Median nerve neuropathy

 

Symptoms and Clinical Presentation of Median Nerve Neuropathy

The symptoms of median nerve neuropathy vary depending on the location and severity of the nerve lesion.

 

Impact of Lesion Level on Symptoms

• Lesions at or above the Elbow (High Lesions): Affect all median nerve functions in the forearm and hand.
• Lesions in the Forearm (e.g., Pronator Syndrome, AIN Syndrome): Affect functions distal to the lesion. AIN syndrome causes pure motor deficits without sensory loss in the hand.
• Lesions at the Wrist (e.g., Carpal Tunnel Syndrome): Primarily affect sensation in the typical median distribution in the hand and motor function of the thenar muscles. Forearm muscle function is spared.
• Brachial Plexus or Cervical Root Lesions:
  • With a lesion of the **C7 spinal nerve root** or the **middle trunk of the brachial plexus**, the function of the median nerve is often partially affected. This can result in a weakening of wrist flexion and forearm pronation (rotation inward), typically in combination with signs of radial nerve involvement (e.g., weakness of wrist/finger extensors), as both nerves receive C7 contributions.
  • Damage to the **lateral cord (external bundle) of the brachial plexus** (which gives rise to the lateral root of the median nerve and the musculocutaneous nerve) can cause a similar partial loss of median nerve function (affecting fibers of its "upper leg" passing from the middle trunk), but in this case, it would be combined with signs of musculocutaneous nerve damage (e.g., weakness of elbow flexion, sensory loss over lateral forearm).
  • With lesions affecting the **C8-T1 spinal nerve roots**, the **lower trunk**, or the **medial cord (internal bundle) of the brachial plexus** (as in Dejerine-Klumpke paralysis), the fibers of the median nerve that constitute its "lower leg" (medial root) suffer. This results in a weakening of the flexors of the fingers and the thenar muscles, usually in combination with signs of ulnar nerve damage.

Motor Deficits

The primary motor functions of the median nerve include forearm pronation, wrist flexion (palmar flexion), and flexion of the fingers (especially the thumb, index, and middle fingers), as well as extension of the middle and terminal phalanges of the index and middle fingers (via lumbrical action). In case of median nerve damage, these functions suffer:

• Weakness or inability to pronate the forearm (turn palm down).
• Weakened wrist flexion.
• Impaired flexion of the thumb, index, and middle fingers. This is often most evident when trying to make a fist – the patient may be unable to fully flex these digits ("hand of benediction" or "median claw" appearance when attempting to make a fist, though the term "median claw" is sometimes debated or used for specific presentations).
• Weakness or paralysis of thumb opposition (touching the tip of the thumb to the tips of other fingers) and abduction.
• Impaired extension of the middle and distal phalanges of the index and middle fingers (due to lumbrical weakness).
• Muscle atrophy, most pronounced in the thenar eminence (the fleshy mound at the base of the thumb), can occur with chronic or severe lesions. This results in a flattening of the palm and adduction of the thumb (bringing it close to and in the same plane as the index finger), creating a characteristic "ape hand" or "simian hand" deformity.

 

Sensory Disturbances

Sensory fibers of the median nerve innervate the skin of the palmar surface of the thumb, index finger, middle finger, and the radial half of the ring finger, as well as the corresponding part of the palm. They also supply the skin on the dorsal aspect of the terminal phalanges (fingertips) of these same digits.

Superficial sensitivity (light touch, pain, temperature) in median nerve neuritis or neuropathy is typically impaired in the hand within the zone free of innervation by the ulnar and radial nerves (i.e., the typical median nerve distribution). Articular-muscular sense (proprioception) with median nerve neuritis is almost always disturbed in the terminal phalanx of the index finger, and often in the middle finger as well.

Pain associated with median nerve damage, especially with partial lesions or entrapment syndromes like CTS, can be quite intense and often takes on a burning, aching, or tingling character (causalgic pain). In severe cases of causalgia, the hand may adopt a bizarre, guarded posture to avoid any stimulation.

 

Autonomic and Trophic Changes

Vasomotor, sudomotor (sweat gland function), and trophic (nutritional) disturbances are also common and characteristic features of median nerve lesions, particularly partial injuries or those with a causalgic component:

• The skin, especially of the thumb, index, and middle fingers, may become bluish (cyanotic) or pale, and feel cold or, conversely, warm and dry.
• Nails may become dull, brittle, and develop striations.
• Skin atrophy can occur, leading to thinning of the fingers (especially the index and middle fingers) and a smooth, shiny appearance ("glossy skin").
• Sweating disorders (anhidrosis - lack of sweat, or hyperhidrosis - excessive sweat) in the median nerve distribution.
• Hyperkeratosis (thickening of the skin).
• Hypertrichosis (excessive hair growth) in the affected area (less common).
• Ulceration of fingertips can occur in severe, long-standing cases due to sensory loss and trophic changes.

These trophic and autonomic disorders, like pain, are often more pronounced with partial rather than complete median nerve damage.

 

Specific Clinical Tests

The main clinical tests to determine movement disorders that occur with damage to the median nerve include:

1. Fist Clasp Test: When the patient attempts to clench their hand into a fist, the thumb, index finger, and often the middle finger do not flex properly or remain extended ("benediction sign" or "preacher's hand" when attempting to make a fist, indicating high median nerve lesion).
2. Impaired Distal Phalanx Flexion: Flexion of the terminal (end) phalanges of the thumb (by flexor pollicis longus) and index finger (by flexor digitorum profundus to index) is impossible or severely weakened. This can be tested by asking the patient to make an "OK" sign (thumb tip to index fingertip) – if AIN or high median nerve is affected, they will form a pincer grip with extended IP joints.
3. Inability to Scratch: The patient cannot scratch with the index finger on a table surface while the hand is pressed firmly down (due to weakness of index finger flexors).
4. Thumb Opposition Test / Pen Test: The patient cannot touch the tip of their thumb to the tip of their little finger, or cannot abduct the thumb perpendicularly away from the palm. They may be unable to hold a strip of paper with a bent thumb (flexor pollicis brevis, opponens) and will instead hold it by adducting the thumb with a straightened IP joint, using adductor pollicis (innervated by the ulnar nerve).
5. Phalen's and Tinel's Signs at the Wrist: Specific for Carpal Tunnel Syndrome.

 

Treatment of Median Nerve Neuropathy

Treatment for median nerve neuritis or neuropathy is selected individually for each case, depending on the underlying cause, severity of symptoms, duration, and findings from diagnostic evaluations. It often includes a combination of conservative procedures, and in some cases, surgical intervention.

 

General Principles and Conservative Management

• Addressing the Underlying Cause:
  • For compressive neuropathies like CTS or pronator syndrome: activity modification, ergonomic adjustments, splinting the wrist in a neutral position (especially at night for CTS).
  • For systemic conditions like diabetes or hypothyroidism: optimal medical management of the underlying disease.
  • For inflammatory conditions: anti-inflammatory medications.
• Pain Management: NSAIDs, neuropathic pain agents (gabapentin, pregabalin, TCAs, SNRIs), topical analgesics.
• Rest and Immobilization: Temporary rest or splinting of the affected limb segment may be beneficial in acute inflammatory or traumatic cases to reduce irritation.

 

Pharmacological Treatment

• Corticosteroids: Oral corticosteroids may be used for short periods to reduce inflammation in acute neuritis or some compressive neuropathies. Local corticosteroid injections are commonly used for carpal tunnel syndrome and can provide significant relief.
• Vitamins: B-complex vitamins (B1, B6, B12), Vitamin C, and Vitamin E are often prescribed as supportive therapy for nerve health, although robust evidence for their efficacy in promoting nerve regeneration in all types of neuropathy is varied.
• Antiviral Drugs: If a viral etiology is suspected (rare for isolated median neuropathy but considered in broader contexts of neuritis).
• Homeopathic Remedies: Some patients opt for homeopathic treatments, though scientific evidence supporting their effectiveness for nerve regeneration is generally lacking.

 

Rehabilitative Therapies

Physical and occupational therapy play a crucial role in recovery and functional improvement.

• Physiotherapy: Exercises to maintain range of motion, nerve gliding exercises to promote nerve mobility, strengthening exercises for weakened muscles, and modalities to reduce pain and inflammation (e.g., ultrasound, heat/cold therapy). Elimination of soreness, tingling, and restoration of sensitivity in the fingers during the treatment of median nerve neuritis is often accelerated with physiotherapy.
• Occupational Therapy: To adapt daily activities, provide assistive devices if needed, and teach joint protection techniques.
• Acupuncture: May be beneficial for pain relief and improving sensory or motor symptoms in some patients.
• Nerve Stimulation and Muscle Stimulation: Transcutaneous Electrical Nerve Stimulation (TENS) for pain, or Neuromuscular Electrical Stimulation (NMES) to maintain muscle mass and promote muscle re-education during nerve recovery.

Surgical Intervention

Surgery is considered if:

• Conservative management fails to provide relief after an adequate trial (e.g., 3-6 months).
• Symptoms are severe or progressively worsening.
• There is evidence of significant motor weakness, thenar muscle atrophy, or severe axonal loss on electrodiagnostic studies.
• A specific compressive lesion (e.g., tumor, cyst) is identified that requires removal.
• Acute nerve transection or severe trauma has occurred.

Surgical procedures include:

• Carpal Tunnel Release: For CTS, involves cutting the transverse carpal ligament to decompress the median nerve.
• Neurolysis: Freeing the nerve from scar tissue or external compression at other sites (e.g., for pronator syndrome).
• Nerve Repair (Neurorrhaphy): Direct suturing of transected nerve ends.
• Nerve Grafting: Using a segment of another nerve to bridge a gap if direct repair is not possible.
• Nerve Transfers: Transferring a healthy nerve or fascicle to reinnervate muscles supplied by the damaged median nerve.
• Tendon Transfers: For permanent motor deficits, to restore some hand function.

 

Differential Diagnosis of Hand/Forearm Neuropathy

Symptoms of median nerve neuropathy need to be differentiated from other conditions affecting the upper limb:

Condition	Key Differentiating Features
Median Nerve Neuropathy (e.g., CTS, Pronator Syndrome)	Symptoms (pain, numbness, tingling, weakness) in median nerve distribution. Positive provocative tests (Tinel's, Phalen's for CTS). EMG/NCS localizes lesion to median nerve.
Cervical Radiculopathy (C6, C7, C8, T1 roots)	Neck pain, radiating arm pain/paresthesias in a dermatomal pattern. Weakness in corresponding myotomes. Reflex changes. Symptoms often worsen with neck movements. Neck MRI diagnostic.
Ulnar Neuropathy (Cubital Tunnel or Guyon's Canal)	Numbness/tingling in 4th (ulnar half) and 5th fingers, weakness of intrinsic hand muscles (interossei, hypothenar). Positive Tinel's at elbow or wrist (ulnar side).
Radial Neuropathy (e.g., "Saturday Night Palsy," Spiral Groove)	Wrist drop, finger drop, weakness of extensors. Sensory loss over dorsal hand/thumb.
Brachial Plexopathy	More widespread weakness and sensory loss involving multiple nerve distributions in the arm/hand, depending on which part of the plexus is affected.
Peripheral Polyneuropathy	Usually symmetrical, distal "stocking-glove" sensory loss and weakness. Multiple nerves affected.
Thoracic Outlet Syndrome (Neurogenic)	Pain, paresthesias, weakness often in ulnar distribution (C8-T1) or entire arm. Symptoms worsen with arm elevation or specific maneuvers.
Musculoskeletal Conditions (e.g., Tenosynovitis, Arthritis)	Localized pain, swelling, tenderness related to joints or tendons. Usually no primary neurological sensory or motor loss unless nerve is secondarily compressed.

 

Prognosis and Potential Complications

The prognosis for median nerve neuropathy varies greatly depending on the cause, severity, duration of symptoms before treatment, and the type of treatment received.

• Mild compressive neuropathies (like early CTS) often respond well to conservative treatment or surgical decompression with good recovery.
• More severe axonal damage or long-standing compression may result in incomplete recovery, persistent weakness, sensory loss, or thenar atrophy.
• Traumatic nerve transections have a more guarded prognosis, even with surgical repair.

Potential complications include:

• Permanent motor weakness and muscle atrophy (especially thenar muscles).
• Chronic pain and paresthesias.
• Loss of fine motor skills and hand dexterity.
• Development of complex regional pain syndrome (CRPS) in some cases.

 

Prevention Strategies

Preventive measures depend on the specific cause but may include:

• Ergonomic workplace adjustments to minimize repetitive stress on the wrist and forearm.
• Regular breaks and stretching exercises for individuals performing repetitive hand tasks.
• Using proper techniques and protective gear to avoid trauma.
• Managing underlying medical conditions like diabetes or rheumatoid arthritis effectively.
• Avoiding prolonged pressure on vulnerable nerve points.

 

When to Consult a Specialist (Neurologist, Hand Surgeon)

Consultation with a neurologist, hand surgeon, or physician specializing in peripheral nerve disorders is recommended if:

• Symptoms of pain, numbness, tingling, or weakness in the median nerve distribution are persistent, progressive, or significantly interfere with daily activities.
• There is noticeable muscle wasting (atrophy) in the thumb area.
• Symptoms follow a significant trauma to the arm, wrist, or hand.
• Conservative measures fail to provide relief.

Early diagnosis and appropriate intervention can improve outcomes and prevent long-term disability from median nerve neuropathy.