4 Clinical Presentation of Thoracic Spinal Compression Abstract The thoracic segment of the spine has unique anatomical and neuroanatomical features that differentiate it from the cervical spine above and lumbosacral spine below. Compression of the thoracic spine may occur due to degenerative and/or spondylotic disease, traumatic injury, infection, or neoplastic disease. Neurological injury can occur on the basis of mechanical compression, and can result in clinical neurological deficits. The clinical presentation of thoracic spinal compression is varied, based on the location and the degree of compression. The clinical features of thoracic cord compression and thoracic radiculopathy are dictated by the longitudinal and cross-sectional neuroanatomy of the spine, and can be identified by characteristic features related to this neuroanatomy. Keywords: thoracic spinal cord, thoracic myelopathy, spinal tracts, thoracic radiculopathy, spastic paraparesis, spinal cord lesion, spinal cord compression Clinical Pearls • Pain due to thoracic spinal compression may be radicular, axial, or claudicatory involving the lower extremities. • Spinal cord compression due to degenerative disease is relatively rare in the thoracic segment, compared with the incidence in the lumbar and cervical segments. • Longitudinal and cross-sectional spinal neuroanatomy allows a careful neurological examination to identify and localize neurological injury due to thoracic spinal compression. The thoracic segment of the spine has unique anatomical and neuroanatomical features that differentiate it from the cervical spine above and lumbosacral spine below. Compression of the thoracic spine may occur due to a number of causes, including degenerative disc disease, spondylotic disease, traumatic injury, infection, or neoplastic disease. Neurological injury can occur on the basis of mechanical compression, and can result in clinical neurological deficits. The spinal cord can be injured adjacent to the site of compression, resulting in thoracic myelopathy. Alternatively, the segmental spinal nerve roots that exit the thoracic vertebral neural foramen can be focally compressed, resulting in thoracic radiculopathy. The clinical presentation of thoracic spinal compression is varied, based on the location and the degree of compression. The clinical features of thoracic cord compression and thoracic radiculopathy are dictated by the longitudinal and cross-sectional neuroanatomy of the spine, and can be identified by characteristic features related to this neuroanatomy. In this chapter, anatomical considerations and pathological processes affecting the thoracic spine will be outlined to provide context for the clinical presentation of thoracic spine lesions. The reader is referred to chapters elsewhere in this text for in-depth review of anatomy and various pathological processes. Subsequently, general and specific patterns of thoracic region spinal compression are described and discussed. The thoracic segment of the spine possesses anatomical features that differentiate it from the cervical and lumbosacral spine. Some of these features serve to protect the thoracic segment from injury, while others render it particularly vulnerable. The thoracic vertebral column is relatively immobile compared with the rostral cervical and caudal lumbosacral spinal segments. The ribs and their anterior articulation with the sternum provide additional skeletal stability to the thoracic spine. Further, the extensive paraspinal and back musculature of this region, including postural muscles, longitudinal muscles, and the scapular limb-girdle musculature serves to strengthen and protect the thoracic spine from external stresses. While the above factors serve to limit injury based on mechanical stressors, additional anatomical factors confer a greater risk of spinal cord injury when structural spine injury does occur to the thoracic spine. The diameter of the thoracic spinal canal, particularly in the rostral thoracic vertebrae, is smaller than that of the cervical and lumbar vertebrae. This increases the likelihood of neurological injury due to compression of the spinal cord within the central canal at these narrower levels.1,2 Additionally, the vasculature of the spinal cord is organized such that there is greater blood flow through the radicular arteries in the cervical and lumbar segments than there is through the radicular branches in the thoracic region. Further, sulcal branches off of the anterior spinal artery are least numerous in the thoracic region. As a result, the cervical and lumbar spinal cord possess a more robust anastomotic vascular network than does the thoracic segment. The thoracic spine represents a vascular watershed region, rendering it especially vulnerable to ischemic injury.3,4 The mechanism of neurological injury on the basis of compression may result from direct deformation and destruction of nervous tissue in cases of extreme compressive forces. If the compressive force is sufficient, the spinal cord can sustain contusion or crush injury, in which there is direct sheering or rupture of axonal processes. This type of injury is particularly relevant in cases of trauma. Alternatively, injuries due to milder repetitive forces, or milder forces sustained over time, may also result in direct injury to neuronal structures through direct axonal injury or by interference with the integrity of neural support cells. The most common pathological mechanism for neurological injury on the basis of compression injury is thought to be ischemia. The spinal cord and the spinal nerve roots are highly perfused tissues. The establishment and maintenance of the action potential is energy dependent, thus nervous tissue is highly metabolic. Compression of nervous tissue in excess of capillary perfusion pressure results in ischemia, and eventually infarction.3,4,5 Spinal cord compression on a degenerative basis involving the thoracic segment is relatively rare. The significantly greater motility of cervical and lumbosacral spinal segments renders these regions more vulnerable to injuries on a mechanical basis than is the thoracic spine, reinforced as it is by the thoracic cage and by the extensive paraspinal and back musculature of this region. Thoracic disc herniations comprise less than 1% of all disc prolapses that come to clinical attention.1,6,7 Other variants of degenerative disease such as facet arthropathy, and calcification of ligaments occur more frequently. Congenital stenosis may be a contributing factor. In addition to degenerative and/or spondylotic disease, various pathological processes can result in spinal cord compression. Tumor and infection are the main considerations in this category. For pathological processes that affect the vertebral bodies indiscriminately, the fact that there are 12 thoracic vertebrae increases the odds that vertebral bodies belonging to this segment may become involved, simply on the basis of larger numerical representation. Bony spinal metastases involve thoracic vertebrae more frequently than they do the lumbar and cervical vertebral bodies, by a ratio of 4:2:1.8 In cases of compressive neurological injury to the thoracic spine, individual consideration is given to injuries involving the spinal roots (radiculopathy) and the spinal cord (myelopathy). Compression injuries in the thoracic spine may cause either or both. Therefore, the clinical syndromes associated with thoracic radiculopathy and myelopathy may occur separately or together. In situations resulting in the compression of both nerve root and spinal cord, one clinical syndrome may predominate, depending on the degree and exact lines of compressive force. The neuroanatomical organization of the spinal cord allows for longitudinal as well as axial plane localization of injury in many cases. Compression of the neural structures within the thoracic spine results in specific patterns of symptoms and neurological deficits. General patterns of thoracic segment injury are described, as are specific identifiable patterns of neurological deficits based on injury location (
4.1 Introduction
4.2 Anatomical Considerations
4.3 Pathological Process of Compression
4.3.1 Mechanism of Neurological Compression Injury
4.3.2 Degenerative Disc Disease and Spondylosis
4.3.3 Other Compressive Pathology
4.4 Clinical Presentation of Thoracic Spinal Compression
Fig. 4.1).
Thoracic Key
Fastest Thoracic Insight Engine
