What is brachalgia?
It is important to make a distinction between neck pain and brachalgia, as the treatment is different, even though they may both be caused by similar conditions. Brachalgia implies pain in the arm due to irritation of one of the nerve roots that go to the arm. This pain usually radiates down the back or the front of the arm and extends below the elbow, often into the fingers. It is frequently associated with numbness or pins and needles and may also cause weakness in the arm. Neck pain may be referred to the shoulder, in much the same way as a heart attack can cause pain in the arm, but this should not be confused with true brachalgia.
What is a disc prolapse?
The disc is composed of two parts. The outer part, or annulus, is composed of many fibres that join the vertebrae together. In cross section this has a similar appearance to the rings of a tree trunk. In the middle is the nucleus, which is the soft part of the disc. This contains a large proportion of water and gradually dries out and shrinks with age, causing the disc space to narrow.
Small tears appear either between these layers or across layers. These can occur with minor injury or normal everyday life. If several of these small tears join together, or less commonly if there is a major injury causing a single large tear, the nucleus (central, soft part of the disc) may squeeze out through the tear. This is called a disc prolapse or herniation or “slipped disc”. In this situation, the disc prolapse (shown in black) may press on a nerve (red) and cause brachalgia.
If the pain persists you will usually have some Xrays. Plain Xrays are of little use and most often the first test will be a CT scan. This will usually show a disc prolapse if one is present (see below).
Occasionally you will need an MRI scan (like the CT but done with a strong magnet) and this usually needs to be ordered by a specialist. This can be very helpful if the disc is in the lower cervical spine as the shoulders tend to cause too much artefact on the CT at this level. The MRI will also show the spinal cord and may be necessary if there is any suggestion that this is being compressed in addition to a nerve root. The MRI below shows a large disc at C5/6 that is compressing the spinal cord.
Fortunately, the vast majority of disc prolapses get better with conservative treatment. The water is gradually absorbed and the disc fragment shrinks, relieving the pressure on the nerve. A few days of rest and then avoidance of excessive neck extension, work above shoulder height and lifting will be necessary. Regular analgesics and possibly an antiinflammatory will help. The severe pain will usually ease after a week or two and then gradually disappear over the next few weeks. Once over the acute phase it is worth seeing a physio to work on an exercise program to reduce the risk of recurrence.
What if it doesn’t get better?
If the pain is not improving as expected, other treatments will be necessary. These include other medications, steroid injections and surgery.
There are a variety of other medications that can be of value in brachalgia. Apart from painkillers, there are two types of drugs that can sometimes help, antidepressants and anticonvulsants. In smaller doses than for their primary use, they can have an effect on chronic pain and reduce the need for analgesics.
Injection of steroid into the epidural space (the space around the nerves in the spinal canal) can sometimes be very beneficial for sciatica but is not done in the neck because of the risk of damaging the spinal cord. Instead, it is often possible to do an xray-guided injection into the area around the affected nerve. It is done by a radiologist who will explain it to you beforehand. You will need to spend a few hours in hospital and should not drive yourself home. In most cases you will notice an improvement in your arm pain immediately from the local anaesthetic and the pain may then recur when this wears off. The steroid takes one to two weeks to take full effect.
There are some occasions where surgery to remove the prolapsed part of the disc is necessary. This is when the pain is so severe that it can no longer be controlled with analgesics (unusual), when there is significant weakness or numbness in the arm or when conservative treatment has been tried for six weeks with little or no benefit. The operation is sometimes done from the front of the neck and sometimes from behind, depending on just where the disc prolapse is. When done from in front, the whole disc is removed and the two adjacent vertebrae are fused together. When done from behind, a small amount of bone is drilled away and only the prolapsed part of the disc is removed. With either operation, the chances of relieving the arm pain are excellent but neck pain may persist. For further information see the Cervical Discectomy Information Guide.
Rarely, the disc prolapse can be large enough to compress the spinal cord rather than just one nerve root. It may then cause severe weakness in the arms and legs and paralysis of bladder and bowel function. This is an emergency and needs urgent surgical treatment.
Other causes of brachalgia
Brachalgia may also be caused by narrowing of the space that the nerve passes through as it leaves the spine (called the foramen). This can be caused by arthritis in the facet joints or narrowing of the disc space, but is usually a combination of both. The picture below shows a normal foramen and the arrows indicate the facet joint behind and the disc in front. As these degenerate they enlarge and narrow the foramen.
This CT scan shows how the enlarged facet joint narrows the foramen and compresses the nerve (blue arrow indicates normal foramen and red arrow shows narrowed foramen).
Foraminal narrowing like this will often be asymptomatic until something happens to aggravate it. This is usually extension of the neck (bending the head backwards). This narrows the foramen and squashes the nerve. This can be one episode of severe extension (eg a fall) or a prolonged episode of a lesser degree of extension (eg painting the ceiling, watching the fireworks, sleeping awkwardly etc). The nerve can then be swollen and irritable, causing severe arm pain and even weakness. In most cases this will settle over six weeks with analgesics just like a disc prolapse and it can also often respond to an injection of cortisone around the nerve. If this fails it is possible to surgically drill away some of the bone to enlarge the foramen, just like the operation for cervical disc prolapse done from the back of the neck.