What is a likely pain diagnosis for a 55‑year‑old man with three‑week low back pain radiating to the posterior right thigh and calf, right L5 sensory loss and weakness, a positive straight‑leg raise test, and magnetic resonance imaging (MRI) showing an L4‑L5 disc herniation?

Lumbar Disc Herniation with L5 Radiculopathy

This patient has lumbar disc herniation with L5 radiculopathy—a specific diagnosis characterized by L4-L5 disc herniation causing nerve root compression, manifesting as posterior leg pain, L5 dermatomal sensory loss, weakness in L5-innervated muscles, and positive nerve tension signs. 1

Clinical Diagnosis

This presentation represents radiculopathy, which is the primary consideration when back pain radiates down the leg in a typical lumbar nerve root distribution. 1 The clinical features that confirm this diagnosis include:

• Anatomic correlation: More than 90% of symptomatic lumbar disc herniations occur at L4/L5 and L5/S1 levels, making this the most common site for this pathology. 1

• Nerve root compression pattern: The L4-L5 disc herniation compresses the L5 nerve root, producing the characteristic posterior thigh and calf radiation pattern described. 1

• Sensory findings: L5 dermatomal sensory loss is a hallmark of L5 radiculopathy from L4-L5 disc herniation. 1

• Motor findings: Weakness in L5-innervated muscles (likely foot/toe dorsiflexion weakness, though not explicitly stated) accompanies the sensory changes. 1

• Positive straight-leg raise: This test demonstrates 91% sensitivity for herniated disc, confirming nerve root tension. 1 The test is positive when it reproduces the patient's sciatica between 30-70 degrees of hip flexion. 2

Differential Considerations

Spinal stenosis can be distinguished from disc herniation because stenosis typically presents as pseudoclaudication (leg pain with walking relieved by sitting/flexion), not the pattern of pain worsening after positional changes seen with mechanical nerve root compression. 1 Additionally, stenosis is more common in patients over 65 years, making it less likely in this 55-year-old. 1

Red flags that would change management urgency must be excluded:

• Cauda equina syndrome: Urinary retention (90% sensitivity), fecal incontinence, and saddle anesthesia require urgent MRI and surgical evaluation. 1
• Malignancy: History of cancer, unexplained weight loss, age >50, or failure to improve after 1 month warrant consideration. 1
• Infection: Fever, IV drug use, or recent infection suggest infectious etiology. 1
• Fracture: Osteoporosis history or steroid use in older patients raise concern. 1

Management Algorithm

Initial conservative management for at least 6 weeks is the standard approach, as most patients improve within the first 4 weeks with noninvasive treatment. 1

Pharmacologic interventions:

• NSAIDs are first-line with good evidence for moderate pain relief in acute radicular pain. 1
• Skeletal muscle relaxants have good evidence for short-term effectiveness in acute low back pain. 1
• Acetaminophen can serve as adjunctive therapy with fair efficacy evidence. 1

Non-pharmacologic interventions:

• Remain active: Advising patients to stay active is more effective than bed rest for acute or subacute low back pain. 1
• Superficial heat has good evidence for moderate benefits in acute presentations. 1
• Spinal manipulation has fair evidence for small to moderate benefits acutely. 1

Imaging timing:

MRI was appropriate in this case because it was obtained after symptoms persisted beyond the initial conservative period, and the patient is a potential surgical candidate. 1 MRI is the imaging study of choice because it accurately depicts soft-tissue pathology, assesses nerve root compression, and evaluates spinal canal patency. 1

Prognosis and Patient Education

The natural history is favorable: Most patients experience substantial improvement in the first month, and the majority of disc herniations show radiographic reabsorption or regression by approximately 8 weeks after symptom onset. 1, 3

When to Escalate Care

Specialist referral within 2 weeks is appropriate for severe radicular pain that is disabling and prevents normal daily activities. 1 For less severe but persistent radicular pain, referral should occur within 3 months. 1

Surgical evaluation should be considered only after a minimum of 6 weeks of failed conservative therapy with documented nerve root compression on imaging. 1 Progressive motor deficits or cauda equina syndrome warrant immediate surgical consultation. 1

Critical Pitfalls to Avoid

• Do not prescribe bed rest—remaining active is more effective than bed rest for recovery. 1
• Do not rush to epidural steroid injections—recent high-quality guidelines strongly recommend against epidural injections for chronic radicular spine pain. 1
• Do not order premature imaging in the absence of red flags, as early imaging does not improve outcomes and increases healthcare costs. 1