Table 2.
Nerve conduction study values needed to be considered “demyelinating”
| NCV (m/s) | DL (ms) | F WAVES (ms) | |||||||
|---|---|---|---|---|---|---|---|---|---|
| LLN | <80%a | <70%b | ULN | > 125%a | >150%b | ULN | >120%a | >150%b | |
| Median | 49 | 39.2 | 34.3 | 4.5 | 5.6 | 6.7 | 31.0 | 37.2 | 46.5 |
| Ulnar | 50 | 40.0 | 35.0 | 3.6 | 4.5 | 5.4 | 32.0 | 38.4 | 48.0 |
| Peroneal | 41 | 32.8 | 28.7 | 6.6 | 8.2 | 9.9 | 58.0 | 69.6 | 87.0 |
| Tibial | 41 | 32.8 | 28.7 | 6.0 | 7.5 | 9.0 | 58.0 | 69.6 | 87.0 |
a
If Amp >80 % LLN
b
If Amp <80 % LLN
If: Median CMAP LLN 4.5 mV; then 80 % LLN = 3.6 mV
Ulnar CMAP LLN 5.0 mV; then 80 % LLN = 4 mV
Peroneal CMAP LLN 2.0 mV; then 80 % LLN = 1.6 mV
Tibial CMAP LLN 4.0 mV; then 80 % LLN = 3.2 mV
NCV nerve conduction velocity
DL distal latency
CMAP compound muscle action potential
LLN lower limit of normal