CT Scan Findings: L4-L5 Disc Bulge with Nerve Root Compression—What It Means

A CT scan of the lumbar spine reveals specific findings at the L4-L5 level that correlate with common causes of lower back and leg pain. Understanding these findings helps patients engage meaningfully with their care team.

Imaging Findings Explained

• Asymmetric disc bulge (extradural, centrally located): The intervertebral disc extends beyond its normal boundary. "Extradural" means outside the dura (thecal sac); "asymmetric" indicates uneven extension, often more to one side.
• Mild thecal sac compression: The bulge presses on the dural sac containing the cauda equina (nerve roots) and cerebrospinal fluid.
• Mild indentation of bilateral exiting nerve roots with bilateral foraminal narrowing—right > left: The L4 and L5 nerve roots exit through the neural foramina at this level. Foraminal narrowing (stenosis) can compress these roots, causing radiculopathy. Right-sided predominance suggests symptoms may be more prominent on the right.
• Mild facet arthropathy at L4-L5: Degenerative changes in the facet joints (posterior spinal joints) — cartilage loss, osteophytes, joint hypertrophy — contributing to stenosis and mechanical pain.

Clinical Correlation Is Essential

Imaging findings ≠ symptoms. Many asymptomatic adults have disc bulges on imaging. The clinical question: Do these findings explain the patient's symptoms?

• Radiculopathy (L4/L5 distribution): Pain, numbness, tingling, weakness in specific dermatomes/myotomes (L4: medial leg/foot, ankle dorsiflexion; L5: lateral leg, dorsum of foot, big toe extension).
• Neurogenic claudication: Leg pain/heaviness with walking/standing, relieved by sitting/forward flexion (if central stenosis predominates).
• Mechanical low back pain: Axial pain worsened by movement, improved with rest.

Management Spectrum

Conservative (First-Line, 6-12 Weeks)

• Physical therapy: Core stabilization, McKenzie extension exercises, nerve glides, posture education.
• NSAIDs (ibuprofen, naproxen) ± muscle relaxants for acute flare.
• Activity modification (avoid aggravating movements; stay active within limits).
• Epidural steroid injections (transforaminal or interlaminar) for radicular pain refractory to PT/meds.

Surgical Indications

• Progressive neurologic deficit (worsening weakness, foot drop).
• Cauda equina syndrome (saddle anesthesia, urinary retention, bowel incontinence) — surgical emergency.
• Intractable radicular pain failing ≥6-12 weeks of structured conservative care.

Surgical Options

• Microdiscectomy (minimally invasive removal of herniated fragment).
• Laminectomy/foraminotomy (decompression of central canal/foramina).
• Fusion (if instability, spondylolisthesis, or extensive decompression needed).

Key Takeaway

These CT findings describe a structural lesion capable of causing symptoms, but treatment decisions rest on clinical correlation. A spine specialist (neurosurgeon, orthopedic spine surgeon, physiatrist) integrates imaging, exam, and patient goals to recommend the right path. Most patients improve with conservative care; surgery is reserved for specific indications.