The author: Professor Yasser Metwally
INTRODUCTION
March 17, 2010 — Thoracic disc disease and herniation is a common etiology for thoracic radiculopathy (Fig. 1). Symptomatic cases of thoracic disc herniation have been reported at almost all thoracic levels [9]. As in other spinal regions, MR imaging has all but replaced CT and myelography in the routine evaluation of thoracic disc disease. The lower thoracic spine (T8–T12 levels) is the most frequent site of occurrence, with the T11–T12 interspace accounting for 26–50% of all thoracic herniations [2–4]. Degeneration is favored as the prevailing cause for thoracic disc herniation, and the lower thoracic segments are most at risk because of the increased motion present at these levels [1]. Despite this degenerative etiology, thoracic disc disease is involved in only 0.15–4% of symptomatic disc herniations of the spine, and they represent <2% of all spinal disc surgeries performed [5,6]. The incidence of thoracic disc herniation is equal between men and women, and the age of onset is generally between the third and sixth decades of life [7].
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Figure 1. A 55-year-old female patient with neck and upper chest pain and previous hardware fusion in the cervical spine. Sagittal (A) and axial (B,C) T2 weighted Mr imaging of the thoracic spine demonstrate a left paracentral disc herniation at the T7–8 level causing cord displacement and deformity. (Click for more details)
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Signs and symptoms
The symptoms associated with thoracic disc herniation are variable and usually include radicular symptoms such as variable pain, parasthesias, dysesthesias, allodynia, and loss of sensation in a segmental distribution across the anterior chest, thorax, and abdomen, depending on which nerve root(s) are affected. For example, T4 radiculopathies usually radiate to the nipple level; T6, the xiphoid; and T10, the umbilicus. First thoracic radiculopathy (T1) radiates into the median arm or ulnar aspect of the hand [8], and for our purposes will be covered in the cervical radiculopathy articles. Additionally, there may be localized axial pain at the level of spine pathology and thoracic radiculopathy. Diagnosis of some patients who report a deep aching-type pain is much more difficult because the pain can mimic other thoracic or abdominal problems such as angina, dyspepsia, or diverticular disease. It seems likely that some patients with atypical abdominal and chest pain have undiagnosed thoracic radiculopathy; however, the extent of this has never been adequately documented.
Physical examination is not a reliable way to diagnose thoracic radiculopathy. There may be localized spine and paraspinal tenderness, and sensory changes in a dermatomal pattern, but this is not universal. Unlike cervical or lumbosacral radiculopathies, there is no reliable way to test for muscle weakness in a myotomal pattern. The muscles that are likely to be affected (paraspinal, intercostal, and abdominal muscles) do not lend themselves to isolated muscle testing. Physical examination is critical, however, to rule out other causes of chest or abdominal pain and assess for myelopathy as discussed below.
There are also reports of thoracic disc herniations causing atypical symptoms. Two such cases involved patients with lower extremity leg pain mimicking that of lumbosacral disc disease and radiculopathy. The patients’ symptoms did not subside until a thoracic herniated nucleus pulposus (HNP) was identified and treated surgically at the involved T10 level [8,9]. Another case involved a patient with predominant shoulder pain and incomplete paraplegia. After an acromioplasty procedure for impingement syndrome failed to improve the patient’s shoulder symptoms, a large lower thoracic disc herniation was identified via MR imaging. Following surgical removal of the thoracic disc, the patient reported complete resolution of his shoulder pain symptoms and improvement in his paraplegia [10]. Thoracic discs generally herniate in a posterior-central or a posterior-lateral direction, and true lateral herniations are rare [11]. The incidence of asymptomatic thoracic disc herniation has been estimated at 37%, and the size of the herniation tends to fluctuate over time in patients who remain without symptoms [12].
The most serious of symptoms related to thoracic disc herniation and radiculopathy is the development of myelopathy. As in the cervical spine, thoracic myelopathy can result in irreversible neurologic dysfunction and threaten spinal cord tracts. It is often the result of spinal cord compression of a large central thoracic disc, a calcified thoracic HNP, an intradural herniation, or compromise of the spinal cord vascular supply [13]. Bladder dysfunction, a wide-based ataxic pattern of gait, and upper motor neuron signs such as positive Babinski sign, ankle clonus, and hyperreflexia should be sought for in a patient with suspected myelopathy. Mild lower extremity paraparesis is the most common symptom associated with thoracic disc herniation with myelopathy [14]. A thorough neurologic examination should be performed on all patients with suspected thoracic disc disease including tests usually reserved for patients with spinal cord injury such as Beevor’s sign and the cremasteric reflex. The coincidence of thoracic degenerative disc disease in a patient with pre-existing myelopathy can present with particularly complex symptoms (Fig. 2).
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Figure 2. A 46-year-old female patient with multiple sclerosis presenting with right-sided midthoracic pain. T2-weighted sagittal (A) and axial (B,C) images of the cervical and thoracic spine. C2–5 region cord lesions caused by demyelinating disease are seen. A small right paracentral disc herniation is seen at the T8–9 level that was felt to be responsible for the patient’s acute symptoms. (Click for more details)
Thoracic spinal stenosis represents another, less common cause of thoracic radiculopathy with myelopathy. It may be defined as the narrowing of the anteroposterior (AP) diameter of the thoracic spinal canal to less than <10 mm. Scheuermann’s disease, achondroplasia, and epidural lipomatosis have been considered conditions that can contribute to, or cause, thoracic spinal stenosis. When present, thoracic spinal stenosis is highly associated with coexisting lumbar spinal stenosis [15].
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Metwally, MYM: Textbook of neuroimaging, A CD-ROM publication, (Metwally, MYM editor) WEB-CD agency for electronic publication, version 11.2a April 2010 [Click to have a look at the home page]







