Lumbar Disc Herniation

Description:

Seen in all age groups, most common ages 35-45
Risk factors include: smoking, sedentary work and full-time motor vehicle driving
Sciatica is found in 40% of patients
50% recover in 1 month, 96% function normally in 6 months

Pathophysiology:

Disc herniation is preceded by degenerative changes inside disc
Circumferential tears in annulus progress to radial tears and lead to herniation
Annulus fibers intact in a contained disc protrusion
Annulus fibers disrupted in noncontained herniation or extrusions, posterior longitudinal ligament intact
Free disc fragments in canal are sequestered herniations, posterior longitudinal ligament disrupted

Signs/Symptoms:

Low back pain
Sciatica = pain radiating down leg in a dermatomal distribution
Coughing, sneezing or Valsalva maneuver exacerbates radiating pain
Prolonged sitting aggravates
Straight leg-raising test is positive in 98% on affected side, 20% on contralateral leg (known as Lasegue and cross-Lasegue signs)
> 90% disc herniations are L4-L5 or L5-S1, L4-5 most common

Level	Nerve Root	Sensory Loss	Motor Loss	Reflex Loss
L1-L3	L2, L3	Anterior Thigh	Hip Flexors	None
L3-L4	L4	Medial Calf	Quadriceps, Tibialis Anterior	Knee Jerk
L4-L5	L5	Lateral calf, dorsal foot	Extensor digitorum longus, Extensor hallicus longus	None
L5-S1	S1	Posterior calf, plantar foot	Gastrocnemius/soleus	Ankle Jerk
S2-S4	S2,3,4	Perianal	Bowel/Bladder	Cremasteric

Anatomic Considerations:

Central herniation: involves central portion of posterior annulus
Paracentral herniation: adjacent to central portion of posterior annulus
Far Lateral herniation: within or just lateral to the neural foramen
Central or paracentral herniations tend to compress the traversing nerve root at a given disc level: a central or paracentral hernation at L4-L5 will compress the traversing nerve root L5, not the exiting nerve root at that level, L4
A far lateral herniation is more apt to involve the foramen, thereby compressing the exiting nerve root at that spinal level. A far lateral L4-L5 herniation would compress exiting L4 nerve root, likely sparing the traversing L5 nerve root.

Imaging:

MRI is the study of choice for diagnosis of a herniated disc
Correlation of clinical symptoms and findings is crucial as 28% of asymptomatic people have evidence of a herniated disc on MRI

MRI of L4-5 disc herniation. A) T1 B) T2 C) T1 post-gadolinium

Treatment:

Goal is to return patient to normal activities as quickly as possible
Recent prospective studies have shown patients treated with surgical discectomy had better results at 1-year follow-up versus patients treated conservatively. Four and ten year follow-up yielded nearly equal function in both groups
Conservative treatment:

Standard or microdiscectomy possible
Equal success rate of 85-95%
Risks of surgery include: dural tear, wrong level exploration, hemorrhage, infection, nerve deficit
Contained disc protrusions may be treated with precutaneous automated discectomy or chemonucleolysis with success rate of up to 75%
Chemonucleolysis is popular technique in Europe, but deaths due to anaphylaxis and other complications dissuade US patients and surgeons

Cauda Equina Syndrome

Descripton:

Injury to the cauda equina between the conus and the lumbosacral nerve roots within the spinal canal, often due to massive disc herniation
Complete cauda equina injury results in loss of nerves to bowel, bladder, perinanal and lower extremities
Often presents as incomplete injury
A surgical emergency

Signs/Symptoms:

Bilateral buttock and lower extremity pain
Bowel and bladder dysfunction (often urinary retention)
Saddle anesthesia (distribution of sensory loss in perianal area, buttocks and posterior lower extremities)
Varying degrees of lower extremity motor deficits

Examination:

Digital Rectal Examination for determination of perianal sensation and sphincter tone essential

Treatment: