Median Nerve Injury: Symptoms, Diagnosis, Treatment

Courtesy: Prof Nabil Ebraheim, University of Toledo, USA

 

1. Median Nerve Compression Sites

• Compression can occur at multiple points along the nerve’s course.

• ~1% of individuals have a supracondylar spur (5 cm above medial epicondyle).

• Struthers’ ligament bridges the spur to the medial epicondyle and can entrap the nerve.

• Median nerve runs under the ligament with the brachial artery or ulnar branch.

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2. Clinical Signs of Struthers’ Ligament Entrapment

• Gradual hand weakness, pain, and sensory loss in median nerve distribution.

• Inability to perform the “OK” sign.

• Positive Tinel’s sign over the spur area (tingling on tapping).

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3. Pronator Teres Syndrome

• Compression of median nerve near elbow; more common in females.

• Median nerve passes between two heads of pronator teres, then between FDS and FDP.

• May be associated with medial epicondylitis.

Symptoms

• Numbness in radial 3½ fingers.

• Weakness in thenar muscles.

• Often misdiagnosed as carpal tunnel syndrome (CTS).

Causes of Compression

• Most common: Between two heads of pronator teres.

• Bicipital aponeurosis thickening.

• FDS fibrous arch.

Clinical Features

• Symptoms worsen with forearm rotation.

• Dull pain in proximal forearm; no night symptoms.

• Tenderness over pronator teres.

• Palmar cutaneous branch (sensory) affected—indicates proximal median nerve involvement, not CTS.

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4. Diagnostic Signs

• CTS tests negative: Tinel, Phalen, compression tests at wrist.

• Tinel’s sign positive at proximal forearm.

• Resisted tests help localize:

  • Forearm pronation + elbow extension ? Pronator teres compression.

  • Elbow flexion + forearm supination ? Bicipital aponeurosis compression.

  • Middle finger FDS contraction ? FDS arch compression.

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5. Carpal Tunnel Syndrome (CTS)

• Pain, numbness, tingling in palm, thumb, index, and middle fingers.

• Symptoms worse at night, awaken patient.

• Patients shake hands to relieve symptoms.

Tests

• Tinel’s sign: Tapping wrist reproduces tingling.

• Phalen’s test: Wrist flexion for 60s increases symptoms.

• Durkan’s test: Thumb pressure over carpal tunnel—most sensitive.

• Hand diagram: Most specific; patient marks symptom areas.

• Thenar atrophy, weakness, clumsiness possible.

• CTS is a clinical diagnosis.

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6. Management Concept

• Carpal tunnel = tunnel through which nerve passes.

• Treatment: Widen tunnel by cutting transverse carpal ligament.

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7. Anterior Interosseous Nerve (AIN) Injury

• AIN is a branch of the median nerve, arises 4–6 cm below elbow.

• Runs on interosseous membrane between FDP and FPL.

• Purely motor nerve, not sensory.

Affected Muscles

• FDP (index and long fingers)

• FPL

• Pronator quadratus

Clinical Signs

• Benediction sign: When making a fist, index and middle fingers do not flex.

• Inability to do “OK” sign: Due to FPL and FDP weakness.

Causes

• Can occur in supracondylar fractures in children.

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8. Important Anatomical & Diagnostic Notes

• Dual innervation of FDP: Medial part by ulnar nerve.

• Terminal AIN branches innervate volar wrist capsule.

• Martin-Gruber connection: May cause intrinsic muscle weakness.

• Differentiate AIN palsy from acute brachial neuritis.

• Median nerve conduction studies may be normal.

• Needle EMG of AIN will show abnormalities (motor involvement only).