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Thoracic Intervertebral Disc Herniation


KEY FACTS

Imaging

  • Small mass in spinal canal contiguous with intervertebral disc

    • Ventral epidural

    • Rare in upper thoracic spine (T1-T3)

  • May enhance peripherally after intravenous contrast material due to granulation tissue or dilated epidural plexus

    • Peripheral enhancement may give “lifted band” or “tent” configuration

Top Differential Diagnoses

  • Osteophyte

    • Sharp margins not arising directly from intervertebral disc level

  • Tumor

    • Homogeneous enhancement

  • Hemorrhage

    • Elongated within epidural space, tends to be posterior

  • Abscess

    • May mimic large herniation with peripheral enhancement

Clinical Issues

  • 5th decade

  • Uncommon entity

  • Thoracic disc surgery uncommon, represents 1-2% of all disc surgery

  • History of Scheuermann disease (kyphosis secondary to multiple Schmorl nodes → vertebral body wedging)

Diagnostic Checklist

  • Calcification (65%)

  • Multiple herniation (14%)

  • T2WI critical because herniation may not be visible on T1WI due to calcification

  • Check and recheck herniation level, counting from C2 and L5 levels

Sagittal T2WI MR shows a large low signal disc extrusion
at T2-T3 effacing the thecal sac and tenting the ventral dura
.

Axial T1WI MR demonstrates the large left-sided extrusion
severely compressing the left side of the cord
.

Sagittal T2WI MR shows multiple large, lower thoracic disc herniations
, which severely compress the cord
at multiple levels. Thoracic herniations are most common from T7-T12.

Sagittal T1WI C+ MR in the same patient shows pronounced peripheral enhancement surrounding the herniations
related to tented and distended epidural plexus and herniation-associated granulation tissue.

TERMINOLOGY

Abbreviations

  • Thoracic disc herniation (TDH)

Synonyms

  • Protruded disc, extruded disc, free fragment, sequestered disc

  • Nonstandard: Prolapse, herniated nucleus pulposus (HNP), rupture

  • Dorsal spinal disc herniation

Definitions

  • Localized (< 50% of disc circumference) displacement of disc material beyond edges of vertebral ring apophyses

IMAGING

General Features

  • Best diagnostic clue

    • Small mass in spinal canal contiguous with intervertebral disc

  • Location

    • Ventral epidural

    • T6 → T11 most common

    • Rare in upper thoracic spine (T1-T3)

  • Size

    • Variable

  • Morphology

    • Protrusion

      • –

        Herniated disc with broad base at parent disc

      • –

        Greatest diameter of herniated disc in any plane greater than distance between edges of base in same plane

      • –

        Focal: < 25% of disc circumference

    • Extrusion

      • –

        Herniated disc with narrow or no base at parent disc

      • –

        Greatest diameter of herniated disc in any plane greater than distance between edges of base in same plane

      • –

        Sequestered or free fragment: Extruded disc without contiguity to parent disc

      • –

        Migrated: Disc material displaced away from site of herniation, regardless of continuity to parent disc

    • Intravertebral herniation (Schmorl node)

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