G1 active recording electrode
G1: fifth digit
Place the active ring electrode around the proximal phalanx of digit V at the proximal fifth MCP region.
Table 2 · p.373 ↗
Sensory study
Upper limb
Ulnar sensory nerve conduction study
Place G1 on the fifth digit and stimulate at the wrist just radial to the flexor carpi ulnaris tendon.
01 · Placement
G1, G2, stimulation and ground landmarks
G2 reference electrode
G2: 4 cm distal to G1
Place the reference ring electrode 4 cm distal to G1 along the little finger, toward the distal MCP and fingertip.
Distance · 4 cm distal to G1
Table 2 · p.373 ↗Stimulation site
Wrist stimulation: just radial to the FCU tendon
Stimulate at the volar wrist 14 cm proximal to G1, immediately radial to the flexor carpi ulnaris tendon; orient the cathode distally.
Distance · 14 cm from G1
Table 2 · p.373 ↗Optional proximal sensory stimulation
Optional below-elbow stimulation
For optional proximal sensory conduction, flex the elbow and stimulate the ulnar nerve in the retrocondylar course just below the medial epicondyle.
Distance · Variable—measure the S1–S2 segment on the patient
Ulnar sensory proximal conduction · p.15 ↗Optional proximal sensory stimulation
Optional above-elbow stimulation
For optional proximal sensory conduction, stimulate above the medial epicondyle along the curved ulnar-nerve path between biceps and triceps.
Distance · Variable—measure the S2–S3 segment on the patient
Ulnar sensory proximal conduction · p.15 ↗Ground region
Ground electrode region
Place the ground over the ulnar wrist crease between the wrist stimulation site and the digit-V recording electrodes.
Table 2 · p.373 ↗02 · Reference values
Adult normal limits
| Measure | Reference limit | Basis |
|---|---|---|
| SNAP onset-to-peak | ≥10 µV | 3rd percentile lower limit |
| SNAP peak-to-peak | ≥9 µV | 3rd percentile lower limit |
| Onset latency | ≤3.1 ms | 97th percentile upper limit |
| Peak latency | ≤4.0 ms | 97th percentile upper limit |
| Conduction velocity | ≥45 m/s | Published 3rd percentile |
03 · Technique
Acquisition conditions
Fixed distance
G1 to wrist stimulation: 14 cm; measure optional proximal segments on the patient
Sensitivity
20 µV/div
Limb position
Below- and above-elbow sensory stimulation is optional and rarely performed
Filter
20 Hz–2 kHz
Sweep
1 ms/div
Temperature
Maintain dorsal hand skin temperature >32°C
Ground
Place the ground between the stimulating and recording electrodes
Primary evidence
Method-matched AANEM reference data
Adult antidromic ulnar sensory reference values for digit V; amplitude is also affected by age and BMI.