Cauda equina syndrome refers to a collection of symptoms and signs that result from severe compression of the descending lumbar and sacral nerve roots. It is considered a diagnostic and surgical emergency.
Cauda equina syndrome is rare with prevalence estimated at approximately 1 in 65,000 (range 33,000 to 100,000) 1. It has, however, been estimated to occur in ~1% (range 0.1-2%) of herniated lumbar discs 2,3.
Cauda equina syndrome can present either acutely or chronically and requires two sets of symptoms/signs 1-3:
- perianal and "saddle" paraesthesia
- bowel, bladder and/or sexual dysfunction
There is a host of associated symptoms and signs, which may be unilateral or bilateral and have a variable presence 1-3,6:
- low back pain
- lower limb paraesthesia and/or motor weakness
- reduction/absence of lower limb reflexes
- decreased rectal tone
Cauda equina syndrome (CES) can be classified into two entities 1,2:
- Incomplete (CES-I): perianal/saddle paraesthesia but urinary retention/incontinence has not fully developed although the loss of urgency or decreased sensation may be present.
- Cauda equina syndrome with retention (CES-R): perianal/saddle paraesthesia with urinary retention or incontinence.
CES-R accounts for ~60% (range 50-70%) and CES-I accounts for ~40% (range 30-50%) of presentations 6.
There is a long list of conditions that can cause cauda equina syndrome (some of these are very rare) 1-3:
- both acute and chronic form may be seen in long-standing ankylosing spondylitis (2nd-5th decades; average 35 years) 7-9
- spinal fracture or dislocation
- epidural haematoma (may also be spontaneous, post-operative, post-procedural or post-manipulation)
- numerous other rare space-occupying lesions (e.g. sarcoid)
- congenital or acquired spinal canal stenosis 3
- recent lumbar spinal surgery 2
- limited value; may demonstrate gross degenerative or traumatic bony disease 2
- useful in patients in whom MRI is contraindicated or not available
- partial or complete blockage of contrast
- may demonstrate an "hourglass" shape to the contrast-filled thecal sac in complete blockage 2
- imaging modality of choice 2,3
- sagittal and axial T1 and T2 sequences are usually sufficient 4
- post-contrast and STIR sequences may be required if infective causes are suspected 3,4
Treatment and prognosis
Cauda equina syndrome is considered a diagnostic and surgical emergency, although there is some debate about the timing of surgery (and depends on acute vs. chronic) but surgical decompression within 24 hours seems to have the best outcomes 1,3,6. Patients with CES-R have a poorer outcome 3. Approximately 20% of patients will have a poor outcome in terms of urological and/or sexual function as well as lower limb paraesthesia and weakness 6.
- 1. McNamee J, Flynn P, O'Leary S et-al. Imaging in cauda equina syndrome-a pictorial review. Ulster Med J.82 (2): 100-8. Free text at pubmed - Pubmed citation
- 2. Gitelman A, Hishmeh S, Morelli BN et-al. Cauda equina syndrome: a comprehensive review. Am J. Orthop. 2009;37 (11): 556-62. Pubmed citation
- 3. Lavy C, James A, Wilson-MacDonald J et-al. Cauda equina syndrome. BMJ. 2009;338 (mar31 1): b936. doi:10.1136/bmj.b936 - Pubmed citation
- 4. Emergency Radiology. Cambridge University Press. ISBN:0521672473. Read it at Google Books - Find it at Amazon
- 5. Wilmink J. Lumbar Spinal Imaging in Radicular Pain and Related Conditions. Springer. ISBN:354093829X. Read it at Google Books - Find it at Amazon
- 6. Gardner A, Gardner E, Morley T. Cauda equina syndrome: a review of the current clinical and medico-legal position. Eur Spine J. 2011;20 (5): 690-7. doi:10.1007/s00586-010-1668-3 - Free text at pubmed - Pubmed citation
- 7. Lan HH, Chen DY, Chen CC et-al. Combination of transverse myelitis and arachnoiditis in cauda equina syndrome of long-standing ankylosing spondylitis: MRI features and its role in clinical management. Clin. Rheumatol. 2007;26 (11): 1963-7. doi:10.1007/s10067-007-0593-2 - Pubmed citation
- 8. Shaw PJ, Allcutt DA, Bates D et-al. Cauda equina syndrome associated with multiple lumbar arachnoid cysts in ankylosing spondylitis: improvement following surgical therapy. J. Neurol. Neurosurg. Psychiatr. 1991;53 (12): 1076-9. Free text at pubmed - Pubmed citation
- 9. Bowie EA, Glasgow GL. Cauda Equina Lesions Associated with Ankylosing Spondylitis. Br Med J. 2011;2 (5243): 24-7. Free text at pubmed - Pubmed citation