G1 active recording electrode
G1: hypothenar eminence
Place G1 over the ADM motor point in the hypothenar eminence, about halfway between the distal ulnar wrist crease and distal transverse palmar crease.
Table 2 · p.373 ↗
Motor study
Upper limb
Ulnar motor nerve conduction study
Place G1 over the hypothenar eminence and stimulate sequentially at the wrist, below elbow, above elbow and axilla.
01 · Placement
G1, G2, stimulation and ground landmarks
G2 reference electrode
G2: just distal to the fifth MCP joint
Place G2 3–4 cm distal to G1 over the hypothenar tendon at the fifth MCP joint, completely off the ADM muscle belly.
Distance · 3–4 cm distal to G1
Ulnar motor technique · p.16 ↗Stimulation site
Wrist stimulation: just radial to the FCU tendon
Stimulate at the wrist immediately radial to the flexor carpi ulnaris tendon, 8 cm from G1; orient the cathode distally.
Distance · 8 cm from G1
Table 2 · p.373 ↗Stimulation site
Below elbow: 4 cm distal to the medial epicondyle
With the elbow flexed 70–90°, stimulate over the ulnar nerve 4 cm distal to the medial epicondyle in the retrocondylar groove.
Distance · 4 cm distal to the medial epicondyle
Table 2 · p.373 ↗Stimulation site
Above elbow: 10 cm proximal along the curved path
Measure 10 cm proximally from S2 along the curved ulnar-nerve path behind the medial epicondyle, ending slightly volar to the triceps between biceps and triceps.
Distance · 10 cm proximal to S2, measured along the curved nerve path
Table 2 · p.373 ↗Stimulation site
Axilla: 10 cm proximal to the above-elbow site
Stimulate in the proximal axilla medial to the biceps and directly over the axillary pulse; higher current may be required for supramaximal stimulation.
Distance · 10 cm proximal to S3
Table 2 · p.373 ↗Ground region
Ground electrode region
Place the ground on the ulnar wrist or medial forearm between the wrist stimulation site and hypothenar recording electrodes.
Table 2 · p.373 ↗02 · Reference values
Adult normal limits
| Measure | Reference limit | Basis |
|---|---|---|
| Distal CMAP amplitude | ≥7.9 mV | 3rd percentile lower limit |
| CV below elbow | ≥52 m/s | 3rd percentile lower limit |
| CV across elbow | ≥43 m/s | 3rd percentile lower limit |
| CV above elbow | ≥50 m/s | 3rd percentile lower limit |
| Distal motor latency | ≤3.7 ms | 97th percentile upper limit |
| CV drop across elbow | ≤15 m/s or 23% | 97th percentile upper limit |
03 · Technique
Acquisition conditions
Fixed distance
G1 to wrist: 8 cm; across-elbow segment: 10 cm
Sensitivity
5 mV/div
Sweep
2 ms/div
Limb position
Elbow flexed 90°
Filter
2–3 Hz–10 kHz
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 ulnar motor reference values, including the across-elbow conduction-velocity drop limit.