Lumbosacral Radiculopathy

Overview

Lumbosacral radiculopathy is dysfunction or irritation of a lumbar or sacral spinal nerve root. It typically causes radiating pain from the lower back or buttock into one leg, sometimes with paraesthesia, sensory loss, weakness or reduced reflexes. The distribution and neurological findings help identify the affected root. The commonest cause is a lumbar disc herniation; degenerative narrowing of the lateral recess or neural foramen is another important cause.

Most patients improve with time and non-operative care. New bladder or bowel dysfunction, saddle sensory change or severe or progressive neurological weakness requires urgent assessment for cauda equina syndrome or another compressive emergency.

Anatomy & Physiology

Lumbar nerve roots descend through the spinal canal and leave through intervertebral foramina. A posterolateral L4–L5 disc herniation usually compresses the traversing L5 root, whereas a foraminal or far-lateral L4–L5 lesion more often compresses the exiting L4 root. The L5–S1 disc commonly affects the traversing S1 root. Pain may result from both mechanical compression and inflammatory irritation of the root.

Aetiology & Risk Factors

Aetiology

• Lumbar disc herniation, particularly with acute or subacute symptoms.
• Degenerative spinal changes: facet hypertrophy, osteophytes and disc-height loss causing lateral-recess or foraminal stenosis.
• Degenerative spondylolisthesis or central canal stenosis, particularly in older adults.
• Less common but important: fracture, spinal infection, malignancy, epidural haematoma or other mass lesions.

Risk Factors

• Increasing age and degenerative disease, heavy or repeated spinal loading, smoking, obesity and previous episodes of back pain or disc disease are associated with radicular presentations.
• A history of cancer, immunosuppression, recent infection, trauma or anticoagulant use should prompt assessment for alternative serious causes when clinically relevant.

Pathophysiology

• Disc material or narrowed bony/ligamentous structures irritate or compress a spinal nerve root.
• Local inflammation and impaired nerve conduction produce radiating neuropathic pain, paraesthesia and, if motor fibres are affected, focal weakness.
• A large central lesion can compress multiple sacral roots and cause cauda equina syndrome.

Imaging abnormalities are common in people without symptoms; a lesion should therefore be interpreted alongside the clinical level and side.

Clinical Manifestations

• Sharp, shooting, burning or electric pain radiating from the back or buttock into a leg, often below the knee with L5 or S1 involvement.
• Numbness or tingling in a corresponding distribution; pain may worsen with coughing, sneezing, straining or sitting in disc-related disease.
• Focal weakness, altered sensation or diminished reflexes may accompany pain. A normal neurological examination does not exclude radicular pain.
• Stenosis may cause symptoms with standing or walking that ease with sitting or spinal flexion; this pattern suggests neurogenic claudication.

Root	Typical pain or sensory region	Motor finding	Reflex
L4	Anterior thigh and medial leg	Knee extension; sometimes ankle dorsiflexion	Reduced patellar reflex
L5	Lateral leg and dorsum of foot, including great toe	Great-toe extension, ankle dorsiflexion; heel walking may be difficult	No consistently reliable routine deep-tendon reflex
S1	Posterior calf and lateral foot	Plantar flexion; toe walking may be difficult	Reduced Achilles reflex

Patterns overlap. Test strength, sensation and reflexes rather than relying on pain location alone.

Diagnosis

Investigations

• No routine imaging initially for uncomplicated acute radiculopathy without red flags; clinical assessment and follow-up guide care.
• MRI lumbar spine: preferred when cauda equina syndrome, serious pathology or progressive neurological deficit is suspected; also consider after persistent disabling symptoms despite conservative care if surgery or an injection is being considered and imaging would change management.
• CT: useful when MRI is unavailable or contraindicated and imaging is necessary, especially for bony pathology; it is less informative for soft tissues and nerve roots.
• Electrodiagnostic studies: consider when symptoms, examination and imaging disagree or a peripheral neuropathy is a plausible alternative. Early testing can be falsely uninformative.
• Blood tests are not routine for uncomplicated radiculopathy; target tests to suspected infection, inflammation or malignancy.Treatment

Initial management

• Explain the generally favourable course, encourage continued normal activity as tolerated and avoid prolonged bed rest.
• Use graded exercise or physiotherapy, tailored to pain and function.
• Consider a short course of an NSAID when appropriate, at the lowest effective dose for the shortest practical duration, after considering gastrointestinal, renal and cardiovascular risk.
• Review symptoms and neurological function, with explicit advice to seek urgent care if red flags arise.

Persistent or severe symptoms

Consider specialist assessment when pain remains disabling or weakness persists despite an adequate period of conservative management. An epidural injection of local anaesthetic and steroid may be considered for acute, severe sciatica, primarily for short-term symptom relief, after discussion of benefits and risks. Consider surgical decompression for persistent sciatica when non-operative treatment has not improved pain or function and the imaging findings match the symptoms. Progressive motor deficit may warrant earlier surgical review.

Emergency management

Suspected cauda equina syndrome or rapidly progressive major neurological deficit requires immediate emergency referral, urgent MRI and spine surgical assessment. Do not defer referral while waiting for routine outpatient investigation.

Complications & Prognosis

Complications

• Persistent radicular pain
• Reduced activity and sleep
• Chronic sensory loss or weakness
• Foot drop.
• Delayed recognition of cauda equina syndrome may result in permanent bladder, bowel, sexual or neurological dysfunction.

Prognosis

• Many episodes improve over weeks to months with conservative care, although symptoms may recur or persist.
• Persistent objective weakness, severe disability or a compressive lesion that fits the clinical findings may justify specialist intervention.
• Clinical recovery and MRI appearance do not always change in parallel.

References

1. National Institute for Health and Care Excellence. Low back pain and sciatica in over 16s: assessment and management (NG59). London: NICE; 2016, updated guidance accessed September 2026.
2. American College of Radiology. ACR Appropriateness Criteria: Low Back Pain. Revised 2021.
3. National Institute for Health and Care Excellence. Suspected neurological conditions: recognition and referral (NG127). London: NICE.