Lumbar / Pelvis

Lumbar Radicular Syndrome in Disc Prolapse

Definition

According to the classification of the International Association for the Study of Pain (IASP,) lumbar radicular pain is defined as pain observed as originating in the lower extremities, and is caused by ectopic activation of nociceptive afferent fibres in a spinal nerve or root or other neuropathic mechanisms. This definition is problematic because ectopic activation of nociceptive afferent fibres is seldom or never proved in a clinical setting.

Lumbar radicular pain must be distinguished from lumbar radiculopathy. In lumbar radiculopathy, there is an objective sensory and/or motor deficit. Although these terms are often used interchangeably in the literature, radicular pain and radiculopathy are not synonymous.

Radicular pain is a symptom that is caused by ectopic impulses, while radiculopathy comprises neurological signs, such as sensory and motor changes.  Radicular pain and radiculopathy can occur at the same time.

Aetiology

Lumbar disc prolapse is the most frequent cause of lumbar radicular pain in patients under 50 years of age. After the age of 50, radicular pain can be caused by spinal degenerative changes, such as narrowing of the intervertebral foramen or lateral recess.

The main risk factors are: male gender, obesity, smoking, history of LBP, fear and depression, work-related factors, bending forwards, heavy manual work, lifting heavy loads, and exposure to vibrations.

Signs and symptoms

The patient may experience the radiating pain as sharp, dull, painful, throbbing or burning. Pain caused by a herniated disc will classically increase by bending forwards, sitting, coughing or physical (over)load. The pain lessens in the supine position and sometimes after walking.

As well as pain, patients often also report paraesthesia in the corresponding dermatome. The distribution of pain according a dermatome can provide information about the segmental nerve root involved. If present, the distribution of paraesthesia in a dermatome is more informative.

Diagnostics

Physical Examination

The diagnostic value of anamnesis, and physical and neurological examinations is still under debate. Only pain distribution is a useful parameter.

The most frequently described clinical test for lumbar radicular syndrome concerns Lasègue's test. If radicular pain can be provoked below 60°, there is a good chance of a lumbar radicular syndrome. The sensitivity of this test can vary, the overall sensitivity being 0.91 with a specificity of 0.26. This specificity decreases when the test is above 60° positive. Lasègue's crossed test is the only one with good specificity (0.88), but this is at the expense of sensitivity (0.29).

There is no consensus about the specificity of other neurological symptoms (paresis, sensory deficit or diminished reflexes).

Practically, neurological examination evaluates whether there are signs of L4 involvement (decreased knee tendon reflex, foot inversion) or S1 involvement (Achilles tendon reflex). L5 involvement may clinically be characterised by a 'drop foot', reduced ankle dorsal flexion and/or reduced dorsal flexion of the toes. S1 involvement includes reduction of plantar flexion.

Additional Somatic Diagnostics

Since the natural history of lumbar radicular pain is favourable in 60-80% of patients, and the pain can spontaneously improve or even disappear completely after six to 12 weeks, additional diagnostics in this acute phase are of little use.

Additional Psycho-cognitive Diagnostics

  • RAND-36 (quality of life)
  • VAS Pain (maximal, minimal, actual, average/week)
  • PCS (catastrophising)
  • HADS (fear and) depression

Multidisciplinary Treatment

Whether or not somatic treatment is indicated is based on the pain diagnosis.  Based on the findings of the pain questionnaires, additional diagnostics and/or multidisciplinary treatment consisting of various non-somatic treatments may be necessary.

Non-somatic Treatment

Somatic Treatment

Pharmacological treatment:

(Sub)acute radicular pain

Chronic radicular pain

  • Tricyclic antidepressants
  • Anticonvulsives: carbamazepine, oxcarbazepine, gabapentine and pregabaline.

Interventional Pain Treatment

(Sub)acute radicular pain

Chronic radicular pain

Invasive Treatment

  • Surgery of a disc prolapse results in the faster reduction of acute radicular pain.
  • Surgery is indicated when there is a neurological deficit in a caudal syndrome.