Acute Back Pain/Radiculopathy, Post-Operative

Kevin R. Moore, MD

DIFFERENTIAL DIAGNOSIS

Common

Intervertebral Disc Herniation, Recurrent
Intervertebral Disc Herniation, Acute
- Intervertebral Disc Herniation, Cervical
- Intervertebral Disc Herniation, Thoracic
- Intervertebral Disc Herniation, Lumbar
- Intervertebral Disc Extrusion, Foraminal
Peridural Fibrosis

Less Common

Post-Operative Infection
- Abscess, Paraspinal
- Abscess, Epidural
- Abscess, Subdural
Post-Operative Complication
- Hematoma
  - Hematoma, Epidural
  - Hematoma, Subdural
- Hardware Failure
- Vertebroplasty Complications
- Bone Graft Complications

Rare but Important

Post-Operative Complication
- Brachial Plexus Traction Injury
- Infarction, Spinal Cord
Post-Operative Infection
- Abscess/Myelitis, Spinal Cord

ESSENTIAL INFORMATION

Helpful Clues for Common Diagnoses

Intervertebral Disc Herniation, Recurrent
- Focal extension of disc material beyond endplate margins at previously operated intervertebral disc level
- Subset of failed back surgery syndrome (FBSS)
- Fat suppression of T1WI (pre- and post-gadolinium) may increase sensitivity for detecting peridural fibrosis and for differentiating fibrosis from disc herniation
Intervertebral Disc Herniation, Acute
- Localized (< 50% of disc circumference) displacement of disc material beyond edges of vertebral ring apophyses
- Unfortunate luck to present with new disc herniation after previous surgery at another level
Peridural Fibrosis
- Scar formation within epidural space following lumbar surgery
- Subset of FBSS
- Fat suppression of T1WI (pre- and post-gadolinium) increases sensitivity for detecting peridural fibrosis and for differentiating fibrosis from disc herniation

Helpful Clues for Less Common Diagnoses

Post-Operative Infection
- Infectious sequelae following operative procedures
- May manifest in one or more areas at operative site including paravertebral tissues and subdural or epidural spaces, but frequently starts in intervertebral disc space
- Abscess, Paraspinal
  - Infection of paravertebral soft tissues surrounding spine
  - Paravertebral enhancing phlegmon or peripherally enhancing liquified collection
- Abscess, Epidural
  - Extradural spinal infection producing abscess formation
  - Frequently spondylodiscitis extends into adjacent epidural space ⇒ enhancing epidural phlegmon ± peripherally enhancing fluid collection
  - May also see isolated epidural abscess without discitis
  - Lower thoracic, lumbar > cervical, upper thoracic
- Abscess, Subdural
  - Purulent pus collection developing in “potential” space between dura and arachnoid
Post-Operative Complication
- Hematoma, Epidural
  - Blood extravasation into the epidural spinal compartment
  - Long segmental extra-axial mass encasing or displacing spinal cord or cauda equina
  - Typically multisegmental, but may be focal when associated with focal fracture or disc extrusion
- Hematoma, Subdural
  - Accumulation of blood between dura and arachnoid
  - Signal characteristics variable depending on age of blood products
- Hardware Failure
  - Mechanical breakdown, malfunction, or malposition of metallic implant
  - May present either with chronic pain or calamitously with acute pain
- Vertebroplasty Complications
  - Cement extravasation into spinal canal, foramen, or vertebral venous plexus
  - Pulmonary artery cement embolization
  - Vertebral osteomyelitis
  - “Bounce back” vertebral fracture
- Bone Graft Complications
  - Graft migration, graft displacement, or graft extrusion
  - Abnormal alignment, position, or placement of graft ± associated neurologic deficit, instability, infection
  - Cervical > thoracic > lumbar

Helpful Clues for Rare Diagnoses

Post-Operative Complication
- Brachial Plexus Traction Injury
  - Stretch injury or avulsion of ≥ 1 cervical roots, brachial plexus
  - Stretch injury: Enlargement or attenuation of stretched (but contiguous) plexus elements
  - Avulsion injury: Attenuated or disrupted proximal roots/rami within or immediately distal to lateral CSF-containing dural sac diverticulum devoid of neural elements ± retracted distal nerve roots, nerve “retraction ball”
- Infarction, Spinal Cord
  - Thoracic spinal cord infarction 2° arterial occlusion (radicular artery)
  - Artery of Adamkiewicz frequently implicated
  - Usually extends to involve more than one vertebral body segment
  - Central hyperintensity on T2WI more common than wedge-shaped involvement of anterior 2/3 of spinal cord
Post-Operative Infection
- Abscess/Myelitis, Spinal Cord
  - Spinal cord infection with necrosis
  - Spinal cord neoplasm mimic; ring-enhancing mass within cord with appropriate clinical history of inflammation/infection is highly suggestive
  - Pyogenic infection most common but granulomatous infections have been described
  - May show positive diffusion (reduced ADC) restriction similar to brain abscess, but lack of diffusion restriction does not exclude abscess

Image Gallery

Sagittal T1 C+ MR in a post-operative patient with recurrent back pain demonstrates a recurrent L4-5 HNP

that ventrally compresses the thecal sac.

Axial T1 C+ FS MR in a post-operative patient with recurrent back pain reveals a large post-operative recurrent disc herniation

(Left) Axial T2* GRE MR reveals a large left cervical disc herniation producing spinal cord deformation and narrowing of the left lateral spinal canal. (Right) Axial T2WI MR depicts a left paracentral thoracic disc herniation that produces mild spinal cord deformation but no significant narrowing of the central spinal canal.

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