Investigations
1st investigations to order
MRI lumbar spine without intravenous contrast
Test
Arrange an emergency MRI of the lumbosacral spine as the first-line investigation for any patient who presents at or is referred to hospital with red-flag symptoms for suspected CES.[1][6][15][16][18][24][37]
Under the NHS England national pathway for suspected CES, MRI should be performed as soon as possible and certainly within 4 hours of the request.[15][18]
MRI is the preferred imaging investigation in the evaluation of suspected CES because of its ability to accurately depict soft-tissue pathology, assess vertebral marrow, and assess the spinal canal patency.[1][37]
A single sagittal T2 weighted sequence is the recommended MRI protocol to screen for cauda equina (CE) compression.[15][18] If CE compression is identified, additional sequences (axial T2 weighted and sagittal T1 weighted) may be needed to inform surgery.[15][18]
If imaging confirms CE compression, make an immediate referral (day or night) for emergency spinal decompression surgery.[15][16][17]
Result
visualisation of lesion and compression of cauda equina
CT lumbar spine without intravenous contrast
Test
If there is an absolute contraindication to MRI (e.g., presence of an MR-unsafe implant), request a CT scan or CT myelogram.[15][18]
CT can delineate whether cauda equina (CE) compression is present but is less precise than MRI at characterising the aetiology of CES.[37]
If imaging confirms CE compression, make an immediate referral (day or night) for emergency spinal decompression surgery.[15][16][17]
Result
visualisation of lesion and compression of neural structures
thecal sac effacement of ≥50% has been proposed as a criterion for identifying CES on CT[39]
bladder scan (pre- and post-void)
Test
A pre- and post-void scan of the bladder can be a useful adjunct to MRI in assessment of urinary retention and completeness of bladder emptying in a patient with suspected CES.[15][40] It can be undertaken while the patient is waiting for MRI scanning but it must not delay MRI scanning or surgery.[15]
Do not use the results of bladder ultrasound in isolation to determine whether an MRI is indicated.[15] Every patient with suspected CES requires an emergency MRI, regardless of the findings of a bladder scan.[15][22]
If the patient is able to void, document the pre-void volume and the post-void residual volume (PVR).[15]
Investigations to consider
CT myelography of the lumbar spine
Test
Assesses the patency of the spinal canal/thecal sac, and the subarticular recesses and neural foramen. It can be useful for surgical planning in patients with CES.[37] Lumbar puncture in the lower segments may exacerbate CES.
Result
shows degree of cord compression
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