Definition
Compression of some or all of the nerve roots in the cauda equina
- bladder dysfunction
- bowel dysfunction
- saddle anaesthesia
- variable motor and sensory loss
Aetiology
HNP
- most common
Epidural haematoma
- post surgical
- spinals and anticoagulation
Epidural abscess
Tumours
- metastatic prostate / lung / breats
Trauma
Chronic stenosis / spondylithesis
Post surgical
- seen post stenosis decompression
- cause unknown
Anatomy
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
Neurology
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
Pathology
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
Issue
Injury to the sacral nerve roots can be permanent
- need early decompression < 24 hours
- otherwise permanent bladder and bowel dysfunction
Symptoms
Two groups
- acute presentation - severe pain
- insidious presentation - stenosis / spondylolithesis
Bladder dysfunction
- difficulty initiating / stopping stream
- progresses to retention
- progresses to overflow incontinence
Bowel
- 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
Signs
Perianal sensation
- may have preserved light touch
- may need pin prick
- S 3,4,5
Rectal tone
- decreased
Bladder
- full
- increased volume on bladder scan
- cannot feel tug on catheter
MRI
Usually a disc will take up > 1/3 of canal diameter
Management
Urgent Decompression
Timing
- 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
Outcomes
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