Within the lumbar spine the nerve roots leave the spinal canal and join up with other nerve roots to form the lumbar and sacral plexus before continuing into the legs. These nerves carry sensory messages from the legs and also relay messages to the muscles within the legs to make them function. Some of these nerves also control the bladder and bowels.
Within the cervical spine the same thing occurs with nerve roots leaving the spine and then forming the brachial plexus on each side of the neck. From here the nerves pass to the arms carrying messages to the muscles within the arms and relaying sensation messages back.
Why Does Nerve Root Pain Occur?
Disorders of nerves can cause pain, numbness, increased sensitivity or weakness of muscles. The pain is often felt in the area of the body supplied by that nerve. It is common for the leg nerves and arm nerves to be affected and this can be caused by something pressing on the nerve within the spinal canal.
Leg Pain/ Sciatica
Lumbar nerve pain (often called ‘sciatica’) generally goes into the leg and extends below the knee. Back pain is usually felt between the lower ribs and the buttocks but may also continue into the leg but does not tend to go below the knee. Often there will be a combination of back and leg pains. In sciatica the leg pain tends to be worse than the back pain. Sciatica is usually caused by a disc prolapse (‘slipped disc’), see Lumbar Disc Prolapse, pressing on the lumbar nerve root but there are other causes, which include spinal stenosis or rare causes such as tumours.
‘Radicular pain’ is a term doctors use to describe pain when it is mainly from a single nerve root.
Leg pain may also be referred from the back for example due to facet joint arthritis. Generally this pain does not go below the knee and is improved by treating the underlying back pain.
Arm Pain/ Brachialgia
Brachial neuralgia (nerve pain in the arm) is very similar to sciatica but comes from the nerve roots within the cervical spine or neck. Again the most common cause is a cervical disc prolapse, but other causes include bony spurs called osteophytes, or rare causes such as tumours or infection. When the spinal cord is compressed this is known as myelopathy.