Brachial neuritis is a condition which causes pain and often neurological symptoms (including sensory problems and weakness) in the shoulder and arm. Unlike other causes of these symptoms it is not connected with an injury to the spine. Instead brachial neuritis is thought to be triggered by an immune system reaction. For this reason it is often precipitated by a period of stress to the body. Common examples of these causes include general anaesthetic as well as post viral illnesses.
Brachial neuritis has also been described as Parsonage Turner Syndrome, Brachial Neuropathy or Neuralgic Amyotrophy.
At its onset, brachial neuritis will most often be felt as an intense pain, often described as burning or toothache like without any obvious incident to cause the onset. The location of these acute pains varies according to the exact part of the brachial plexus affected but commonly the pain is felt radiating from the bottom of the neck to the outer aspect of the shoulder or towards the shoulder blade are. During this acute period of pain, patients and clinicians may both explain the symptoms away as a nerve root impingement in the neck and treatment will often be directed at this. Due to the intensity of pain during the initial weeks, individuals may not notice significant power loss or sensory symptoms at this time.
Following the initial acute symptoms patients may notice an ongoing, lower grade pain in a similar location. However, individuals may now notice some neurological symptoms. These may include some tingling, pins and needles or numbness in certain areas of the shoulder blade and shoulder area. In some cases these sensory symptoms may radiate to the arm. Weakness may be the most prominent complaint of individuals once the acute pain has settled. Depending on the extent of the condition as well as the exact nerve affected, the weakness will manifest in different ways. Often, the nerves affecting the scapular will be significantly denervated and this may often result in a condition known as “winging” of the scapular or an inability to rotate the scapula to lift the arm fully.
Brachial neuritis is a rare condition and studies have found it affects only one to two persons in one hundred thousand. Due to the uncommon nature of the condition and the fact that there is normally no obvious musculoskeletal injury, misdiagnosis is common in the early stages of the condition.
Cervical nerve root impingement or compression is often diagnosed in the early stages due to the familiarity of the symptoms. MRI scans are an appropriate initial diagnostic test which in the case of brachial neuritis will demonstrate no nerve root pressure. This exclusion will point the clinician to the diagnosis of possible brachial neuritis which can then be confirmed with more specialist tests.
Electromyography is a specialised test designed to measure muscles response to a stimulated nerve. It works by placing current through deep needles inserted in the muscles. If conducted in the initial phase of the condition this test can reliably diagnose brachial neuritis. If conducted at a later date there may or may not be a positive result.
In almost all cases, brachial neuritis will partially improve and the most important factor in improvements is a patient’s general health and age.
Unfortunately, in as much as twenty five per cent of cases individuals may suffer a further onset of brachial neuritis after they have recovered from their first episode.
Fortunately, due to inherent reserves within the way in which our muscles function, physiotherapy exercises can help to maximise any improvements made in the denervated nerves. Our nerves supply our muscles with power in thousands of blocks known as motor units. Without training, we are only able to recruit a small number of these motor units. However, with specialised exercises the number of motor units we are able to recruit dramatically increases. Thus, even if there is only partial recovery of a denervated nerve (leading to less motor units available), we are able to gain significant strength in weakened muscles by recruiting a greater percentage of the motor units available.
The exact physiotherapy programme administered or prescribed will be dependent on the severity of weakness and the exact muscles affected.
In the common circumstance of scapular winging, the programme will involve optimising the activity or strength of the serratus anterior muscle. Exercises may involve push up variations or reaching or punching exercises which load the muscle preferentially. The serratus anterior muscle is in fact often referred to as the “punching muscle”.
When the weakness involves denervation of the trapezius muscle then exercises will be tailored to improving the upward rotation of the scapular. In this circumstance exercises may involve vertical reaching tasks up a wall and in later stages may involve shoulder raises.