How do you differentiate clinically between extramedullary intramural and extramedullary extramural spinal cord lesions?

Differentiating Clinical Symptoms and Signs of Extramedullary Intradural vs. Extramedullary Extradural Spinal Cord Lesions

MRI is essential for definitive diagnosis, but distinct clinical patterns can help differentiate extramedullary intradural from extramedullary extradural spinal cord lesions based on their characteristic presentation and progression. 1

Anatomical Context

• Extramedullary intradural: Located within the dural sac but outside the spinal cord
• Extramedullary extradural: Located outside the dural sac but can still compress the spinal cord

Clinical Differentiation

Pain Characteristics

• Extramedullary intradural lesions:

  • More likely to present with radicular pain following specific dermatomes
  • Pain often worse at night or when lying down
  • Pain typically precedes neurological deficits by months
  • Pain may be bilateral and asymmetric

• Extramedullary extradural lesions:

  • More likely to present with localized back pain
  • Pain often exacerbated by movement, coughing, or sneezing
  • Pain may have a more rapid progression
  • More likely to have percussion tenderness over the affected area

Neurological Symptoms

• Extramedullary intradural lesions:

  • Slower, more insidious progression of neurological deficits
  • Early sensory symptoms with paresthesias
  • Brown-Séquard syndrome (ipsilateral motor weakness and proprioceptive loss with contralateral pain and temperature loss) more common
  • Asymmetric neurological deficits are typical

• Extramedullary extradural lesions:

  • More rapid progression of neurological deficits
  • Earlier motor involvement with weakness
  • More symmetric neurological deficits
  • More likely to present with myelopathy signs (spasticity, hyperreflexia)
  • May have more pronounced sphincter dysfunction earlier in the course 1

Symptom Progression

• Extramedullary intradural lesions:

  • Typically show a slower, more indolent course
  • Progression over months to years
  • Symptoms may wax and wane

• Extramedullary extradural lesions:

  • Often show a more rapid clinical deterioration
  • May have a more acute presentation, especially with epidural abscesses or hematomas
  • More likely to have constitutional symptoms if infectious or malignant 1

Clinical Examination Findings

• Extramedullary intradural lesions:

  • Sensory level may be less well-defined
  • Motor weakness often follows a root distribution initially
  • Reflexes may be diminished at the level of the lesion and increased below

• Extramedullary extradural lesions:

  • More likely to have a well-defined sensory level
  • Motor weakness often follows a more segmental pattern
  • More likely to have early sphincter dysfunction
  • Vertebral tenderness to palpation more common 1, 2

Red Flags That Help Differentiate

• Suggesting extradural pathology:

  • History of cancer (metastatic disease)
  • Fever and elevated inflammatory markers (infection)
  • Rapid progression over days (abscess, hematoma)
  • Severe localized back pain
  • History of trauma or anticoagulation (hematoma)

• Suggesting intradural pathology:

  • Very slow progression
  • Predominant radicular symptoms
  • History of neurofibromatosis (schwannomas)
  • Female sex and older age (meningiomas)
  • Minimal or absent vertebral pain 1, 3

Common Pitfalls in Clinical Differentiation

1. Mistaking myelopathy for radiculopathy: Careful examination of reflexes, sensory levels, and Babinski sign is essential

2. Overlooking sphincter dysfunction: Always inquire about bladder and bowel symptoms as these may indicate more severe compression

3. Failing to recognize the Brown-Séquard pattern: This is more common with intradural lesions and can be subtle

4. Attributing symptoms to degenerative disease: Especially in older patients, extramedullary lesions may be misdiagnosed as spondylosis 1, 4

Diagnostic Confirmation

While clinical features provide important clues, MRI remains the gold standard for definitive diagnosis:

• MRI spine without and with contrast is the preferred imaging modality for suspected spinal cord lesions
• Contrast enhancement patterns differ between intradural and extradural lesions
• T1-weighted images help differentiate lesion types and locations
• T2-weighted images best demonstrate cord compression and edema 1

Remember that while these clinical patterns are helpful, there is significant overlap, and definitive diagnosis requires appropriate imaging studies.