What is Brachial Plexitis?
Brachial plexitis is a condition that starts with sudden shoulder pain, then progresses to weakness and a loss of feeling in the shoulder and upper arm. Several studies and reports have provided further information on this condition. Yet, the most critical findings were from a study by Parsonage and Turner in 1948, which involved 136 patients and provided an in-depth understanding of the condition’s history.
Since that report, the condition has been referred to by many different names, including Parsonage-Turner syndrome, neuralgic amyotrophy (painful muscle weakness), acute brachial neuropathy (sudden nerve disease in the arm), acute brachial plexitis, idiopathic brachial plexopathy (arm nerve disease of unknown cause), idiopathic brachial neuritis (arm nerve inflammation of unknown cause), paralytic brachial neuritis (paralysing arm nerve inflammation), and brachial radiculitis, among others.
What Causes Brachial Plexitis?
Brachial plexitis, a condition that causes pain, weakness, or loss of movement in your arm and shoulder, comes in two forms: one that happens for unknown reasons (idiopathic), and one that’s passed down in families (hereditary).
The exact cause of idiopathic brachial plexitis is unknown, but it’s often seen after a viral infection, upper respiratory tract infection, or recent vaccination. In fact, about 25% to 55% of people develop this condition after an infection, and 15% after a vaccination. Infectious causes might include a variety of viruses and bacteria, including smallpox, anaplasmosis, influenza, parvovirus B19, cytomegalovirus, HIV, typhoid fever, and Borrelia burgdorferi. Apart from infections, other factors like strenuous exercise, pregnancy, and complications after surgery could also lead to this condition.
As for the hereditary form, it’s a condition that can be inherited from parents and tends to strike repeatedly. Scientists think that this form happens due to a genetic mutation that makes less of a certain type of proteins known as septins.
There have also been reports linking brachial plexitis with COVID-19 infection and vaccination. Furthermore, there are instances where it has been observed as a sign of sickle cell disease and as a potential side effect of stem cell transplants.
Risk Factors and Frequency for Brachial Plexitis
Brachial plexitis, a condition that affects the nerves in the arm, is relatively rare, with about 1.64 cases happening per 100,000 people each year. It’s more commonly seen in males than in females, with different studies showing that for every female affected, there can be between 2 to 11.5 males. This condition can occur at any age, even as young as 3 months old, and as old as 75 years. However, it most often starts between the ages of 30 to 70 years.
Signs and Symptoms of Brachial Plexitis
People with this medical condition often have a history of a viral infection or a recent vaccination. The most common first sign is sudden, severe pain which happens in 95% of patients. This pain is usually constant, can change in intensity, and can get worse if you move your shoulder or arm. Resting your shoulder and bending your elbow can provide some relief. This pain can last from 2 to 3 hours and can even last more than 8 weeks.
The pain felt by patients can be described in different ways:
- Shoulder pain, possibly extending to the upper arm (39.7%)
- Neck pain, spreading down the arms (35.4%)
- Pain in the back of the chest wall, spreading to the arm, front of the chest wall, or both (18.8%)
- Pain following the path of the lower brachial plexus (6.1%)
After the pain starts, patients often feel weak. This weakness can happen suddenly for 80% of people and can occur at the same time as the pain or a little bit after. About 50% of people will feel weak in the shoulder, and around 10% have weakness in a single peripheral nerve. There are also some cases where patients suffer from diaphragmatic paralysis due to the neuropathy of the unilateral or bilateral phrenic nerve. It generally affects one side of the body (66% of cases) rather than both sides (34%). Among those who experienced it on one side, 54% had it on the right side. In about 20% of cases, a winged scapula can be observed.
Sensory issues were reported in 78% of cases, with paresthesias – a sensation of prickling, tingling, or creeping on the skin – reported in 35%. They usually affect the upper arm or the radial aspect of the forearm. Additional, less common symptoms include autonomic dysfunction, craniofacial abnormalities, and unusual skin folds.
Testing for Brachial Plexitis
While there isn’t a direct laboratory test that can diagnose brachial plexitis, a condition affecting the network of nerves near the neck and shoulder, other techniques and studies can offer vital evidence towards this diagnosis. These techniques include shoulder MRI scans, electromyography, and nerve conduction studies.
An MRI scan of the shoulder could show changes in the body’s tissues (referred to as ‘T2 signal hyperintensities’) during the early stretch of the illness. These changes happen due to swelling from nerve damage. As the disease progresses or becomes chronic, these T2 signals could remain, and new ‘T1 linear hyperintensities’ may appear due to fat buildup in the affected muscles. Although a regular MRI of the brachial plexus (the nerve network being affected) might not pick up the small changes related to brachial plexitis, a specialized MRI called magnetic resonance neurography could show thickening and abnormally intense signals during the initial phase of the illness, which might persist as the disease evolves.
Electromyography, which assesses the health of muscles and the nerves that control them, is vital for evaluating nerve damage in the brachial plexus. However, it should be conducted about three weeks after the symptoms first appear for results to be significant. Findings from electromyography might indicate acute denervation, which is a sign of muscle or nerve damage. If the test is done further into the disease progression (about three to four months), it might indicate chronic denervation and early signs of nerve regrowth. Nerve conduction studies, which evaluate the speed of conduction of electrical impulses through a nerve, could also help in the process. While usually normal in brachial plexitis, they might show blocks in the conduction pathway located closer to the spinal cord.
Importantly, brachial plexitis can only be confirmed once other possible conditions have been ruled out. Therefore, these tests primarily help to exclude the possibility of other conditions rather than directly confirming brachial plexitis.
Treatment Options for Brachial Plexitis
Brachial plexitis is usually treated using a conservative approach, which primarily focuses on easing pain (analgesia) and physiotherapy rehabilitation. The pain can be managed effectively using non-steroidal anti-inflammatory drugs. Some research suggests using corticosteroids early in the disease’s progression could reduce pain and the time it takes to recover from the weakness, but the significance of this is still not fully understood.
Physiotherapy rehabilitation plays a vital role in reducing pain and weakness and helps regain muscle strength and function. This therapy could include methods like kinesiotherapy, which involves movement and exercise; transcutaneous electrical nerve stimulation, which uses electrical signals to relieve pain; deep dermal therapy, that works on the deeper layers of the skin; cryotherapy, which uses extreme cold; and functional electric stimulation that helps regain muscle function.
What else can Brachial Plexitis be?
When diagnosing brachial plexitis, which is an inflammation of a bundle of nerves in the shoulder, doctors have to consider a wide range of possible causes. These can include but are not limited to:
- Acute poliomyelitis, a viral infection affecting the nerves
- Amyotrophic lateral sclerosis, a neurodegenerative disease
- Brachial plexus tumor
- Cervical disc disease
- Cervical lesions
- Mononeuritis multiplex, a nerve disorder
- Neoplastic infiltration of the brachial tube, a type of nerve disease
- Non-traumatic compressive nerve injuries, injuries occurring due to pressure on the nerves
- Traction injury to the brachial plexus
- Traumatic compressive nerve injury
Identifying brachial plexitis among these possible causes involves very detailed patient history, thorough medical examinations, and the right tests. This thorough evaluation is essential to accurately diagnosing and treating the condition.
What to expect with Brachial Plexitis
The outlook for people with brachial plexitis, an inflammation of the nerves in the arm, used to be considered quite good. However, a study showed that of 246 people with this condition who were followed for three or more years, about two-thirds still experienced pain and weakness. Severe tiredness may also be a symptom for about one third of people with this condition. Most people with brachial plexitis that occurs for no known reason (idiopathic) don’t experience a relapse of symptoms.
However, another study that followed 84 patients found that only 4 of them (about 5%) saw their pain and weakness return. A different study found a higher rate of recurrence, with about 26% of cases experiencing a return of symptoms over a six-year period. Still, this means that more than 70% of people with brachial plexitis do not see their condition return.
If a person experiences several recurrences of brachial plexitis, doctors might consider the possibility of a hereditary condition called neuralgic amyotrophy, which causes repeated episodes of severe pain and muscle weakness.
