MRI Lumbar Spine — suspected cauda equina syndrome
Conus medullaris to the sacrum. Where the history raises the possibility of a higher lesion, extend to whole-spine coverage rather than repeating later.
Typical, not policy
Timings, volumes and delays here are representative values drawn from published guidance. Scanner generation, injector, cardiac output and local preference all move them. Confirm against your department's own protocol before you rely on a number.
When to use it
- Bilateral sciatica, saddle anaesthesia, new bladder or bowel dysfunction, or reduced anal tone — the classic emergency presentation.
- Rapidly progressive bilateral lower limb weakness with back pain.
- Unexplained urinary retention with back pain.
- Post-operative deterioration after lumbar surgery with new sphincter symptoms.
Technique
- Sagittal T1 and T2 plus axial T2 through the levels of interest is sufficient to answer the compressive question; a full elective protocol is not required out of hours.
- Axial imaging must cover every level with sagittal narrowing, because the degree of thecal sac compromise is an axial measurement.
- Where the sensory level or history is not clearly lumbar, whole-spine sagittal survey first avoids a second scan.
- A limited protocol trades some information for speed; that trade is the point, and the study should be extended if the limited series is equivocal.
Where it goes wrong
- Waiting for a full elective protocol slot and losing the time advantage that the limited study exists to buy.
- Sagittal images only, leaving canal compromise unquantified.
- Assuming a normal lumbar study excludes the syndrome when the history suggests a conus or thoracic lesion.
- Not extending coverage in a patient with a cancer history, where the cause may be at a level well above the lumbar spine.
Clinical questions that reach this study
Contrast
None
- The compressive question is unenhanced. Contrast is added only if an infective or neoplastic cause is suspected on the unenhanced images.
Acquisition
- Breathing
- Free breathing. This is a short, focused, time-critical acquisition.
- Preparation
- Suspected cauda equina syndrome is an emergency pathway with its own timing expectations, not a routine lumbar request. Say whether the patient has had previous lumbar surgery and at which level — it changes whether contrast is worth adding. Patients with severe pain may need analgesia before scanning to complete the axial series.
Safety checks this protocol carries
Derived from the contrast agent and phases above, not authored here — which is why they cannot drift apart from what the protocol actually does.
- MR safety screening for implants and foreign bodies· radiographer at scan