Lumbar Radicular Pain
Radicular pain is generated by discharges from a dorsal root or dorsal root ganglion. Inflammation plays an important role as simple compression does not necessarily result in pain. Radicular pain may or may not be associated with radiculopathy. Disc herniation is the most common cause of radicular pain. The pain is often described as travelling along the length of the limb in a narrow band two to three inches wide. L4, L5, and S1 pain patterns have significant overlapping pain areas.
Radicular pain is distinct from somatic referred pain. Radicular pain is shooting and band-like. Somatic referred pain on the other hand is constant in position, poorly localised, diffuse, and aching in quality.
Sensory Deficit Maps with Nerve Block
In 1993 Nitta et al looked at dermatome patterns by doing fluoroscopically guided spinal nerve anaesthetic blocks in patients with radicular pain. They found the following sensory deficits.
Inadvertent Pain Maps during TFI
Furman et al in 2019 mapped lower limb radicular symptoms based on inadvertent pain patterns during supraneural transforaminal injections, the data is modified in table format below. They confirmed that history and pain charts cannot predict the nerve root level. The buttock is a very common pain referral location across all nerve roots, while pain in the thigh and leg frequently follows dermatomal distributions. A significant limitation of the study is that injectate in transforaminal injections frequently traverses segment levels.
Radiculopathy occurs when conduction is blocked in the axons of a spinal nerve or its roots. When the sensory axons are affected the patient develops numbness, while when the motor axons are affected then weakness develops. Radiculopathy can be a result of compression or ischaemia. Radiculopathy does not cause pain in either the back or the legs. It is purely a neurological loss. Radiculopathy may be associated with somatic referred pain or with radicular pain.
|Disc Disorders||Disc Herniation|
- Bogduk On the definitions and physiology of back pain, referred pain, and radicular pain. Pain 2009. 147:17-9. PMID: 19762151. DOI.
- Bogduk, Nikolai. Clinical and radiological anatomy of the lumbar spine. Chapter 15. Edinburgh: Elsevier/Churchill Livingstone, 2012
- Nitta et al. Study on dermatomes by means of selective lumbar spinal nerve block. Spine 1993. 18:1782-6. PMID: 8235861. DOI.
- Furman & Johnson Induced lumbosacral radicular symptom referral patterns: a descriptive study. The spine journal : official journal of the North American Spine Society 2019. 19:163-170. PMID: 29800710. DOI.