Disc Contour Abnormality

Jeffrey S. Ross, MD

DIFFERENTIAL DIAGNOSIS

Common

Intervertebral Disc Bulge
Disc Pseudobulge
Protrusion, Intervertebral Disc
- Cervical
- Thoracic
- Lumbar
Extrusion, Intervertebral Disc
- Cervical
- Thoracic
- Lumbar
Free Fragment, Intervertebral Disc
- Cervical
- Thoracic
- Lumbar
Intervertebral Disc Extrusion, Foraminal
Intervertebral Disc Herniation, Recurrent
Peridural Fibrosis
Osteophyte
OPLL
Epidural Mass
- Metastasis
- Lymphoma
- Epidural Abscess
- Epidural-Subdural Hematoma

Less Common

Discal Cyst
Hardware Malposition
Meningioma (Calcified)
Schwannoma (Foraminal)
Limbus Vertebra

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Main differential point is whether or not lesion is contiguous to the intervertebral disc, or abutting the disc
- Additional key findings include signal on T1, T2 images relative to nearby intervertebral disc; presence or absence of enhancement
- Large extrusion and protrusion should not have homogeneous or intense central enhancement

Helpful Clues for Common Diagnoses

Intervertebral Disc Bulge
- Circumferential disc “expansion” beyond the confines of vertebral endplates
- > 50% of disc circumference
- Up to 40% of asymptomatic adults will have bulging disc
- Short radius of extension beyond disc margin ≤ 3 mm
Disc Pseudobulge
- “Uncovering” of disc related to spondylolisthesis
- Smooth generalized extension of disc margin without focal defect
Protrusion, Intervertebral Disc
- Triangular focal disc abnormality with base broader than apex
- Anterior extradural mass in contiguity with the disc space
Extrusion, Intervertebral Disc
- Base of herniation is narrower than portion extending into epidural space
- May be associated with sequestered or “free fragment”
- Larger extrusion commonly show peripheral enhancement with granulation tissue
Intervertebral Disc Extrusion, Foraminal
- Obliterated perineural fat in neural foramen on sagittal images
- May enhance peripherally
- Contiguous to disc on parasagittal images
Intervertebral Disc Herniation, Recurrent
- Contiguous with intervertebral disc margin
- Central lack of enhancement, with peripheral granulation tissue enhancement common
- Distinguish from peridural fibrosis by nonenhancing component, mass effect
Peridural Fibrosis
- Scar formation within epidural space after lumbar surgery
- Infiltration of epidural/perineural fat by enhancing soft tissue density (intensity)
- Smooth marginated soft tissue, usually without mass effect
- Typically slightly increased in T2 signal relative to disc herniation
- Homogeneously enhances
Osteophyte
- Variable in MR signal due to relative presence of bone, red marrow, or fatty marrow
- Often associated with disc degeneration and disc bulge/herniation
- Typical “claw” configuration from adjacent endplates
OPLL
- Flowing multilevel ossification posterior to vertebral bodies
- Narrows AP dimension of canal and produces cord compression
- May show low T1 signal (cortical bone) or high T2 signal (fatty marrow)
- Typical “upside down T” or “bowtie” configuration on axial images
Epidural Abscess
- Epidural mass with peripheral enhancement
- Associated with findings of disc space infection (endplate irregularity and erosion, disc and body T2 hyperintensity, irregular enhancement)
Epidural-Subdural Hematoma
- Acute may show isointense T1 signal, with subacute T1 hyperintense
- Long segmental extra-axial mass encasing or displacing cord or cauda equina
- Rarely focal, as when associated with focal fracture or disc extrusion