Technical factors EMG/NCS 2

Question 1

When does Wallerian degeneration start for motor fibers and sensory fibers?

Answer 1

Motor fibers = 3 to 5 days

Sensory fibers = 6 to 10 days

Question 2

What pathology can cause decreased CMAP amplitude?

Answer 2

Neuropathy, myopathy, radiculopathy, NMJ disorder and motor neuron disease

Question 3

What is sural sparing and when is it seen?

Answer 3

Preserved sural SNAPs with abnormal median and ulnar SNAPs in first few weeks of AIDP

Question 4

What is the best predictor of poor prognosis in AIDP?

Answer 4

Low CMAP amplitudes

Question 5

What are the SNAP responses in spinobulbar muscular atrophy (Kennedy’s disease)?

Answer 5

Severely diminished or absent as a result of degeneration of the dorsal root ganglia

Question 6

In a lower trunk/medial cord brachial plexopathy, what is unique about the median and ulnar nerve responses?

Answer 6

Median SNAPs preserved (Median sensory travels through upper trunk and lateral cord)

Median motor abnormal

Ulnar SNAPs and motor abnormal

Question 7

True or False

In demyelinating neuropathies, the speed of conduction velocity correlates with the degree of weakness

Answer 7

False

Question 8

Upper trunk brachial plexopathy. Difference between median motor and sensory studies.

Answer 8

Median motor is normal. Median (and radial) sensory studies may be abnormal

(Median sensory fibers travel through the upper trunk and lateral cord)

Question 9

Are fibs and PSWs seen in NMJ disorders?

Answer 9

No except in botulism

Question 10

NCS findings in neurogenic thoracic outlet syndrome

Answer 10

Medial antebrachial cutaneous almost always abnormal

Median motor fibers more affected than ulnar motor fibers

Question 11

What industrial toxin can cause a motor > sensory neuropathy?

Answer 11

Organophosphates