Wartenberg's Syndrome

Course of the SBRN

• Origin: Leaves the main Radial Nerve at the elbow (Radio-capitellar joint).
• Forearm: Runs deep to the Brachioradialis (BR) muscle belly.
• Emergence: Pierces the deep fascia between the Brachioradialis and ECRL tendons at the junction of the middle and distal thirds of the forearm.
• Distal: Runs superficial to the Anatomical Snuffbox to supply the dorsum of the hand.

The nerve becomes subcutaneous approximately 9cm proximal to the radial styloid.

Site of Compression

• The Exit: The fascial band connecting BR and ECRL allows the nerve to exit.
• Scissoring: During pronation, the ECRL crosses under the BR, effectively "scissoring" the nerve between the tendons.
• External: Because it becomes subcutaneous here, it is easily compressed by watches, handcuffs, or casts.

This is the most common site of compression (unlike CTS which is at the wrist).

Etiological Types

• Compressive: External (Watch, Cast, Handcuff).
• Dynamic: Repetitive pronation/supination (Scissoring).
• Traumatic: Direct blow, venipuncture injury (Cephalic vein is close).
• Scarring: Post-De Quervain's release (Neuroma).

Iatrogenic injury is a significant cause of litigation.

Dellon's Classification (Neuroma)

• Type I: Pain in nerve distribution.
• Type II: Pain + Tinel's sign.
• Type III: Pain + Tinel's + Static 2-point discrimination loss.

Type III indicates more severe axonal damage.

History

• Pain: Burning, shooting pain over the dorsum of the thumb and index finger.
• Aggravation: Wrist movement, tight sleeves, watches.
• Night: No night perception (unlike CTS).
• History: Ask about handcuffs or new watches.

Symptoms are often purely sensory, with NO motor weakness.

Physical Exam

• Tinel's Sign: Positive over the nerve (approx 9cm proximal to radial styloid). The most reliable sign.

• Finkelstein's Test: Often Positive! Traction on the nerve causes pain. Differentiate by palpating the tendons (De Quervain's) vs the nerve (Wartenberg's).

• Dellon's Test: Hyperextension of wrist + Adduction of thumb (stretches nerve).

• Sensation: Reduced over dorsal webspace (First web).

• Sensation: Reduced over dorsal webspace (First web).

Comparing sensation to the contralateral side is crucial.

Ultrasound

• Utility: Excellent for visualizing the nerve.
• Findings: Swelling of the nerve proximal to the fascia. "Notch" sign.
• Dynamic: Can observe the nerve being compressed during pronation.
• Cysts: Can exclude a ganglion cyst compressing the nerve.

Always look for a ganglion (occult) if history is unclear.

MRI

• Role: Excluding other pathology (e.g., scaphoid fracture, tumors).
• Nerve: May show neuritis (high signal) but less sensitive than US for small superficial nerves.

MRI is better for deep lesions or bone pathology.

Nerve Conduction Studies

• Sensory: SNAP (Sensory Nerve Action Potential) of radial nerve may be reduced or absent.
• Comparison: Compare with contralateral side (amplitude drop greater than 50% is significant).
• Note: Often normal in dynamic cases.

A normal NCS does not exclude the diagnosis (clinical diagnosis dominates).

Non-Operative (Mainstay)

• Remove Cause: Stop wearing watches, bracelets. Loosen casts.
• Splinting: Thumb spica or wrist splint to reduce excursion.
• Desensitization: Massage, textures.
• Corticosteroids: Injection around the nerve (Avoid intraneural!). Can be curative.
• Success: 70-80% resolve with conservative care.

Removing the external compression is the single most important step.

Surgical Decompression

• Indication: Failure of conservative care (greater than 6 months), persistent pain.
• Outcome: Variable. High risk of dissatisfaction.
• Key: Patient expectation management.

Surgery should only be offered if the diagnosis is certain and blocks confirmed it.

Neurolysis

• Incision: Longitudinal over the course of the nerve (8-10cm proximal to styloid).
• Identify: Find the nerve emerging between BR and ECRL.
• Release: Divide the deep fascia binding the two tendons.
• Trace: Follow distally (avoiding branches).
• Protection: Handle nerve gently (Vessel loops).
• Fascia: Ensure no "scissoring" remains in pronation.

The release is simple but locating the nerve in scar tissue can be hard.

Neuroma Management

• Problem: If a painful neuroma exists (from previous injury).
• Option 1: Burying (in muscle/bone).
• Option 2: Capping.
• Option 3: Neurectomy (accept numbness to cure pain).

This is a salvage situation.

Outcomes for neuroma surgery are notoriously unpredictable.

Surgical Complications

• Neuroma Formation: The most feared complication; extremely painful and difficult to treat.
• Incomplete Release: Failure to fully decompress the nerve leads to persistent symptoms.
• Recurrence: Scarring can reform the fascial band causing re-entrapment.
• Iatrogenic Nerve Injury: Direct injury during dissection worsens prognosis.
• Wound Complications: Infection, dehiscence, or hypertrophic scarring.

Careful patient selection and meticulous technique are essential.

Complications of Untreated Disease

• Chronic Pain: Persistent burning and dysesthesia affecting quality of life.
• Numbness: Progressive sensory loss in the radial dorsal hand.
• CRPS Development: Complex Regional Pain Syndrome (Type II) may develop.
• Hyperesthesia: Increased sensitivity making normal activities painful.
• Psychological Impact: Chronic pain affects sleep, work, and mental health.

Early intervention prevents progression to chronic pain syndromes.

Expected Outcomes by Treatment

• Conservative Management: 70-80% resolution with removal of compressing agent alone.
• Corticosteroid Injection: 60-70% improvement; may need repeat injection.
• Surgical Decompression: 74% good/excellent outcomes in well-selected patients (Lanzetta 1993).
• Neuroma Surgery: Unpredictable; 50-60% improvement at best.
• Chronic Cases: May require multidisciplinary pain management.

Patient selection is the key determinant of surgical success.

Prognostic Factors

• Duration: Shorter duration (under 3 months) associated with better outcomes.
• Etiology: External compression (watch, handcuff) has best prognosis.
• Iatrogenic Cause: Post-surgical cases have poorer outcomes due to scarring.
• CRPS Development: Poor prognostic sign requiring specialist input.
• Age: Younger patients generally recover better.
• Psychological Factors: Anxiety and catastrophizing predict poorer outcomes.

Address underlying cause to prevent recurrence.

Recovery Timeline

• Neurapraxia (External Compression): 6-12 weeks for full recovery.
• Axonotmesis (Moderate Injury): 3-6 months; may have residual symptoms.
• Neurotmesis (Severe Injury): Permanent deficit unless nerve repaired.
• Post-Surgical Recovery: 3-6 months for optimal surgical outcome.
• Desensitization Programs: May require 6-12 months of consistent therapy.

Serial assessment helps identify patients failing to progress.