Cauda Equina



Compression of some or all of the nerve roots in the cauda equina

- bladder dysfunction

- bowel dysfunction

- saddle anaesthesia

- variable motor and sensory loss





- most common


Epidural haematoma

- post surgical

- spinals and anticoagulation


Epidural abscess



- metastatic prostate / lung / breats




Chronic stenosis / spondylithesis


Post surgical

- seen post stenosis decompression

- cause unknown




Spinal cord ends at L1 / conus medullaris

- L3 in children

- spinal cord appears to migrate proximally with growth

- relative greater growth of the spinal column


Conus medullaris

- attached to coccyx

- filum terminale


Dural sac containing L2 - S5


Urination / bladder control


Stretch receptors in bladder wall

- as distension occurs

- afferent signal travels up pelvic splanchnic nerves (S2/3/4)

- sacral cell bodies send signal back via efferent in same nerves

- produce contraction of detrusor muscle

- parasympathetic control


Cauda Equina

- lower motor nerve injury to S2-4 nerve roots

- flaccid bladder / overflow incontinence


Conus medullaris injury

- upper motor nerve changes at that level

- detrusor muscle spastically contracts and causes incontinence





Lower motor neurone symptoms in leg

- weakness

- sensory loss

- decreased / absent reflexes


Bladder dysfunction


S2-4 disruption

- parasympathetic nerves

- promote bladder emptying

- contract detrusor & relax internal sphincter


Unable to feel bladder filling


Unable to void

- retention

- eventual overflow




Nerve roots

- very susceptible to compression

- don't have 3 layers like peripheral nerve roots

- endoneurium only

- then CSF and dura


May develop ischaemia

- radicular arteries

- form of compartment syndrome




Injury to the sacral nerve roots can be permanent

- need early decompression < 24 hours

- otherwise permanent bladder and bowel dysfunction




Two groups

- acute presentation - severe pain

- insidious presentation - stenosis / spondylolithesis


Bladder dysfunction

- difficulty initiating / stopping stream

- progresses to retention

- progresses to overflow incontinence



- unable to feel or control / incontinence


Other symptoms

- severe back pain

- severe sciatica

- lower leg weakness and parasthesia 

- saddle anaesthesia / can't feel toilet paper




Perianal sensation

- may have preserved light touch

- may need pin prick

- S 3,4,5


Rectal tone

- decreased



- full

- increased volume on bladder scan

- cannot feel tug on catheter




Usually a disc will take up > 1/3 of canal diameter




Urgent Decompression



- evidence of improved outcomes for decompression within 48 hours versus > 48 hours

- no evidence for < 24 hours

- reasonable to do so as soon as able




Buchner and Schiltenwolf Orthopedics 2002

- 17 / 22 regained full urinary function


Outcome likely related to

- duration of symptoms / timing of decompression

- severity of initial symptoms / signs / bladder dysfunction