Thoracic Spinal Pain
Definition
Thoracic spinal pain is pain perceived anywhere in the region bounded superiorly by a transverse line through the tip of the spinous process of T1, inferiorly by a transverse line through the tip of the spinous process of T12, and laterally by vertical lines tangential to the most lateral borders of the erector spinae muscles.
This area may be subdivided into upper, middle and lower thirds. Pain felt lateral to this area constitutes posterior chest wall pain and not thoracic spinal pain
Epidemiology
There are no formal population studies on the incidence or prevalence of thoracic spinal pain as an entity. Estimates from pain clinics suggests 16% as a presenting complaint and a prevalence of 12%. There are no data from general practice describing the incidence of thoracic spinal pain as a presenting complaint
The natural history is unknown.
For risk factors there is only one study among male infantry recruits which found that an increased lumbar lordosis was the only predictive factor.
Aetiology
The aetiology in most cases is unknown. The strongest evidence supports the zygapophysial joints, thoracic discs, interspinous ligaments, and potentially the costovertebral joints.
Somatic Referral from Another Site: Pain can be referred from cervical structures (zygapophysial joints, cervical muscles, cervical discs) to the thoracic spine. (see Cervical Pain Maps)
Uncommon Causes
Disc Protrusion: This condition is distinct from discogenic pain and should only really be considered in the presence of neurological signs. It is rare with 0.5-1.8% of all surgical discs. The M:F incidence is equal, and the peak prevalence is in the 4th to 6th decades. 75% occur below T8, with the peak being T11-12. Central protrusions are more common than lateral protrusions. The prevalence of asymptomatic disc bulging is as high as 37% using MRI.
Fracture: Osteoporotic fracture has a prevalence of 0.4-0.6%. The peak sites of T7-8, T11, and L1. Normal bone densitometry and radiographs are not completely reliable. Greater deformity is correlated with more pain. Fracture should be considered in those over the age of 60.
Infection: The pre-test probability is less than 0.01% but it may persist for a long time
Malignancy: Spinal metastases are reported as being most common in the thoracic spine (T4, T11), however they are still rare. The higher rate of thoracic involvement may be due to greater number of vertebrae. Study suggests pretest probability of 0.63% similar to lumbar data. The predictive power of clinical features not available but may be similar to the lumbar spine
Inflammatory Arthritis: It is unusual to present with just thoracic pain.
Clinical Features
Somatic Referred Pain
Just as somatic sources of cervical spine pain can be referred to the thoracic spine, there can be somatic referred pain from thoracic spine structures to the posterior and anterior chest wall and upper limbs.
The pain is deep, aching and poorly localised. The spread is 0.5 segments superior to 2.5 segments inferior, which can help predict the level. It doesn't radiate further than the posterior axillary line. It also hasn't been reproduced in the arm below T1. The lower thoracic segments may refer to the lumbar spine and gluteal region. The so-called "T4 syndrome" with arm pain is not corroborated.
Neurological Features
Central disc protrusion may cause spinal stenosis and compression with myelopathy. This can result in leg weakness, spasticity, ataxia, numbness, or bowel or bladder disturbance. Central disc herniation at T12-2 can cause conus medullaris syndrome which is a combination of both upper and lower motor neuron deficits.
Lateral disc protrusions may cause radicular pain and radiculopathy, for example lower quadrant pain with T12 nerve root irritation, which can mimic appendicitis or diverticulitis.
Investigations
In the presence of red flags, plain films and inflammatory markers are the first screening tests.
