The Ultimate Guide to Radial Nerve Entrapment

Written by Giovanni Bruno

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What is radial nerve entrapment?

Radial nerve entrapment is a pathology characterized by the mechanical compression of the radial nerve as it passes through the Radial Tunnel; for this reason radial nerve entrapment can also be called “Radial Tunnel Syndrome”. The radial tunnel is an anatomical area defined by the radial head to the inferior border of the supinator muscle. The boundaries are formed by the supinator, extensor carpi radialis longus, extensor carpi radialis brevis, and brachioradialis muscles.

The radial nerve is one of the main nerves that provides sensory and motor function to the back of the arm and back of the forearm. Allowing us to move our arm, wrist and hand. The radial nerve originates from the posterior cord of the brachial plexus and contains nerve fibers from nerve roots C5-T1. (The brachial plexus is the main nerve network that supplies the skin and muscles of the upper extremity).

The radial nerve divides into the superficial radial (near the skin surface) and posterior interosseous nerves (at the back) at the level of the lower forearm. The posterior interosseous nerve runs along the radius before reaching the supinator muscle, a common site of entrapment. The radial nerve innervates the triceps muscle, the extensor muscles of the wrist, fingers and thumb. It also controls the sensation control of the hand. The nerve itself is divided into different branches, which represent the different sites of potential neurological compression. The most affected site is the posterior interosseous nerve at the level of the proximal forearm.

Radial nerve compression can occur in 3 different areas of the arm:

  • The axila (the armpit)
  • Spiral groove (located in the middle portion of the humerus)
  • Forearm (at the supinator muscle)

The most common site of compression is at the arcade of Frohse.This is a fibrous arch at the lower edge of the supinator muscle.

What are the symptoms of radial nerve entrapment?

The symptoms of radial nerve entrapment change according to the site of compression, but typically you may feel:

  • Numbness and tingling sensation from the back of your arm (triceps area) down to the fingers.
  • Issues or inability in extending your arm and your fingers.
  • Difficulty in making pinching or grasping movements.
  • Wrist drop – this is when you cannot lift your wrist.
  • Pain in the elbow area.

Radial nerve entrapment has some common manifestations with “Tennis Elbow Syndrome” because the only symptom could be a decreasing in grip strength or a subtle fall in forearm movement performance. Other syndromes which the Radial Tunnel Syndrome can mismatch with are: Posterior Interosseous Nerve Syndrome (PIN) and De Quervain’s Syndrome.

An accurate differential diagnosis must be done to exclude one syndrome to another, however pain during the middle finger extension is considered a distinctive sign for radial tunnel syndrome rather than just pain during forearm supination.

Determining the exact location of the pain in the forearm, is the primary step in diagnosing Radial Tunnel syndrome.

What are the causes of radial nerve entrapment?

The main causes of radial nerve entrapment are typically related to a secondary nerve injury due to compression, traction, direct trauma or overuse movements (Benjamin B, et al 2020). Radial nerve entrapment is more prevalent in women typically around the age of 30 to 50 years old.

The most common causes include:

  • Fracture of the humerus.
  • Awkward arm positions assumed during sleep.
  • Falling or direct trauma to the arm.
  • Continued pressure onto the wrist.
  • Sports and work accidents.
  • Some systemic conditions such as kidney diseases and diabetes can cause inflammation and fluid retention leading to a mechanical compression on the radial nerve.

How is radial nerve entrapment diagnosed?

The diagnosis of radial nerve entrapment is performed through physical orthopedic testing and imaging. If you think you’ve injured your radial nerve seek advice from your doctor or local osteopath or physiotherapist. Your healthcare professional will ask you about your symptoms and your clinical history trying to pinpoint the cause of injury.

During the physical examination, you will be asked to move your wrist, arm, and hand. The quantity and quality of movement will be compared to your unaffected arm. An assessment of the power and integrity of the nerves in your upper extremity will also be performed. The healthcare professional will check for any weakness or reduction in muscle tone.

Orthopedic tests will then be carried out. The most commonly used tests for radial tunnel assessment are: resisted forearm supination and resisted middle finger extension. The tests are considered positive if they cause pain.

Depending on the severity and presentation of your symptoms, the healthcare professional may refer you for further examinations. These may include blood tests to exclude any vitamin deficiency, kidney issues or changing in thyroid function. These tests are useful to check for any signs of other conditions that can cause damage to your nerves, such as diabetes or liver disease.

Your doctor may also refer you for a CT scan or an MRI to look for diseases within your head, neck or in the shoulders area. Typically issues in those areas may cause pressure on your radial nerve.

Among the other diagnostic imaging that your GP can prescribe there is also the electromyography (EMG) and nerve conduction test. The purpose of these tests are to measure the quality of your nerve impulses and show whether there is damage to the radial nerve.

What are the treatment options for radial nerve entrapment?

Initially it is advised to avoid muscular activities that aggravate your symptoms. Specifically avoiding any forceful, repetitive movements of extension and supination of the wrist and fingers.

As a first line of treatment, your doctor may prescribe anti-inflammatory medications, anesthetic creams and in more severe cases corticosteroid injection may be deemed necessary.

Some healthcare providers can offer you transcutaneous electrical nerve stimulation (TENS) to treat your radial nerve. This therapy involves placing several adhesive electrodes on the pain site. The electrodes deliver gentle electrical impulses to the affected area which may help relieve muscle tension and reduce pain.

You may be suggested by your healthcare practitioner to wear a splint to support your wrist or to do stretching exercises to restore muscle flexibility and mobility.

Physical therapy including osteopathy and physiotherapy can be used in the treatment of radial nerve entrapment. The aim of these therapies are to restore muscle flexibility, joint mobility and reduce the mechanical compression on the radial nerve. Both therapies will aim to reduce the muscle tension around the wrist, forearm and arm. An osteopath will treat your entire body looking not just at your forearm, but also at your posture to make sure that nothing will interfere with your radial nerve. A physiotherapist will aim to improve the sliding of your tendons and your radial nerve prescribing you exercises and giving you advice on how to adjust your daily habits.

As a last option your GP may suggest a surgical intervention to decompress the radial nerve. Surgery is normally recommended when conservative options have failed over a period of 3 months, and in severe cases where the wrist becomes extremely weak and extending the fingers is difficult. The surgical treatment is characterized by the releasing of any possible site of nerve entrapment. Surgery is likely to reduce your symptoms or make them disappear entirely. After the surgery you referral to a physical therapist is most likely in order to restore mobility and function of the muscles in the upper extremity.

How long does radial nerve entrapment last?

How long you will suffer with radial tunnel syndrome depends on the severity of your clinical symptoms. With conservative treatments you should be able to feel some improvements within 10-12 weeks.

With surgery, the recovery process is longer and can take up to 6 – 8 months. This is due to rehabilitation time after the operation. Sometimes this can take longer due to the risk of post surgical complications such as infection, pain, incomplete recovery of function and scar tissue development.

How can I prevent radial nerve entrapment?

Not all causes of radial nerve entrapment can be avoided. However there are a few things that can be done which may reduce your risk:

  • Avoid repetitive arm and wrist movements or putting prolonged pressure on your wrist and your forearm.
  • Stretch your wrist and arms (such as 2-3 sessions per week). This could help improve your muscle flexibility and mobility.
  • When working, take breaks every couple of hours and switch between tasks that require different movements.
  • Working in a cold environment may increase stiffness in your joints so if you’re working outdoors make sure to wear gloves to protect your fingers,hands and wrists.
  • Using a hot water bottle or a heat patch after daily activities may help in reducing muscle tension and joint stiffness.

What are the best exercises for radial nerve entrapment*?

Wrist extensor stretch. Stretch your arm out in front of you, point your palm facing towards you and your fingers pointing down. Pull the hand towards your body until you start to feel a stretch. Keep the elbow extended but not locked. Hold the stretch for 15 seconds and repeat up to 7 times.

Radial nerve stretch. In a standing position, with your affected arm and hand reach backwards slightly with your palm up and your arm internally rotated. Bend your head towards the opposite side of your arm (if your affected arm is the right, bend your head to the left towards the left shoulder) . Hold the position for 10 seconds and relax. If you feel any tingling or numbness reduce the intensity of the stretch or stop the exercise all together.

Wrist extensors muscles strengthening exercise. This exercise can be performed with a resistance band or a dumbbell (make sure to use the right weight for you). Rest your forearm on your knee, or the table, and place your foot on one end of the band (if you’re using it). Wrap the other end around your hand. Place your wrist in a flexed position (your palm is pointing down). Start extending your wrist (bringing the back of your hand towards your forearm). Make sure to keep the forearm still and in a neutral position. Slowly come back to the starting position and repeat 12 times.

It is recommended to get the OK from your osteopath, physical therapist or GP before trying out any of these exercises.

References

Buchanan, B., Maini, K. and Varacallo, M. Radial Nerve Entrapment. Stat Pearls. 2021

NHS Website

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