What is Axillary Nerve Injury?
Injuries to the peripheral nerve, such as axillary nerve damage, can range from mild pain to serious muscle weakness. Usually, this type of injury can be managed without surgery, but in some cases, surgical intervention may be necessary. If these injuries are not diagnosed and treated properly, they can cause permanent disability and significantly affect a person’s quality of life. Axillary nerve damage, resulting in shoulder weakness and loss of sensation, is somewhat rare but should still be considered during diagnoses.
Let’s look at the anatomical journey of the axillary nerve. It branches off from the main nerve structure in the arm, running behind the main blood vessel in the arm, the axillary artery. It then travels below the shoulder joint and travels alongside the blood vessel that circles the upper arm bone. After that, it splits into two parts: one part goes to the front and middle of the deltoid muscle of the shoulder, and the other part goes to the back of the deltoid and a small muscle near the shoulder blade called the teres minor. Eventually, it ends up as a nerve that provides sensation to the side of the shoulder. The axillary nerve plays a key role in both arms and is primarily linked with the C5 nerve but also a little with the C6 nerve.
The axillary nerve powers two main muscles in our arms: the deltoid and the teres minor. The deltoid helps with different shoulder movements. The main duty of the middle part of the deltoid muscle is to lift the arm sideways. The part of the deltoid muscle near the front helps to flex the shoulder and twist it inward, while the part near the back helps to extend the shoulder and twist it outward. The teres minor helps to externally rotate the arm. Both the deltoid and teres minor provide stability to the shoulder joint, with the teres minor playing a more significant role. Additionally, the axillary nerve also carries sensation from the side of the shoulder. Finally, it’s worth noting that while some studies suggest that the axillary nerve supplies the long head of the tricep muscle, recent analysis indicates this may not be the case.
What Causes Axillary Nerve Injury?
Damage to the axillary nerve can happen alongside other nerve injuries in the area of the body where the arm and neck join. These nerve problems are often caused by physical injuries, overstretching the nerves, a certain condition affecting the space at the back of the shoulder, or an inflammation of the nerves (also known as Parsonage-Turner syndrome).
It’s common for this type of nerve injury to occur in young people due to the shoulder joint being pushed forward or stretched too far out to the side.
Risk Factors and Frequency for Axillary Nerve Injury
An Axillary nerve mononeuropathy is a somewhat rare condition. It often happens along with injuries to the brachial plexus, which is a group of nerves that run from the neck to the arm. This type of injury is not very common, but when brachial plexus injuries do occur, an axillary nerve injury happens around 0.3 to 6% of the time. Interestingly, during shoulder surgeries, this kind of injury jumps to 6 to 10% of all brachial plexus injuries.
Recent studies have indicated that the risk of this kind of nerve damage goes up with age, especially in cases of glenohumeral dislocation, which is a displacement of the shoulder joint. It was found that around 65% of people over 40 who had this issue were diagnosed with an axillary nerve injury via an examination called electromyography – or EMG for short.
Another condition called brachial neuritis, which involves inflammation of these same nerves, is seen in about 1 to 3 people in 100,000 every year. Interestingly, women seem to be more likely to get this condition than men.
Signs and Symptoms of Axillary Nerve Injury
When we talk about the main symptoms of this condition, the first thing to mention is a feeling of weakness when lifting the arm to the side, with or without numbness in the shoulder area. At times, patients may also display weakness when trying to rotate the shoulder outward, but this isn’t always noticeable due to the work of a particular muscle, the infraspinatus. If the patient has had a dislocation or fracture, there will be clear signs of injury present during a physical examination. This weakness in lifting or rotating the arm may particularly affect two muscles, the deltoid and teres minor.
However, it’s important to remember that not all patients will report muscle weakness or numbness, especially if they’re experiencing acute (sharp and severe) pain and have a limited range of movement. Some patients may develop what’s known as a compressive neuropathy following a non-penetrating injury to the deltoid muscle. In other cases, patients may come in with localized pain followed by a condition known as brachial neuritis. Patients who have a condition called quadrilateral space syndrome (QSS) usually show vascular symptoms like bluish or pale skin color change in the upper extremity and small blood spots, in addition to nerve-related symptoms.
Testing for Axillary Nerve Injury
For a correct medical procedure, it is important to collect comprehensive information about a patient’s history. This should include the start time of symptoms, the factors that ease or worsen them, the nature of these symptoms, whether they spread to other areas, the intensity of pain (if there is any), and when they occur. The patient should be asked specifically about issues like injuries, localized weakness, numbness and tingling, bluish skin, limitations in movement, and pain.
A physical check-up should begin with looking at the upper body area to check if there are any signs of injury. The doctor should then touch the neck and upper body area on the same side to assess tenderness and muscle tightness, followed by checking the range of movement. The doctor should focus on the axillary nerve and shoulder while also checking the spinal accessory, suprascapular, long thoracic, musculocutaneous, and radial nerves.[2] Special tests exist that specifically check the deltoid and teres minor muscles and they will be important if there isn’t any injury, muscle strain, or tendinitis. Some of these tests are the swallow-tail, deltoid extension lag, and Bertelli which assess the weakness in the deltoid muscle.[12][13] The function of the teres minor muscle is evaluated using the external rotation lag, drop arm, and Patte tests.[14]
Imaging tests such as X-rays of the shoulder can help identify fractures after a traumatic event. An MRI of the shoulder should be conducted if a nerve condition caused by compression or inflammation is suspected or in cases where a long-lasting nerve condition has caused muscle to waste away. The most reliable method for confirming the diagnosis is EMG. An EMG can also be helpful in establishing a patient’s initial state which can help in assessing recovery.[2]
Treatment Options for Axillary Nerve Injury
Injuries to the axillary nerve, which is located in the shoulder, can usually be treated non-surgically, but surgery may be required in some cases. If the injury is not caused by trauma, the patient should undergo a type of test called an EMG within a month, and start physical therapy. In cases where the axillary nerve is injured due to a traumatic shoulder incident, many patients can recover without surgery, but there’s a risk of permanent paralysis. However, when the shoulder injury is addressed and the shoulder joint positioned back in place, surgery is often not required. The treated shoulder is then kept immobile for 4-6 weeks in younger patients or 7-10 days in older ones, followed by comprehensive rehabilitation to restore muscle strength and shoulder flexibility.
Surgery may be considered in cases of closed trauma, which is sometimes a type of injury in which the skin is not broken, if the EMG test shows no improvement after three months. However, immediate surgical management may be required for acute nerve lesions. Possible surgical procedures include neurorrhaphy, neurolysis, and nerve grafting. In patients with long-term muscle wasting, muscle transfer might be considered as a treatment option.
For patients with neuropraxia, a less severe type of nerve injury, full recovery is expected over a period of 6-12 months. The muscle weakness associated with this condition typically resolves itself without any specific treatment. For those with axonotmesis, another type of nerve damage, the recovery rates are around 70% to 80% and recovery often takes several months. These patients should be monitored over time with repeated EMG tests to check for nerve regeneration. If there are no signs of recovery by 6-9 months, surgical exploration may be considered. For those with neurotmesis, the most severe form of nerve injury, recovery is not possible without surgical intervention.
What else can Axillary Nerve Injury be?
When a doctor is trying to diagnose a problem with the axillary nerve, the nerve that gives sensation to the shoulder, they also need to consider these possible conditions that might show similar symptoms:
- Cervical radiculopathy (condition affecting the nerve roots in the neck)
- Thoracic outlet syndrome (condition affecting the nerves between the collarbone and first rib)
- Rotator cuff tear (injury to the shoulder)
- Brachial plexopathy (damage to the brachial plexus, a network of nerves in the spine that control the shoulder, arm, and hand)
- Quadrilateral space syndrome (compression of the axillary nerve in the shoulder)
- Brachial neuritis (inflammation of the brachial plexus)
- Glenohumeral fracture/dislocation (breaking or dislocation of the shoulder joint)
- Subacromial impingement syndrome (pain due to irritation of the tissues of the shoulder blade)
- Herpes zoster (also known as shingles, a viral disease causing painful skin rashes)
The doctor needs to perform the appropriate tests and procedures to identify the correct cause.
What to expect with Axillary Nerve Injury
Most cases of axillary nerve injury, which usually occur from a dislocation of the shoulder joint, are mild and recovery often happens within seven months. According to a comprehensive review, 85% of patients who received nerve graft surgeries and 79% of those who had nerve transfer procedures achieved significant muscle strength (rated 4/5 or more) within one and a half to two years after the operation.
Possible Complications When Diagnosed with Axillary Nerve Injury
When the axillary nerve, which runs through the armpit (also known as the axillary region), is damaged for a long time, it can lead to certain lasting problems. These include a constant numb feeling in the outer part of the shoulder, shrinkage of the deltoid and teres minor muscles (these are muscles in your shoulder and back), and possible long-term nerve pain.
Recovery from Axillary Nerve Injury
Frizziero and his team created a two-month recovery plan for those suffering from axillary nerve damage. This plan is split into two stages. The first stage concentrates on recovering shoulder blade movement, shoulder joint stability, and enhancing the strength of the deltoid muscle – a large muscle in your upper arm. The second stage aims to get you back to normal functioning with a special focus on movement control, posture, and your body’s sense of position in space.
Preventing Axillary Nerve Injury
The axillary nerve, found in the shoulder area, is the nerve most often damaged when the shoulder is dislocated. If the axillary nerve is slightly damaged, it generally heals on its own within 3 months. However, if the injury to the axillary nerve is severe, surgery may be required for treatment. It’s also worth noting that athletes who take part in contact sports are at a higher risk. This type of injury can happen if the nerve gets squeezed or damaged during physical trauma.
