Ulnar Neuropathy


Article Author:
Jan Michael Lleva


Article Editor:
Ke-Vin Chang


Editors In Chief:
William Gossman


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Trevor Nezwek
Radia Jamil
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Steve Bhimji
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Nazia Sadiq
Hajira Basit
Phillip Hynes
Tehmina Warsi


Updated:
6/4/2019 8:26:33 PM

Introduction

The ulnar nerve has several potential compression sites along its course. Although the elbow is the most common site of compression, the ulnar nerve is also susceptible to injury at the wrist, forearm, and upper arm. Prevention of compression and early diagnosis/treatment is important for its prognosis because the treatment outcome is usually disappointing once the nerve has axonal damage.

The C8 and T1 nerve roots merge to form the lower trunk of the brachial plexus which continues as the medial cord to give rise to the ulnar nerve. The ulnar nerve then courses along the upper arm medial to the brachial artery, in proximity to the median nerve. Just above the elbow, the ulnar nerve courses posteriorly to pass through the retroepicondylar groove between the medial epicondyle and olecranon process. It then passes underneath the humeroulnar aponeurotic arcade (HUA), which is a dense aponeurosis between the tendon attachments of the flexor carpi ulnaris (FCU). The area beneath the HUA is also called the cubital tunnel. The nerve then passes through the belly of the FCU muscle and out through the deep flexor-pronator aponeurosis.  At the forearm, it innervates the FCU and the flexor digitorum profundus (FDP). At the mid to distal forearm, the palmar ulnar cutaneous branch (PUC) splits from the ulnar nerve and enters the hand ventral to the Guyon canal and gives sensory innervation to the skin at the hypothenar area. Distal to the bifurcation of the PUC, the dorsal ulnar cutaneous (DUC) branch separates from the main trunk, curves around the ulna, and provides sensory innervation to the dorsum of the skin of the medial hand, medial half of the fourth digit, and fifth digit.

The main trunk of the ulnar nerve enters through the Guyon’s canal at the level of the distal wrist crease. The proximal wall of Guyon’s canal is formed by the pisiform bone and the distal wall by the hook of the hamate. The roof is formed by the palmaris brevis muscle, and the floor is formed by the combination of the transverse carpal ligament, the hamate, and the triquetrum bone. A thick band is formed at the outlet  (pisohamate hiatus) connecting the hook of the hamate to the pisiform bone. In the canal, the nerve separates into the superficial sensory branch and the deep palmar motor branch. The superficial sensory branch provides sensory innervation to the palmar aspects of the medial half of the fourth digit and the fifth digit. Before the nerve exits through the pisohamate hiatus, the motor fibers branch off from the deep palmar motor branch to innervate the hypothenar muscles (abductor digiti minimi, flexor digiti minimi, opponens digiti minimi, and palmaris brevis).  The deep palmar branch gives motor innervation to the adductor pollicis, the deep head of the flexor pollicis brevis, the third and fourth lumbricals, and the three palmar and four dorsal interossei muscles.[1]

Etiology

The second most common upper extremity entrapment neuropathy is ulnar neuropathy at the elbow (UNE). At the elbow, the ulnar nerve lacks protective cover in the ulnar groove. This causes its susceptibility to external compression. Repetitive elbow flexion and extension, arthritic changes, and valgus deformities at the elbow increase its vulnerability to injury. In some individuals, the ulnar nerve may be subluxed out of the retroepicondylar groove medially over the medial epicondyle during elbow flexion. In a study investigating patients with UNE, the pressures recorded between the ulnar nerve and overlying arcade increased up to above 200 mm Hg in elbow flexion or during isometric contraction of the flexor carpi ulnaris muscle. In contrast, the pressure was less than 19 at elbow extension.[2]

Repetitive movement that exerts pressure on the ulnar wrist and hypothenar eminence predisposes the ulnar nerve to develop neuropathy. Wrist fractures and compressive mass lesions may also cause ulnar neuropathy at the wrist (UNW).

Epidemiology

There are limited studies of incidence and prevalence rates for ulnar neuropathy. In a study in the general population in Italy, incidence was 20.9%, with males affected more than females.[3] In a population-based survey in Egypt, crude prevalence rates showed that ulnar neuropathy at the elbow was the second most common type of entrapment.[4]

Pathophysiology

Neurapraxia of the ulnar nerve is often seen with mild injury. However, moderate-to-severe injuries of the nerve will present as axonotmesis, or in severe cases, neurotmesis.

History and Physical

Symptoms of ulnar neuropathy at the elbow usually start slowly unless it is associated with trauma. The patient may have numbness and paresthesia,  radiating distally to the ulnar aspect of the hand, the fifth digit and the ulnar aspect of the fourth digit. It is usually associated with elbow flexion, particularly at night. Unless it is associated with an acute injury to the elbow, pain is not a dominant feature; however, some patients may complain of pain due to overuse of the forearm flexors such as the FCU.

 Sensory symptoms involving the fifth digit and medial half of the fourth digit may indicate an ulnar neuropathy at the wrist. However, similar findings can be seen in ulnar neuropathy at the elbow. It is suggested that the fibers destined for the FCU, PUC, and DUC lie in individual fascicles at the elbow in a deep dorsolateral position, rendering them less susceptible to damage.[5]This renders them less susceptible to injury in UNE, and may cause difficulty in distinguishing UNE from ulnar neuropathy at the wrist. However, if there is an involvement of the entire ring finger or in contrast, total sparing, the diagnosis of cervical radiculopathy or brachial plexopathy should be taken into account.

When the disease gets worse, the symptom may progress to constant numbness and paresthesia and weakness of the innervated muscles. Weakness may start from clumsiness and loss of hand dexterity. This may then progress to a decrease in handgrip and pinch strength (Froment sign). In more severe cases, there may be atrophy of the hand intrinsic muscles and clawing of the fourth and the fifth digits, classically known as claw hand.[6]

Ulnar neuropathy at the wrist and hand can range from pure sensory to pure motor deficits. The most common type of ulnar neuropathies at the wrist is compression of the deep palmar branch. Ulnar neuropathies of the wrist and hand are divided into 3 types. Type I is a lesion of the ulnar nerve just proximal to or within the Guyon canal involving deep and the superficial branches; this causes mixed motor and sensory deficits and subsequent weakness of all the ulnar hand muscles. Type II is a lesion involving the deep branch which causes a pure motor deficit with a varied pattern of weakness based on the compression site. Type III lesion is limited to the superficial branch, causing purely sensory deficits to the palmar aspect of the medial half of the fourth digit and the fifth digit. The sensory loss in type I and type III lesions spares the dorsal aspect of the hand and fingers and the hypothenar eminence due to the more proximal innervations from the DUC and the PUC, respectively.[7]

Evaluation

Diagnosis traditionally relies on clinical history, physical examination, and electrodiagnostic studies. It has been suggested that combination of electromyography (EMG) and nerve conduction velocity (NCV) tests can improve diagnostic accuracy by mapping out the location of pathological compression of the ulnar nerve, which would provide a relatively early diagnosis in patients who have symptoms suggestive of ulnar nerve lesions.

Ultrasound (US) has also been suggested as a screening and follow-up imaging modality in patients with ulnar neuropathy at the elbow, as US can detect the morphologic changes and the extent of the ulnar nerve lesion at the elbow. A recent meta-analysis showed that in healthy participants, the ulnar nerve cross-sectional area at various locations at the elbow rarely exceeds 10 mm, and this can be considered a cutoff point for diagnosing ulnar nerve entrapment at the elbow region.[8] Another study suggested that by measuring ulnar nerve cross-sectional area with MRI or US at 1-cm proximal to the medial epicondyle, patients with and without UNE could be discriminated by using a cutoff threshold of 11.0 mm.[9] It is also suggested that the ulnar nerve-swelling ratio can be a complementary tool for diagnosing ulnar neuropathy at the elbow, and other potential sonologic indicators include presence of intra-neural vascularity, increased flattening ratio, and enlarged intra-neural hypoechoic fraction, although further research is needed.[10]

Treatment / Management

There are 2 main conservative treatments:  reducing the frequency of external compression on the nerve and flexion of the elbow joint. This is expected to decrease the stress placed on the ulnar nerve. The use of elbow splints, elbow pads or sleeves, and physical therapy have been suggested. For patients with mild to moderate symptoms, conservative treatment can be administered. It was shown that in patients with mild symptoms, conservative treatments are proven to be beneficial in about 90% of the patients; however, only 38% of the patients with moderate symptoms respond well a non-operative method.[11]

Injection procedures have also been proposed for the treatment of ulnar neuropathy at the elbow. However, studies with ultrasound-guided corticosteroid injections at the elbow have shown controversial results.[12][13]

Surgical treatment becomes a consideration for patients with persistent symptoms, with accompanying sensory changes and muscle atrophy. Several surgical methods have been described, for example, decompression, anterior transposition techniques, and medial epicondylectomy. A systematic review showed that simple decompression and decompression with transposition are equally effective in idiopathic UNE. However, the decompression surgery with transposition is associated with more wound infections than simple decompression.[14]

Enhancing Healthcare Team Outcomes

The ulnar nerve has several potential compression sites along its course. Although the elbow is the most common site of compression, the ulnar nerve is also susceptible to injury at the wrist, forearm, and upper arm. When the primary care provider and nurse practitioner come across patients with ulnar nerve dysfunction, it is important to refer these patients to the neurologist and hand surgeon to first confirm the diagnosis and treatment.  Prevention of compression and early diagnosis/treatment is important for its prognosis because the treatment outcome is usually disappointing once the nerve has axonal damage. There are 2 main conservative treatments:  reducing the frequency of external compression on the nerve and flexion of the elbow joint. This is expected to decrease the stress placed on the ulnar nerve. The use of elbow splints, elbow pads or sleeves, and physical therapy have been suggested. For patients with mild to moderate symptoms, conservative treatment can be administered. It was shown that in patients with mild symptoms, conservative treatments are proven to be beneficial in about 90% of the patients; however, only 38% of the patients with moderate symptoms respond well to a non-operative method.[11]


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Ulnar Neuropathy - Questions

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A patient complains of numbness of the fifth digit and the medial half of the fourth digit. What nerve is involved?

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A laborer presents with complaints of weakness in his grip of the left hand. He is an electrician, and for the past five months, he has noticed that his grip has steadily been getting weaker. He denies any abnormal sensation or injury to the arm or hand. The image of his left hand is shown. Further exam shows that he no sensory loss. Where is his nerve pathology located?

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A 41-year-old male construction worker presents with a 6-month history of numbness on the medial aspect of the hand and the fourth and fifth digits on the left hand. He also notes occasional tingling sensations on the medial aspect of the forearm. He is a non-smoker, does not drink alcohol, and denies history of weight loss. On physical examination, there is atrophy of the intrinsic muscles of the hand. What diagnostic test should be initially requested?



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A patient with has a history of right elbow dislocation three months ago. He now presents due to tingling sensations in the palmar and dorsal aspects of the medial hand, the fourth digit, and the fifth digit of his right hand. The Froment sign is positive. What muscle is weak?



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A 65-year-old male comes in due to a 6-month history of weakness on the right hand. He states that he has numbness on the medial aspect of the forearm, the medial aspect of the hand, the 4th digit, and the 5th digit. The provider does a physical examination which showed atrophy of the first dorsal interosseus muscle, weakness of the adductor digiti minimi, and positive Froment sign. The left hand had no symptoms and was normal on physical examination. He declares that this is a case of ulnar neuropathy at the elbow, right. Which of the previous statements would indicate that a different diagnosis should be considered?



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A 54-year-old male comes in due to "clawing" of the right hand and numbness on the medial aspect of the hand on the medial half of the fourth digit and on the 5th digit on the right hand. Physical examination gives a working impression of ulnar neuropathy at the elbow. Which muscle is most likely to have abnormalities on an EMG-NCV study?



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A 35-year-old male comes into the clinic due to a 2-month history of tingling sensations on the right hand. He denies any history of trauma, no exposure to hazardous chemicals, and no history of weight loss. One year ago, he started his job as a desk clerk. He claims that he observes proper seating and typing ergonomics during work, and tries to rest for 2 minutes for every 30 minutes of typing. However, he does claim that he spends the entire day typing. He has also been going to the gym for six months. He notes "snapping" sensation on his elbow during pull-ups and wide-arm push-ups but with no associated pain. His trainer informed him this is just the ligaments adapting to his workload. On physical examination, there was no tenderness on palpation of the right elbow and right hand. Manual muscle testing was 5/5 on both upper extremities except 3/5 on the right abductor digiti minimi; normal sensation on both hands except 20% sensory deficit on the 5th digit on the right, and normal deep tendon reflexes, bilaterally. Froment sign is positive on the right. Prayer sign is negative bilaterally. Phalen and Hoffman signs are negative bilaterally. What are the diagnosis and probable cause?



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Ulnar Neuropathy - References

References

Caliandro P,La Torre G,Padua R,Giannini F,Padua L, Treatment for ulnar neuropathy at the elbow. The Cochrane database of systematic reviews. 2016 Nov 15     [PubMed]
Landau ME,Campbell WW, Clinical features and electrodiagnosis of ulnar neuropathies. Physical medicine and rehabilitation clinics of North America. 2013 Feb     [PubMed]
Chang KV,Wu WT,Han DS,Özçakar L, Ulnar Nerve Cross-Sectional Area for the Diagnosis of Cubital Tunnel Syndrome: A Meta-Analysis of Ultrasonographic Measurements. Archives of physical medicine and rehabilitation. 2018 Apr     [PubMed]
Terayama Y,Uchiyama S,Ueda K,Iwakura N,Ikegami S,Kato Y,Kato H, Optimal Measurement Level and Ulnar Nerve Cross-Sectional Area Cutoff Threshold for Identifying Ulnar Neuropathy at the Elbow by MRI and Ultrasonography. The Journal of hand surgery. 2018 Jun     [PubMed]
Chen IJ,Chang KV,Wu WT,Özçakar L, Ultrasound Parameters other than the Direct Measurement of Ulnar Nerve Size for Diagnosing Cubital Tunnel Syndrome: a Systemic Review and Meta-analysis. Archives of physical medicine and rehabilitation. 2018 Jul 25     [PubMed]
Dellon AL,Hament W,Gittelshon A, Nonoperative management of cubital tunnel syndrome: an 8-year prospective study. Neurology. 1993 Sep     [PubMed]
Robertson C,Saratsiotis J, A review of compressive ulnar neuropathy at the elbow. Journal of manipulative and physiological therapeutics. 2005 Jun     [PubMed]
Werner CO,Ohlin P,Elmqvist D, Pressures recorded in ulnar neuropathy. Acta orthopaedica Scandinavica. 1985 Oct     [PubMed]
Idler RS, General principles of patient evaluation and nonoperative management of cubital syndrome. Hand clinics. 1996 May     [PubMed]
Shea JD,McClain EJ, Ulnar-nerve compression syndromes at and below the wrist. The Journal of bone and joint surgery. American volume. 1969 Sep     [PubMed]
Hong CZ,Long HA,Kanakamedala RV,Chang YM,Yates L, Splinting and local steroid injection for the treatment of ulnar neuropathy at the elbow: clinical and electrophysiological evaluation. Archives of physical medicine and rehabilitation. 1996 Jun     [PubMed]
vanVeen KE,Alblas KC,Alons IM,Kerklaan JP,Siegersma MC,Wesstein M,Visser LH,Vankasteel V,Jellema K, Corticosteroid injection in patients with ulnar neuropathy at the elbow: A randomized, double-blind, placebo-controlled trial. Muscle     [PubMed]
Mondelli M,Giannini F,Ballerini M,Ginanneschi F,Martorelli E, Incidence of ulnar neuropathy at the elbow in the province of Siena (Italy). Journal of the neurological sciences. 2005 Jul 15     [PubMed]
Khedr EM,Fawi G,Allah Abbas MA,El-Fetoh NA,Zaki AF,Gamea A, Prevalence of Common Types of Compression Neuropathies in Qena Governorate/Egypt: A Population-Based Survey. Neuroepidemiology. 2016     [PubMed]

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