Degenerative Lumbar Disc Disease

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FACTS

  • Mechanical pathology: flexion and axial loading
  • Lumbar disc herniation most commonly occurs at L4–5 and L5–S1.
  • Radicular symptoms arise from nerve root compression; central herniations may cause CES, which is a surgical emergency.
  • Most cases improve with conservative therapy; urgent surgery is for progressive neurologic deficits or CES.
  • Correlate dermatomes/myotomes carefully — imaging may show multiple levels but the exam localizes the symptomatic one.
 
Key principle: Disc Herniation Types and Traversing vs. Exiting Nerve Roots 
Herniation Type
Nerve Roots Impacted
Example
Central / Paracentra
traversing nerve root (nerve roots below)
L4-5 disc affects L5/S1 nerve root
Far Lateral / Foraminal
exiting nerve root(nerve root at that level)
L4-5 disc affects affects only L4 nerve root
notion image
 

HPI

  • Onset: sudden after lift/twist vs gradual.
  • Pain type: radicular (sharp, shooting), axial low-back pain, distribution (L4/L5/S1).
  • Weakness: foot drop, knee extension weakness, difficulty with heel/toe walking.
  • Sensory changes: numbness/paresthesias in dermatome.
  • Red flags:
    • Bowel/bladder dysfunction (retention, incontinence).
    • Saddle anesthesia.
    • Rapidly worsening weakness.
    • Fever, chills, weight loss (consider abscess/malignancy).
  • Functional impact: ambulation tolerance, ability to stand, worsening with cough/Valsalva.
  • What treatments have you tried?
    • pain meds (steroids, NSAIDs)
    • SNRB
    • ESI
    • physical therapy

PHYSICAL EXAM

Focused neuro exam:
  • Motor
    • L3–4 (Femoral): knee extension.
    • L4: ankle dorsiflexion (tibialis ant.).
    • L5: great toe extension (EHL).
    • S1: plantarflexion.
  • Sensory: anterior thigh (L3), medial shin (L4), dorsum of foot (L5), lateral/plantar foot (S1).
  • Reflexes: patellar (L4), Achilles (S1).
  • Straight Leg Raise: reproduces radicular pain between 30–70°.
  • Gait: heel walking (L5), toe walking (S1).
  • Check for CES: perianal sensation, rectal tone, PVR if urinary symptoms.

IMAGING

  • MRI lumbar spine without contrast is the study of choice.
    • Identify level, size, midline vs foraminal, nerve root displacement, and presence of severe canal stenosis.
    • Note any paracentral L4–5 herniation impinging on L5 root, or L5–S1 impinging on S1 root.
  • CT lumbar spine: useful if MRI unavailable or patient can’t tolerate MRI; good for bony stenosis.
  • X-rays: limited use; may show alignment or instability.
  • If red flags for infection or tumor, order MRI with contrast.

A/P

Admit for surgery only if:
  • progressive motor deficit
Conus Medullaris / Cauda Equina Syndrome
 
Surgical options:
  • normal sagittal alignment, facet anatomy → MCD
 

Examples

A 65 year old male who presented with R LBP radiating to buttock with subjective leg weakness showing a Right eccentric L3-4 disc extrusion causing severe compression of thecal sac.
A 65 year old male who presented with R LBP radiating to buttock with subjective leg weakness showing a Right eccentric L3-4 disc extrusion causing severe compression of thecal sac.
 
A 40 year old female with an L4-5 central disc protrusion with flavum thickening and facet hypertrophy resulting in severe canal and lateral recess stenosis. This patient had midline LBP with
A 40 year old female with an L4-5 central disc protrusion with flavum thickening and facet hypertrophy resulting in severe canal and lateral recess stenosis. This patient had midline LBP with