This study was to determine the normal range of the conduction time of F wave between the axilla and the spinal cord, defined as Axillary F Central Latency (AFCL), in normal adults.

In fifty healthy adults (28 men and 22 women), 100 median and ulnar nerves were examined. the AFCL was 10.19⁑2.88 msec (mean⁑3 S.D.) for median nerve, 9.89⁑2.70 msec (mean⁑3 S.D.) for ulnar nerve, and 10.02⁑2.64 msec (mean⁑3 S.D.) for median or ulnar nerve.

On the basis of these findings, an AFCL of more than 12.66 msec, or a discrepancy of the AFCL greater than 1.87 msec and 1.89 msec in the same median and ulnar nerves respectively between the two sides suggests an abnormality involving the proximal nerve segment.

The prolonged AFCL has been found in patients with right brachial plexopathy and left cervical radiculopathy.

In conclusion, this F wave study is valuable in diagnosis of a proximal neuropathy or myelopathy in upper extremity.