Diagnostic Guidelines
Imaging Modality Protocols (MRI vs. CT)
Selecting the correct diagnostic imaging modality maximizes clinical utility, minimizes patient radiation, and ensures rapid access to surgical reviews.
Clinical Presentation Decision Matrix
Use this clinical matrix to choose the first-line imaging modality based on the patient's presenting symptoms:
| Clinical Presentation | First-line Modality | Protocol Specifications & Details |
|---|---|---|
| Acute Radiculopathy / Sciatica Leg/arm pain matching nerve root pathway | MRI Spine (Non-contrast) | MRI Cervical or Lumbar Spine without contrast. Excellent for soft-tissue visualization of disc herniation, canal narrowing, and nerve root compression. |
| Suspected Myelopathy / Cord Compression Hand clumsiness, gait imbalance, hyperreflexia | Urgent MRI Spine (Non-contrast) | MRI Cervical or Thoracic Spine without contrast. Directly visualizes spinal cord compression and intramedullary signal changes (T2-hyperintensity). |
| Chronic Mechanical Low Back Pain Isolated back pain, arthritic stiffness | Plain X-ray / Conservative | Neurosurgical referral is rarely indicated for isolated LBP. Start with plain upright X-rays. MRI is NOT indicated unless red flags or radiating nerve pain are present. |
| Suspected Intracranial Tumour / Meningioma Progressive focal deficit, headaches, seizures | MRI Brain (With Contrast) | MRI Brain with and without Gadolinium contrast. Contrast enhancement is critical to delineate tumour margins, vascularity, and mass effect. |
| Suspected Brain Aneurysm / AVM Suspected vascular lesion or family screening | MRI Brain + MRA | MRI Brain with Magnetic Resonance Angiography (MRA). Non-invasive screening. Catheter angiography remains the gold standard if details are needed. |
| Acute Thunderclap Headache / Trauma Sudden severe pain, suspected hemorrhage | Urgent CT Brain (Non-contrast) | Non-contrast CT Brain is the first line to detect acute blood (subarachnoid/intracranial haemorrhage) or acute skull fractures. |
Managing MRI Contraindications
If a patient requires an MRI but has absolute contraindications, high-resolution CT scans should be substituted:
Absolute MRI Contraindications
- Non-MRI-compatible cardiac pacemakers or defibrillators.
- Metallic foreign bodies in the orbit (eye) or brain.
- Certain older metallic aneurysm clips or cochlear implants.
Substituted CT Protocol
- Spine: High-resolution CT Spine with Multiplanar Reconstruction (MPR) to evaluate bony canal stenosis.
- Brain: High-resolution CT Brain with contrast or CT Angiography (CTA) if vascular pathology is suspected.