What are the normal latency and amplitude values for the lateral antebrachial cutaneous nerve?

Normal Lateral Antebrachial Cutaneous Nerve Values

The normal lateral antebrachial cutaneous nerve (LACN) onset latency is 1.7 ± 0.2 ms with an upper limit of normal of 2.0-2.1 ms, and the normal amplitude is 18 ± 10 μV with a lower limit of normal of 5-6 μV, when measured at a standardized 10-cm distance using antidromic technique. 1

Latency Parameters

• Onset latency: Mean of 1.7 ± 0.2 ms, with the 97th percentile (upper limit of normal) at 2.0 ms 2
• Peak latency: Mean of 2.2 ± 0.2 ms, with both the 95th and 97th percentile values at 2.5 ms 1
• When using a 14-cm distance (older technique), the mean latency to peak is 2.8 ms with a conduction velocity of 61.5 m/s 3

Amplitude Parameters

• Onset-to-peak amplitude: Mean of 18 ± 10 μV, with the 3rd percentile (lower limit of normal) at 5 μV 1
• Peak-to-peak amplitude: Mean of 22 ± 15 μV, with the 3rd percentile at 6 μV 1
• The LACN amplitude tends to be larger than the medial antebrachial cutaneous nerve in 76% of subjects 3

Additional Waveform Characteristics

• Rise time: Mean of 0.5 ± 0.1 ms 1
• Duration: Mean of 1.1 ± 0.2 ms 1
• Area: Mean of 11 ± 7 nV-s 1

Side-to-Side Comparison

• Onset latency difference: Mean of 0.1 ± 0.2 ms between sides, with an upper limit of normal of 0.3 ms 2, 1
• Peak latency difference: Mean of 0.1 ± 0.2 ms between sides 1
• Amplitude differences: Up to 67% side-to-side decrease in onset-to-peak amplitude can be within normal range 2

Comparison with Medial Antebrachial Cutaneous Nerve

• When comparing the LACN to the medial antebrachial cutaneous nerve in the same limb, both onset and peak latencies have a mean difference of 0.0 ± 0.2 ms with an upper limit of normal of 0.3 ms 2
• This comparison is useful because both nerves should have similar latencies when measured at the same distance 2

Important Technical Considerations

• Standardized distance: All modern normative values are based on a 10-cm measurement distance using antidromic technique 2, 1
• Success rate: Sensory nerve action potentials can be obtained in 98% of healthy subjects 3
• Age effects: Increasing age is associated with lower mean amplitudes, but this does not affect the lower limits of normal 1
• Body mass index effects: Higher BMI is associated with lower amplitudes but does not change the lower limits of normal 1
• Gender differences: Minimal sex effects on latency values, though some measurement parameters show small differences 3

Clinical Pitfalls

• The LACN amplitude tends to be larger than the medial antebrachial cutaneous nerve, so comparing absolute amplitudes between these two nerves is not appropriate 3
• In some subjects, the LACN is technically easier to study than the medial antebrachial cutaneous nerve 3
• The nerve consistently emerges from the lateral margin of the biceps brachii tendon and pierces the deep fascia distal to the interepicondylar line in 84.4% of cases 4