EMG/NCS EXAM QUESTIONS AND
ANSWERS
What do EMG and NCS's provide information on? - Correct Answers -location of lesion
in peripheral nervous system, type of nerve fibers involved (motor/sensory/mixed),
component of nerve injured (axon/demyelinating/both), severity (neuropraxia,
axonotmesis, neurotmesis), and prognosis
What are limitations of EMG and NCS? - Correct Answers -can't assess all components
of PNS (sympathetic NS), only assesses largely myelinated IA fibers (motor and
sensory) and not temp/pain fibers, many nerves not amenable to NCS, DOES NOT
ASSESS CNS
What is a neural conduction study? - Correct Answers -recording and measurement of a
compound nerve and compound muscle action potential elicited in response to a single
supramaximal electrical stimulus under standardized conditions, measures latency,
amplitude, and duration
What is repetitive nerve stimulation? - Correct Answers -specialized NCS testing
technique for diseases of the NMJ; must test that the muscle is weak
What is normal for a muscle at rest on EMG? - Correct Answers -muscle should be
quiet, no electrical activity
What is abnormal insertional activity on EMG? - Correct Answers -occurs for >200 ms
after you stop moving the pin, accompanied by fibrillation potentials and positive waves
What is diagnostic electromyography? - Correct Answers -recording and study of
insertional, spontaneous, and voluntary electrical activity of a muscle using a needle
electrode; muscle is evaluated under three conditions: insertion, rest, voluntary
contraction (min/max)
***What does EMG and NCS assess? - Correct Answers -required for a complete
assessment of a LOWER MOTOR NEURON:
anterior horn cell
nerve root=radiculopathy
plexus=plexopathy
peripheral nerve=mononeuropathy or polyneuropathy
neuromuscular junction
muscle=myopathy
ANSWERS
What do EMG and NCS's provide information on? - Correct Answers -location of lesion
in peripheral nervous system, type of nerve fibers involved (motor/sensory/mixed),
component of nerve injured (axon/demyelinating/both), severity (neuropraxia,
axonotmesis, neurotmesis), and prognosis
What are limitations of EMG and NCS? - Correct Answers -can't assess all components
of PNS (sympathetic NS), only assesses largely myelinated IA fibers (motor and
sensory) and not temp/pain fibers, many nerves not amenable to NCS, DOES NOT
ASSESS CNS
What is a neural conduction study? - Correct Answers -recording and measurement of a
compound nerve and compound muscle action potential elicited in response to a single
supramaximal electrical stimulus under standardized conditions, measures latency,
amplitude, and duration
What is repetitive nerve stimulation? - Correct Answers -specialized NCS testing
technique for diseases of the NMJ; must test that the muscle is weak
What is normal for a muscle at rest on EMG? - Correct Answers -muscle should be
quiet, no electrical activity
What is abnormal insertional activity on EMG? - Correct Answers -occurs for >200 ms
after you stop moving the pin, accompanied by fibrillation potentials and positive waves
What is diagnostic electromyography? - Correct Answers -recording and study of
insertional, spontaneous, and voluntary electrical activity of a muscle using a needle
electrode; muscle is evaluated under three conditions: insertion, rest, voluntary
contraction (min/max)
***What does EMG and NCS assess? - Correct Answers -required for a complete
assessment of a LOWER MOTOR NEURON:
anterior horn cell
nerve root=radiculopathy
plexus=plexopathy
peripheral nerve=mononeuropathy or polyneuropathy
neuromuscular junction
muscle=myopathy
