Cubital Tunnel Syndrome

Cubital Tunnel Syndrome

KEY FACTS

Terminology

• Cubital tunnel syndrome (CUTS)

Due to compression of ulnar nerve at cubital tunnel
• Symptoms can also be due to ulnar nerve traction and friction secondary to instability

Imaging

• Best diagnostic clue: Swollen ulnar nerve within cubital tunnel
• 3 elements of CUTS should be routinely evaluated

Space-occupying lesion in cubital tunnel

– Ganglia, synovitis, osteophytosis, muscle, or tumor

Compression of ulnar nerve with swelling

– Ulnar nerve cross-sectional area measured proximal to tunnel and within tunnel

– The more swollen the ulnar nerve, the greater the likelihood of CUTS

– If cross-sectional area of ulnar nerve at cubital tunnel ≥ 10 mm², sensitivity 76%, specificity 61% for CUTS

– Alternatively, ulnar nerve cross-sectional area in tunnel should not be > 1.5x cross-sectional area in mid- to distal arm region

Ulnar nerve instability

– As elbow flexes, olecranon and roof of cubital tunnel move distally, allowing ulnar nerve to sublux

– Subluxation or luxation: Present in 25% of CUTS patients; 20% of normal subjects

Pathology

• 80% of patients with CUTS will have positive findings (either encroachment onto cubital tunnel, nerve swelling, or luxation/subluxation)
• 40% of patients with CUTS will have same positive findings on asymptomatic contralateral side

Diagnostic Checklist

• More swollen ulnar nerve = more likely possibility of CUTS
• In CUTS due to ulnar nerve instability, cubital tunnel encroachment and neural swelling may be less pronounced

TERMINOLOGY

Abbreviations

• Cubital tunnel syndrome (CUTS)

Synonyms

• Ulnar neuropathy at elbow
• Cubital tunnel

“Ulnar neural groove,” “retrocondylar groove,” or “epicondyle-olecranon groove”

Definitions

• Symptoms secondary to compression or irritation of ulnar nerve at cubital tunnel

2nd most common peripheral entrapment neuropathy after carpal tunnel syndrome

IMAGING

General Features

• Best diagnostic clue

Swollen ulnar nerve within cubital tunnel
• Location

Between medial epicondyle of humerus and olecranon
• Size

Normal nerve cross-sectional area is 6-12 mm²
• Morphology

Fusiform appearance on longitudinal scanning due to localized swelling

Radiographic Findings

• Radiography

Elbow osteoarthritis with osteophytic impingement into cubital tunnel, especially with hypertrophic osteoarthropathy

Elbow deformity from old trauma, chronic inflammatory arthropathy

MR Findings

• T2WI

Swelling of ulnar nerve with hyperintensity
• DWI

May show nerve compression before electrophysiologic abnormality

Ultrasonographic Findings

• Compression, swelling, and subluxation of ulnar nerve within cubital tunnel

Unlike carpal tunnel syndrome, there are 2 elements to CUTS

– Compressive neuropathy when cubital tunnel encroachment and neural swelling are dominant features

– Noncompressive neuropathy (i.e., ulnar nerve instability) when recurrent subluxation/luxation results in nerve stretching and friction neuritis

In noncompressive neuropathy, cubital tunnel encroachment and neural swelling may be less pronounced

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Tags: Diagnostic Ultrasound Musculoskeletal

Apr 9, 2020 | Posted by admin in MUSCULOSKELETAL IMAGING | Comments Off

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