Pronator teres syndrome

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Pronator teres syndrome
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Pronator teres syndrome is a compression neuropathy of the median nerve at the elbow. It is rare compared to compression at the wrist (carpal tunnel syndrome) or isolated injury of the anterior interosseous branch of the median nerve (anterior interosseous syndrome).

Contents

Symptoms

Compression of the median nerve in the region of the elbow or proximal part of the forearm can cause pain and/or numbness in the distribution of the distal median nerve, and weakness of the muscles innervated by the anterior interosseous nerve: the flexor pollicis longus ("FPL"), the flexor digitorum profundus of the index finger ("FDP IF"), and the pronator quadratus ("PQ"). [1] [2] [3] The pain tends to be at the wrist joint, in the distribution of the terminal branch of the anterior interosseous nerve, and is exacerbated by sustained pronation (i.e., wrist down). [4] The weakness of the FPL and FDP IF is painless, but causes people to "drop things" and have a sense of loss of dexterity. Pinching with the wrist flexed magnifies the expression of this weakness, by reducing resting tension on the muscles of pinch. For instance, "child-proof" prescription pill bottles may be difficult to open. People easily adapt to this weakness without conscious effort or self-awareness, by using 1) the next muscles down, which are innervated by a different nerve, or 2) using ligaments to give resistance, pinching laterally against the index finger or against the side of the end of the thumb, or 3) by what is called "tenodesis," which in this case is extension of the wrist joint, which tightens the muscles on the palm side of the hand. These adaptations on a moment-to-moment basis do not cause problems, but over time in loose-jointed patients, such as many women and people with collagen disorders such as Ehlers Danlos Syndrome, the adaptations can cause soft tissue failures that can become painful, particularly at the base of the thumb and in the proximal forearm (i.e., "Tennis Elbow" in a non-tennis player). [5]

Causes

The most common cause is entrapment of the median nerve between the two heads of the pronator teres muscle. Other causes are compression of the nerve from the fibrous arch of the flexor superficialis, or the thickening of the bicipital aponeurosis. [6] ⁠ [7] [8] [9]

Anatomy

The median nerve passes through the cubital fossa and passes between the two heads of pronator teres muscle into the forearm. It then runs between flexor digitorum superficialis and flexor digitorum profundus muscles and enters the hand through the carpal tunnel. [10]

It innervates most of the flexor muscles in the forearm and hand. Its sensory component supplies the skin of the palm, thumb, index and middle finger as well as half the ring finger, and, importantly and often forgotten, the bones of the wrist.

In the proximal forearm it gives rise to the anterior interosseous nerve which innervates the flexor of the thumb (FPL), the flexor digitorum profundus of the index finger (FDP IF), and the pronator quadratus, and terminates in a sensory branch to the bones of the wrist, i.e., the carpal tunnel. Compression of the proximal median nerve results in weakness of these three muscles, and can cause aching pain in the wrist on the basis of the sensory nerve to the carpal bones.

Diagnosis

The most common chief complaint is intermittent pain in the wrist, associated with sustained pronation, frequently misinterpreted by patients and providers as "tendonitis." This is usually accompanied by the perception of "hand weakness," and "dropping things." The characteristic physical finding is tenderness over the proximal median nerve, with ensuing numbness in the hand in less than a minute, and/or numbness in the hand with resisted pronation of the forearm in less than a minute. [11] [12]

The flexor pollicis longus and FDP of the index finger are weak, leading to impairment of pinching firmly. This reflects involvement of the anterior interosseous nerve. [13]

Sensory changes may be found in the first three fingers as well as in the palm, indicating impairment of the median nerve proximal to the flexor retinaculum, but tend to involve the sensation of the entire hand going numb at night, with any pressure on the median nerve on the areas at the inside of the elbow. [14] [15]

The clinical and electrophysiological features of pronator teres syndrome are quite different from patients with carpal tunnel syndrome or pure anterior interosseous syndrome, and are typically normal. [16] [17] Proper localisation is crucial to treatment options. [18] [19]

Conduction velocity of the median nerve in the proximal forearm may be slow but the distal latency and sensory nerve action potential at the wrist are normal. [20]

Although MRI may show denervation atrophy of the affected muscles, its role in the evaluation of pronator teres syndrome is unclear. [21] ⁠

If the EMG or the MRI are abnormal for the pronator teres muscle and the flexor carpi radialis, this implies that the problem is at or proximal to the elbow, as the takeoff of the nerves to these muscles occurs proximal to the elbow.

Treatment

Injection of corticosteroids into the pronator teres muscle may produce relief of symptoms. [22]

Massage therapy can also provide relief for individuals experiencing this condition. [23]

Surgical decompression can provide benefit in selected cases. [24] [25] [26] [27]

Related Research Articles

Median nerve Nerve of the upper limb

The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus.

The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers. It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.

Flexor digitorum superficialis muscle

Flexor digitorum superficialis is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints.

The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in anatomy, technically, means only the region of the upper arm, whereas the lower "arm" is called the forearm. It is homologous to the region of the leg that lies between the knee and the ankle joints, the crus.

Ulnar nerve Nerve which runs near the ulna bone

In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is common. This nerve is directly connected to the little finger, and the adjacent half of the ring finger, innervating the palmar aspect of these fingers, including both front and back of the tips, perhaps as far back as the fingernail beds.

Wrist drop Medical condition

Wrist drop is a medical condition in which the wrist and the fingers cannot extend at the metacarpophalangeal joints. The wrist remains partially flexed due to an opposing action of flexor muscles of the forearm. As a result, the extensor muscles in the posterior compartment remain paralyzed.

Upper limb

The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist and knuckle joints. In humans, each upper limb is divided into the arm, forearm and hand, and is primarily used for climbing, lifting and manipulating objects.

Ulnar artery Artery of the forearm

The ulnar artery is the main blood vessel, with oxygenated blood, of the medial aspects of the forearm. It arises from the brachial artery and terminates in the superficial palmar arch, which joins with the superficial branch of the radial artery. It is palpable on the anterior and medial aspect of the wrist.

The flexor pollicis longus is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus.

The pronator teres is a muscle that, along with the pronator quadratus, serves to pronate the forearm. It has two attachments, to the medial humeral supracondylar ridge and the ulnar tuberosity, and inserts near the middle of the radius.

Posterior interosseous nerve

The posterior interosseous nerve is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminished in size compared to the deep branch of the radial nerve. The nerve fibers originate from cervical segments C7 and C8.

Anterior interosseous artery

The anterior interosseous artery is an artery in the forearm. It is a branch of the common interosseous artery.

Anterior interosseous nerve

The anterior interosseous nerve is a branch of the median nerve that supplies the deep muscles on the anterior of the forearm, except the ulnar (medial) half of the flexor digitorum profundus. Its nerve roots come from C8 and T1.

The posterior compartment of the forearm contains twelve muscles which are chiefly responsible for extension of the wrist and digits, and supination of the forearm. It is separated from the anterior compartment by the interosseous membrane between the radius and ulna.

Carpal tunnel

In the human body, the carpal tunnel or carpal canal is the passageway on the palmar side of the wrist that connects the forearm to the hand.

Ulnar nerve entrapment Medical condition

Ulnar nerve entrapment is a condition where the ulnar nerve becomes physically trapped or pinched, resulting in pain, numbness, or weakness, primarily affecting the little finger and ring finger of the hand. Entrapment may occur at any point from the spine at cervical vertebra C7 to the wrist; the most common point of entrapment is in the elbow. Prevention is mostly through correct posture and avoiding repetitive or constant strain. Treatment is usually conservative, including medication, activity modification and exercise, but may sometimes include surgery. Prognosis is generally good, with mild to moderate symptoms often resolving spontaneously.

Ulnar claw

An ulnar claw, also known as claw hand, or 'spinster's claw' is a deformity or an abnormal attitude of the hand that develops due to ulnar nerve damage causing paralysis of the lumbricals. A claw hand presents with a hyperextension at the metacarpophalangeal joints and flexion at the proximal and distal interphalangeal joints of the 4th and 5th fingers. The patients with this condition can make a full fist but when they extend their fingers, the hand posture is referred to as claw hand. The ring- and little finger can usually not fully extend at the proximal interphalangeal joint (PIP).

Anterior interosseous syndrome is a medical condition in which damage to the anterior interosseous nerve (AIN), a distal motor and sensory branch of the median nerve, classically with severe weakness of the pincer movement of the thumb and index finger, and can cause transient pain in the wrist.

Median nerve palsy Medical condition

Injuries to the arm, forearm or wrist area can lead to various nerve disorders. One such disorder is median nerve palsy. The median nerve controls the majority of the muscles in the forearm. It controls abduction of the thumb, flexion of hand at wrist, flexion of digital phalanx of the fingers, is the sensory nerve for the first three fingers, etc. Because of this major role of the median nerve, it is also called the eye of the hand. If the median nerve is damaged, the ability to abduct and oppose the thumb may be lost due to paralysis of the thenar muscles. Various other symptoms can occur which may be repaired through surgery and tendon transfers. Tendon transfers have been very successful in restoring motor function and improving functional outcomes in patients with median nerve palsy.

Palmaris profundus muscle

Palmaris profundus is a rare anatomical variant in the anterior compartment of forearm. It was first described in 1908. It is usually found incidentally in cadaveric dissection or surgery.

References

  1. ↑ Kalliainen LK, Ericson WB. "Management of Compressive Neuropathies of the Upper Extremity," Chapter 70, Grabb and Smith's Plastic Surgery, 8th Edition, Chung K et al, Editors. Lippincott Williams & Wilkins, 2018
  2. ↑ Hartz, C R, R L Linscheid, R R Gramse, and J R Daube. "The pronator teres syndrome: compressive neuropathy of the median nerve." The Journal of Bone and Joint Surgery. American Volume 63, no. 6 (July 1981): 885-90. PMID   7240329.
  3. ↑ Wertsch, J J, and J Melvin. "Median nerve anatomy and entrapment syndromes: a review." Archives of Physical Medicine and Rehabilitation 63, no. 12 (December 1982): 623-7. PMID   6756339.
  4. ↑ Ericson WB, Singh V. "Median Nerve Entrapments," in "Peripheral Nerve Entrapments: Clinical Diagnosis and Management, " Trescot AM, Editor. Springer, April, 2016. p369-382.
  5. ↑ Ericson WB, Wolman R. "Orthopedic Management of the Ehlers Danlos Syndromes," American Journal of Medical Genetics, Part C, Seminars in Medical Genetics, Volume 175C, Number 1, March, 2017. p188-194.
  6. ↑ Johnson, R K, M Spinner, and M M Shrewsbury. "Median nerve entrapment syndrome in the proximal forearm." The Journal of Hand Surgery 4, no. 1 (January 1979): 48-51. PMID   759503.
  7. ↑ Farrell, H F. "Pain and the pronator teres syndrome." Bulletin of the Hospital for Joint Diseases 37, no. 1 (April 1976): 59-62. PMID   974290.
  8. ↑ Martinelli, P, A S Gabellini, M Poppi, R Gallassi, and E Pozzati. "Pronator syndrome due to thickened bicipital aponeurosis." Journal of Neurology, Neurosurgery, and Psychiatry 45, no. 2 (February 1982): 181-2. PMC   1083053.
  9. ↑ Fuss, FK, and GH Wurzl. "Median nerve entrapment. pronator teres syndrome." Surgical and Radiologic Anatomy 12, no. 4 (December 1, 1990): 267-271. doi : 10.1007/BF01623702.
  10. ↑ Fuss, FK, and GH Wurzl. "Median nerve entrapment. pronator teres syndrome." Surgical and Radiologic Anatomy 12, no. 4 (December 1, 1990): 267-271. doi : 10.1007/BF01623702.
  11. ↑ Hartz, C R, R L Linscheid, R R Gramse, and J R Daube. "The pronator teres syndrome: compressive neuropathy of the median nerve." The Journal of Bone and Joint Surgery. American Volume 63, no. 6 (July 1981): 885-90. PMID   7240329.
  12. ↑ Morris, H H, and B H Peters. "Pronator syndrome: clinical and electrophysiological features in seven cases." Journal of Neurology, Neurosurgery, and Psychiatry 39, no. 5 (May 1976): 461-4. PMC   492308.
  13. ↑ Wertsch, J J, and J Melvin. "Median nerve anatomy and entrapment syndromes: a review." Archives of Physical Medicine and Rehabilitation 63, no. 12 (December 1982): 623-7. PMID   6756339.
  14. ↑ Ericson WB, Singh V. "Median Nerve Entrapments," in "Peripheral Nerve Entrapments: Clinical Diagnosis and Management, " Trescot AM, Editor. Springer, April, 2016. p369-382.
  15. ↑ Bridgeman, C, S Naidu, and M J Kothari. "Clinical and electrophysiological presentation of pronator syndrome." Electromyography and Clinical Neurophysiology 47, no. 2: 89-92. PMID   17479724.
  16. ↑ Ericson WB, Singh V. "Median Nerve Entrapments," in "Peripheral Nerve Entrapments: Clinical Diagnosis and Management, " Trescot AM, Editor. Springer, April, 2016. p369-382.
  17. ↑ Johnson, R K, M Spinner, and M M Shrewsbury. "Median nerve entrapment syndrome in the proximal forearm." The Journal of Hand Surgery 4, no. 1 (January 1979): 48-51. PMID   759503.
  18. ↑ Wertsch, J J, and J Melvin. "Median nerve anatomy and entrapment syndromes: a review." Archives of Physical Medicine and Rehabilitation 63, no. 12 (December 1982): 623-7. PMID   6756339.
  19. ↑ Bridgeman, C, S Naidu, and M J Kothari. "Clinical and electrophysiological presentation of pronator syndrome." Electromyography and Clinical Neurophysiology 47, no. 2: 89-92. PMID   17479724.
  20. ↑ Morris, H H, and B H Peters. "Pronator syndrome: clinical and electrophysiological features in seven cases." Journal of Neurology, Neurosurgery, and Psychiatry 39, no. 5 (May 1976): 461-4. PMC   492308.
  21. ↑ Ferdinand, Brett D, Zehava Sadka Rosenberg, Mark E Schweitzer, Steven A Stuchin, Laith M Jazrawi, Salvatore R Lenzo, et al. "MR imaging features of radial tunnel syndrome: initial experience." Radiology 240, no. 1 (July 2006): 161-8. PMID   16793976.
  22. ↑ Morris, H H, and B H Peters. "Pronator syndrome: clinical and electrophysiological features in seven cases." Journal of Neurology, Neurosurgery, and Psychiatry 39, no. 5 (May 1976): 461-4. PMC   492308.
  23. ↑ Lowe, W. "Pronator Teres Syndrome." Massage Today, no. 5 (May, 2007).
  24. ↑ Johnson, R K, M Spinner, and M M Shrewsbury. "Median nerve entrapment syndrome in the proximal forearm." The Journal of Hand Surgery 4, no. 1 (January 1979): 48-51. PMID   759503.
  25. ↑ Hartz, C R, R L Linscheid, R R Gramse, and J R Daube. "The pronator teres syndrome: compressive neuropathy of the median nerve." The Journal of Bone and Joint Surgery. American Volume 63, no. 6 (July 1981): 885-90. PMID   7240329.
  26. ↑ Farrell, H F. "Pain and the pronator teres syndrome." Bulletin of the Hospital for Joint Diseases 37, no. 1 (April 1976): 59-62. PMID   974290.
  27. ↑ Kalliainen LK, Ericson WB. "Management of Compressive Neuropathies of the Upper Extremity," Chapter 70, Grabb and Smith's Plastic Surgery, 8th Edition, Chung K et al, Editors. Lippincott Williams & Wilkins, 2018
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