, amplitude, and duration

Time delay between ______ and the evoked _______ can be measured

e-stim application

action potential

CNAP and CMPA can be used to help detect?

axonal damage or loss

if the graphs aren’t showing desired shape, amplitude, duration, what can we deduce?

that there is a deficit/problem somewhere

nerve conduction test examines?

motor or sensory function

nerve conduction tests allow the clinician to determine?

• Peripheral motor, sensory or mixed nerve damage

• Location of peripheral lesion

• Number of nerves involved

• if lesion is progressing or nerve recovering

• Is this consistent with a peripheral or systemic disorder?

what is the process of how CMAP functions?

1. stimulation of peripheral nerve

2. AP propagation in alpha MN axons

3. activation of skeletal muscle

4. recording electrodes pick up signal

CMAP amplitude is affected by?

the total number of motor axons sending AP to the muscle

number, size of muscle fibers + placement of recording electrodes

what is the time from the initial electrical stimulation to the initial negative deflection of the CMAP?

latency

the latency period accounts for what?

the time for the AP to travel to the nerve, then to NMJ, junction transmission time, and the first AP in the muscle to begin

what is a primary measure in nerve conduction studies?

latency value

The CMAP amplitude increases as more _______ are stimulated

muscle fibers

latency is measured from multiple stimulation sites along the nerve to calculate what?

motor nerve conduction velocity for different segments of the nerve

motor nerve conduction velocity is reported in?

meters per second

in motor nerve dysfunction, what can happen to the conduction velocity or AP?

decreased conduction velocity → latency is going to be longer than it should be

absent AP

cold can _____ nerve conduction velocity

DECREASE

what can cause motor nerve dysfunction?

nerve compression or demyelination

T/F certain pathologic conditions can increase conduction velocity in nerves

FALSE! no condition can

what types of electrodes are used for sensory nerve testing?

needle or surface electrodes

what type of shocks for sensory nerve fibers?

single, short electrical shocks

sensory AP is bigger/smaller in amplitude than motor

SMALLER

T/F sensory nerve testing is also testing latency period

TRUE

what is the purpose of nerve conduction testing?

to determine if the underlying pathology in a peripheral nerve is localized to a single segment or is spread over long nerve segments

what are the general principles of nerve conduction testing?

1. both motor and sensory conduction studies should be performed when possible

2. several segments should be examined

3. contralateral nerves should be examined

4. both upper and lower limbs should be examined

5. testing should be performed at the appropriate time

what nerves are commonly test?

• median

• ulnar

• radial

• deep fibular

• tibial

what nerve lesion has localized slowing of conduction, the axon is not degenerating

→ may be from compression like crutch palsy, often see paresthesia

neuropraxia

what nerve lesion has partial to complete axon disruption without damage to the connective tissue like the endoneurial tubes

→ may see numbness, motor weakness

axonotmesis

what nerve lesion has axonal disruption with damage to the connective tissue often associated with trauma?

→ weakness, numbness, may have denervation

neurotmesis

what is recording electrical signals in a muscle at rest or during voluntary contraction?

electromyography (EMG)

Can find abnormal EMGs indicative of?

myopathy or neuropathy

for needle EMG, what are the 3 types of electrodes?

positive, negative, ground

you want to examine electrical signals at what places during needle EMG?

• insertion

• muscle at rest

• muscle during minimal contraction

• muscle during maximal contraction

what should the normal insertion activity be?

brief, high frequency firing

50 - 200 ms

needle insertion is associated with _____ _____ of muscle fibers

mechanical stimulation

what type of muscle has reduction in insertional activity?

fibrotic or atrophic muscles

what type of conditions would have increased insertional activity?

acute denervation, MD, injury that has just occurred

do we see a lot of resting electrical activity in healthy muscle?

NO

May see very low amplitude activity if have needle electrode at the neuromuscular junction

Other electrical activity is usually abnormal

what shows spontaneous discharge of one or more muscle fibers

fibrillation potentials

you may see fibrillation potentials in what conditions?

denervation, myopathy, MD, MG

positive sharp waves on EMG in resting muscle indicates?

spontaneous electrical discharge from myopathy

what does MUP stand for?

motor unit potentials

smaller or larger than normal MUPs can indicate?

myopathies or neuropathies

MUP measure from muscle fibers that are ___ to needle electrode

CLOSE! PROXIMAL!

normal motor unit parameters?

Amplitude

200 mV - 300 mV

what are normal motor unit parameters?

Duration

5 - 15 msec

what are normal motor unit parameters?

Rise time

100 - 200 msec (< 500 msec)

what are normal motor unit parameters?

frequency

5 - 15 per sec (< 60/sec)

what are the general principles of electromyographic testing?

1. exam muscles both above and below the suspected site of the nerve

2. exam muscles innervated by nerves other than the suspected one

3. sampling of EMG activity of the full cross-section of each muscle

4. exam contralateral muscles

5. perform exam at the appropriate time

what uses visual or auditory signals to provide feedback about a physiologic response?

biofeedback

what can you use biofeedback for?

• muscle movement/relaxation

• respiratory rate

EMG records activity of?

the neural signaling in skeletal muscle

what process?

CNS activates alpha motor neurons → more number recruited, higher force that is recorded by EMG

recruitment

what process?

CNS controls the frequency of activation of motor neurons in a contracting muscle?

→ higher frequency, more force recorded by EMG

rate coding

EMG amplitude helps quantify if you have increased ____, ______. or both

recruitment

rate coding

T/F have a linear increase in EMG voluntary contraction in fatigued muscle, or non-isometric contraction of muscle

FALSE!!! NON-LINEAR

indications for biofeedback?

• Pelvic floor training

• Strength and mobility after neural damage, like CVA

• Use to train motor control

• Combine with physical therapy

what patient characteristics make them good for biofeedback?

• Need some voluntary control

• Motivation

• Cognitive ability

• Typically use for 1 muscle or muscle group at at time

what is the electrode placement for biofeedback?

Over muscle belly

have 2 recording electrodes and 1 reference electrode

are the electrodes place close or far in biofeedback?

typically use close spacing

why would you want to use wider space in between biofeedback electrodes?

larger muscle volume, more cross talk

why would you want to use narrow space in between biofeedback electrodes?

less muscle volume, less cross talk

how does biofeedback help muscle strength?

positive reinforcement for mm activation, even if not able to actively move the joint

cues for muscle contraction

level detection can provide ____ or ____ feedback if the pt met the present level

visual or auditory

how to progress strength using biofeedback?

• increase target threshold

• decrease gain

• increase time to contract muscle

why would you want to use the below tone setting for biofeedback?

Muscle relaxation

• spasticity or motor control, coordination

• To make more difficult

• Increase gain

• Decrease target threshold