Cauda Equina Syndrome

Cauda equina syndrome (CES) is a neurosurgical emergency which occurs when there is compression of the cauda equina.

Pathophysiology

Occurs due to direct compression of the cauda equina. The spinal cord terminates into a structure called the conus medullaris, usually at the L1/L2 level. Distal to this is the cauda equina (Latin for tail of horse due to its appearance) - a bundle of nerves carrying the nerve roots for L2-S5 and the coccygeal nerve. Its function is critical:

• Motor: Innervation of the pelvic floor muscles, lower limbs and anal sphincter
• Sensory: Sensation around the perineum and lower limbs
• Autonomic: Provides parasympathetic supply to the bladder as well as to the pelvic organs i.e. reproductive organs and digestive organs.

Causes

• Lumbar disc herniation: Particularly at the L4/L5 or L5/S1 level
• Trauma: For example, from a fracture
• Spinal stenosis
• Primary malignancy
• Metastases
  • Prostate
  • Renal
  • Lung
  • Breast
  • Thyroid
• Discitis
• Iatrogenic: For example, due to haematoma forming after spinal anaesthesia or lumbar puncture

Risk Factors

• History of disc herniation
• Heavy lifting
• Obesity
• Female

Clinical Features

• Lower back pain
• Bilateral sciatica: Can be unilateral or may begin as unilateral and progress to involve both legs. Bilateral sciatica is a red flag.
• Urinary retention: Due to disruption of autonomic nerves
• Saddle anaesthesia: Numbness or paraesthesia in the saddle region – asking patients if they can feel the toilet paper when they wipe their bottom is a good way of assessing this.
• Lower limb paraesthesia
• Lower limb weakness: Alongside other features of lower motor neuron disease such as hyporeflexia/areflexia.
• Bladder/bowel dysfunction: This can be in the form of urinary retention/constipation, or urinary/faecal incontinence.
• Reduced/loss of anal tone
• Sexual dysfunction: Erectile dysfunction or loss of vaginal sensation

Investigations

Bedside

• A full neurological exam checking the dermatomes and myotomes of the lower limbs specifically is extremely important with CES. Mostly lower motor neuron signs will be seen i.e., hypotonia/areflexia etc.
• Pre and post-void bladder scan: Important to assess for bladder dysfunction. Urinary retention is a red flag.
• Catheter tug: No sensation when a catheter is being tugged is another red flag.
• PR examination: There is some debate with regards to the value of a PR examination but it is essentially used to assess anal tone by asking the patient to squeeze, as well as perianal sensation.

Bloods

• FBC, U&E, CRP: Baseline
• Clotting screen: Pre-operative
• Group & save: Pre-operative

Imaging

• MRI Whole Spine: This is the mainstay of diagnosis.
• CT Myelogram: Sometimes done as an alternative to patients who are unable to have an MRI due to contraindications.

https://en.wikipedia.org/wiki/Cauda_equina_syndrome#/media/File:MRI_of_the_lumbar_spine_with_abscess_in_the_posterior_epidural_space,_causing_cauda_equina_syndrome.jpg

MRI demonstrating Cauda Equina syndrome

Differential Diagnosis

• Musculoskeletal pain: From strain of paraspinal muscles
• Radiculopathy: Occurs when there is disruption in spinal nerve/nerve root conduction. It results in weakness/paraesthesia/anaesthesia. Radicular pain can occur as a consequence of irritation of the spinal nerve tissue. This most commonly occurs secondary to nerve compression e.g. from a disc prolapse or from degenerative changes in the spine.
• Sciatica: ‘Shooting pain’ from buttock/lower back, down the back of the leg.
• Discitis: Should be suspected in patients with fever and raised inflammatory markers, particularly if there is a history of IVDU or immunosuppression.

Management

The mainstay of treatment is surgical decompression. This is often done via a laminectomy which involves removal of the lamina part of the vertebra, which enables decompression of the spinal cord.

References

https://www.ncbi.nlm.nih.gov/books/NBK537200/#:~:text=Cauda%20equina%20syndrome%20(CES)%20results,the%20L3%2DL5%20nerve%20roots.

https://spinal.co.uk/wp-content/uploads/2023/08/National-Suspected-Cauda-Equina-Pathway-February-2023-FINAL-V1-1.pdf