Cubital Tunnel Syndrome

Manuel F. Dasilva, M.D.
Katia A. Dasilva, B.A.

Basic Information

Definition

Cubital tunnel syndrome is a compressive or entrapment neuropathy of the ulnar nerve as it traverses the cubital tunnel at the elbow (Fig. E1). The cubital tunnel lies between the medial epicondyle of the humerus and the olecranon process of the ulna. The roof of the cubital tunnel is formed by a fascial band (Osborne’s ligament) between the two heads of the flexor carpi ulnaris. The floor consists of the medial collateral ligament and olecranon.

FIG.E1

Cubital tunnel.

Original art by Dr. DaSilva

ICD-10CM CODES
G56.2	Lesion of ulnar nerve, unspecified upper limb

Epidemiology & Demographics

Cubital tunnel syndrome is the second most commonly diagnosed compressive neuropathy of the upper extremity after carpal tunnel syndrome, and it is the most common ulnar nerve neuropathy. Its incidence is 24.7 cases per 100,000 persons per year. Men are more frequently affected than women at a 2:1 ratio.

Physical Findings & Clinical Presentation

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Patients often complain of numbness and paresthesia along the distribution of the ulnar nerve (little finger and medial half of ring finger); pain rarely occurs in the hand.
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Pain is typically localized to the cubital area, but symptoms can affect the medial epicondyle and forearm.
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Complaints of hand grip problems (weakness) or hand clumsiness are common.

The following provocative maneuvers and physical signs are helpful in identifying ulnar neuropathy when interpreted in the proper clinical context.

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Positive Tinel’s sign at elbow over the ulnar groove—highest negative predictive value
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Positive elbow flexion test (flexion of elbow with wrist extended for 30 seconds reproduces symptoms)
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Pressure provocation test (direct pressure over cubital tunnel for 60 seconds elicits symptoms)
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“Scratch collapse” test (positive if temporary loss of external rotation resistance occurs after examiner scratches over the compressed ulnar nerve)
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Signs of old trauma or elbow instability (valgus stress)
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Ulnar nerve may sublux over medial epicondyle with elbow motion
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Weakness or atrophy of intrinsic musculature of hand in longstanding cases
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Duchenne’s sign, also known as intrinsic minus or claw hand; caused by paralysis of lumbrical and interosseous muscles (clawing is usually worse in ring and small fingers)
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Masse’s sign—hand appears flattened due to hypothenar muscle paralysis
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Wartenberg’s sign—caused by weakness of interossei: weak adduction of small finger
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Froment’s sign—compensation by thumb flexor (flexor pollicis longus, median-nerve innervated) for diminished thumb pinch strength (paralysis of adductor pollicis, which is innervated by ulnar nerve)

Etiology

Cubital tunnel syndrome can be idiopathic or caused by some predisposing factors:

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Blunt trauma, fractures
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Metabolic derangements (e.g., diabetes)
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Compression during general anesthesia
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Hemophilia (leading to hematomas)
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Cigarette smoking
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Chronic pressure over ulnar groove from occupational stress, unusual elbow positioning
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Cubitus valgus deformity secondary to old trauma (childhood supracondylar fracture)
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Subluxation of ulnar nerve
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Repeated stretching during throwing motion
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Elbow synovitis, osteophytes
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Local muscular hypertrophy
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Increased cubital tunnel pressure, particularly in elbow flexion

Diagnosis

In most patients, a thorough history and physical examination are sufficient to make the diagnosis. Laboratory, electrophysiologic, and imaging studies can help support the diagnosis.

Differential Diagnosis

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Medial epicondylitis
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Carpal tunnel syndrome
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Cervical disc disease (radiculopathy)
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Thoracic outlet syndrome
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Ulnar nerve compression at wrist (Guyon’s canal)
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Guillain-Barré syndrome
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Amyotrophic lateral sclerosis
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Pancoast tumor

Workup

Laboratory Studies

Specific laboratory studies can help rule out predisposing conditions:

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Complete blood count
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Folate and vitamin B₁₂ levels
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Urinalysis
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Thyroid function tests
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Renal function tests
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Fasting blood glucose
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Hemoglobin A1C
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Inflammatory markers (ESR, CRP), antinuclear antibodies (ANA)
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HIV, hepatitis, and Lyme serology

Imaging Studies

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Radiographs of the elbow should be obtained in all patients.
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Radiographs of the neck and chest may be done to rule out suspected conditions such as cervical disc disease or Pancoast tumor.
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High-resolution ultrasound can be a valuable adjunct to the diagnosis and may identify the structural etiology of nerve compression. Because of the real-time nature of ultrasound evaluation, dynamic testing can be done and ulnar nerve subluxation may be observed during elbow flexion and extension motions.
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Trials of diagnostic ultrasound have shown a strong correlation between greater ulnar nerve cross-sectional area at the elbow and presence of cubital tunnel syndrome diagnosed by electrodiagnostic criteria.
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MRI (Fig. E2) may be useful in patients in whom history, physical examination, and electrophysiologic studies fail to support the diagnosis.

FIG.E2

Cubital tunnel syndrome.

Coronal T1-weighted (A) and coronal short tau inversion recovery (B). Magnetic resonance (MR) images show a ganglion cyst *(arrowheads)* within the cubital tunnel, producing compression and displacement of the ulnar nerve *(arrows)*. C, Axial T2-weighted MR image distal to the elbow joint demonstrates an enlarged and hyperintense ulnar nerve *(arrowhead)* and early denervation with edema of the flexor carpi ulnaris muscle *(arrow)*.

From Pope TL, Bloem HL, Beltran J, Morrison WB, Wilson DJ: *Musculoskeletal imaging*, ed 2, Philadelphia, 2014, Saunders.

Electrodiagnostic Studies

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Nerve conduction tests and electromyography are useful to confirm the clinical diagnosis and can help localize the site of compression.

Treatment

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Nonsurgical options:
1. ○
  
  Activity modification; avoiding prolonged/repetitive flexion of elbow
2. ○
  
  Anterior shell splint limiting flexion to 45 degrees to be worn at night
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  Elbow pads to relieve pressure; physical and occupational therapy
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  Pain control and alleviation of sensory symptoms using NSAIDs, tricyclic antidepressants, or anticonvulsants
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If nonsurgical options fail to control symptoms or if the patient has significant muscle weakness or atrophy, then surgical options are available:
1. ○
  
  Endoscopic cubital tunnel release
2. ○
  
  Ulnar nerve decompression in situ
3. ○
  
  Anterior transposition of the ulnar nerve

Disposition

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There is a tendency toward spontaneous recovery with mild or moderate or intermittent symptoms if provocative causes are avoided.
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If muscle atrophy has developed, recovery of strength may be incomplete despite treatment.

Referral

Surgical referral is needed in cases of failed medical management. Patients with constant symptoms or muscle atrophy usually require surgical treatment.

Pearls & Considerations

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A good history and physical examination and knowledge of the sensory and motor innervation of the upper extremity are usually sufficient to make the diagnosis.
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Patients with mild, intermittent symptoms can have spontaneous recovery if provocative cases are avoided.
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Medical management should be attempted, but if symptoms are persistent or if significant hand muscle weakness or atrophy is present, then surgery may be indicated.
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In patients with advanced findings, electromyogram/nerve conduction studies can help predict nerve and muscle function recovery after surgery.
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Surgical decompression has been shown to be successful in most cases. More recently, endoscopic decompression techniques have been described.

Ferri – Cubital Tunnel Syndrome