Thoracic Disk Herniation

Matthew G. Zmurko

Thoracic disk herniations are less frequent than cervical and lumbar herniations because the thoracic spine has increased stability provided by the thoracic rib cage. The majority of thoracic disk herniations occur below T8 as the thoracic spine transitions into the more mobile lumbar spine. Like disk herniations in the cervical and lumbar regions, most thoracic disk herniations respond to non-operative management.

Classification

Thoracic disk herniations are classified according to their location and nature. The location is centrolateral if the majority of the herniation is medial to the lateral margin of the thecal sac. It is a lateral disk herniation if the majority is lateral to the thecal sac. The nature of the disk herniation may be described as soft or hard. Soft disk herniations usually occur in the younger population and result from acute and often traumatic injuries. Hard disk herniations are more chronic in nature and result from the degenerative process, which may lead to calcification of the disk. Calcified disks are associated with a higher incidence of intradural herniations.

Workup

History

Thoracic disk herniations present with a wide range of symptoms that often mimic other pathologic conditions. Often these patients have undergone extensive medical workups to rule out cardiac, pulmonary, and/or gastric abnormalities. It is during these workups that diagnostic imaging may show an incidental thoracic disk herniation.

Patients typically present with axial pain, radicular pain, or myelopathy. Axial pain is the most common symptom. Thoracic radiating pain typically follows a dermatomal distribution anterolaterally around the chest wall. Myelopathic symptoms present in a multitude of ways. Often patients may present with difficulty ambulating because of a sense of heaviness or weakness in the lower extremities, increased spasticity, or changes in proprioception. Bowel or bladder dysfunction is not uncommon in symptomatic thoracic disk herniations.

Physical Examination

Examination begins with a thorough inspection of the patient’s posture and gait pattern. Myelopathic patients can present with a wide range of gait patterns due to their loss of proprioception, increased spasticity, and generalized weakness of the lower extremities. Percussion of the thoracic spine may reproduce radicular symptoms. Sensory level identification is an important localizer of symptoms, as motor examination of the thoracic innervated muscles is less specific in the thoracic spine (Table 27.1).

The presence or absence of pathologic reflexes is an important component of the examination. The Romberg sign is useful to elicit changes in proprioception. Ankle clonus, Babinski reflex, and/or superficial abdominal reflex may indicate the potential for an upper motor neuron lesion or compression of the thoracic spine. The presence of abnormal reflexes is a good indication to proceed with further diagnostic imaging of the thoracic spine.

Spinal Imaging

Magnetic resonance imaging (MRI) is the gold standard, as it is noninvasive and provides excellent soft-tissue resolution. MRIs are helpful in evaluating intrinsic cord edema suggestive of myelomalacia, which may result from compression of the spinal cord. MRIs may have difficulty in differentiating calcified disks from soft disks and may overestimate the degree of spinal cord compression. Therefore, it is not unreasonable to also obtain a computed tomography (CT) scan or CT myelogram to clarify this information further (Fig. 27.1). CT scans may make it easier to localize the level of disk involvement by counting up from the sacrum or from the most inferior rib.

Table 27.1 Corresponding Sensory Dermatomes of the Thoracic Spine