Ulnar nerve entrapment
Anatomy of ulnar nerve
SpecialtyNeurology Edit this on Wikidata

Ulnar nerve entrapment is a condition where pressure on the ulnar nerve as it passes through the cubital tunnel causes nerve dysfunction (neuropathy). The symptoms of neuropathy are paresthesia (tingling) and numbness (loss of sensibility) primarily affecting the little finger and ring finger of the hand. Ulnar neuropathy can progress to weakness and atrophy of the muscles in the hand (interossei and small and ring finger lumbricals). Symptoms can be alleviated by attempts to keep the elbow from flexing while sleeping, such as sticking one’s arm in the pillow case, so the pillow restricts flexion.

Signs and symptoms

In general, ulnar neuropathy will result in symptoms in a specific anatomic distribution, affecting the little finger, the ulnar half of the ring finger, and the intrinsic muscles of the hand.

The specific symptoms experienced in the characteristic distribution depend on the specific location of ulnar nerve compression. The hallmark symptoms of ulnar neuropathy at the elbow is paresthesia (tingling). This can progress to a loss of sensibility. Muscle weakness is usually experienced as a loss of dexterity.

Ulnar neuropathy at the wrist is associated with variable symptoms, as the ulnar nerve separates near the hand into distinct motor and sensory branches.

In cubital tunnel syndrome (ulnar neuropathy at the elbow), sensory and motor symptoms tend to occur in a certain sequence. Initially, there may be intermittent paresthesia and loss of sensibility of the small and ulnar half of the ring fingers. Next is constant numbness (loss of sensibility). The final stage is intrinsic hand muscle atrophy and weakness.

In contrast, when ulnar neuropathy occurs at the wrist (Guyon canal syndrome), motor symptoms predominate. There may be an ulnar claw hand from imbalance between the muscles innervated by the ulnar nerve in the forearm (which are functioning normally) and those in the hand (which are weak). The back of the hand will have normal sensation.[1]

Diagnosis

Ulnar nerve damage that causes paralysis to these muscles will result in a characteristic ulnar claw position of the hand at rest. Clinical tests such as the card test for Froment's sign, can be easily performed for assessment of ulnar nerve. However, a complete diagnosis should identify the source of the impingement, and radiographic imaging may be necessary to determine or rule-out an underlying cause.[2]

Imaging studies are not routinely used. Ultrasound or MRI may reveal enlargement of the ulnar nerve proximal to the cubital tunnel. Variations in anatomy such as the anconeus epitrochlearis muscle are common and their relationship to ulnar neuropathy is uncertain.[3]

Differential diagnoses

Symptoms of ulnar neuropathy or neuritis do not necessarily indicate an actual physical impingement of the nerve; any injury to the ulnar nerve may result in identical symptoms. In addition, other functional disturbances may result in irritation to the nerve and are not true "impingement". For example, anterior dislocation and "snapping" of ulnar nerve across the medial epicondyle of the elbow joint can result in ulnar neuropathy.[4]

Entrapment of other major sensory nerves of the upper extremities result in deficits in other patterns of distribution. Entrapment of the median nerve causes carpal tunnel syndrome, which is characterized by numbness in the thumb, index, middle, and half of the ring finger. Compression of the radial nerve causes numbness of the back of the hand and thumb, and is much rarer.[5]

A simple way of differentiating between significant median and ulnar nerve injury is by testing for weakness in flexing and extending certain fingers of the hand. Median nerve injuries are associated with difficulty flexing the index and middle finger when attempting to make a fist. However, with an ulnar nerve lesion, the pinky and ring finger cannot be unflexed when attempting to extend the fingers.[6]

Some people are affected by multiple nerve compressions, which can complicate diagnosis.[7]

Classification

Ulnar nerve entrapment is classified by location of entrapment. The ulnar nerve passes through several small spaces as it courses through the medial side of the upper extremity, and at these points the nerve is vulnerable to compression or entrapment—a so-called "pinched nerve". The nerve is particularly vulnerable to injury when there has been a disruption in the normal anatomy. The most common site of ulnar nerve entrapment is at the elbow, followed by the wrist.[8]

Causes or structures which have been reported to cause ulnar nerve entrapment include:[9]

Cubital tunnel syndrome

The most common location of ulnar nerve impingement at the elbow is within the cubital tunnel, and is known as cubital tunnel syndrome.[10][7] The tunnel is formed by the medial epicondyle of the humerus, the olecranon process of the ulna and the tendinous arch joining the humeral and ulnar heads of the flexor carpi ulnaris muscle.[11] While most cases of injury are minor and resolve spontaneously with time, chronic compression or repetitive trauma may cause more persistent problems. Commonly cited scenarios include:

Compression of the ulnar nerve at the medial elbow may occasionally be caused by an epitrocheloanconeus muscle, an anatomical variant.[12]

Ulnar tunnel syndrome

Main article: Ulnar tunnel syndrome

Ulnar nerve impingement along an anatomical space in the wrist called the ulnar canal is known as ulnar tunnel syndrome (or Guyon canal's syndrome).[13] Recognized causes of ulnar nerve impingement at this location include local trauma, fractures, ganglion cysts,[14] and classically avid cyclists who experience repetitive trauma against bicycle handlebars.[15] This form of ulnar neuropathy comprises two work-related syndromes: so-called "hypothenar hammer syndrome," seen in workers who repetitively use a hammer, and "occupational neuritis" due to hard, repetitive compression against a desk surface.[14] This syndrome can be categorized into three zones based on the localization of the ulnar nerve within the Guyon's canal.[16]

Prevention

Cubital tunnel syndrome may be prevented or reduced by maintaining good posture and proper use of the elbow and arms, such as wearing an arm splint while sleeping to maintain the arm is in a straight position instead of keeping the elbow tightly bent.[7][17] A recent example of this is popularization of the concept of cell phone elbow and game hand.[17]

Treatment

The most effective treatment for cubital tunnel syndrome is surgical decompression. The most safe and effective operation is in-situ decompression +/- medial epicondylectomy.[18]

For pain symptoms, medications such as NSAID, amitriptyline, or vitamin B6 supplementation may help although there is no evidence to support this claim.[citation needed]

Mild symptoms may first be treated non-operatively, with the following:[citation needed]

It is important to identify positions and activities that aggravate symptoms and to find ways to avoid them.[7] For example, if the person experiences symptoms when holding a telephone up to the head, then the use of a telephone headset will provide immediate symptomatic relief and reduce the likelihood of further damage and inflammation to the nerve. For cubital tunnel syndrome, it is recommended to avoid repetitive elbow flexion and also avoiding prolonged elbow flexion during sleep, as this position puts stress of the ulnar nerve.[19]

Cubital tunnel decompression surgery involves an incision posteromedial to the medial epicondyle which helps avoid the medial antebrachial cutaneous nerve branches. The ulnar nerve is identified and released from its fascia proximally and distally up to the flexor carpi ulnaris heads. After release, flexion and extension of the arm are performed to ensure there is no subluxation of the ulnar nerve.[20]

Prognosis

Following surgery, on average, 85% of patients report an improvement in their symptoms[18]

Most patients diagnosed with cubital tunnel syndrome have advanced disease (atrophy, static numbness, weakness) that might reflect permanent nerve damage that will not recover after surgery.[21] When diagnosed prior to atrophy, weakness or static numbness, the disease can be arrested with treatment. Mild and intermittent symptoms often resolve spontaneously.[7]

Epidemiology

People with diabetes mellitus are at higher risk for any kind of peripheral neuropathy, including ulnar nerve entrapments.[7]

Cubital tunnel syndrome is more common in people who spend long periods of time with their elbows bent, such as when holding a telephone to the head.[7] Flexing the elbow while the arm is pressed against a hard surface, such as leaning against the edge of a table, is a significant risk factor.[7] The use of vibrating tools at work or other causes of repetitive activities increase the risk, including throwing a baseball.[7]

Damage to or deformity of the elbow joint increases the risk of cubital tunnel syndrome.[7] Additionally, people who have other nerve entrapments elsewhere in the arm and shoulder are at higher risk for ulnar nerve entrapment. There is some evidence that soft tissue compression of the nerve pathway in the shoulder by a bra strap over many years can cause symptoms of ulnar neuropathy, especially in very large-breasted women.[7]

See also

References

  1. ^ Aguiar, Paulo Henrique; Bor-Seng-Shu, Edson; Gomes-Pinto, Fernando; Almeida- Leme, Ricardo Jose de; Freitas, Alexandre Bruno R.; Martins, Roberto S.; Nakagawa, Edison S.; Tedesco-Marchese, Antonio J. (March 2001). "Surgical management of Guyon's canal syndrome, an ulnar nerve entrapment at the wrist: report of two cases". Arquivos de Neuro-Psiquiatria. 59 (1): 106–111. doi:10.1590/S0004-282X2001000100022. PMID 11299442.
  2. ^ Read, John W; Perko, Mark (May 2010). "Ultrasound diagnosis of subacromial impingement for lesions of the rotator cuff". Australasian Journal of Ultrasound in Medicine. 13 (2): 11–15. doi:10.1002/j.2205-0140.2010.tb00151.x. PMC 5024859. PMID 28191078.
  3. ^ a b Miller TT, Reinus WR (September 2010). "Nerve entrapment syndromes of the elbow, forearm, and wrist". American Journal of Roentgenology. 195 (3): 585–94. doi:10.2214/AJR.10.4817. PMID 20729434.
  4. ^ Carroll, John (3 October 2011). "Snapping Triceps". RadSource.
  5. ^ Buchanan, Benjamin K.; Maini, Kushagra; Varacallo, Matthew (2022). "Radial Nerve Entrapment". StatPearls. StatPearls Publishing. PMID 28613749. Retrieved 4 August 2022.
  6. ^ "Ulnar Nerve Entrapment at the Elbow (Cubital Tunnel Syndrome) - OrthoInfo - AAOS". www.orthoinfo.org. Retrieved 4 August 2022.
  7. ^ a b c d e f g h i j k Cutts, S. (2007). "Cubital tunnel syndrome". Postgraduate Medical Journal. 83 (975): 28–31. doi:10.1136/pgmj.2006.047456. PMC 2599973. PMID 17267675.
  8. ^ Posner, MA (September–October 1998). "Compressive ulnar neuropathies at the elbow: I. Etiology and diagnosis". J Am Acad Orthop Surg. 6 (5): 282–288. doi:10.5435/00124635-199809000-00003. PMID 9753755. S2CID 16254326.
  9. ^ Guardia, Charles. "Ulnar Neuropathy". Medscape. Retrieved 4 May 2014.
  10. ^ Thakker, Arjuna; Gupta, Vinay Kumar; Gupta, Keshav Kumar (December 2020). "The Anatomy, Presentation and Management Options of Cubital Tunnel Syndrome". The Journal of Hand Surgery Asian-Pacific Volume. 25 (4): 393–401. doi:10.1142/S2424835520400032. ISSN 2424-8363. PMID 33115358. S2CID 226051048.
  11. ^ Moore, Keith L. (2010). Clinically Oriented Anatomy 6th Ed. Baltimore, MD: Lippincott, Williams and Wilkins. p. 770. ISBN 978-07817-7525-0.
  12. ^ Erdem Bagatur, A.; Yalcin, Mehmet Burak; Ozer, Utku Erdem (1 September 2016). "Anconeus Epitrochlearis Muscle Causing Ulnar Neuropathy at the Elbow: Clinical and Neurophysiological Differential Diagnosis". Orthopedics. 39 (5): e988–991. doi:10.3928/01477447-20160623-11. ISSN 1938-2367. PMID 27398787.
  13. ^ "Guyon's Canal Syndrome".
  14. ^ a b Shea JD, McClain EJ (1969). "Ulnar-nerve compression syndromes at and below the wrist". J Bone Joint Surg Am. 51 (6): 1095–1103. doi:10.2106/00004623-196951060-00004. PMID 5805411.
  15. ^ Patterson JM, Jaggars MM, Boyer MI (2003). "Ulnar and median nerve palsy in long-distance cyclists. A prospective study". Am J Sports Med. 31 (4): 585–589. doi:10.1177/03635465030310041801. PMID 12860549. S2CID 22497516.
  16. ^ Aleksenko, Dmitri; Varacallo, Matthew (2023), "Guyon Canal Syndrome", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 28613717, retrieved 24 August 2023
  17. ^ a b Thomas, Jennifer (2 June 2009). "'Cell Phone Elbow' -- A New Ill for the Wired Age". HealthDay News. Archived from the original on 5 April 2017. Retrieved 2 June 2009.
  18. ^ a b Wade, Ryckie G.; Griffiths, Timothy T.; Flather, Robert; Burr, Nicholas E.; Teo, Mario; Bourke, Grainne (24 November 2020). "Safety and Outcomes of Different Surgical Techniques for Cubital Tunnel Decompression: A Systematic Review and Network Meta-analysis". JAMA Network Open. 3 (11): e2024352. doi:10.1001/jamanetworkopen.2020.24352. PMC 7686867. PMID 33231636.
  19. ^ Guardia, Charles F (24 August 2014). "Ulnar Neuropathy Treatment & Management: Non-surgical therapy". Medscape.
  20. ^ [1], Ilyas A, Herman Z. Cubital Tunnel Release. J Med Ins. 2017;2017(206.4) doi:https://jomi.com/article/206.4
  21. ^ Mallette, Paige; Zhao, Meijuan; Zurakowski, David; Ring, David (2007). "Muscle Atrophy at Diagnosis of Carpal and Cubital Tunnel Syndrome". The Journal of Hand Surgery. 32 (6): 855–8. doi:10.1016/j.jhsa.2007.03.009. PMID 17606066.

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