Nerve Conductions Studies

Median sensory recording the  index and middle  fingers.

Ulnar sensory recording the llittle finger.

Radial sensory recording the dorsal thumb.

Median motor recording the abductor pollicis brevis with F-Waves.

Ulnar motormotor recording the abductor digiti minimi with F-Waves

If median nerve findings are borderline or negative with a high clinical suspicion, perform one or two of the listed additional comparison studies as needed.

Compare the latency difference between the:

• Using a distance of 8 cm for each compare the difference in latencies between the Median Palmar mixed Nerve (orthodromic) and Ulnar Palmar Mixed Nerve (orthodromic). A median latency prolonged at least 0.5 mSec or more compared to the ulnar is considered significant.

• Using a distance of 8 cm for each compare the difference in latencies between the Median and Ulnar motor nerves- Recording the 2nd Lumbrical and interossei.  A median latency prolonged at least 0.4 mSec  or more compared to the ulnar is considered significant.

• Using a distance of 12-14 cm for each compare the difference in latencies between the median ring sensory response and the ulnar ring sensory response. A median latency prolonged least 0.4 mSec or more compared to the ulnar is considered significant.

• Using a distance of 10-12 cm for each compare the difference in latencies between the median thumb  sensory response and the dorsal thumb sensory response. A median latency prolonged at least 0.4 mSec or more compared to the radial is considered significant.

If there is evidence of moderate or severe CTS, or the patient has bilateral symptoms, or the referring physician requested both hands, perform the median sensory and median motor with f-waves, and one or two of the comparison studies as needed.

Needle Examination

Perform needle exam on the symptomatic limb.  Test the minimum of one muscle innervated by the C5, C4, C7, C8 and T1 spinal roots including a thenar muscle innervated by the median nerve of the symptomatic limb (traditionally the abductor pollicis brevis).