Principles of Nerve Conduction Studies (NCS) ; Lecture

Question 1

What is the principal goal of nerve conduction studies (NCS)?

Answer 1

To localize the problem, define the nature of the pathology, assess its severity, and, in some cases, infer the aetiology.

Question 2

NCS serves as an extension of the _________, helping narrow the _________ diagnosis.

Answer 2

clinical examination; differential.

Question 3

True/False: NCS alone can always confirm the exact cause of neuropathy.

Answer 3

False (it often needs correlation with clinical findings).

Question 4

What are the three connective tissue layers of a peripheral nerve?

Answer 4

Endoneurium.
Perineurium.
Epineurium.

Question 5

Peripheral nerves are formed from plexuses or directly from _________ projections of the spinal cord.

Answer 5

ventral.

Question 6

True/False: Myelinated axons conduct signals faster than unmyelinated axons.

Answer 6

True.

Question 7

What is the resting membrane potential of a nerve fiber?

Answer 7

-90mV.

Question 8

During depolarization, sodium channels open, allowing _________ ions to enter, making the inside of the membrane _________ charged

Answer 8

sodium; positively.

Question 9

True/False: Action potentials are an “all-or-none” phenomenon.

Answer 9

True.

Question 10

How does myelin affect nerve conduction?

Answer 10

Myelin acts as an insulator, forcing current to travel longitudinally down the axon to the nodes of Ranvier, allowing saltatory conduction and increased speed.

Question 11

How does temperature affect nerve conduction studies?

Answer 11

Cooling slows conduction velocity.
Increases amplitude and duration of responses.

Question 12

Myelination is completed by age _________, and nerve conduction velocity declines progressively after age _________.

Answer 12

4-5; 60.

Question 13

True/False: Taller individuals tend to have slower conduction velocities due to nerve tapering distally.

Answer 13

True.

Question 14

Match the nerve injury type with its characteristics:

Neuropraxia.
Axonotmesis.
Neurotmesis.

Answer 14

Neuropraxia: Conduction block, preserved axonal continuity, good prognosis.
Axonotmesis: Axonal disruption with intact epineurium, Wallerian degeneration, variable prognosis.
Neurotmesis: Complete nerve disruption, no response, poor prognosis.

Question 15

_________ is the failure of nerve conduction without axonal damage, often referred to as conduction block.

Answer 15

Neuropraxia.

Question 16

True/False: Wallerian degeneration occurs in both axonotmesis and neurotmesis.

Answer 16

True.

Question 17

What are the two main types of NCS?

Answer 17

Sensory nerve conduction studies.
Motor nerve conduction studies.

Question 18

Slow responses in NCS suggest _________ loss, while low-amplitude responses indicate _________ loss.

Answer 18

myelin; axonal.

Question 19

True/False: F-waves allow assessment of proximal portions of the nerve.

Answer 19

true.

Question 20

What is the purpose of F-waves in NCS?

Answer 20

To evaluate the entire nerve, including the proximal segments.
Detect proximal demyelination or conduction delays.

Question 21

What are the key types of generalized neuropathies?

Answer 21

Axonal (e.g., diabetes, alcohol).
Demyelinating (e.g., GBS, CIDP).
Hereditary (e.g., HMSN, HNPP).

Question 22

Guillain-Barré Syndrome (GBS) has _________ onset and reaches its nadir within _________ weeks.

Answer 22

acute; 4.

Question 23

True/False: Diabetes is associated with multiple patterns of neuropathy, including autonomic and small-fiber neuropathy.

Answer 23

True.

Question 24

A diabetic patient complains of burning feet at night and dizziness. What types of neuropathy should be suspected?

Answer 24

Small-fiber neuropathy and autonomic neuropathy.

Question 25

What are common examples of focal compressive neuropathies?

Answer 25

Carpal tunnel syndrome (CTS).
Ulnar neuropathy at the elbow (UNE).
Peroneal neuropathy at the fibular neck.

Question 26

Wrist drop is caused by _________ neuropathy at the _________

Answer 26

radial; spiral groove.

Question 27

True/False: Mononeuritis multiplex involves multiple nerves affected at atypical entrapment sites.

Answer 27

true

Question 28

What conditions commonly cause mononeuritis multiplex?

Answer 28

Vasculitis, diabetes.

Question 29

What are the patterns of diabetic neuropathy?

Answer 29

Generalized sensorimotor axonal neuropathy.
Diabetic amyotrophy (proximal neuropathy).
Autonomic neuropathy.
Small-fiber neuropathy.
Mononeuritis multiplex.

Question 30

Proximal diabetic neuropathy often occurs during a switch to _________ due to poor glycemic control and is associated with _________ loss and pain.

Answer 30

insulin; weight.