Correlations

Question 1

Wallerian degeneration occurs after how many days in motor nerves?

Answer 1

In 3 to 5 days

Question 2

Wallerian degeneration occurs after how many days in sensory nerves?

Answer 2

In 6 to 10 days

Question 3

After Wellarian degeneration, nerve conduction studies change how?

Answer 3

Decreased amplitude and preservation of conduction velocities and distal latency

Question 4

Why does Amplitude for motor studies decline earlier then sensory studies after WD occurs

Answer 4

Failure first at the neuromuscular junction

Question 5

What is the demyelinating range for CV and DL?

Answer 5

CV less than 75% of the lower limit of normal

DL more than 130% of the upper limit of normal

Question 6

What is the only change seen on EMG after acute transaction of a nerve?

Answer 6

Decreased recruitment on needle EMG

Question 7

How long does it take for sharps and fibs to develop in paraspinals after a nerve root lesion?

Answer 7

2 weeks

Question 8

How long does it take #fail to develop in the distal leg after a nerve root lesion?

Answer 8

6 weeks

Question 9

How does MUAP morphology change with reinnervation?

Answer 9

They become longer in duration, higher in amplitude, and polyphasic, reflecting increased numbers of muscle fibers per motor unit.

Question 10

How do EMG results change months to years after reinnervation?

Answer 10

Spontaneous activity disappears leaving only reinnervated MUAPs with decreased recruitment on needle. Motor and sensory nerve amplitudes may also improve.

Question 11

What is characteristic of acquired demyelinating neuropathy’s like GBS?

Answer 11

Conduction block that occur at non-entrapment sites

Question 12

What is characteristic of inherited demyelinating neuropathy’s like CMT?

Answer 12

Demyelination which results only in uniform slowing.

Question 13

What is the only abnormality on needle EMG in a pure demyelinating lesions with conduction block?

Answer 13

Reduced recruitment

If there is only decreased conduction velocity needle EMG is normal.

Question 14

Changes after hyper acute (

Answer 14

Normal nerve conduction studies and normal EMG except for decreased recruitment. Late responses are usually normal, unless the nerve has been completely transected proximally.

Question 15

Changes with axonal loss seen after several days but less than several weeks?

Answer 15

Increased distal latency and Increased amplitude and conduction velocity on NCS. Decreased recruitment on EMG.

Question 16

Changes with axonal loss seen after several weeks but less than months?

Answer 16

Increased distal latency and Increased amplitude and conduction velocity on NCS. Decreased recruitment AND sharps and fibs on needle EMG.

Question 17

Changes with axonal loss seen after a couple of months?

Answer 17

Increased distal latency and Increased amplitude and conduction velocity on NCS. Decreased recruitment, sharps and fibs, AND long duration high amplitude polyphasics on needle EMG.

Question 18

Changes with axonal lost seen after months to years?

Answer 18

Normal to increased distal latency and normal to I ncreased amplitude and conduction velocity on NCS. Decreased recruitment and long duration high amplitude polyphasics on needle EMG. No sharps and fibs.

Question 19

Why do you sensory amplitudes often decrease with demyelinating lesions, including conduction block?

Answer 19

Due to temporal dispersion and phase cancellation.

Question 20

EMG findings with myopathic lesions?

Answer 20

Sensory and motor NCS are usually normal. Except in Myotonic dystrophy where CMAP amplitudes maybe decreased only.

On needle EMG sharps, fibs, CRDs, and myotonia are seen. There is normal to early recruitment. And there are short duration, low amplitude polyphasics.

Question 21

What myopathies are associated with myotonic discharges?

Answer 21

Myotonic Dystrophy and Myotonia Congenita

Question 22

What myopathies are associated with fibrillation potentials?

Answer 22

Inflammatory or necrotic myopathies including polymyositis and dystrophies.

Question 23

What myopathies are associated with denervating features?

Answer 23

Polymyositis and inclusion body myositis.

Question 24

EMG findings with neuromuscular junction lesions?

Answer 24

Sensory NCS are always normal.
Postsynaptic lesions (MG) demonstrate decreased motor amplitude after RNS
Presynaptic lesions (LE and Botox) demonstrate decreased motor amplitude at rest that increases after RNS
EMG usually does not demonstrate spontaneous activity.
MUAP morphology and recruitment are usually normal

Question 25

How do you differentiate chronic neuropathic from chronic myopathic?

Answer 25

In chronic neuropathic there is reduced recruitment where with chronic myopathic recruitment is always normal too early.

Question 25

What is the only NMJ disorder that demonstrates spontaneous activity on EMG?

Answer 25

Botulism but only because the NMJ is so severely blocked that the muscle fibers are effectively denervated, resulting in sharps and fibs.

Question 26

EMG findings at the level of spinal cord injury?

Answer 26

Decreased recruitment and neuropathic changes due to anterior horn cell involvement.

Question 27

EMG findings for mononeuritis multiplex (multiple mononeuropathies)?

Answer 27

Asymmetrical non-length dependent nerve changes in bilateral extremities usually from underlying vasculitic neuropathy.

Question 28

EMG findings seen in the inherited demyelinating polyneuropathy’s like CMT.

Answer 28

Uniform slowing without conduction blocks on NCS. Mild decrease in Amplitude.
Distal affected more than proximal.
Lower extremities affected more than upper extremities.
Symmetrical.
Neuropathic findings on EMG.

Question 29

Key findings of an acquired demyelinating polyneuropathy like (CIDP)?

Answer 29

Conduction block at non-entrapment sites.

Asymmetric NCS even where there is a parent clinical symmetry.

Question 30

EMG findings for radiculopathy?

Answer 30

Normal sensory conduction studies.
Normal motor conduction studies unless muscles used for recording are innervated by involved nerve roots in a severe radiculopathy.
Neuropathic findings on EMG limited to one myotome including the paraspinals.

Question 31

What virus can cause polyradiculopathy?

Answer 31

cytomegalovirus

Question 32

How do you differentiate polyradiculopathy and motor neuron disease?

Answer 32

Clinically, patients with motor neuron disease won’t have any sensory complain or findings of UMN disease.
On NCS/EMG there is no real difference.

Question 33

EMG findings with motor neuron disease?

Answer 33

Normal sensory studies. Normal motor studies or decreased amplitude demonstrating axonal loss. Neuropathic findings on EMG in multiple myotomes, thoracic paraspirals, and bulbar muscles.

Question 34

What myopathies preferentially affect the distal muscles?

Answer 34

1. Myotonic dystrophy
2. Inclusion body myositis
3. Distal inherited myopathy

Question 35

Possibilities when a patient has sensory loss with normal sensory nerve action potentials?

Answer 35

1. The lesion is proximal to the dorsal root ganglia.
2. There is a proximal demyelinating lesions.
3. There is a hyper acute axonal loss lesion.

Question 36

When is pure motor loss seen a nerve conduction studies?

Answer 36

1. Motor neuron disease (fasciculations and increased reflexes).
2. Radiculopathy or polyradiculopathy (pain and sensory changes).
3. NMJ disorders (change with RNS)
4. Myopathy (decreased MUAP amplitudes)

Question 37

When trying to localize a lesion in mononeuropathy what phrase should be used?

Answer 37

“At or proximal to the take off to the most proximal abnormal muscle”