This case illustrates a large thoracic disc protrusion with subsequent cord compression.

Thoracic disc herniation accounts for only 0.25 – 0.75% of all disc herniations ¹. Thoracic disc herniations are classified based on:

1. Location: central/posterolateral/lateral. Most thoracic disc herniations are central ².

2. Imaging characteristics: soft or classified at the time of presentation. 30–70 % of these herniations demonstrate some form of calcification ².

The thoracic spine is a rigid transition zone between the more mobile cervical and lumbar regions. Its stability is facilitated by its articulation with the surrounding thoracic rib cage. There are two facets from each rib head on either side that articulate with vertebral bodies from T2 to T10. In addition, the facets of T1 through T10 are angled at 60° to the transverse plane and 20° to the coronal plane, affording further stability, particularly during lateral flexion and rotation.

Thoracic disc herniations are most common at the T8 – T12 level, with a higher propensity for occurrence at T11–12¹. This is due to the fact that 11th and 12th ribs are not joined to the sternum and also do not form a true articulation with the transverse process of their own vertebra. Furthermore, the facets at these levels transition to a more medial angulation in the coronal plane. Whilst this allows for allowing for greater flexion and extension, it is less effective in resisting rotational forces.  Consequently, the lower thoracic spine is biomechanically more susceptible to larger loads or compressive forces and therefore has a higher incidence of degeneration and associated disc herniation ³.

Clinical presentation is highly variable and is dependent on multiple factors including location and size of the herniations, the degree and duration of nerve and/or cord compression and the degree of vascular compromise ³. There are no pathognomic symptoms for thoracic disc herniations, but patients can present with ⁴:

• pain - Radiating up or down the spine; thoracic or abdominal pain; intercostal neuralgia; nonradicular pain

• sensory and/or motor deficits in one or both legs; neurogenic claudication

• dysfunctional urination, defecation, or even sexual dysfunction

• myelopathy which can include muscle weakness and paraparesis than can progress to a severe state of complete paraplegia ²

Physical exam findings include hyperreflexia, positive Babinski, sustained clonus, wide-based gait, positive Romberg, and/or spasticity and deficits in sensation ranging from dermatomal paresthesias to complete sensory loss ^1,2.

Imaging modality of choice is in those patients where thoracic disc disease and/or herniation is suspected is an MRI, looking for:

• sequestered disc fragment

• T2 cord signal change (myelomalacia)

• nerve root compression

• spinal cord compression with/without central canal stenosis

• loss of csf signal at the level of compression

Calcification of the disc, if present, is difficult to appreciate on MR imaging of the spine, and as such CT imaging may also be required.

Treatment options include conservative measures with analgesia and exercise-guided therapies (physiotherapy, hydrotherapy). Surgical intervention is reserved for patients with myelopathy,  progressive neurologic deterioration, severe or intractable radicular pain and/or radicular pain that has failed conservative treatment.

Case courtesy of Dr. Frank Gaillard