GGC - MSK Index
Radicular Pain
Definition
Pain evoked by ectopic discharges emanating from a dorsal root or its ganglion (Bogduk, 2009).
Cause
Herniation of a lumbar disc is the most common cause, with inflammation of the affected nerve (Bogduk, 2009).
Presentation
- Lancinating, electric shock like pain
- Travelling along the length of the lower limb (Bogduk, 2009)
Radiculopathy
Definition
Radiculopathy is a neurological state in which conduction is blocked along a spinal nerve or its roots. When sensory fibres are blocked, numbness is the symptom and sign. When motor fibres are blocked weakness ensues.
Diminished reflexes occur as a result of either sensory or motor block. The numbness is dermatomal in distribution and the weakness is myotomal.
Radiculopathy can occur in the absence of pain and radicular pain can occur in the absence of radiculopathy (Bogduk, 2009) therefore radiculopathy is not defined by pain. It is defined by objective neurological signs.
Cause
Usually due to compression or injury to a nerve root in the lumbar spine. The axons of these nerves are either compressed directly or are rendered ischaemic by compression of their blood supply.
The 3 most common ways that compress or irritate an exiting nerve root include
- Herniation of a disc posterolaterally
- Degeneration of disc causing decreased height causing narrowing of neural foramen
- Both formation of osteophytes and hypertrophied joints, can contribute to narrowing of the neural foramen
The exact pathogenesis of Lumbar radiculopathy is unclear.
Prevalence
Less than 5%
Presentation
Back pain associated with radiculopathy is often unilateral. Pain radiation depends on the involved nerve root, although some distributional overlap may exist.
Sensory or motor dysfunction may be present without significant pain (Eubanks, 2010; Yoon, 2011).
Signs of lumbar radiculopathy may include postural changes (e.g. antalgic posture, fixed flexion) restricted and painful back movements, muscle wasting and neurological signs (CKS NICE, 2015).
Frequent signs and symptoms include varying degrees of sensory loss, reduction of muscle power with or without evidence of muscle wasting and reduction or absence of reflexes as well as anaesthesias, dysesthesias and paraesthesia's related to nerve roots (NASS).
In subjects with confirmed radiculopathy (from nerve conduction studies), as many as 31% will have no weakness and as many as 45% will have no sensory abnormalities detected on physical examination. This is due to significant overlap of dermatomes which results in each segment of skin receiving sensory information from more than one spinal nerve.
Weakness requires degeneration or conduction block of a relatively large proportion of axons contributing to a particular muscle. Nearly all muscles receive innervations from more than one spinal nerve (De Luigi, 2011).