Neuro: Peripheral Neuropathy

Front 1

What are 3 structures of the Neuron that are susceptilbe to damage?

Back 1

1. Cell Body
2. Axon
3. Schwann Cell

Front 2

What does "Wallerian Degeneration" impact of the cell nerve?

Back 2

caused by physical injury of impact
- Damages axon

Front 3

Why does "Wallerian Degeneration" of the axon cause muscle atrophy?

Back 3

The axon is key for DELIVERING TROPHIC FACTORS to muscle and nerve

Front 4

What does "Segmental Demylination" impact?
-what does it not impact?

Back 4

impacts: Schwann cells (myelination)

does not impact - axon

Front 5

what causes "Axonal Degeration" aka "Dying Back"

Back 5

metabolic or toxic damage
-distal portion of nerve dies

Front 6

Cell bodies of what two types of neurons are located in the CNS (specifically, gray matter of spinal cord)

Back 6

1. Motor Neuron
2. Autonmic neurons*
(autonomic neuron cell bodies located both in CNS and PNS)

Front 7

Where 2 cell bodies are located in the PNS?

Back 7

-Sensory neurons (Dorsal Root Ganglion)
2. Autonomic neurons (paravertebral or prevertebral ganglion)
*not autonomic neuron cell bodies can be located both in spinal cord (CNS) and Ganglion (PNS)

Front 8

What are 2 trends (functionally related) w/ loss of function?

Back 8

1. Motor Loss (CNS)
2. Sensory Loss (PNS)
**this is b/c of where cell bodies of these nerves are located

Front 9

PNS axon components vary with respect to ?

Back 9

level of myelination and diameter
-may be myelinated, unmyelinated, large or small diameter

Front 10

Large myelinated motor PNS axons are involved in?

Back 10

Skeletal muscle

Front 11

Multiple choice SENSORY axons (PNS) answer choices include:
-Large diameter myelinated
-Small diameter myelinated
-Small diameter UNmyelinated

*sharp and localized pain
**COOL temperature?

Back 11

Small Diameter myelinated
(mnemonic: when you're cold, you like to get SMALL (to conserve body heat) and wear a coat (MYELINATED)

Front 12

Multiple choice SENSORY axons (PNS) answer choices include:
-Large diameter myelinated
-Small diameter myelinated
-Small diameter UNmyelinated

*aching/buring and less localized pain
**WARM temperature

Back 12

Small diameter UNmyelinated
(mnemo: don't wear a coat (myelination) when hot)

Front 13

Multiple choice SENSORY axons (PNS) answer choices include:
-Large diameter myelinated
-Small diameter myelinated
-Small diameter UNmyelinated

**muscle spindle (MS) light touch, vibration, position, spinocerebellar input

Back 13

Large myelinated
**sometimes the large guys are the most sensitive

Front 14

What is the main diff., with regard to specific sensational feelings of
-Large diameter myelinated
-Small diameter myelinated
-Small diameter UNmyelinated

Back 14

larger in diameter, more responds to small changes

smaller in diamter, less localized pain, more achy

Front 15

Large myelinated motor axons vs small myelinated motor axons:
innvervates skeletal muscle or innervates muscle spindle?

Back 15

LARGE myelinated --> Skeletal muscle (large muscle)

SMALL myelinated --> muscle spindle (small muscle spindle)

Front 16

Autonomics:
Small diameter myelinated vs unmyelinated?

-preganglionic or post-ganglionic?

Back 16

Small diameter myelinated autonomic --> Preganglionic (white ramus)

Small diameter unmyelinated autonomic? --> postganglionic (gray ramus)

Front 17

Axon disruption:
-Axonotmesis or Neurotmesis?

Back 17

Axonotmesis

-Neurotmesis is axon AND associated supportive tissue disruption

Front 18

axon AND associated supportive tissue disruption:
-Axonotmesis or Neurotmesis?

Back 18

Neurotmesis

Axonotmesis is axon only

Front 19

What can cause -Axonotmesis or Neurotmesis

Back 19

Physical force trauma which produce compression and trauma
*ie., can cause
-ischemia (compression of vasa nervorum (blood vessels nerves)
-myelin sheath compression
-axonotmesis
-neurotmesis

Front 20

Where are spinal nerves typically compressed?

Back 20

Vertebral formen via a herniated disc

Front 21

Where is the ulnar nerve typically compressed?

Back 21

-elbow in the cubital tunnel or the carpal tunnel

Front 22

where is the median nerve typically compressed?

Back 22

carpal tunnel

Front 23

Traction during birth can injure?

Back 23

brachial plexus

Front 24

Penetrating injuries are caused by

Back 24

lots of things, but mainly stabbing or gunshot wounds

Front 25

Endogenous disturbance of nerve metabolism?

Back 25

diabetes or renal failure

Front 26

Exogenous disturbance of nerve metabolism?

Back 26

alcohol or chemotherapeutic agents

Front 27

Genetic disturbance of nerve metabolism?

Back 27

Charcot Marie Tooth DZ (CMT)

Front 28

Idiopathic disturbance of nerve metabolism?

Back 28

Amytrophic Lateral Sclerosis (ALS) aka "Lhou Ghreig's"

Front 29

2 big causes/dz's associated with inflammatory attack on Schwann cell, axon, or cell body?

Back 29

1. Guillain Barre (GBS) after infection or vaccination can have AUTOIMMUNE
2. CANCER (paraneoplastic)

Front 30

Why does ischemia cause your arm to go to sleep?

Back 30

1. Disturbs Axon Metabolism
2. Blocks action Potential propagation
**pressure to local capillaries causes decrease in local nutrients

Front 31

How long does it take to produce local nerve ischemia and how quickly does it go away

Back 31

Onset w/in minutes

Recovery w/in minutes

Front 32

What type of axons are most susceptible to local nerve ischemia injury?
Sensory more or motor more?

Back 32

-Large myelinated axons
Sensory > motor
*local anesthetics mimic situation

Front 33

What does PROLONGED local nerve COMPRESSION do?

Back 33

Damages Schwann cells (myelination)

Does NOT damage axon itself

Front 34

How are Schwann cells damaged during compression (aka, technical term)

Back 34

Intussuscept (push into each other like a car crash) in area of compression

Front 35

What is Neurapraxia (as opposed to Axonotmesis or Neurotmesis)

Back 35

Neurapraxia - only the myelin sheath is damaged (axon itself is okay)

**conduction only fails at site of compression

Front 36

What if try to stimulate nerve downstream of compression site (of conduction block/neurapraxia)

Back 36

can stim downstream, but CANNOT stim upstream

-axons remain intact distal to lesion and respond to electrical stim.

Front 37

What is the onset and recovery of Neurapraxia(conduction block)

Back 37

Onset - over hours

Recovery - over WEEKS to Months

Front 38

Why does recovery from Neurapraxia (conduction nerve block) take weeks to months?

Back 38

break down and regrow schwann cell

Front 39

Is there atropy distal to lesion (Neurapraxia/conduction block)

Back 39

Not really- Axonal transport still preserved, so still transporting trophic factors

Front 40

What is the basic component of the peripheral motor system?

Back 40

Motor unit

Front 41

What all makes up the motor unit?

Back 41

cell body
axon
terminal branches
neuromuscular junctions
muscle fibers

Front 42

What is the basic electrophysiological compoenet of the recorded response during nerve conduction studies?

Back 42

Motor Unit Potential (MUP)

Front 43

How do you test nerve conduction?

Back 43

-basically
1. electrically stimulate nerve trunk
2. this produces NERVE ACTION potentials which activate MOTOR UNITS
3. Record MOTOR UNIT RESPONSE

Front 44

What is the response in a nerve conduction study termed?

Back 44

Compound Muscle Action Potential (CMAP) or M-wave

Front 45

What is the Compound Muscle Action Potential (CMAP) or M-wave?

Back 45

Summation of the Motor Unit Potential responses (the sum of all of the basic electrophysiological compenets of recorded response)

Front 46

Does the Compound Muscle Action Potential (CMAP) or M-wave INCREASE or DECREASE in size as more axons are activated by INCREASING stimulus?

Back 46

Compound Muscle Action Potential (CMAP) or M-wave INCREASES - more motor neurons are activated

Front 47

When are measurements for nerve conduction studies made?

Back 47

at the full "maximal level"
-strong enough stimulus that all axons are recruited

ie: normal hand muscle ~150 units

Front 48

Does the nerve trunk contain many or few motor axons?

Back 48

many -- strong stimuli can recruit more and more axons to elicit response

Front 49

What is latency?

Back 49

Conduction time

Front 50

How do you calculate Conduction Velocity?

Back 50

CV = segment length/segment time

**measure distances from where stimulate nerve from tendon insertion

Front 51

(strictly for a reference point) about what is median n. conduction velocity?

Back 51

UE's 50-65 m/s
LE's 40-50 m/s

Front 52

What will you observe in a nerve conduction study if there is a CONDUCTION BLOCK?

Back 52

ABRUPT DROP OFF in CMAP AMPLITUDE
***hallmark of of focal demyelinating lesion

Front 53

How does the response amplitude distal to the lesion site of a focal demyelinating lesion?

Back 53

It is normal

Front 54

How does the response amplitude distal to the lesion site of an axonal damage neuron look?

Back 54

no response

Front 55

How long should you wit to do nerve conduction study after injury?

Back 55

wait about a week b/c if interruption can take 5-6 days to manifest/break down

Front 56

How does one recover from a focal demylenating lesion?

Back 56

-local dismantling, then REBUILDING of myelin sheath

-demyelination and remyelination
-Schwann cells divide

Front 57

What is characteristic of the Schwann cells that recover after a focal demylenating lesion? Is conduction velocity same?

Back 57

New internodes are shorter than original "INTERCALATED SEGMENTS"

- speed may not return to normal

Front 58

What happens (repair process) to physical disruption of axons distal to injury site?

Back 58

"Wallerian degeneration"

Front 59

Wallerian degeneration involves both (what kinds of changes)

Back 59

Neuronal

Axonal

Front 60

What are some neuronal changes with Wallerian Degeneration and when occur?

Back 60

-w/in a few days after injury

- Cell body swells
-Nissl substance breaks up
- RNA synthesis increases

Front 61

What are some Axonal changes with Wallerian Degeneration and when occur?

Back 61

-onset about 5 days after injury

-myelin degeneration
-axonal atrophy

Front 62

W/ physical disruption of axons distal to injury site, can one tell a difference between axonotmesis (axon) and neurotmesis (axon and supporting perineurium)?

Back 62

No, all we know is that there is axonal atrophy

Front 63

Distally, what kind of nerve response to electrical stimulation do we get if there is physical disruption of axons?

Back 63

Impaired or Absent

Front 64

physical disruption of axons, what happens to target structures and why??

Back 64

Atropy

-lack of "trophic" factors normally transported by AXON

Front 65

physical disruption of axons, how does recovery occur/how long?

Back 65

months to about 2 years (1mm/day)

=regeneration of injured axons by sprouting of surviving axons (Reinnervation)

Front 66

Even though there is reinnervation with axonal damage, why is degree of recovery usually "fair to none at all"

Back 66

some axons may end in different destinations than original "aberrant reinnervation"
*needle EMG can detect beginning reinnervation b/4 being clinically evident

Front 67

What does needle EMG recording inserted into normal muscle show
-at rest
-in activation

Back 67

-at rest - silence

-activation - normal motor unit potentials

Front 68

What does needle EMG recording inserted after axonal disruption of neuron w/ muscle show
-at rest

Back 68

SPONTANEOUS M. FIBER action potentials

aka "FIBRILLATION"

Front 69

What does needle EMG recording inserted after axonal disruption of neuron w/ muscle show
-in activation

Back 69

reduced # (or absent) voluntary motor unit potentials

Front 70

What is fibrillation?

Back 70

sponataneous m. fiber action potentials seen at rest w/ axonal disruption of nerve

Front 71

The Radicle is composed of?

Back 71

Dorsal and Ventral Roots +
Spinal Nerve

Front 72

How can the nerve beomce compressed in the spinal foramen?

Back 72

Herniated nucleus pulposus ("soft disc")
Osteophyte ("hard disc")

Front 73

What is the term for when the nerve comes compressed in the spinal forament?

Back 73

Radiculopathy

Front 74

What territories does Radiculopathy affect?

Back 74

motor (myotome)
sensory (dermatome)
joint/soft tissue sensory (sclerotome)
territories of compressed nerve
**This is a single nerve compression

Front 75

Pattern of involvement in limb reater that explainable by a single nerve or nerve root lesion?

Back 75

Plexopathy

Front 76

What observe w/ Uppter Trunk Brachial Plexopathy (hint, word plexus, associated w/ Plexopathy)

Back 76

weak shoulder abduction
external rotation and elbow flexion

Front 77

What might observe with lumbar plexopathy in a diabetic?

Back 77

severe spontaneous hip and leg pain
weaknes of hip flexion, adduction, and knee extension
sensory loss in anterior thigh and medial lower leg

Front 78

Just for knowledge, a few etiologies of plexopathy?

Back 78

-trauma
-inflammation after vaccinations or systemic infections
-compresion by cervical rib or retroperitoneal hematoma
-hereditary
-idiopathic

Front 79

What is an abnormality localized to a single peripheral nerve (segment?)

Back 79

Mononeuropathy

Front 80

What is the eitology of a mononeuropathy?

Back 80

nerve compressed in a potentially constrictive or superfical unprotected site

Front 81

carpal tunnel syndrome?

Back 81

median nerve at wrist

Front 82

cubital tunnel syndrome?

Back 82

ulnar nerve at elbow

Front 83

saturday night palsy

Back 83

radial nerve in spiral groove

Front 84

foot drop

Back 84

peroneal nerve at the fibular head

Front 85

bell's palsy

Back 85

facial nerve in stylomastoid canal

Front 86

meralgia paresthetica

Back 86

lateral cutaneous nerve of thigh

Front 87

Defectits do not correspond to single nerve or nerve root
-bilateral and symmetric pattern
-distal segmnets involved initially (length dependent)
-sensation usually more abnormal than motor function

Back 87

Polyneuropathy general features

Front 88

W/ polyneuropathy, is sensation or motor function more abnormal?

Back 88

sensation usually more abnormal

Front 89

Where are muscle stretch reflexes with polyneuropathy reduced or absent?

Back 89

ankle, then knee

Front 90

Where do abnormalities tend to move as polyneuropathy worsens?

Back 90

toes, feet, ankle, midshin, fingers, hands

Front 91

Polyneuropathy assoicated w/ metabolic disturbances?

Back 91

diabetes
renal failure

Front 92

Polyneuropathy assoicated w/ toxins

Back 92

alcohol
chemotherapeutic drugs

Front 93

Polyneuropathy assoicated w/ autoimmune inflammation

Back 93

GBS (guillain barre)

Front 94

Polyneuropathy assoicated w/ hereditary factors?

Back 94

Charcot Marie Tooth DZ (CMT)