Diagnosis and treatment of thoracic disc herniation

Workers injured as a result of significant trauma or lifting activities may present with symptoms of a thoracic disc herniation (TDH).

Diagnosis
Diagnosis can be challenging, since the estimated incidence of symptomatic TDH is approximately one in a million per year,[1] and 0.25% to 0.75% of total incidents of symptomatic spinal disc herniations.[2] Incidence is highest in males between ages 40 and 60. An accurate diagnosis of TDH requires strong clinical diagnosis with imaging confirmation.

Imaging detects a high frequency of incidental disc lesions in the thoracic spine. The MRI results of 90 asymptomatic individuals in one study revealed thoracic disc lesions in 74%, of which 29% demonstrated spinal cord deformation.[3]

TDH presents with three clinical finding patterns:
1.    Axial (back dominant) pain in the mid- to lower-thoracic spine.
2.    Radicular pain that may accom-pany axial pain, occur in a derma-tomal distribution, or be accompanied by sensory changes.
3.    Thoracic myelopathy with weakness and impaired balance—physical examination potentially reveals wide-based gait, increased lower-extremity muscle tone and clonus, hyperreflexia of lower extremities compared to upper extremities, and negative Hoffman’s sign.

Clinical findings for TDH are not specific and may overlap with nonspinal and spinal conditions. Nonspinal causes include intrathoracic or intra-abdominal conditions, or musculoskeletal conditions, such as soft tissue disorders or rib fractures. Red-flag spinal conditions need to be considered.

Where TDH is clinically suspected, investigations should include upright radiographs of the spine to rule out obvious causes of thoracic back pain such as neoplasm or bone/joint injury. MRI is sensitive to detecting TDH.

Treatment
The natural history for most TDH is benign, and nonsurgical treatment is appropriate for the majority of cases. Accepted treatment includes activity modification, over-the-counter analgesics, nonsteroidal anti-inflammatory medication, and physiotherapy. In the acute phase, passive modalities may be used, but after that, the focus should switch to active rehabilitation including low-impact aerobic activity, range of motion, and strengthening, with emphasis on extension exercise. Individuals with radicular symptoms may benefit from intercostal nerve block.

Surgery is generally reserved for individuals presenting with objective neurological compromise. An absolute indication for surgical intervention is progressive myelopathy. Relative indications for surgery include stable myelopathy without significant functional deficit and radicular pain that is not improving. Surgical referral should be expedited where neurologic compromise results in myelopathy with functional impairment or in progressive myelopathy.

Surgical approaches to TDH have evolved. Laminectomy was abandoned because of poor outcomes and supplanted by anterior discectomy by thoracotomy. Recent advances include a variety of minimally invasive techniques, the selection of which is based on the disc herniation morphology.

Treatment outcomes depend on the patient and pathophysiological factors. Younger patients with acute soft-disc herniation usually respond well to both nonoperative and operative treatment. Older individuals with longer duration of symptoms and disc osteophyte formation respond less favorably.

Published guidelines for post-TDH activity resumption are not available. Compared to the cervical and lumbar spine, the thoracic spine warrants a more conservative approach to resuming activity where impact and heavier forces are involved. Space for the spinal cord in the thoracic spine and blood supply to the spinal cord are less than in the cervical and lumbar regions. Return to activity can be on a graduated basis with restrictions on impact and heavier activity until core strength and flexibility have normalized, neurologic impairment recovers, and imaging demonstrates no functional stenosis. Where these criteria are not met, activity involving heavy loading on the spine may need to be permanently restricted.

For further information or assistance with a worker patient with possible TDH, please contact a medical advisor in your nearest WorkSafeBC office.
—John Paul Thompson, MD 
WorkSafeBC Orthopaedic Consultant

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This article is the opinion of WorkSafeBC and has not been peer reviewed by the BCMJ Editorial Board.

References

1.    Carson J, Gumpert J, Jefferson A. Diagnosis and treatment of thoracic intervertebral disc protrusions. J Neurol Neurosurg Psychiatry 1971;34:68-77.
2.    Brown CW, Deffer PA Jr, Akmakjian J, et al. The natural history of thoracic disc herniation. Spine (Phila Pa 1976) 1992;17(6 suppl):S97-S102.
3.    Wood KB, Garvey TA, Gundry C, Heithoff KB. Magnetic resonance imaging of the thoracic spine: Evaluation of asymptomatic individuals. J Bone Joint Surg Am 1995;77:1631-1638.