What is the diagnosis?

Lumbar Radiculopathy (L5 Nerve Root)

This patient has L5 radiculopathy secondary to L5-S1 disc herniation with lateral recess and foraminal stenosis, confirmed by the constellation of clinical findings (grade I gastrocnemius weakness, absent Achilles reflex, positive straight leg raise) that correlate directly with MRI evidence of nerve root compression. 1

Clinical Diagnostic Features

The diagnosis of lumbar radiculopathy is established through specific clinical and radiographic correlation 2:

• Radiculopathy is defined as dysfunction of a nerve root associated with pain, sensory impairment, weakness, or diminished deep tendon reflexes in a nerve root distribution 2
• Sciatica (pain radiating down the leg below the knee in sciatic nerve distribution) is the most common symptom of lumbar radiculopathy, suggesting nerve root compromise from mechanical pressure or inflammation 2
• The positive straight-leg-raise test (reproduction of sciatica when leg raised between 30-70 degrees) indicates nerve root tension and is a specific indicator of nerve root compression 2, 1

Specific L5 Nerve Root Findings

This patient's presentation is classic for L5 radiculopathy 3, 4:

• Motor deficit: Grade I weakness of gastrocnemius muscle (ankle plantar flexion weakness) 1
• Reflex changes: Absent Achilles reflex 1
• Functional impairment: Ambulating with a limp due to motor weakness 1
• Pain distribution: Radiating symptoms consistent with L5 nerve root distribution 4

Radiographic Correlation

The MRI findings directly support the clinical diagnosis 1:

• 6 mm left and central disc herniation at L5-S1 level 1
• Lateral recess stenosis causing nerve root compression 1
• Foraminal stenosis at the corresponding level where L5 nerve root exits 1
• The American College of Radiology emphasizes that MRI findings showing nerve root compression at the corresponding level must correlate with clinical symptoms and neurological deficits 1

Diagnostic Pitfalls to Avoid

Critical consideration: While disc herniations typically cause symptoms at the adjacent level, non-adjacent radiculopathy can occasionally occur 5, 6:

• An L2/3 disc herniation can rarely cause L5 radiculopathy through atypical mechanisms 5
• Contralateral radiculopathy from ipsilateral disc herniation may occur due to migrated epidural fat 6
• However, in this case, the L5-S1 disc herniation with lateral recess and foraminal stenosis at the same level makes this the straightforward diagnosis 1

Exclusion of Alternative Diagnoses

Before confirming lumbar radiculopathy, the following must be excluded 2:

• Spinal stenosis (narrowing of spinal canal causing neurogenic claudication - leg pain with walking/standing, relieved by sitting) 2
• Cauda equina syndrome (urinary retention/incontinence, bilateral motor weakness, saddle anesthesia) - this is a surgical emergency 2
• Cervical or lumbar degenerative disease with nerve root compression at other levels 2
• Peripheral neuropathy (such as diabetic neuropathy, which would show symmetric distal findings rather than dermatomal distribution) 2
• Vascular claudication (distinguished from neurogenic claudication by relief with standing still rather than requiring sitting/flexion) 2

Duration and Conservative Treatment Failure

The one-year symptom duration with failed conservative management supports the diagnosis and indicates appropriateness for surgical consideration 1:

• Symptoms exceeding 6 weeks with objective neurological deficits warrant consideration of surgical intervention 1
• This patient has tried multiple conservative treatments (chiropractic care, home exercise, medication) without improvement 1
• The American College of Physicians recommends patients try conservative treatments before surgical intervention, which has been satisfied in this case 1

Diagnostic Confirmation

The diagnosis is definitively established by the triad of 1, 4:

1. Clinical symptoms: Radicular pain pattern with functional impairment
2. Objective neurological deficits: Motor weakness (grade I gastrocnemius) and reflex loss (absent Achilles)
3. Radiographic correlation: MRI showing disc herniation with nerve root compression at the exact level corresponding to clinical findings