Introduction
- Nerve affected
Nerve affected | Location: compression syndrome | Anatomical entrapment |
Median | Wrist: carpal tunnel | Under the transverse carpal ligament |
Median | Proximal forearm: pronator syndrome | Compression between the two heads of pronator teres or fibrous arch of flexor digitorum superficialis |
Anterior interosseous nerve | Proximal forearm: anterior interosseous nerve | Compression between the two heads of pronator teres or fibrous arch of flexor digitorum superficialis |
Ulnar | Wrist | Guyon’s canal |
Ulnar | Distal arm/elbow: cubital tunnel | Between the two heads of flexor carpi ulnaris, ligament of Osborne, arcade of Struthers |
Radial | Forearm/Elbow: posterior interosseous entrapment | Arcade of Froshe, between the heads of supinator |
- Numbers
- Most common
- Carpal tunnel syndrome (CTS)
- Accounts for about 90% of all entrapment neuropathies in the upper limb
- Annual incidence of 0.1– 0.35%
- Prevalence 1% and 7% in the European population
- Annual incidence
- Ulnar nerve syndromes (0.03%)
- Radial nerve syndromes (0.003%)
- Meralgia paresthetica (4.3 per 10 000 person- years)
- General
- Aka
- Distal brachial plexal injuries
- Peripheral nerve palsies are common and the management of them can be simple as long as your clinical examination and subsequent diagnoses is accurate.
- Due to
- Acute compression
- Chronic compressions
- Traumatic injuries.
- Nerve injured
- Most common
- Median nerve
- Ulnar nerves
- Less common
- Radial
- Common peroneal nerve palsies
Classification
Type | Dfn, features | Causes/specific syndromes |
Mononeuropathy | One peripheral nerve involved | • Injury/iatrogenic • Compression/entrapment |
Polyneuropathy | Diffuse lesions of many nerves involved: • Distal nerves > prox nerves involved • Motor + sensory (incl. pain) fibers involved | • Endocrinological diseases (DM, hypothyroidism) • Alcohol • Vitamin B12 deficiency • Heavy metals • Meds (e.g., chemotherapy) • Radiotherapy • Charcot–Marie–Tooth II (CMT II) |
Mononeuritis multiplex | > 2 nerves involved in non-contiguous areas (simultaneous OR sequential) | • Autoimmune diseases (systemic lupus erythematosus [SLE], RA, sarcoid) • Vasculitis (polyarteritis nodosa) |
Plexopathy | Brachial OR lumbosacral plexus involved | • Trauma • Brachial neuritis (Parsonage–Turner syndrome) |
Location
Arcade of struthers | Medial head of triceps/intermuscular septum | Ulnar nerve |
Arcade of osbourne | Flexor carpi ulnaris | Ulnar nerve |
Arcade of frosche | Supinator | Radial nerve |
Ligament of struthers | Supracondylar process/medial epicondyle | Median nerve |
Clinical features
Finding | Key Features |
Ape hand | Loss of thumb opposition and abduction due to median nerve damage |
Hand of benediction | On attempting to make a fist, only 4th and 5th digits flex at IPJs. Loss of flexion of digits 2 + 3 at MCPJ and IPJs due to median nerve palsy affecting lumbricals 1 + 2, median part of FDP |
Volkman’s contracture | Permanent flexion contracture of the hand at the wrist resulting in clawing of hand and fingers. Usually due to ischemia of long forearm flexors which then become fibrotic and short |
Claw hand | On attempting to extend fingers, digits 4 + 5 remain in clawed position (MCPJ extension, flexed IPJs). Affects 4th and 5th digits with low ulnar nerve lesions (below mid-forearm), but complete claw hand can be seen if both low ulnar and median nerve injury occur together. Ulnar nerve lesions above mid-forearm do not produce clawing as there is also weakness of ulnar half of FDP |
Hoover test | Aimed to distinguish organic from non-organic leg weakness using principle of synergistic contraction. Perform by holding the heel of the normal leg while asking patient to straight leg raise the weak leg against resistance. Normally examiner will feel heel push down as they try to raise the weak leg—absence suggests lack of effort to either leg |
Tinel’s test | Percussion over an (irritated) nerve elicits a sensation of pins and needles in the distribution of the nerve |
Froment’s sign | While grasping a piece of paper between thumb and index finger (palm flat) as it is pulled away, weakness of adductor pollicis (ulnar nerve) will result in compensatory flexion of thumb PIPJ to try and hold on to it |
Hoffman’s reflex | Tapping the nail or flicking the terminal phalanx of the middle/ring finger results in flexion of the terminal phalanx of the thumb. Suggests cervical cord pathology |
Spurling’s sign | Hyperextension of head and rotation towards symptomatic extremity (± pressing down on patients head) reproduces radicular symptoms due to narrowing of intervertebral foramina |
Inverted radial reflex | Diminished brachioradialis reflex with reflex contraction of finger flexors. Suggests C5 pathology |
Phalen’s test | Holding wrist in complete forced flexion for up to 1 min, aiming to draw lumbricals into the carpal tunnel and compress the median nerve to reproduce symptoms. Reverse Phalen’s test involves forced extension (prayer position) |
Lasegue’s sign | Straight leg raising test is considered positive if pain or paresthesia occur in a radicular distribution at less than 60° of elevation. Lowering the leg and dorsiflexing the ankle will exacerbate symptoms. Allowing the foot to rest on the table by flexing the knee will reduce pain (bowstring sign). Most specific for L5 or S1 root compression |
Fajersztajn sign | Crossed straight leg raising test is usually positive with a large central disc protrusion. Raising the unaffected leg with patient supine produces radicular pain in the affected extremity |
Femoral stretch test | Useful for distinguishing between sciatica involving L2 and L3 nerves and those involving L4 to S1. With the patient lying prone, the knee is passively flexed and the hip passively extended to elicit thigh pain |
Pinch sign | Patient attempts to forcefully pinch the tips of index finger and thumb together to make an “OK” sign but AIN palsy causing weakness of FDP to digits 2 + 3 and FPL results in extension of terminal phalanges. As a result finger pulp rather than tips touch |
Wartenberg’s sign | Abducted little finger at rest due to weakness of 3rd palmar interosseous muscle in ulnar nerve palsy |
Pathophysiology
- Mechanism of nerve injury
- Compression
- Alteration of epineural blood flow → ischaemia
- Time
- Acute pressure
- Causes endoneural oedema →
- Altering intraneuronal transport
- Increased endoneural pressure disrupts micro-neural circulation → dynamic ischaemia of the nerve → present as intermittent paraesthesia + increased sensory thresholds
- Progressive pressure
- Causes localized demyelination → persistent paraesthesia, numbness, and changes in dexterity.
- Chronic pressure
- Causes diffuse demyelination + axonal degeneration → muscle wasting, permanent sensory abnormalities, and pain
- All nerves glide through specific pathways as they pass peripherally to their target organ.
- It is these pathways composed of bone, ligament, fibrous tunnels, muscle origins and insertions that not only enable effective nerve movement and gliding but also are the potential source of nerve compression.
- For example,
- Guyon canal compression
- It is the cubital tunnel ‘pulley system’ (intermuscular septum, arcade of Struthers, epicondylar groove and origin of the flexor carpi ulnaris) that allows for effective movement of the ulnar nerve about the elbow with excursion of 9.8 mm and 14.5 mm in the forearm during flexion and extension of the elbow
- However, it is these same structures which we divide to relieve nerve compression.
- Connective tissue elements, both within and surrounding each nerve, increase where each nerve crosses a joint.
- This change can contribute to the symptoms of compression as alteration in blood flow to this surrounding sleeve can lead to fibrosis and thickening thus promoting nerve compressive symptoms and interfering with the natural intraneural and extraneural gliding mechanisms (Rempel et al., 1999; Mackinnon, 2002).
Double crush concept
- Compression along the course of the nerve even if insufficient to cause symptoms but leaving the nerve more susceptible to a secondary site of compression.
- It is then this two- level compression that then yields symptoms.
- Relieving the nerve compression at one of the sites might be enough to provide symptomatic relief and traditionally the more distal site is addressed first (Upton and McComas, 1973).
Management
- Surgery + rehabilitation
- Indicated
- Non-advancing positive Tinel’s sign at the sight of the nerve entrapment.
- Technique
- Nerve decompression
- Nerve Repair
- Performed using a microscope or loupes with fine nylon suture material and fibrin glue.
- Either an epineural repair or fascicle group repair are utilized.
- Peripheral nerves cannot be repaired under tension as this will fail.
- Nerve grafting
- Nerve grafts are required when it is felt that nerve repair will be under tension
- Commonly used grafts (cutaneous nerves)
- Sural
- Antebrachial cutaneous nerves
- Nerve and tendon transfers
- If there is no chance at direct repair or the distance too long
- To provide useful limb function.
- Outcome
- Affected by
- Presence of
- Excellent allied health professionals (occupational therapists and physiotherapists), who can assess and rehabilitate the patients afterwards.
Clinical differences between radiculopathy and neuropathy
Feature | Radiculopathy | Neuropathy |
Sensory distribution | Fuzzy | Discrete |
Muscle atrophy | No (rare) | Yes |
- Utilize patterns of innervation to differential diagnosis
- Sensory nerve distribution
- Motor innervation
Wallerian degeneration
- Is a process that results when a nerve fiber is cut or crushed, in which the part of the axon separated from the neuron's cell body degenerates distal to the injury.
- Wallerian degeneration is not a typical cell death mechanism, since neurons undergoing this process remain alive.
Summary
Nerve | Common site of palsy | Muscles affected | Sensation | Key examination |
Median nerve (C5–T1) | • Delto-pectoral fascia • Supracondylar process + ligament of Struthers • Carpal tunnel | • Lumbricals 1 & 2 • Opponens pollucis • Abductor pollucis brevis • Flexor pollucis brevis • Wasting thenar bulk | Radial predominately volar 1st three webspaces | • Thenar wasting • Phalen’s and Durkin’s tests |
AIN (C5–T1) from median | • Kiloh–Nevin • Superficial arch of FDS • Lacertus fibrosus • Superficial head of pronator teres | • Flexor digitorum profundus radial half • Pronator quadratus • Flexor pollicis longus | n/a | • Unable to make OK sign • Weak resisted pronation |
Ulnar nerve (C8–T1) | • Cubital tunnel syndrome (5 sites) • Guyon’s canal | • Lumbricals 3 and 4 • All interossei • Adductor pollicis • Deep head of Flexor pollicis brevis • Wasting hypothenar bulk | Ulnar / 4th webspace | • Froments test • Hypothenar + 1st DIO wasting • Wartenberg’s and Jeanne’s sign |
Radial nerve (C5–T1) | • Accessory subscapularis–teres–latissimus muscle • Subscapular artery • Triangular interval • Lateral intermuscular septum | • Triceps brachii • Aconeus • Brachioradialis • Extensor carpi radialis longus/brevis • Supinator • Entire posterior compartment, extensors, and abductor pollicis longus | Lateral/posterior upper arm and elbow and hand—radial dorsal predominately 1st three webspaces | • Classical wrist drop depends on level |
PIN from radial | • Radial tunnel syndrome | • Extensor carpi radialis brevis (normally from radial nerve) • Extensor digitorum communis • Extensor digiti minimi • Extensor carpi ulnaris • Supinator • Abductor pollicis longus • Extensor pollicus brevis • Extensor pollicus longus • Extensor indicis proprius | Sensory fibres to dorsal wrist capsule, no cutaneous | • Pain • Finger metacarpal extension weakness • Wrist drop |
Common peroneal nerve (L4–S2) | • Above knee • Fibula neck • Below knee | • Deep: Anterior compartment: Tibialis anterior, extensor Halluces longus, extensor Digitorum longus, Peroneus tertius. • Superficial: Lateral compartment: Peroneus brevis and longus | Lateral sural nerve (L2–3) upper lateral calf/knee; Superficial peroneal (L4–S1) calf and dorsum of foot—lateral border; Deep peroneal (L4/5) 1st webspace only | • Foot drop • TA, EHL, and extensor digitorum longus (EDL) weakness in varying degrees |
Q&A
- Which muscle of the thumb has a dual innervation?
The flexor pollicis brevis has a dual innervation by the median and ulnar nerves
- What are the symptoms of posterior interosseous neuropathy?
Finger extension weakness including the thumb with no wrist drop or sensory loss. The posterior interosseous nerve may be entrapped at the arcade of Frohse, which is a fibrous band that the nerve goes through when it dives into the supinator muscle
- What must be ruled out in a patient with wrist drop?
Lead poisoning