Carpal tunnel syndrome vs Cubital tunnel syndrome

1. Carpal tunnel syndrome

Definition

Causes and risk factors

• Idiopathic, often bilateral
• Repetitive wrist use and vibration exposure
• Pregnancy
• Diabetes mellitus
• Obesity
• Hypothyroidism
• Rheumatoid arthritis, synovitis, gout
• Acromegaly, amyloidosis, renal dialysis

Clinical features

• Nocturnal tingling, burning, or numbness
• Paresthesia in thumb, index, middle, and radial half of ring finger
• Symptoms may radiate into forearm
• Shaking the hand may relieve symptoms, the “flick sign”
• Clumsiness, reduced grip, dropping objects
• Late: thenar wasting and weakness of thumb opposition/abduction

Examination

• Tinel sign: tapping over carpal tunnel reproduces median-distribution paresthesia
• Phalen test: wrist flexion provokes symptoms
• Durkan carpal compression test: direct compression over carpal tunnel reproduces symptoms
• Test thumb abduction/opposition and look for thenar atrophy
• Sensation over the thenar eminence is usually spared, as the palmar cutaneous branch leaves the median nerve proximal to the tunnel.

Investigations

• Diagnosis is often clinical.
• Nerve-conduction studies and EMG are useful in atypical presentations, suspected severe disease, differential diagnosis, and before surgery.
• Ultrasound can show median-nerve enlargement.
• The 2024 AAOS guideline states that a clinical CTS-6 assessment can diagnose many patients without routine EMG/nerve-conduction testing or ultrasonography; MRI is not recommended for routine diagnosis. See the AAOS guideline update.

Management

• Neutral-position wrist splint, particularly at night
• Modify aggravating activity
• Treat associated conditions
• Local corticosteroid injection can give short-term relief and may be useful diagnostically

• Carpal tunnel release, dividing the transverse carpal ligament
• Indications:
  • Persistent symptoms despite appropriate conservative management
  • Thenar weakness or atrophy
  • Severe electrodiagnostic abnormality
  • Constant sensory loss or progressive deficit
• Open mini-incision and endoscopic release have similar long-term results according to AAOS.

2. Cubital tunnel syndrome

Definition

Causes and risk factors

• Repeated or prolonged elbow flexion
• Leaning on the medial elbow
• Occupational pressure or unusual elbow positioning
• Previous elbow fracture, deformity, valgus elbow, osteophytes
• Synovitis, ganglion, or other local mass
• Ulnar-nerve instability or subluxation over the medial epicondyle

Clinical features

• Numbness and tingling in little finger and ulnar half of ring finger
• Symptoms are often worse with elbow flexion, telephone use, driving, or sleep
• Medial elbow ache
• Reduced grip and pinch strength
• Difficulty with fine finger movements
• Late findings:
  • First dorsal interosseous and hypothenar wasting
  • Weak finger abduction/adduction
  • Froment sign positive
  • Clawing of ring and little fingers in advanced disease

Examination

• Tinel sign at cubital tunnel
• Elbow-flexion test: sustained flexion reproduces ulnar paresthesia
• Assess ulnar nerve subluxation during elbow flexion
• Test:
  • Finger abduction/adduction
  • First dorsal interosseous bulk
  • Froment sign
  • Sensation in little finger and ulnar ring finger

Investigations

• Nerve-conduction studies and EMG localize and grade ulnar neuropathy and help exclude cervical radiculopathy or other neuropathy.
• Plain elbow radiographs if bony deformity, arthritis, or prior trauma is suspected.
• Ultrasound may show nerve enlargement, dynamic subluxation, or a mass.

Management

• Avoid sustained elbow flexion and direct pressure on elbow
• Night-time elbow-extension splint or a towel/pillow around elbow
• Ergonomic/workplace modification
• Avoid resting the elbow on hard surfaces

• In-situ decompression: release of constricting structures around ulnar nerve
• Anterior transposition: subcutaneous, intramuscular, or submuscular, particularly if the nerve subluxates/instability exists or in selected revision cases
• Medial epicondylectomy in selected anatomy

High-yield differentiation

• CTS = median nerve at wrist = lateral 3½ digits
• CuTS = ulnar nerve at elbow = medial 1½ digits
• CTS: thenar wasting and weak thumb opposition
• CuTS: interosseous wasting, weak finger abduction/adduction, Froment sign, ulnar clawing
• CTS provocation: Phalen, Durkan, Tinel at wrist
• CuTS provocation: elbow flexion test, Tinel at elbow, nerve subluxation assessment

Referral red flags

• Progressive motor weakness or muscle wasting
• Constant sensory loss
• Clawing or loss of fine hand function
• Symptoms not improving with splinting/activity modification
• Trauma, mass, severe pain, or suspected cervical radiculopathy