Upper extremity nerve entrapments are a common cause of pain and disability. The increase in repetitive motions associated with occupational and recreational environments usually is singled out as the primary cause of these problems. Many individuals with nerve entrapment symptoms will seek the care of a massage practitioner.

If a client comes to you with an upper extremity pain condition, you want to accurately identify that problem so you can determine if it warrants massage treatment or referral to another health professional. In some cases, a condition might have symptoms that very closely mimic a different pathology. If you don't identify the condition correctly, your treatment is not going to be as effective.

The symptoms of pronator teres syndrome (PTS) can be identical to those of carpal tunnel syndrome because they both involve compression of the median nerve. PTS may be underdiagnosed by medical professionals because its symptoms are so closely related to carpal tunnel syndrome, which is a much more well-known condition.¹

PTS develops from compression of the median nerve by the pronator teres muscle, and is sometimes referred to as pronator syndrome. The term pronator syndrome also can include median nerve compression by other structures in the elbow, such as the ligament of Struthers or the bicipital aponeurosis (lacertus fibrosus).²

As the median nerve passes the elbow, it runs between the two heads of the pronator teres muscle, where the nerve may be compressed (Figure 1). Compression can be due to muscle hypertonicity or fibrous bands within the muscle pressing on the nerve.³ In some cases, pressure is placed on the nerve by anatomical anomalies, such as the nerve traveling deep to both heads of the pronator teres.⁴ In this situation, the nerve might be compressed against the ulna by the pronator teres muscle itself.

PTS results from repetitive motions that cause hypertonicity in the pronator teres. Occupational activities such as hammering, cleaning fish, or performing any activity that requires continual manipulation of tools can cause overuse of the pronator teres. The hypertonicity then causes nerve compression, and the symptoms are felt in the anterior forearm and the median nerve distribution in the hand (Figure 2). Women are affected more than men, although the reason for this is not clear.

Most symptoms of nerve compression radiate distal to the site of compression. Aching forearm pain and paresthesia, along with pain in the median nerve distribution in the hand, are likely to be PTS and should not be assumed to indicate carpal tunnel syndrome.

While PTS and carpal tunnel syndrome both affect the median nerve and have similar symptoms, there are distinct differences. PTS pain is exacerbated by repetitive elbow flexion, and symptoms arise in the forearm as well as the hand. Carpal tunnel syndrome is aggravated by wrist movements, and pain is not experienced as much in the forearm. In both cases, atrophy is possible in the thenar muscles of the hand, which are innervated by branches from the median nerve.

There are several other ways to identify PTS and distinguish it from carpal tunnel syndrome. Clients with carpal tunnel syndrome frequently report night pain, while individuals with PTS generally do not.¹ Prolonged wrist flexion during sleep aggravates carpal tunnel syndrome because it decreases the space in the carpal tunnel and presses on the median nerve. Because wrist flexion does not affect the pronator teres muscle, this wrist position does not increase nerve compression symptoms in PTS.

An evaluation procedure called the pronator teres test also is helpful in identifying the condition. The client stands with the elbow in 90 degrees of flexion. The practitioner then places one hand on the client's elbow for stabilization and the other hand grasps the client's hand in a handshake position. The client holds this position as the practitioner attempts to supinate the client's forearm (forcing the client to contract the pronator muscles). While holding the resistance against pronation, the practitioner extends the client's elbow (Figure 3). If the client's pain or discomfort is reproduced, there is a good chance of median nerve compression by the pronator teres. The client should keep the elbow relaxed during the test, because holding the elbow firmly in flexion will not allow elbow extension.

Pronator teres syndrome is most commonly caused by muscular compression of the median nerve. Therefore, it is a condition that is effectively treated with massage. However, it is important that the practitioner accurately identify the problem so treatment can be directed to the proper region of the upper extremity.

Author's note: The content of this article is excerpted from: Lowe W. Orthopedic Assessment in Massage Therapy. Sisters, OR: Daviau-Scott; 2006.

References

1. Dawson D, Hallett M, Wilbourn A. Entrapment Neuropathies, 3^rd ed. Philadelphia: Lippincott-Raven; 1999.
2. Wertsch JJ, Melvin J. Median nerve anatomy and entrapment syndromes: a review. Arch Phys Med Rehabil, Dec 1982;63(12):623-627.
3. Tulwa N, Limb D, Brown RF. Median nerve compression within the humeral head of pronator teres. J Hand Surg [Br],  1994;19(6):709-710.
4. Nebot-Cegarra J, Perez-Berruezo J, Reina de la Torre F. Variations of the pronator teres muscle: predispositional role to median nerve entrapment. Arch Anat Histol Embryol, 1991;74:35-45.