sciatica

epidemiology

Incidence

· life-time 10-40%

· annual 1-5%

Factors

· M:F = 1:1

· peak incidence age 42

· most common disc is L4-5

Natural history

· cauda equina syndrome 2%

· muscle weakness 5-20%

· recovery

· 1 mth 30%

· 6 mths 50%

· 2 yrs 80%

· 5 yrs 90%

· weakness just as likely to resolve as pain

· no long-term difference with surgery

· surgery provides more rapid end-point

classification

Bulge

· annulus intact

General

· diffuse

Localised

· usually posterolateral

Prolapse

· annulus disrupted

Protrusion

· nucleus contained by outer fibres of annulus

Extrusion

· nucleus broken through annulus but under PLL

Sequestration

· fragment of disc free in canal

clinical features

Symptoms

Pain

· predominantly in leg

· in dermatomal distribution

· worse with sitting

Neurology

· numbness and pins & needles

· weakness

· cauda equina syndrome

· saddle anaesthesia

· urinary retention and overflow incontinence

Signs

Tension sign

· Lasegue’s sign

· positive in 97%

· cross Lasegue sign

· positive in 20%

· reverse Lasegue sign

· femoral nerve

Investigations

CT myelogram

Myelogram

· accuracy of 67-100%

· images entire lumbar spine with sagittal image

· invasive

· risks

· contrast reaction

· post LP headache

CT scan

· transverse image

· allows visualisation of lateral lesions

· lateral or foraminal herniation

· lower radiation dose

· no adverse reactions

· outpatient procedure

· images limited number of levels

Combination

· more sensitive (78% vs 71%)

· as specific (76%)

· more accurate (77% cf 74%)

MRI

· combines advantages of myelogram and CT scan

· sagittal and transverse images

· images entire lumbar spine

· no adverse reactions

· other advantages

· no radiation

· reveals pathological states of disc and vertebra

· identifies intradural pathology

· useful in postoperative lumbar spine

· with administration of gadolinium

· can distinguish epidural fibrosis from recurrent disc herniation

treatment

Nonoperative

· bed rest for 7 days

· non-narcotic analgesics and NSAIDs

Operative

· indicated in 10% of patients

Indications

Absolute

· cauda equina syndrome

Relative

· progressive neurological deficit

· all 6 features of

· leg pain > back pain

· neurological symptoms consistent with root irritation

· neurological signs consistent with root irritation

· positive straight leg raise

· radiological findings consistent with symptoms and signs

· pain > 6 wks

Chemonucleolysis

· use of chymopapain to dissolve nucleus of disc

Advantages

· no incision

· less scar

· more rapid recovery

Disadvantages

· only indicated for contained disc

· back spasm (20%)

· anaphylaxis (0.1%)

Results

· 70%

Percutaneous discectomy

· removal of disc with cutting / suction probe

Advantages

· same as chemonucleolysis

Disadvantages

· only indicated for contained disc

Results

· 60%

Discectomy

Advantages

· suitable for noncontained disc

· best results

Disadvantages

· incision

· more scar

· slower recovery

Results

· 90%