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  Nerve Pain       Entrapment Neuropathy      
 
 
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Introduction

Entrapment neuropathy (neuralgia, neuritis, pinched or trapped nerve) is caused by physical compression or irritation of major nerve trunks and peripheral nerves, producing distant nerve pain symptoms. Certain sites in the body are more likely to produce nerve entrapment because of anatomical vulnerability (design fault). In some cases compression of blood vessels may also occur producing signs of poor peripheral circulation.

Symptoms in the arms can be caused by the nerve compression at the following sites:-

  • Neck - Thoracic Outlet Syndrome (Costo-clavicular Syndrome, Cervical Rib Syndrome, Scalenus Anterior Syndrome).
  • Shoulder - Supraclavicular Neuritis.
  • Elbow - Ulnar Neuritis, Median Neuritis, Radial Neuritis.
  • Wrist - Carpal Tunnel Syndrome, Ulnar Neuritis.

Symptoms in the legs can be caused by nerve compression at the following sites:-

  • Hip - Piriformis Syndrome, Meralgia Paraesthetica.
  • Lower Leg - Compartment Syndrome.
  • Foot - Tarsal Tunnel Syndrome, Medial Plantar Neuritis, Digital Neuritis, Deep Peroneal Neuritis.

Treatment in the pain clinic consists of joint and muscle mobilisation (reducing muscle spasm and tissue swelling, increasing the amount of physical space for the trapped nerve), injections (reducing nerve inflammation), and surgical decompression (enlarging the available space for the trapped nerve when conservative treatments have failed).

Neck

Thoracic Outlet Syndrome is caused by compression of the brachial plexus (main nerve bundle to the arm) and brachial vessels (artery and vein) in the root of the neck. It can produce a mixture of nerve compression symptoms in the arm and shoulder including pain, pins and needles, numbness, weakness, and circulation changes (sweating, blueness, blotchiness).

  • Compression can occur in three separate places:-
    • Costo-clavicular Syndrome occurs when the space between the collar bone (clavicle) and first rib is narrowed. This can be due to a congenital abnormality, or due to poor posture with rounded shoulders e.g. large breasts with a poorly fitting bra.
    • Cervical Rib Syndrome occurs when there is an extra rib or tight fibrous band connecting the 7th cervical vertebra with the sternum. The brachial plexus then has to pass over this extra structure causing nerve and vessel compression when the arm and shoulder are placed in certain positions. Symptoms most often occur down the inner arm to the little finger due to compression of the 8th cervical and 1st thoracic parts of the plexus.
    • Scalenus Anterior Syndrome (much rarer) occurs when the brachial plexus and vessels are trapped between the anterior and middle scalene muscles (similar to piriformis syndrome in the buttock).
  • Clinical Findings
    • In slim patients the cervical rib can be felt just above the collar bone.
    • Some patients have symptoms when the armed is pulled downwards, and others when the arm is elevated. Relief of the symptoms occurs when the arm is moved in the opposite direction.
    • Adson's Test is used to look for suspected compression. The patient looks to the affected side taking a deep breath. The examiner lifts the arm away to the side to 90 degrees, and notes whether the radial pulse disappears. However there are many false positives, as the radial pulse may disappear in normal people as the head of the humerus (upper arm bone) compresses the brachial vessels when the arm is taken beyond 90 degrees.
    • Bruit - performing the tests above may cause compression of the subclavian artery, producing a bruit (murmur) audible with the stethoscope.
  • Investigations
    • X-rays of the chest and neck may reveal a bony cervical rib but not a tight fibrous band.
    • MRI scanning is the most useful investigation for revealing soft tissue anatomical abnormalities.
    • Subclavian angiography (dye test) may confirm subclavian vessel compression.
    • EMG (Electromyography) studies may confirm nerve dysfunction due to nerve compression.
  • Treatment
    • Spinal Manipulation to the lower neck and upper thoracic spine, and attention to posture can increase the space between the clavicle and the 1st rib in costo-cervical syndrome. Breast reduction and a properly fitting bra is advised for some women with over-large breasts.
    • Exercises to stretch the scalene muscles and related tight tissues can relief scalene muscle syndrome.
    • Surgery is sometimes required to remove a cervical rib, part of the 1st rib, or rarely the lower part of the scalene muscles. 
Shoulder

Suprascapular Neuritis - causes include compression of the suprascapular nerve at the back of the shoulder.

  • Anatomy
    • The suprascapular nerve is a branch of the brachial plexus (C5+C6). It is sensory to the shoulder joint, and motor to the infraspinatus and supraspinatus muscles.
    • The nerve is liable to injury as it travels through the suprascapular notch where it is spanned by the transverse ligament.
    • Types of injuries include overuse of the arm and excessive traction. 
  •  Clinical Findings
    • Neuralgic pain often radiates to the C5 and C6 dermatomes i.e. to the point of the shoulder and down to the outside aspect of the forearm.
    • In some cases the radiation of pain is vague.
    • Direct pressure over the nerve in the notch with the examining finger can reproduce the local and referred pain down the arm.
    • Prolonged entrapment of the nerve leads to visible wasting of the supraspinatus and infraspinatus muscles. 
  • Investigations
    • EMG can help to confirm the diagnosis.
  • Treatment
    • Rest can help reduce tissue swelling in the notch in the initial phases.
    • Suprascapular nerve block with local anaesthetic and steroid can also help reduce swelling and pain.
    • Surgery in resistant cases to release the transverse ligament.
Elbow

Ulnar Neuritis at the elbow is caused by compression or irritation of the ulnar nerve as it runs behind the elbow joint.

  • Anatomy
    • The nerve runs just inside the tip of the elbow (where your funny bone is) lying in a groove called the cubital canal and covered by the arcuate ligament.
    • Most cases of compression occur at the level of this ligament, but can also  occur between the two heads of flexor carpi ulnaris muscle just below the elbow joint.
  • Causes
    • Direct blow to the elbow.
    • Fractures of the elbow joint.
    • Repetitive injuries like flexing the elbow (overuse) or leaning on it.
    • Arthritis leading to joint deformity (rheumatoid).
  • Clinical Findings
    • Pain and tingling in the elbow and down the inside of the forearm to the little finger and half the ring finger (ulnar nerve territory). Clinical numbness on sensory testing.
    • Feeling the ulnar nerve in the groove or tapping it (positive Tinel's sign), may reproduce symptoms down the forearm and into the little finger.
    • Clumsiness of the hand due to weakness of the muscles supplied by the ulnar nerve. Clinical weakness on testing.
  • Investigations
    • EMG may help to differentiate between ulnar neuritis and other causes of C8 and T1 nerve irritation (cervical disc lesion, thoracic outlet syndrome),
  • Treatment
    • Avoid local repetitive trauma - consider using protective elbow pads.
    • Avoid elbow flexion in the short term (not for chronic cases).
    • Injections of LA / steroid may help either in the ulnar groove or between the two heads of flexor carpi ulnaris. Beware local nerve injury by the needle.
    • Surgery - moving the nerve out of the groove and into the front part of the elbow joint may help (Ulnar Transposition).

Median Neuritis at the elbow is much less common than ulnar neuritis. 

  • Anatomy
    • The median nerve crosses in front of the lower humerus (arm bone) to the front of the elbow joint, and then passes between the two heads of pronator teres to reach the forearm.
    • Some people have an anatomical abnormality at the elbow consisting of a spur called the Supracondylar Process, which forms a tunnel at the inside edge of the humerus bone covered by the Ligament of Struthers. The median nerve can be compressed in this tunnel.
    • In others the nerve is compressed between the two heads of pronator teres muscle below the level of the elbow joint.
  • Clinical Findings
    • Sensory symptoms involve the outer three and a half fingers. Clinical numbness on testing.
    • Weakness in the hand and forearm depends upon which level the compression occurs at involving forearm pronation, wrist flexion, and opposition of the thumb.
    • If pronator teres is the problem, then the symptoms will be aggravated by pronation of the forearm (elbow straight, palm down).
  • Investigations
    • EMG, X-rays and MRI scanning are the investigations of choice.
  • Treatment
    • Surgical decompression may be helpful.

Radial Neuritis at the elbow is much less common than ulnar neuritis.

  • Anatomy
    • The radial nerve at the elbow divides into two branches
    • The sensory (superficial) branch supplies the outer forearm, base of the thumb, and back of the hand.
    • The motor (deep) branch supplies the extensor muscles of the forearm, and is often known as the posterior interosseus nerve. It pierces the supinator muscle before entering the forearm.
  • Clinical Findings
    • Compression of the superficial branch causes pain and sensory symptoms in the forearm down to the base of the thumb. Numbness on clinical testing.
    • The deep branch can be injured by direct blows to the forearm, and be compressed by an acutely inflamed arthritic elbow joint, causing pain and weakness of the wrist and forearm.
    • Wasting of the extensor forearm muscles may be found in long standing cases, causing weakness of wrist and finger extension.
    • Supinator Syndrome occurs when the radial nerve is compressed by the supinator muscle during repeated pronation/supination movements of the forearm.
  • Investigations
    • EMG is the investigation of choice.
  • Treatment
    • Rest in acute cases. Splints, physiotherapy, occupational therapy, and modification of work place activities in chronic cases.
Wrist

Carpal Tunnel Syndrome is caused by compression of the median nerve at the level of the wrist.

  • Anatomy
    • The transverse carpal ligament forms the roof of the carpal tunnel, through which pass the flexor tendons and the median nerve.
    • The median nerve supplies sensation to the thumb, index, middle and half of the ring finger, as well as the motor supply to some of the muscles of the hand.
  • Causes - Anything that reduces the volume of the carpal tunnel can cause median nerve compression:-
    • Overuse
      1. Occupational stress - either repetitive wrist flexion or extension whilst gripping firmly, may cause inflammation (tenosynovitis) of the flexor tendon sheaths (outer tendon lining).
      2. Rheumatoid arthritis patients are more prone to tendon sheath inflammation especially when using a walking stick.
    • Previous injury
      1. Colles fracture
      2. Subluxation of the Lunate bone
      3. Osteoarthritis
      4. Wrist ganglion formation (out-pouching of the wrist joint capsule)
      5. Various metabolic conditions have been associated with it - gout, hypothyroidism, acromegaly, amyloidosis
  • Clinical Findings
    • Pain, tingling, and numbness in the outer three and a half fingers supplied by the nerve. The pain is most often felt at night, disturbing sleep, and relieved by dangling the arm out of bed. Some patients also describe pain radiating up to the forearm, arm, shoulder and neck.
    • Weakness / clumsiness of some of the muscles in the hand.
    • A proper examination of the neck, shoulder, and upper limb neurology is needed to exclude other causes of nerve entrapment in the neck and upper limb.
    • The pain can be reproduced by pressing over the carpal tunnel with the thumb for about 1 minute.
    • Tapping over the nerve (Tinel's sign) can also reproduce tingling of the affected fingers.
    • Positive Phalen's Test - place both hands together palm to palm, both wrists extended to 90 degrees, with the forearms totally horizontal, and the hands close to the chest - the affected hand will tingle after 1-2 minutes.
    • Positive Reverse Phalen's Test - do the same as above except with the hands back to back.
  • Investigations
    • EMG should help to localise the level of the nerve compression.
    • X-rays to assess the degree of osteoarthritis in the wrist.
    • Investigations to exclude the metabolic disorders mentioned above.
  •   Treatment
    • Rest with a neutral splint, worn only at night if necessary.
    • NSAIDs rarely help
    • Injections around the nerve as it lies in the carpal tunnel can be useful. Beware injecting directly into the nerve.
    • Gentle manipulation and mobilisation of the wrist joint in osteoarthritis can be useful. Particular attention should be paid to the range of wrist extension and suppleness of the flexor muscles.
    • Surgery to decompress the carpal tunnel by releasing the transverse ligament, when conservative methods have failed and there is definite weakness in the hand - Before Surgery - After Surgery
    • - BMJ Review - Carpal Tunnel Syndrome (253 KB)

Ulnar Neuritis is caused by compression of the ulnar nerve at the level of the wrist.

  • Anatomy
    • The ulnar nerve travels with the ulnar artery in the tunnel of Guyon, covered by the transverse carpal ligament. At the level of the wrist it divides into superficial sensory and deep motor branches.
    • The superficial sensory branch supplies the skin over the hypothenar eminence (soft part of the inside palm), the little finger, and half of the ring finger.
    • The motor branch supplies the muscles of the hypothenar eminence and other muscles of the fingers and thumb.
  • Causes
    • Trauma - Colles fracture, flexor tendonitis, acute blow to the open palm, occupational trauma.
    • Ganglion of the wrist joint may compress the nerve in the tunnel.
  • Clinical Findings
    • Pain, numbness and tingling in the ulnar fingers when the superficial branch is involved.
    • Weakness of the hypothenar muscles, interossei, and thumb adduction.
    • Tinel's sign positive (tapping) and symptoms also reproduced by firm pressure over the nerve for 1-2 minutes.
  • Treatment
    • As for Carpal Tunnel Syndrome above.
Hip

See Piriformis Syndrome

Meralgia Paraesthetica is caused by compression of the lateral femoral cutaneous nerve of thigh.

  • Anatomy
    • The lateral femoral cutaneous nerve is a branch of the lumbar plexus originating from the 2nd and 3rd lumbar nerve roots.
    • The nerve travels to the thigh by passing under or through the inguinal ligament in its own tunnel. At this point it sharply angulates and is therefore vulnerable to compression.
    • It is purely a  sensory nerve and supplies an area of skin on the outside of the mid to lower thigh.
  • Causes
    • Direct injury in the groin (trauma and hernia surgery).
    • Increased abdominal girth associated with obesity and pregnancy.
    • Repetitive hip flexion.
  • Clinical Findings
    • Pain, itching, tingling and numbness on the outside part of the mid to lower thigh.
    • Symptoms can be reproduced with direct pressure with a finger over the inguinal ligament, or by extending the hip joint backwards.
  • Investigations
    • EMG may be useful, but the diagnosis is usually made clinically.
  •  Treatment
    • Rest initially for acute symptoms (not for the chronic condition)
    • Weight loss, avoidance of tight clothing / belts around the waist.
    • Injections in the form of several nerve blocks using LA/ steroid mixtures in and around the nerve tunnel at the level of the inguinal ligament.
    • Surgery to decompress the nerve when all else fails.
Lower Leg

Compartment Syndromes occur after acute or chronic swelling in any of the four muscle compartments of the lower leg - anterior (front), posterior (back), medial (inner), and lateral (outer). Each compartment is surrounded by tough fibrous tissue called fascia which is relatively inelastic.

Acute compartment syndromes occur when there is a sudden critical rise in pressure within the compartment leading to loss of arterial blood flow, nerve damage and muscle death (necrosis due to oxygen starvation).

Chronic compartment syndromes occur due to smaller rises in pressure which are sufficient to cause pain, but which do not normally cause an acute syndrome.

Anterior Compartment Syndrome

  • Anatomy
    • The anterior compartment contains muscles which pull the toes and foot upwards towards you (tibialis anterior, extensor digitorum), and the deep peroneal nerve (sensory nerve to the skin between the first and second toes).
  • Causes
    • Unaccustomed running.
    • Tibial / fibular fractures.
    • Direct blow to the leg.
  • Clinical Findings
    • Pain in the front of the shin after exercise, which rapidly becomes severe.
    • The pain is worsened by having the toes pulled passively downwards, or by actively bringing the foot upwards towards you.
    • The skin at the front of the shin may be red and hot.
  • Treatment
    • An acute anterior compartment syndrome is a medical emergency. Unrelieved pressure in the compartment causes necrosis of the muscles and a permanent foot drop with numbness between the first and second toes. Urgent surgical fasciotomy is necessary to relieve the pressure in the compartment.
    • Patients with chronic anterior compartment syndrome develop pain on exercise which causes them to stop and rest. They are normal between attacks. Exercise modification and sometimes elective surgical fasciotomy are required.

Medial Compartment Syndrome

  • Anatomy
    • The medial compartment is deep in the leg and contains muscles which move the foot upwards and the toes downwards  away from you (tibialis posterior, flexor hallucis longus, flexor hallucis longus), and the posterior tibial nerve (sensory to the sole of the foot).
  • Causes
    • Overuse especially in athletes especially after running on a hard surface or a change in running shoe.
  • Clinical Findings
    • The medial compartment is the most commonly affected. It presents as pain and tenderness at the inside edge of the mid to lower shin bone (tibia), and is often known as "Shin Splints".
    • The pain starts at the beginning of a running session, and becomes worse if the exercise is continued.
    • There is often warmth and redness over the affected part of the leg.
    • The symptoms may be reproduced on examination by passively pushing the foot down or actively raising it against resistance.
  • Treatment
    • Rest and strapping to prevent excessive plantar flexion.
    • Stretching exercise for the medial compartment muscles
    • Injections may be useful if a local trigger point can be palpated (not usually in then acute phase).
    • Attention to running shoes and postural problems in the foot.
    • Surgery to release the tight fascial compartment.

Lateral Compartment Syndrome

  • Anatomy
    • The lateral compartment contains muscles which evert the ankle (turning your foot out), and the lateral popliteal nerve.
  • Causes
    • Acute unaccustomed exercise.
  • Clinical Findings
    • Fairly rare syndrome, but may occur several hours after exercise.
    • May present with pain in the outside shin, an inversion foot drop (foot turned in), and distal sensory changes.
  • Treatment
    • This is another medical emergency with urgent surgery (fasciotomy) required to prevent acute muscle necrosis and permanent nerve damage.

Posterior Compartment Syndrome

  • Anatomy
    • The posterior compartment contains powerful muscles which move the foot downwards away from you (plantar flexion) e.g. standing on tip toe. The main muscles are soleus, gastrocnemius and plantaris. They join together to form the Achilles tendon which attaches to the back of the heel.
  • Causes
    • Acute compartment syndrome can be caused by unaccustomed exercise.
    • Chronic compartment syndrome can occur after previous tibial fractures.
  • Clinical Findings
    • Severe calf pain after exercise with altered sensation in the sole of the foot, and weakness of plantar flexion.
    • Pain can be reproduced by stretching the calf muscles during passive dorsiflexion, and also during active plantar flexion.
  • Treatment
    • The acute syndrome requires urgent surgical fasciotomy to prevent muscle necrosis and permanent nerve damage.
Foot

Tarsal Tunnel Syndrome is similar to Carpal Tunnel Syndrome in the wrist, causing pain and numbness in the heel and toes.

  • Anatomy
    • The posterior tibial nerve runs just behind the inside ankle bone in a tunnel covered by the flexor retinaculum.
    • The tunnel also contains the tendons of muscles tibialis posterior, flexor digitorum longus and flexor hallucis longus.
    • The posterior tibial nerve divides in the tunnel to form the medial and lateral plantar nerves. The medial nerve supplies the inside heel skin and the inside three and a half toes. The lateral nerve supplies the outside one and a half toes.
  • Causes
    • Tenosynovitis of the tendons in the tarsal tunnel caused by overuse.
    • Trauma - falls on to the feet from a height.
    • Postural abnormalities of the foot e.g. forefoot pronation (flat footed).
    • Rheumatoid arthritis.
  • Clinical Findings
    • Burning pain, tingling and numbness in the sole of the foot and toes.
    • May initially come on after prolonged standing, but may be continuous in the later stages.
    • Sometimes pain radiates up the leg as well as into the foot.
    • There is tenderness over the tendons in the tarsal tunnel with a positive Tinel's sign (tapping).
    • There may be clinical numbness in the sole of the foot, and weakness of downward movements of the toes.
  • Treatment
    • Correct any deformities in the foot with orthotic devices.
    • Injection of LA/steroid into the tarsal tunnel from above may be useful.
    • Surgical decompression if all else fails.

Medial Plantar Neuritis

  • Anatomy - The medial plantar nerve is a branch of the posterior tibial nerve (see above). It may be trapped in the abductor hallucis muscle to the big toe.
  • Frequent causes include direct trauma, or a badly fitting arch support.
  • Symptoms are similar to tarsal tunnel syndrome, except with symptoms confined to the inner part of the sole of the foot.
  • Treatment includes orthotic assessment, LA/steroid injections, and surgical decompression.

Digital Neuritis

  • Anatomy - The digital nerves run between the long bones of the foot (metatarsals) to supply the toes.
  • They may become compressed at the level of the head of the metatarsal bone as they travel in a small canal. A small nerve swelling may develop called a Morton's Neuroma.
  • Symptoms include burning pain and tingling in the forefoot with shooting pain into the toes, usually made worse by walking or walking in high heels (excessive toe extension).
  • A tender spot may be located on examination between the heads of two adjacent metatarsal bones which reproduces the pain in the foot and toes. Grasping the forefoot and squeezing gently compresses the nerve/neuroma between the metatarsal heads reproducing symptoms in the toes.
  • Treatment includes orthotic support, avoidance of high heeled shoes, LA/steroid injections, mobilisation of the metatarsal bones, and surgical decompression and removal of the neuroma if present.

Deep Peroneal Neuritis

  • Anatomy - The deep peroneal nerve travels in the front of the ankle and enters the top of the foot by passing under a fibrous band called the extensor retinaculum. It goes on to supply sensation to an area of skin between the first and second toes, and the extensor hallucis longus muscle (moves big toe upwards).
  • It may be injured after direct ankle trauma, or by tightly fitting lace up shoes.
  • Symptoms include pain, 1st / 2nd toe numbness and tingling, and weakness of big toe dorsiflexion.
  • Treatment includes avoiding pressure over the front of the ankle, and LA/steroid injections.
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