Low Back Pain
- Welzack Chapter 49 Low Back Pain1
Pain type
Nociceptive
Nociceptive back pain refers to pain caused by noxious stimulation of structures in lumbar spine2. This type of pain is typically described as dull and aching2.
Somatic referred pain
Pain is perceived in regions innervated by nerves other than those that innervate the site of noxious stimulation2.
Somatic referred pain is a distinct form of pain different from visceral referred pain or radicular pain2.
In the low back, somatic referred pain is generally produced when nerve endings innervating structures in the spine (IVD, Z Joints, or the SI joint) experience noxious stimuli2. Once this occurs, the noxious stimuli is sent through the nerve ending to the 2nd order neuron in the spinal cord, where other unrelated nerves also converge2. As a result of this convergence, the brain may receive these noxious stimuli and mistakenly perceive pain as originating from one of the other nerves that converges at that 2nd order neuron2.
Somatic referred pain is generally perceived as dull, aching, gnawing, and/or expanding pressure2.
Somatic referred pain generally covers a wide area and is difficult to localize but a patient can easily identify center/core2.
Once established, somatic referred pain is fixed and will not migrate2. Segmental maps are not consistent between studies/amongst subjects
The pattern of somatic referred pain is not dermatomal, since this would be irritation of the nerve/nerve root relevant to the site of noxious stimuli and would be considered radicular pain2.
In cases of low back somatic referred pain, patients the symptoms are generally in the gluteal region and proximal thigh but some cases extend as far as the foot2.
The somatic referred pain pattern corresponds to segmental innervation of deep tissues in limb like muscles/joints2.
Radicular back pain
Radicular pain refers to pain evoked by ectopic discharges of nociceptive stimulation from a dorsal root or the dorsal root ganglion (DRG) or a peripheral nerve2. Disc herniation = common cause or inflammation of affected nerve Lancinating quality of pain, traveling along length of lower limb in a band no more than 2-3 inches wide. Squeezing/pulling normal nerve roots does not produces radicular pain, only if nerve roots have been previously inflamed does mechanical stimulation evoke radicular pain For compression alone to be painful, it would involve the DRG (based on animal studies) Evokes discharges in Abeta and A delta and C fibers Radicular pain is not only due to a discharge in nociceptive afferents, due to a heterospecific discharge in the affected nerve. Evoked sensation is unpleasant but not exactly pain in a nociceptive sense Qualities are lancinating, shocking, electric. (more than just nociceptive afferents discharging) Sciatica?
Radiculopathy
Neurological state where conduction is blocked along spinal nerve or its roots Numbness is the symptom and sign Weakness ensues when motor fibers are blocked Diminished reflexes occur due to a sensory or motor block Numbness is DERMATOMAL and weakness is MYOTOMAL Not defined by pain, defined by neurological signs. Radiculopathy and radicular pain commonly occur together but Radiculopathy can occur in absence of pain Radicular pain can occur in absence of radiculopathy FALSE: Segmental origin of radicular pain can be determined from its distribution (NOT TRUE) Patterns of L4,L5 and S1 radicular pain CAN NOT be distinguished from each other Segments can be established when radicular pain occurs with radiculopathy. The derm distribution of numbness NOT PAIN allows the segment of origin to be determined.
Interventions
Exercise Induced Hypoalgesia (EIH)
EIH refers to a generalized improvement (reduction) in pain or pain sensitivity during or after exercise3. This form of hypoalgesia lasts ≤30 min after a single bout of exercise3. EIH is generally widespread3.
Aerobic exercise elicits greater effects of EIH than anaerobic3. Resistance training is more localized and leads to greater reduced pain sensitivity local to muscle contraction and these effects decrease more distal from the site of muscle contraction3. EIH is more variable in chronic pain populations More frequently impaired: with pain/pain sensitivity decreasing/unchanged or sometimes increasing in response to exercise