NCS

Acceptable Amplitude/Conduction Velocity Drop
NERVE SITE AMP DROP CV DROP
Ulnar Motor Across Elbow -- 15 m/s or 23%
Fibular Motor Ankle to below fibular head 32% --
Fibular Motor Across fibular head 25% 6 m/s or 12%
Tibial Motor Ankle to knee 10.3 mV or 71% --
Canterbury Scale CTS
Grade 0 Normal Normal findings in all tests
Grade 1 Very Mild Only detected in 2 sensitive tests
Grade 2 Mild SNCV F2 < 40m/s, DML <4.5msec
Grade 3 Moderate Preserved SNAP, 4.5< DML <6.5ms
Grade 4 Severe Absent SNAP, 4.5< DML <6.5msec
Grade 5 Very Severe Absent SNAP, DML>6.5msec
Grade 6 Extremely Severe Absent SNAP, CMAP<0.2mV (peak to peak)
EMG Result across elbow Padua Grade
No motor slowing (CV > 50m/s AND AE > BE) Negative
Motor slowing CV < 10ms Minimal

Motor slowing CV > 10m/s OR Absolute CV < 50m/s

Mild

As Mild AND Sensory AP < 6uV

Moderate
As Mild AND Absent Sensory AP Severe