# Compressive Myelopathy and Cauda Equina Syndrome

> Compressive myelopathy and cauda equina syndrome for NEET-PG Medicine, comparing cervical cord compression with conus and root lesions and surgical urgency.

- Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/compressive-myelopathy-and-cauda-equina-syndrome
- Exam / course: NEET-PG · Subject: Medicine
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Bradley's Neurology in Clinical Practice; Adams and Victor's Principles of Neurology
- How to cite: "Compressive Myelopathy and Cauda Equina Syndrome", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/compressive-myelopathy-and-cauda-equina-syndrome

## Direct answer

Compressive myelopathy is spinal cord compression that produces upper motor neuron signs below the level of the lesion, most often from cervical spondylosis. Cauda equina syndrome is compression of the lumbosacral nerve roots below the conus, producing flaccid leg weakness, areflexia, saddle anaesthesia and urinary retention. Cauda equina compression with retention is a surgical emergency, whereas cervical myelopathy is decompressed electively when progressive or severe.

## What you must remember

- **Conus level:** The spinal cord ends at the conus, around L1 to L2 in adults, so compression below that point damages nerve roots rather than the cord.
- **Cervical myelopathy:** Upper motor neuron signs below the level, with brisk reflexes, a positive Hoffmann sign, clonus and clumsy hands.
- **Cauda equina:** Lower motor neuron signs in the legs, with reduced ankle jerks, asymmetric weakness, saddle anaesthesia and painless overflow retention.
- **Conus medullaris:** Early, symmetric bladder and bowel involvement with saddle loss, and knee jerks often preserved while ankle jerks are lost.
- **Lhermitte sign:** An electric shock down the spine on neck flexion, typical of cervical cord compression.
- **Red flag:** Retention with saddle anaesthesia needs urgent MRI of the lumbosacral spine and surgical decompression.
- **Imaging:** MRI is the investigation of choice, with the cervical spine imaged for myelopathy and the lumbosacral spine for cauda equina.

## Separating cord from root compression at the bedside

Cord and root lesions look different because the cord ends at the conus and the cauda equina lies beyond it. The table compares the three compressive levels by their most useful bedside features.

| Feature | Cervical myelopathy | Conus medullaris | Cauda equina |
|---|---|---|---|
| Level | Cervical cord | Conus, about T12 to L2 | Lumbosacral roots below L2 |
| Reflexes | Brisk below the level | Knee often kept, ankle lost | Ankle lost, knee reduced |
| Bladder | Urgency, later retention | Early, symmetric retention | Late, overflow, often asymmetric |
| Saddle sensation | Usually spared | Present early | Present, may be patchy |
| Leg pattern | Spastic, broad-based gait | Symmetric weakness | Asymmetric flaccid weakness |

A hyperreflexic limb with a positive Hoffmann sign points above the conus, while an areflexic leg with saddle loss points below it. Retention with saddle loss needs urgent surgery, even though cervical myelopathy is usually managed on a planned timescale when it is mild. Gait and hand function help place a cord lesion, while the timing of bladder change and the pattern of saddle loss help place a root lesion.

## Where the exam tries to catch you

Examiners often hide the level inside the case stem, so read the reflexes and the bladder history together.

- **Trap:** Treating clumsy hands with normal leg reflexes as peripheral neuropathy — **Correct:** bilateral hand clumsiness with brisk reflexes and a Hoffmann sign points to cervical myelopathy.
- **Trap:** Treating cauda equina bladder symptoms as a urinary infection — **Correct:** new retention with saddle anaesthesia is a surgical emergency, so perianal sensation and rectal tone must be checked first.
- **Trap:** Assuming all bladder dysfunction means a conus lesion — **Correct:** a conus lesion causes early, symmetric involvement with knee jerks often preserved, while cauda equina gives more asymmetric leg signs.

## Frequently asked questions

### Which reflex pattern points to cervical spondylotic myelopathy?

Cervical spondylotic myelopathy produces brisk knee and ankle reflexes, a positive Hoffmann sign and clonus below the level of compression. Upper limb reflexes may be brisk or, at the level of the lesion, reduced, and the plantar response is extensor. Bilateral upper motor neuron signs below the lesion point to a cord rather than a root cause.

### Why is saddle anaesthesia so important in cauda equina syndrome?

Saddle anaesthesia reflects compression of the S2 to S4 roots that supply the perianal and perineal skin, and it is an early sign of cauda equina syndrome. Its presence with urinary retention or faecal incontinence makes the condition a surgical emergency. Perianal sensation should be tested in every patient with low back pain and leg symptoms.

### Where does a disc prolapse most often cause cauda equina syndrome?

Cauda equina syndrome from a large central disc prolapse most often occurs at L4 to L5 or L5 to S1, where many roots are compressed in the thecal sac. Central prolapse is the dangerous variant because it presses on several roots at once. A lateral prolapse usually produces unilateral root signs instead.

### How does conus medullaris syndrome differ from cauda equina syndrome?

Conus medullaris syndrome damages the sacral cord segments at the tip of the spinal cord, causing early, symmetric bladder and bowel dysfunction and saddle anaesthesia. Knee jerks may be preserved while ankle jerks are lost. Cauda equina syndrome damages the nerve roots below the conus, giving asymmetric leg pain and flaccid weakness with more pronounced root signs.