The nerves supplying a major part of our body come from the spinal cord, which lies inside a bony structure along the back known as the vertebral column (commonly known as the backbone). The spinal nerves leave the confines of the vertebral column through small spaces between the vertebrae (the bones that make up the vertebral column). In some individuals, the nerves coming out of the vertebral column may get compressed (or pinched) by the surrounding structures.
Compression of the spinal nerves usually cause symptoms such as pain, tingling sensations or numbness. These symptoms are mostly localized to the chest, arms, abdomen or the pelvis. The compression of spinal nerves can occur in any part of the vertebral column: cervical (neck), thoracic (upper back) or lumbar (lower back).
Compression of thoracic nerves is technically known as thoracic radiculopathy. Thoracic nerve compression is less common than nerve compression in the cervical (neck) or lumbar (lower back) regions. This is because the thoracic vertebrae are less mobile than the cervical and the lumbar vertebrae. However, when these nerves are compressed the effects are mainly seen on the arms and chest.
Read more on upper arm pain.
Anatomy of Thoracic Spine
The thoracic part of the vertebral column is made up of twelve thoracic vertebrae. These thoracic vertebrae are separated from each other by cartilaginous discs known as the intervertebral discs. These intervertebral discs act as shock-absorbing cushions, and also facilitate the movement between the vertebrae that allow various bending actions of the backbone. Spinal nerves that emanate from the spinal cord at the thoracic level traverse the spaces between the thoracic vertebrae. Compression of these thoracic nerves is a relatively rare occurrence, because thoracic vertebrae do not have much involvement in movements like bending and flexing. However, pinching or compression of thoracic nerves do occur in some instances.
Causes of Pinched Thoracic Nerve
The following are some of the causes of thoracic nerve compression.
Herniated thoracic intervertebral disc
A common cause of spinal nerve compression in any part of the vertebral column is intervertebral disc herniation. Herniation of intervertebral disc refers to a bulging of the intervertebral disc that is normally sandwiched between the vertebrae. This results in a protrusion of the inner disc contents, which can compress the spinal nerve in the surrounding region. Herniated intervertebral discs can cause nerve compression both within the vertebral canal and at locations where the spinal nerves exit the vertebral canal.
Degenerative thoracic intervertebral discs
The intervertebral discs have a soft gelatinous central part that is surrounded by a hard outer covering. The hard outer covering undergoes a gradual degeneration with age due to constant wear and tear caused by daily movements of the spine. Degeneration of the outer hard shell allows the internal soft portion of the intervertebral disc to protrude out. This may put pressure on the nearby spinal nerves. Thoracic nerve compression due to degenerative thoracic intervertebral discs is a rare occurrence. When it does happen, the degeneration of thoracic discs may take years to develop.
Trauma to the thoracic region of the back
Herniation of intervertebral discs may also happen due to trauma. A sudden traumatic force to the back of the thoracic region may cause herniation of thoracic intervertebral discs, and lead to compression of the thoracic nerves. This can happen in road accidents or contact sports.
Spinal stenosis refers to a narrowing of the spinal canal. This is usually caused by degenerative changes caused by normal wear and tear, and is usually seen in old age. However, spinal stenosis is not common in the thoracic region.
Long thoracic nerve compression
The long thoracic nerve may get compressed during activities such as carrying heavy back packs for a long period of time. Heavy labor may also stretch this nerve. Long thoracic nerve compression does not involve much pain. However, it impairs the movement of the arms over the head. Winging of shoulder blade (technically known as scapula) may also occur.
Usually, the condition resolves on its own if activities that result in nerve compression are avoided for a period of 6 to 12 months. For example, carrying heavy backpacks on shoulders should be avoided. Exercises to strengthen the shoulder and back muscles may also help. If all else fails, surgery may be considered as the last treatment option.
Thoracic Outlet Syndrome
Compression of thoracic nerves may also occur in the thoracic outlet, which refers to the space between the first rib and the collar bone (also known as the clavicle). This condition is also referred to as neurogenic thoracic outlet syndrome. The thoracic outlet provides a passage for nerves of the brachial plexus. The nerves of the brachial plexus supply the shoulders, arms and hands.
Muscular movements and sensations from these body parts depend on the proper functioning of the nerves in the brachial plexus. When these nerves get compressed, a variety of symptoms may appear in the body regions that are supplied by the compressed nerves. These symptoms may include pain and numbness in the neck and the shoulders, numbness and tingling sensations in the fingers on the affected side, pain in the hand and arm on the affected side, and muscular weakness in the arm that manifests as a weakening of the hand grip.
Thoracic outlet syndrome can be caused by multiple factors. Trauma caused by vehicle accidents, falls, repetitive motion injuries, sports activities, and poor posture may contribute to the development of thoracic outlet syndrome. In some cases, the presence of an extra cervical rib (caused by a congenital defect) may also lead to compression of nerves of the brachial plexus and result in thoracic outlet syndrome. In some cases, no cause may be identified (a situation termed as idiopathic).
Diagnosis and Treatment
Diagnosis of thoracic outlet syndrome depends on the patient’s case history, physical examination, x-ray imaging, MRI scan, electromyography, and nerve conduction velocity tests. Treatment of thoracic outlet syndrome is mostly conservative, and may include muscle strengthening exercises for the shoulders, relaxation techniques, and exercises to help maintain good posture.
If these measures do not provide relief or if the condition is particularly severe with persistent symptoms, then medications (such as ibuprofen) may be given to relieve pain. Muscle relaxant medications may also be helpful in some cases. Surgery remains the last option because surgical procedures might further injure the brachial plexus. However, it is an option if other treatment measures prove ineffective.