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Cauda equina syndrome



Nervous system


Central nervous system disorders
Central and peripheral nervous system disorders
Peripheral nervous system disorders
Autonomic nervous system disorders
Nervous system pathology review

Cauda equina syndrome


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High Yield Notes
3 pages

Cauda equina syndrome

8 flashcards

USMLE® Step 1 style questions USMLE

2 questions

USMLE® Step 2 style questions USMLE

1 questions

A 76-year-old man is brought to the emergency department to evaluate acute-on-chronic low back pain. Several years ago, the patient was diagnosed with prostate cancer, but he elected to forego treatment and was lost to follow-up. Today, the patient was brought in by family members after he could not get out of bed. The patient states, “I can’t lift my legs, and I woke up covered in my stool.” The patient has no other significant medical history or medication use. Temperature is 37.0 °C (98.6 °F), pulse is 105/min, respirations are 18/min, blood pressure is 176/65 mmHg, and O2 saturation is 97% on room air. Physical examination shows a cachectic male in moderate distress. The patient has diffuse lumbar spinal tenderness to palpation and 2/5 strength of the lower extremities bilaterally. The patient’s pelvic x-ray is demonstrated below. Which of the following additional clinical features most indicates this patient’s clinical condition?

Reproduced from: Wikipedia


Cauda equina syndrome is a condition caused by damage to the bundle of peripheral nerves protruding from the bottom of the spinal cord, called the cauda equina.

The latin words cauda equina mean horse’s tail, which is what early anatomists thought this nerve bundle looked like.

The spinal column is made of individual bones, called vertebrae.

Each vertebra is made of a large anterior portion called the body, and the posterior part called the vertebral arch.

The central cavity between the body and the arch is called the vertebral foramen.

Now the spinal column is made of 33 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal.

Other than C1 and C2, each two adjacent vertebrae are, separated by an intervertebral disc, which allows for a slight movement of the vertebrae, and acts as a shock absorber.

The sacral and coccygeal vertebrae are fused together to form the sacral bone and coccyx, or tailbone respectively.

Now if you cut the spinal column in half lengthwise you can see that all the vertebral foramina together form the vertebral, or the spinal canal, which is occupied by the spinal cord.

The spinal cord is connected to the brain and travels through the spinal canal to the second lumbar vertebra, where it ends in a cone, called conus medullaris.

There are 31 pairs of nerves originating from the spinal cord called spinal nerves; there are 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal.

Each nerve leaves the spinal canal through the corresponding intervertebral foramen, which are openings between two adjacent vertebrae.

Since the spinal cord is shorter than the spinal canal, the nerves of the lumbar, sacral and coccygeal regions have to travel down the spinal canal to reach their corresponding openings, forming a nerve bundle below the spinal cord called the cauda equina.

These nerves carry motor innervation for the genitals, both internal and external anal sphincter, detrusor vesicae, which is a muscle in the bladder that contracts during urination, and muscles of the leg.

They are in charge of the knee and ankle reflexes.

Skin sensations of the legs and pelvis are also carried by these nerves.

Cauda equina syndrome is caused by compression, trauma, or damage to multiple nerves of the cauda equina.

Large lumbar disc herniation is the most common cause of cauda equina syndrome.

And poor posture, traumas, physical activity, and strong rotational movement can cause herniations where the intervertebral disc bulges out and compress the nerves or spinal cord.

This is similar to sciatica, but the herniation is usually larger, and more nerves are compressed, including those that control the bladder and reproductive organs.

Compression can also be caused by spinal stenosis which is the narrowing of the vertebral foramen in the lumbar vertebrae.

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  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Cauda Equina Syndrome" Journal of Pain & Palliative Care Pharmacotherapy (2014)
  6. "Cauda Equina Syndrome Due to Lumbar Disc Herniation: a Review of Literature" Folia Medica (2017)