Sensory nerve conduction studies of the L-1/L-2 Dorsal rami.

OBJECTIVE

This report describes a technique for performing sensory nerve conduction studies of the lateral cutaneous branches of the dorsal rami of the L-1/L-2 nerve roots for use in the evaluation of unilateral low back pain without lower limb referral.

SUBJECTS: Eleven healthy adult volunteers (9 men and 2 women) ranging in age from 25 to 36 years with no current complaint of low back pain.

DESIGN

Prospective determination of reference sensory nerve conduction values using a deep near nerve stimulation technique.

RESULTS

Reproducible sensory nerve action potentials were evoked in all subjects. The mean distal onset latency was 3.5 +/- 0.7msec with a mean conduction velocity of 59.5 +/- 11m/ sec and a mean SNAP amplitude of 3.6 +/- 2.7 microV. The mean side-to-side difference in onset latency was 0.5 +/- 0.4msec.

CONCLUSIONS

This study demonstrates a simple and reliable electrodiagnostic technique that may be useful in the evaluation of certain patients with unilateral low back pain. An onset latency of > 4.9msec (mean + 2 SD) or a side-to-side latency difference of > 1.3msec (mean + 2 SD) may represent a low back pain syndrome in which the cutaneous branches of the L-1 or L-2 dorsal rami have a primary role and which is possibly caused by entrapment of one of the cutaneous branches as it traverses the iliac crest in a fibro-osseous tunnel.