Motor NCS Normal values Flashcards
What is normal latency and Amp of Median motor evoked potential?
Motor recorded over APB, stimulated 8 cm proximal.
ULN for DML 4.2
LLN for amp 4.1mV
(Buschbacher)
What is normal latency and Amp of Ulnar motor evoked potential?
Recorded over ADM, stimulated 8 cm proximal,
ULN for DML 3.7
LLN amp 7.9 mV (Buschbacher) (Preston/Shappiro have amp >6 mV)
DML and amp of Radial motor?
Recorded over EI, stimulated 4-6 cm proximal,
Avg DML 2.1 ms (buschbacher)
LLN amp2mV (Preston/Shappiro)
Minimal F waves
for average height
Median <31ms
DML and amp of Tibial N
Recorded over AH, stimulated 8 cm proximal,
ULN for DML is 6.1
LLN for amp is4.4(Buschbacher)
DML and amp of Peroneal N
Recorded over EDB, stimulated 8 cm proximal,
ULN for DML is 6.5
LLN for amp is1.3(Buschbacher)
What are filter and screen settings with motor NCS?
Low freq filter (high pass) 2-10 Hz
High freq filter (low pass) 10KHz
Sweep speed 2-5 ms/div
Gain 5 mV/div
What is normal latency of Tibial H reflex? tests tibial/S1
upper limit of normal from side to side is 2.0ms (buschbacher)
latencies like f waves are based on height and age
30-35ms for h reflexes
What is normal latency of Median H reflex? tests median/C6,7
upper limit of normal from side to side is 1.0ms (buschbacher)
upper limit of normal for latency is 18.9 ms (buschbacher)
Mean onset latency is 15.9 (buschbacher)
Axillary motor to Deltoid
stimulate at Erb’s point
ULN for DML 5.4
ULN of increased latency from side to side is 0.5 ms.
LLN for amp 4.6
Long Thoracic to serratus anterior
Monopolar or concentric needle over digitation of 5th rib at mid axillary line, reference electrode 2 cm caudal, ground electrode over 12th rib at anterior axillary line.
Stimulate at Erb’s point
DML (concentric) <=5.1 ms
Musculocutaneous to biceps
stimulate at Erb’s point
ULN for DML 5.6 ms
ULN of increased latency from side to side is 0.4 ms
LLN for amp 4.0 (buschbacher)
Suprascapular to supraspinatus and infraspinatus
stimulate at Erb’s point
active recording electrode is 2cm medial to midpoint of spine of scapula for supraspinatus
active recording electrode is 2cm inferior to midpoint of spine of scapula for infraspinatus.
ULN for DML is 4.3 for SS and 4.8 for IS
LLN for amp is 1.5 mV
ULN for s-s increased latency is 0.7 ms (supraspinatus) and 0.4 ms (infraspinatus)
What happens if you lower the high frequency filter during a motor study?
you filter out the faster conducting fibers and therefore have increased onset latency.
may have slight decrease in amp
What happens if you raise the low frequency filter during a motor study?
you filter out the slower conducting fibers and therefore have decreased amplitude.
Femoral to VMO? femoral N/post division of lumbar plexus/L2-4
Gain 1 mV/div
Sweep 2 ms/div
S1 8-10 cm proximal to active recording electrode
S2 below inguinal lig lateral to femoral A
S3 above inguinal lig lateral to femoral A 10 cm proximal to S2
DML >3.7 ms over 14 cm is prolonged (RMUoHP handout)
amp < 500 microV is reduced
NCV < 50 m/s for either S2-S1 or S3-S1 is slow.
do not calculate NCV for S3-S2 (RMUoHP handout)
Thoracodorsal N to Latissimus Dorsi?
supine arm abducted to 90 degrees Stimulate in axilla Active recording electrode is on posterior axillary line at level of inferior pole of scapula Reference of ipsilateral flank DML <= 2.7ms amp Mean 4.1 mV ULN decrease in amp s-s is 50%
Facial
Buschbacher Preauricular (anterior to ear) stim latency to nasalis range 2.8-4.1 ms Mean 3.57 ms Postauricular stim latency to nasalis range is 3.2-4.4 ms with Mean 3.88 ms
Preston Shapirro
Nasalis amp >=1 mV distal latency <=3.1 ms
Spinal Accessory
active recording over UT ~9 cm lateral to SP of C7
Reference 3 cm lateral
Stim posterior triangle of neck 1-2 cm posterior to the posterior border of SCM and slightly above the midpoint
Onset latency range 1.7-3.0ms
Peak to peak amp >3-4 mV
