WHAT IS ULNAR NERVE ENTRAPMENT?
Ulnar nerve entrapment or impingement is a disorder that involves physical compression of the ulnar nerve (Cutts, 2007). Entrapment of the ulnar nerve can theoretically occur at any place along the nerve’s pathway; however, impingement of a nerve occurs most commonly in the areas of joints, this is due to the narrow space the nerve occupies in these regions and the movement that occurs at these points. Entrapment of a nerve may involve constant, prolonged compression or repetitive compression (Wojewnik & Bindra, 2009).
Specifically, ulnar nerve entrapment occurs most commonly at the elbow, this is known as Cubital tunnel syndrome (Cutts, 2007). This is the second most occurring nerve entrapment syndrome in the human body (Cutts, 2007). Less commonly, the ulnar nerve can be compressed at the wrist, this is termed Ulnar tunnel syndrome or Guyon’s canal syndrome (Robertson & Saratsiotis, 2005).
For the purpose of this article, compression occurring in cervical spine will not be discussed, as this is medically termed a cervical radiculopathy (compression of the exiting nerve roots).
ANATOMY
The ulnar nerve originates from the medial cord of the brachial plexus. The medial cord is predominantly made of nerve fibres from the C8 and T1 nerve roots (Robertson & Saratsiotis, 2005). The ulnar nerve navigates down the medial arm, just medial to the brachial artery, before it traverses through the intermuscular septum and passes into the posterior compartment of the arm. It then passes behind the medial epicondyle (cubital tunnel) at the elbow and then into the anterior forearm through the two heads of flexor carpi ulnaris (Robertson & Saratsiotis, 2005). It descends through the forearm between flexor digitorum superficialis and profundus, where it gives off a series of branches before passing over the ulnar side of the flexor retinaculum (carpal tunnel) and into the hand through Guyon’s canal, where it finally branches into a series of nerves within the hand (Landau & Campbell, 2013).
ANATOMICAL IMAGE OF THE ULNAR NERVE IN THE ARM
The ulnar nerve innervates a series of muscles within the forearm and hand. The movement of these muscles greatly varies depending on their location, however many play integral roles in coordinating wrist and hand movements such as gripping and finer dexterity tasks (Landau & Campbell, 2013). Additionally, the ulnar nerve, and its branches, provide sensation to the dorsal and palmar aspects of the medial hand, 5th digit and the medial aspect of the 4th digit (Robertson & Saratsiotis, 2005).
WHAT ARE THE SIGNS AND SYMPTOMS OF ULNAR NERVE ENTRAPMENT?
Common symptoms of ulnar nerve entrapment include (Cutts, 2007; Robertson & Saratsiotis, 2005; Wojewnik & Bindra, 2009):
- Tingling and/or numbness of the medial hand and/or little finger (5th digit) and the medial part of the ring finger
- Pain within the above distribution
- Clumsiness of the hand
- Clawing of the hand
- Wasting of the small muscles of the hand and/or ulnar sided muscles
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Symptoms involving sensory changes are more common in the early stages of the condition and as it prolongs motor changes may become apparent.
The symptoms of ulnar nerve entrapment can vary depending on the location at which compression occurs (Cutts, 2007). For example, compression occurring within the hand may present with either sensory or motor changes as the nerve may have branched into a cutaneous (sensory) or motor nerve, whereas at the elbow (in the cubital tunnel) the ulnar nerve is still comprised of both sensory and motor fibres, therefore more likely to present with a combination of symptoms. Other conditions such as diabetes mellitus can increase the risk of nerve compressive disorders (Cutts, 2007).
DO I HAVE AN ULNAR NERVE ENTRAPMENT SYNDROME?
The diagnosis of ulnar nerve entrapment largely begins with the distribution of symptoms and presentation that is detailed in the above section. Clinicians examination will usually involve assessment of strength of the intrinsic muscles in the hand, specifically the ‘card test’ assessing for Froment’s or Jeanne’s sign. Identifying the location of compression can also be done clinically by percussing over the nerve, particularly at locations where the ulnar nerve is most superficial i.e. the wrist and elbow. A positive Tinel’s sign can be an indication of where the nerve is compressed.
Causes for nerve compression may be intrinsic or extrinsic, or even a combination of both. Understanding the cause of compression is an important aspect of diagnostics. Extrinsic causes for nerve compression are varied and are often related to a behaviour or biomechanical aspect of performing a task. Some common behaviours that may lead to the development of ulnar nerve compression are (Cutts, 2007; Wojewnik & Bindra, 2009):
- Resting on elbows/forearms/hands i.e. whilst typing, driving or cycling on handlebars
- Sleeping with arm behind head
- Intense exercise involving repetitive movement of the elbow i.e. bench press or bicep curls
- Trauma to the medial elbow or medial palmar surface of the hand
Intrinsic factors may include (Li, Lou, & Lu, 2018; Wojewnik & Bindra, 2009):
- Anatomical variations, either at the cubital tunnel or Guyon’s canal
- Ganglion cysts, either within the nerve or in relation to the compact space the nerve passes through
- Fracture, both recent and old – may lead to anatomical deformity
- Dislocation of the elbow
Imaging studies (ultrasound or MRI) can be utilised to define the presence of damage to a nerve (Landau & Campbell, 2013; Robertson & Saratsiotis, 2005; Wojewnik & Bindra, 2009). Changes to the nerve itself may be observed or where innervation of a muscle is compromised, the muscle in question can demonstrate changes. Imaging can also be useful in identifying intrinsic causes for ulnar nerve entrapment syndromes.
Additionally, nerve conduction studies can be useful in diagnosing ulnar nerve entrapment. However, a negative result does not always indicate that nerve compression is not present (Landau & Campbell, 2013). In the early stages of this condition, nerve damage may not have progressed to a stage that compromises the electrical conduction of the nerve.
TREATMENT OF ULNAR NERVE ENTRAPMENT SYNDROMES
Both conservative and surgical treatments are utilised in cases of ulnar nerve entrapment. Selecting what is most appropriate is based largely on the severity of the condition as well as the likely cause. It is suggested that conservative treatment is most effective in cases where patients exhibit mild-moderate symptoms (Kooner, Cinats, Kwong, Matthewson, & Dhaliwal, 2019).
Conservative treatment options are varied, and their appropriateness depends on each case. Treatments can include (Cutts, 2007; Kooner et al., 2019; Robertson & Saratsiotis, 2005; Wojewnik & Bindra, 2009):
- Activity and load modification
- Biomechanical education and modification
- Neural mobilisation techniques and exercises
- Joint mobilisation
- Soft tissue massage
- Night-time splinting or bracing
- Anti-inflammatory medication
One review study of conservative treatments indicated that activity/biomechanical modification, education and splinting were the most effective methods. However, unfortunately there is a paucity of high-quality evidence evaluating treatment options for this condition (Kooner et al., 2019). It is also recommended that conservative treatment be trialled for a period of 6-12 weeks in mild-moderate cases before surgical treatment is considered (Kooner et al., 2019).
Surgical methods for the treatment of ulnar nerve entrapment also vary and are chosen based on a similar criterion to that of non-operative treatments. In cases where compression is mild and symptoms do not involve motor changes, simple open or endoscopic decompression is highly effective (Wojewnik & Bindra, 2009). Surgical interventions involving the re-structuring of the surrounding area appear to be more effective at decompressing the nerve (Adkinson, Zhong, Aliu, & Chung, 2015; Wojewnik & Bindra, 2009). For example, an epicondylectomy at the elbow can relieve compression within the cubital tunnel, though the risk of complications, such as a subluxing nerve post-surgery, is greater (Adkinson et al., 2015; Carlton & Khalid, 2018). Lastly, transposition surgery of the ulnar nerve may also be an option. This allows for thorough decompression and examination of the nerve, however there is a greater risk of compromising the blood supply to the nerve and potential nerve damage (Adkinson et al., 2015; Carlton & Khalid, 2018). Ultimately, success relates highly to degree of damage and symptoms prior to treatment, therefore early diagnosis and management where possible is imperative for good outcomes (Carlton & Khalid, 2018).
DIFFERENTIAL DIAGNOSIS
Neuropathy of the ulnar nerve can occur for other reasons than compression. Other possible diagnosis for ulnar neuropathy include (Cutts, 2007; Robertson & Saratsiotis, 2005):
- Repetitive subluxation of the ulnar nerve
- Occlusion of the brachial artery – be aware of ulnar neuropathy symptoms post upper limb surgery
- Infection
- Alcohol related
Other conditions that may present similarly to ulnar nerve entrapment syndromes include (Robertson & Saratsiotis, 2005; Wojewnik & Bindra, 2009):
- Cervical radiculopathy – specifically of the C8/T1 nerve root
- Thoracic outlet syndrome
- Peripheral vascular disease
- Double crush syndrome – other areas of compression in addition to the ulnar nerve
REFERENCES
Adkinson, J. M., Zhong, L., Aliu, O., & Chung, K. C. (2015). Surgical Treatment of Cubital Tunnel Syndrome: Trends and the Influence of Patient and Surgeon Characteristics. J Hand Surg Am, 40(9), 1824-1831. doi:10.1016/j.jhsa.2015.05.009
Carlton, A., & Khalid, S. I. (2018). Surgical Approaches and Their Outcomes in the Treatment of Cubital Tunnel Syndrome. Front Surg, 5, 48. doi:10.3389/fsurg.2018.00048
Cutts, S. (2007). Cubital tunnel syndrome. Postgrad Med J, 83(975), 28-31. doi:10.1136/pgmj.2006.047456
Kooner, S., Cinats, D., Kwong, C., Matthewson, G., & Dhaliwal, G. (2019). Conservative treatment of cubital tunnel syndrome: A systematic review. Orthop Rev (Pavia), 11(2), 7955. doi:10.4081/or.2019.7955
Landau, M. E., & Campbell, W. W. (2013). Clinical features and electrodiagnosis of ulnar neuropathies. Phys Med Rehabil Clin N Am, 24(1), 49-66. doi:10.1016/j.pmr.2012.08.019
Li, P., Lou, D., & Lu, H. (2018). The cubital tunnel syndrome caused by intraneural ganglion cyst of the ulnar nerve at the elbow: a case report. BMC Neurol, 18(1), 217. doi:10.1186/s12883-018-1229-7
Robertson, C., & Saratsiotis, J. (2005). A review of compressive ulnar neuropathy at the elbow. J Manipulative Physiol Ther, 28(5), 345. doi:10.1016/j.jmpt.2005.04.005
Wojewnik, B., & Bindra, R. (2009). Cubital tunnel syndrome – Review of current literature on causes, diagnosis and treatment. Journal of Hand Microsurgery, 1(2), 76-81.