A Woman With Generalized Increased Insertional Activity on EMG

A 41-year-old woman with no past medical history was referred for an EMG because of right shoulder pain. She denies neck pain. There was no family history. She denies stiffness.

Physical examination was unremarkable, except for some tenderness to palpation of the shoulder joint. Muscle strength, reflex, and sensory exams were normal.

Laboratory studies included a normal creatine kinase (CK) level.

An EMG Test was Performed

Motor Nerve Conduction

Nerve and Site	Muscle	Latency (ms)	Ref. (ms)	Amplitude (mV)	Ref. (mV)	Distance (mm)	Velocity (m/s)	Ref. (m/s)
R. Peroneal
Ankle	EDB	4.69	≤6.50	3.4	≥2.0	90
Fibula (head)	EDB	11.25		3.2		300	45.7	≥44.0
Popliteal fossa	EDB	12.71		3.1		80	54.9	≥44.0
R. Median
Wrist	APB	3.69	≤4.40	6.5	≥4.0	70
Elbow	APB	8.77		5.5		300	59.0	≥49.0
R. Ulnar
Wrist	ADM	3.02	≤3.30	11.7	≥6.0	30
Below elbow	ADM	7.19		10.5		220	52.8	≥49.0
Above elbow	ADM	9.06		11.1		120	64.0	≥49.0

F-Wave Studies

Nerve	F-Latency (ms)	Ref. (ms)	M-Latency (ms)
R. Peroneal—EDB	12.5	≤56.0	48.4
R. Median—APB	30.0	≤31.0	8.8
R. Ulnar—ADM	30.5	≤32.0	9.1

Sensory Nerve Conduction

Nerve and Site	Rec. Site	Peak Latency (ms)	Ref. (ms)	Amplitude (µV)	Ref. (µV)	Segments	Distance (mm)
R. Sural—Ankle (Calf)
Calf	Ankle	3.2	≤4.4	12	≥6.0	Calf–ankle	140
R. Ulnar—Digit V (Antidromic)
Wrist	Dig V	2.7	≤3.1	22	≥17.0	Wrist–Dig V	110
R. Median—Digit II (Antidromic)
Wrist	Dig II	2.5	≤3.5	42	≥20.0	Wrist–Dig II	130
R. Median—Palmar (Orthodromic)
Mid-palm	Wrist	1.8	≤2.2	55	≥50.0	Mid-palm–wrist	80