What is the likely cause and best course of treatment for a patient with left lower-limb pain and sensory loss due to lumbar spondylosis with L4-L5 posterior annular tear, diffuse disc bulge, and facet arthropathy?

L4-L5 Radiculopathy: Conservative Management First, Decompression if Failed

The patient's left lower-limb pain and sensory loss is almost certainly due to L4-L5 nerve root compression from the documented disc bulge, annular tear, and facet arthropathy—not the thoracic pathology—and should be treated with a structured 6-12 week conservative protocol before considering surgical decompression alone (not fusion, unless instability develops). 1, 2

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Why L4-L5 is the Culprit (Not Thoracic)

• Unilateral radicular pain with foot numbness matches L5 nerve root compression at L4-L5, which is the most common site for lumbar radiculopathy 1, 2
• Thoracic ligamentum flavum hypertrophy at T10-T12 produces bilateral myelopathic symptoms (spasticity, hyperreflexia, band-like sensory levels), not unilateral leg pain 2
• The focal T10 syrinx is clinically irrelevant unless it is large and expanding, which is not described here 2
• MRI-confirmed L4-L5 disc bulge with annular tear and facet arthropathy directly correlates with the clinical presentation of left leg radicular pain and sensory loss 1

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Mandatory Conservative Treatment Protocol (6-12 Weeks)

Surgery is not indicated until comprehensive conservative management has failed for at least 6 weeks, as recommended by the American College of Radiology and Congress of Neurological Surgeons 1, 2

Required conservative interventions:

• Formal structured physical therapy for at least 6-8 weeks (not just home exercises) 2
• Trial of neuroleptic medications (gabapentin or pregabalin) for neuropathic pain 2, 3
• NSAIDs or COX-2 inhibitors for inflammatory pain control 3
• Epidural steroid injection or transforaminal injection targeting the L5 nerve root if pain persists beyond 4-6 weeks 2, 4, 3
• Prostaglandin E1 (if available regionally) may help neurogenic symptoms 3

Red flags requiring urgent surgery (bypass conservative care):

• Progressive motor weakness (foot drop, inability to toe-walk)
• Cauda equina syndrome (bowel/bladder dysfunction, saddle anesthesia)
• Severe, incapacitating pain unresponsive to medications 3

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Surgical Decision: Decompression Alone vs. Fusion

Decompression alone is appropriate for this patient unless instability is documented 1, 2

The patient does NOT have spondylolisthesis or documented instability, which are the primary indications for fusion in lumbar stenosis 1, 2

Evidence supporting decompression without fusion:

• Class II evidence shows 96% good/excellent outcomes with decompression + fusion in patients with spondylolisthesis, but only 44% with decompression alone in that specific population 1
• However, in patients WITHOUT spondylolisthesis (like this case), decompression alone is sufficient and avoids the 31-40% complication rate associated with instrumented fusion 1, 2
• Fusion should be reserved for documented instability (>5mm translation on flexion-extension films), spondylolisthesis, or when extensive decompression creates iatrogenic instability 1, 2

When to add fusion at L4-L5:

• If intraoperative findings reveal instability (excessive facet resection required for adequate decompression) 1, 2
• If flexion-extension radiographs show >5mm translation (not mentioned in this case) 1
• If there is Grade 1 or higher spondylolisthesis (not present here) 1, 2

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Surgical Technique if Conservative Management Fails

Microdiscectomy or laminectomy/foraminotomy at L4-L5 is the procedure of choice 1, 2

• Target the L5 nerve root in the lateral recess and foramen, addressing the disc bulge and facet hypertrophy 1, 4
• Avoid excessive facet resection (>50% of facet joint), which creates iatrogenic instability requiring fusion 1
• Outpatient surgery is appropriate for single-level decompression without fusion 2

Expected outcomes:

• 86-92% of patients report significant improvement in leg pain and function after appropriate decompression 2
• Sensory loss may improve but often persists partially if nerve compression has been prolonged 5
• Motor weakness typically recovers if intervention occurs before permanent axonal damage 5

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Common Pitfalls to Avoid

Do not fuse L4-L5 without documented instability or spondylolisthesis

• Fusion increases complication rates from 6-12% (decompression alone) to 31-40% (instrumented fusion) 1, 2
• Fusion does not improve outcomes in stenosis without instability 1

Do not operate on the thoracic spine

• Thoracic decompression will not relieve unilateral leg radiculopathy and exposes the patient to unnecessary surgical risk 2

Do not skip conservative management

• Lack of formal physical therapy is a critical deficiency that must be addressed before surgery is considered medically necessary 2

Do not ignore adjacent level pathology

• If symptoms persist after L4-L5 decompression, re-evaluate for L5-S1 or L3-L4 involvement (not mentioned in this case but common) 2

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Monitoring for Instability Post-Decompression

• Obtain flexion-extension lumbar radiographs 6-12 weeks post-decompression if back pain worsens or new symptoms develop 1
• >5mm translation or >10° angular motion indicates instability requiring delayed fusion 1
• 6% of patients develop late instability after extensive decompression without fusion, so long-term follow-up is essential 1