Cauda equina syndrome

Published on 02/04/2015 by admin

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Last modified 22/04/2025

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91 Cauda equina syndrome

Instruction

This patient has bowel and bladder dysfunction; examine the lower limbs.

Salient features

History

• Ask the patient whether there is pain (usually projected to the perineum and thighs); these are root pain in the dermatomes L2 or L3 or S2 or S3 (whereas pain in L4, L5 or S1 distribution is commonly attributed to disc disease)

• Determine whether there is a history of trauma and ‘neural claudication’ (where the patient develops root pain and leg weakness, usually a foot drop while walking that rapidly recovers with resting)

• Pain in the anterior thigh, wasting of the quadriceps muscle, weakness of the foot invertors (caused by L4 root lesion) and an absent knee jerk

• Obtain history of leukaemia or prostatic carcinoma (primaries for bony metastases).

Examination

• Flaccid, asymmetrical paraparesis

• Knee and ankle jerks are diminished or absent

• Saddle distribution of sensory loss up to the L1 level

• Plantars downgoing.

Diagnosis

This patient has flaccid paraparesis with saddle anaesthesia caused by cauda equina syndrome (lesion) caused by a compressive lesion (aetiology).

Advanced-level questions

What is the relationship of the spinal cord to the vertebra?

The spinal cord extends from the foramen magnum to the interspace between the twelfth thoracic (dorsal) and first lumbar spines, although the thecal membranes may extend down the body of the second sacral vertebra. To determine the spinal segments in relation to the vertebral body:

• For cervical vertebrae add 1

• For thoracic 1–6 add 2

• For thoracic 7–9 add 3

• The lumbar segments lie opposite the tenth and eleventh thoracic spines and the next interspinal space

• The first lumbar arch overlies the sacral and coccygeal segments.

Remember: The sacral segments are compressed into the last inch of the cord known as the conus medullaris, which is located behind the T9 to the L1 vertebra.

At which vertebral level is the lesion in cauda equina syndrome?

A lesion in the spinal canal at any level below the T10 (dorsal) vertebra can cause cauda equina syndrome.

How would you differentiate between cauda equina and conus medullaris syndrome?

The cauda equina consists of lower spinal roots (T12 to S5) and hence a lesion causes lower motor neuron signs, whereas the conus medullaris is the lowest part of the spinal cord and lesions result in upper motor neuron signs. Both conus and cauda lesions result in a mixed picture. In its purest form, conus medullaris syndrome presents with sphincter disturbances, saddle anaesthesia (S3–S5), impotence and absence of lower extremity abnormalities.

What are the causes of cauda equina syndrome?

• Centrally placed lumbosacral disc or spondylolisthesis at the lumbosacral junction

• Tumours of the cauda equina (ependymoma, neurofibroma).

What are the types of cauda equina syndrome in adults?

• The lateral cauda equina syndrome: pain in the anterior thigh, wasting of the quadriceps muscle, weakness of the foot invertors (caused by L4 root lesion) and an absent knee jerk. Causes include neurofibroma, a high disc lesion.

• The midline cauda equina syndrome: bilateral lumbar and sacral root lesions. Causes include disc lesion, primary sacral bone tumours (chordomas), metastatic bone disease (from prostate) and leukaemia.

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