Normal values of F wave in lower extremities of 73 healthy individuals in Iran.

F wave latency has been shown to be a simple and valuable method in evaluation of proximal part of peripheral nerves. According to our previous study of F wave of upper extremity nerves (1), maximum normal F wave latency for the median nerve was 28 ms with stimulation at wrist and 25 ms with stimulation at elbow. These values for the ulnar nerve were 29 ms and 25 ms respectively. Maximum normal difference between right and left F wave latency with wrist stimulation was 2 ms for median nerve and 2.5 ms for ulnar nerve. Maximum normal difference between median and ulnar nerve F latency was 3.5 ms with stimulation at wrist. In this study we measured F wave of lower extremity nerves in 73 healthy individuals in Shiraz. Maximum normal F wave latency for tibial nerve was 55 ms with stimulation at ankle and 46 ms with stimulation at popliteal area. Maximum normal F wave latency for the peroneal nerve was 54 ms with stimulation at ankle and 47 ms with stimulation at fibular head. Mean F ratio for both nerves was 1.29 with stimulation at knee. Maximum normal difference in F wave latency between right and left lower extremities was 3.5 ms with stimulation at ankle and 3 ms with stimulation at knee for the peroneal nerve. These values were 3 ms and 2.5 ms for the tibial nerve respectively. Maximum normal difference in F wave latency between tibial and peroneal nerve was 4 ms with stimulation at ankle and 3 ms with stimulation at knee.