AssessmentsCauda equina syndrome
USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 60-year-old woman comes to the emergency department because of urinary incontinence and bilateral medial thigh paresthesia for the past 3 hours. Her past medical history is noncontributory. She says symptoms suddenly started with mild back pain that is gradually worsening. She is now unable to feel toilet paper on her perineum when wiping after urination. Which is the most appropriate next step in management?
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.