EMG-NCS

Question 1

Fasciculations vs fibrillations

Answer 1

Fasciculations are visible to the naked eye. Seen in neurogenic diseases.

Fibrillations are detectable only on EMG-NCS. Seen in neurogenic and myogenic diseases.

Question 2

Neurogenic disorders result in . . .

Myogenic disorders result in . . .

Answer 2

. . . a reduced number of motor units

. . . smaller motor units

Question 3

Denervated muscles become. . .

Answer 3

. . . supplied by intact neurons.

So, in a neurogenic disorder, the number of motor units may decrease, but the remaining ones actually become larger/carry more muscle fibers per nerve fiber.

Question 4

During rest, EMG in neurogenic disease will show. . .

Answer 4

. . . oscillations due to loss of inhibitory signals

Question 5

“Interference pattern” on EMG

Answer 5

Rapid and differentially sized oscillations, normally seen in strong muscle contraction of a healthy patient.

In neuropathy, this is replaced by discrete potentials.

In myopathy, this is replaced by fewer, less irregular oscillations.