Clarification of the pronator reflex

The pronator reflex has been used in evaluating the 6th and 7th cervical roots. It has been described as a muscle stretch reflex of the pronator muscles; however, a review of the literature did not elucidate which muscles are active in this reflex. We examined 10 healthy subjects with surface electromyograms recorded over the pronator quadratus and pronator teres and used a Teca reflex hammer to produce a muscle stretch and trigger the electromyogram sweep. A reproducible response was found in all patients when recordings were made over the pronator teres (mean latency, 9.7 +/- 1.8 ms). No response was found in any of the subjects when recordings were made over the pronator quadratus. We conclude that the pronator reflex represents a muscle stretch reflex of the pronator teres (and not the pronator quadratus), which would make it helpful in evaluating C6 and C7 root lesions.