15. Cauda Equina Syndrome

Question 1

What is the cauda equina?

Answer 1

A bundle of spinal nerves and spinal nerve roots that consists of L2-5 and S1-5.

• Formed by the nerve roots caudal (distal) to the level of the termination of the spinal cord at L1/L2.

Question 2

What does the cauda equina supply + innervate?

Answer 2

The nerves of the cauda equina supply:

1. Sensation to the lower limbs, perineum, bladder and rectum
2. Motor innervation to the lower limbs and the anal and urethral sphincters
3. Parasympathetic innervation of the bladder and rectum

Question 3

What is the piece of dura in the middle of the cauda equina called?

Answer 3

Conus medullaris

Question 4

What happens to the nerves in the cauda equina?

Answer 4

They still exit the spinal cord at their respective vertebral level.
For the cauda equina nerves, this is L3-L5, S1-S5, C0

Question 5

Describe the structure of the cauda equina.

Answer 5

The spinal cord tapers down at the end in a section called the conus medullaris.

The nerve roots exit either side of the spinal column at their vertebral level (L3, L4, L5, S1, S2, S3, S4, S5 and Co).

Question 6

What is cauda equina syndrome (CES)?

Answer 6

A surgical emergency where the nerve roots of the cauda equina at the bottom of the spine are compressed

Question 7

Briefly describe the pathophysiology of cauda equina syndrome.

Answer 7

Spinal compression at or distal to the L1 nerve root disrupts sensation and movement. It is a surgical emergency.

Question 8

What causes damage to the cauda equina?

Answer 8

Damage to spine at or distal to L1

Question 9

What is the most common cause of cauda equina syndrome?

Answer 9

Herniated lumbar disk - MOST COMMONLY at L4/5 and L5/S1

Question 10

Give 5 signs of cauda equina syndrome.

Answer 10

1. Leg weakness = flaccid + areflexic (LMN signs)
2. Bilateral sciatica (pain radiates down the leg to the foot).
3. Saddle anaesthesia.
4. Bladder/bowel dysfunction.
5. Erectile dysfunction.
6. Bilateral or severe motor weakness in the legs
7. Reduced anal tone on PR examination

Question 11

What investigation might you do to see if someone has cauda equina syndrome?

Answer 11

Visualisation of lesion and compression of neural structures

1. 1st line - Rectal exam
   -> reduction/lack of of anal tone
2. MRI of Lumbar spine without IV contract - GOLD STANDARD
   -> urgent!!
3. CT of Lumbar spine without IV contract

Question 12

Management of cauda equina syndrome.

Answer 12

1. Immediate hospital admission
2. Emergency MRI scan to confirm or exclude cauda equina syndrome
3. Neurosurgical input to consider lumbar decompression surgery
   -> surgical decompression within 48 hrs

Question 13

Give 3 complications of cauda equina syndrome.

Answer 13

• Paralysis of lower limbs
• Permanent bladder
• Bowel and sexual dysfunction

Question 14

Differential diagnosis of cauda equina syndrome.

Answer 14

1. Mechanical back pain or prolapsed lumbar disc
2. Fracture of lumbar vertebrae due to trauma
3. Spinal tumour
4. Spinal cord compression
5. Conus medullaris syndrome

Question 15

How can you distinguish cauda equina syndrome from spinal cord compression?

Answer 15

1. Cauda equina syndrome ONLY affects lower motor neurones.
   Spinal cord compression affects both UMN and LMN so, you will also see some hyperreflexia.
2. Depending on the cause, spinal cord compression could be gradual onset (e.g. in spinal stenosis), BUT cauda equina syndrome is always a sudden onset.