sciatica

see also:

• The adult with back pain in the ED
• mechanical musculo-skeletal lower back pain
• high lumbar disc prolapse
• lumbar disc prolapse
• historical aspects of sciatica
• Vic. Health patient information sheet - back pain (pdf)

• acute and acute exacerbations of chronic back pain are a very common presentation to an adult ED
• many of these have pain radiating down a leg or buttock with or without paraesthesiae or weakness and are thus given a clinical diagnosis of “sciatica” with a presumptive cause of lumbar disc prolapse

• very common particularly in 35-60 year old adults who account for almost 2/3rds of ED presentations with diagnosis of “sciatica”
• peak ages at ED presentation are 44-47yrs
• average age at lumbar discectomy is 42 years
• very uncommon in those under age 25 years or the elderly (who are more likely to have degenerative bone disease, osteoporotic crush fractures or red flag conditions such as abdominal aortic aneurysm (AAA) as a cause rather than acute disc prolapse)
• of those patients requiring surgery for their disc prolapse, ~50% were at L4/5 disc and 47% were at L5/S1 disc with only 3-4% at levels higher than these.
• the mechanisms of pain are multifactorial and involve nerve root impingement (radicular neuropathic pain), facet joint pain, sacro-iliac joint pain, muscular spasm pain, inflammatory mediators, local neuropeptides, and nitric oxide
• rare extra-spinal causes of sciatica include:
  • sciatic herniae - a pelvic floor hernia mainly in older women may cause pressure on the sciatic nerve
  • inadvertent intramuscular injection in the gluteal region in the sciatic nerve
  • traumatic posterior dislocation of the hip
  • thigh haematoma
  • total hip replacement surgery
  • infective causes:
    • perianal / supra-levator / ischio-rectal abscess extending above levator ani muscle and tracking along the sciatic nerve causing inflammation or pressure on the sciatic nerve near the ischial tuberosity
    • abdominal infections can also spread into the pelvis along the iliopsoas muscles or along the iliac vessels
  • primary nerve sheath tumors
  • pelvic and abdominal tumors can cause pressure effect or invasion of the sciatic nerve
  • pelvic endometriosis
  • uterine leiomyomas
  • pyriformis syndrome
  • pregnancy
  • aneurysm of the external iliac artery
  • radiotherapy
  • osteoarthritis of the sacroiliac or hip joints
  • sacroilitis

• more common in industrialised countries
• genetic predisposition may be relevant but not as yet clearly identified
• men and women equally affected
• weakness of the trunk extensor muscles may be a factor
• prospective studies controlled for age, isometric lifting strength and the degree of cardiovascular fitness were NOT predictive of back injury, but did help in rehabilitation
• it is thought the following predispose to injury:
  • heavy physical work
  • lifting
  • prolonged static work postures
  • simultaneous bending and twisting
  • exposure to vibration
  • sneezing or coughing

• low back pain radiating down one buttock and or leg
• pain is usually a mix of:
  • segmental symptoms
    • presumed to be due to local disc-related pain with referred pain
    • pain is midline in low back and can radiate to buttocks or thigh but not below knee, usually unilateral but may be bilateral
  • neural compression symptoms:
    • severe shooting or spasmodic electric pains in the dermatomal distribution of the nerve root often on a background more constant neuropathic type of pain
    • may be associated with paraethesiae, muscle weakness, and loss of reflexes
• possible objective unilateral neurologic findings in one leg but usually only subjective findings unless severe nerve root involvement
  • upper lumbar disc prolapse is much less common (2% of prolapses):
    • see high lumbar disc prolapse
    • these tend to affect more than one nerve root perhaps due to the narrower spinal anatomy
    • L1 root causes pain in groin
    • L2 root causes pain in ant-medial thigh
    • L3 root causes pain in ant-lateral thigh
    • may impact the conus medullaris
    • as L2 and L3 are mainly distributed to the femoral nerve, unlike sciatic nerve root compression, SLR will generally be little effected but hip extension, which stretches the femoral nerve, is likely to exacerbate the pain
    • patients may have reduced knee jerk, and may develop wasting of quads and secondary knee instability
  • lower lumbar disc prolapse:
    • the most common site by far and the cause of typical “sciatica” or sciatic N root compression symptoms
    • pain worse on attempting to touch toes or on straight leg raising (SLR)
    • SLR that produces pain in the opposite leg carries a high probability of disk herniation
    • L3/4 disc prolapse generally affects the L4 nerve root
    • L4/5 disc prolapse generally affects the L5 nerve root
    • L5/S1 prolapse generally affects the S1 nerve root
  • see dermatomes
    • L2 ⇒ low back - just above buttock, ant/lat thigh
    • L3 ⇒ ant. thigh
    • L4 ⇒ ant/lat. proximal lower leg, medial foot including 1st two toes dorsally
    • L5 ⇒ ant/lat. distal lower, lateral foot dorsally
    • S1 ⇒ buttock, posterior thigh, posterior leg, sole of foot, dorsum lateral edge of foot including 5th toe
  • myotomes:
    • L2 ⇒ hip flexion
    • L3 ⇒ quads, patellar reflex
    • L4 ⇒ patellar reflex (with L3)
    • L5 ⇒ extensor hallucis longus ⇒ may cause foot drop
    • S1 ⇒ ankle jerk (with S2) ⇒ weak plantar flexion (weak tip toe walk)
• absence of red flag conditions such as cauda equina syndrome (CES)

• exclude back pain red flag conditions
  • in particular, exclude cauda equina, acute spinal cord compression, spinal abscess, and AAA as all of these will need IMMEDIATE Rx
  • acute neurology such as new foot drop or objective numbness may warrant urgent neurosurgical referral
• plain Xrays are NOT useful unless major trauma or the patient is elderly with presumed osteoporosis and even then, a CT would be a better modality
• CT scan is usually not warranted for acute neurology without trauma as MRI scan is the imaging modality of choice but this is usually only embarked upon in patients with either:
  • evidence suggestive of cauda equina syndrome (CES) or spinal infection
  • objective significant new neurology
  • severe ongoing pain preventing mobility
• CT scan or MRI scan for low back pain is NOT clinically helpful if there are no red flags such as possible cauda equina syndrome, tumour, fracture or sepsis
  • MRI scan in the absence of red flags, whilst giving the patient “objective” information regarding the status of discs, does not improve the back pain but does increase the risk of neurosurgical referral, and potential neurosurgery procedure despite the fact that long term outcomes of these procedures are similar to patients not having these procedures¹⁾
• management for the vast majority is thus:
  • analgesia (non-steroidal anti-inflammatory drugs (NSAIDs) and paracetamol (acetaminophen))
  • education
  • manage the patient's anxiety (expectations regarding pain and short term restriction of activities, return to work, prognosis, etc) as excessive anxiety will exacerbate the perception of pain
  • supportive care perhaps in an ED observation unit if not able to self-manage at home due to severe pain
  • aids to assist getting out of bed (most need to roll onto stomach to achieve this during acute pain), putting on socks and shoes (this can be nearly impossible due to the muscle spasm and pain)
  • modification of unrealistic expectations
    • most patients with acute sciatica WILL have some persisting pain for weeks or a few months (10% take longer than 6-7 weeks to settle) which will be exacerbated by poor posture, prolonged sitting, heavy lifting or repeated twisting movements
    • surgery is NOT the solution for most patients
    • patients WILL need to modify their lifestyle to avoid future exacerbations
    • the aim is NOT total relief of pain (as this usually means excessive adverse effects from analgesics), but sufficient pain relief to allow mobilisation and self-care
    • patients will benefit from gentle mobilisation (eg. walking) as this reduces muscle spasm and maintains protective muscle power
    • patients will need to reduce weight if obese and strengthen abdominal muscles to help protect their back
    • there is NO quick fix - there is much the patient will need to actively do to get back to normality
  • those with severe pain / spasm may benefit from referral to physiotherapists
  • patients with financial compensation do MUCH worse as they often fail to do the hard rehabilitation work, and instead just rely on opiates and opioids with resultant dependence issues.
• other potential non-surgical therapies
  • these physical therapies are very unlikely to be able to reduce the disc herniation or have long term benefits
  • nerve root injections
    • may provide short term relief in some patients with severe pain due to nerve root impingement
  • spinal “manipulation”
    • its use is controversial with no or little evidence for long term benefits and generally not advised
    • may improve short term muscle spasm
  • basic spinal axial traction
    • its use is controversial with no or little evidence for long term benefits and generally not advised until further research demonstrates efficacy
    • a very small MRI study in patients without low back pain showed 42% body weight horizontal traction for 30min can increase lower lumbar disk space height esp. posteriorly ²⁾
    • may improve short term pain for up to 2 weeks but can increase the risk of lumbar injury and does not improve spinal mobility ³⁾⁴⁾
  • motorized non-surgical spinal decompression therapy (NSDT)
    • has recently been introduced as a type of motorized traction therapy often with computer control algorithms
    • its use is controversial and generally not advised until further research demonstrates efficacy however small studies seem to show benefit in pain reduction for those with subacute or chronic pain ⁵⁾⁶⁾

• include depression, dysthymia, somatiform pain disorder, substance abuse disorder, personality factors, anxiety disorder, neuropsychological barriers (eg. dementia, brain injury), etc.

• include anxiety, fear, panic, psychophysiological response, loss of control, abnormal dependence

• include anxiety, depression, post-traumatic stress disorder, anger, hostility, substance abuse, somatiform pain disorder, symptom magnification, duration since injury, disability mindset

• job dissatisfaction or conflict
• compensated unemployment
• family dynamics
• accepted norms
• legal influences
• financial security
• age-related

• consider assessing yellow flags for identifying psychosocial barriers to recovery:
  • ascertain the following potential barriers:
    • presence of beliefs that back pain is harmful or potentially severely disabling
    • fear-avoidance behaviour (avoiding a movement or activity due to misplaced anticipation of pain) and reduced activity levels
    • tendency to low mood and withdrawal from social interaction
    • an expectation that passive treatments rather than active participation will help.
  • ask about:
    • Have you had time off work in the past with back pain?
    • What do you understand is the cause of your back pain?
    • What are you expecting will help you?
    • How is your employer responding to your back pain? Your co-workers? Your family?
    • What are you doing to cope with back pain?
    • Do you think that you will return to work? When?

• non-organic signs and symptoms
• verbal/non-verbal behaviour dissociation
• compensable nature of injury
• seeking disability status for social welfare
• psychological factors as above
• requests for opiates and opioids
• repeated failed Rx for back pain or other illnesses

• Modic changes (MC) type I on MRI scan occur six times more frequently in the low back pain population than in the general population
• the evolution of MC takes years
• MC's are classified into 3 types:
  • type 1 consists of fibro vascular tissue
  • type 2 is yellow fat
  • type 3 is sclerotic bone
• in the vertebrae, MC is seen in relation to vertebral fractures, spondylodiscitis, disc herniation, severe disc degeneration, injections with chymopapain, and acute Schmorl's impression
• a new hypothesis postulated in 2008 suggested that a substantial proportion of patients with chronic low back pain associated with disc disease have “Modic” microfractures on MRI scan and this subgroup may have an anaerobic bacterial infection of the spine
• the Danish group of H.B. Albert published in Eur Spine J 22:689 2013 (pdf) their findings which suggest:
  • patients with infected herniated nucleus material by anaerobic bacteria in lumbar disc herniation develop in 80 % new MC I in adjacent vertebrae
  • those patients with low back pain and MC I after disc herniation improved highly statistically significant on all outcome measures under an antibiotic protocol