Cauda equina syndrome (CES) is relatively rare, and yet its diagnosis is invoked with a fair amount of frequency in acute care settings. This is not unwarranted, as it is a crippling disease that is a bona fide surgical emergency. If attended to in too delayed a fashion, a patient can be left paralyzed, incontinent, and impotent. In this Medmastery lesson, from our Neurology Masterclass: Managing Emergencies course, we review the detailed management of cauda equina syndrome so you can confidently manage it if it comes your way.
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Cauda Equina syndrome is relatively rare, and yet its diagnosis is invoked with a fair amount of frequency in acute care settings. This is not unwarranted, as it is a crippling disease that is a bonafide surgical emergency. If attended to in to delay to fashion, a patient can be left paralyzed, incontinent and impotent.
The syndrome is most often caused by the sudden herniation into the spinal canal of a very large amount of intervertebral disc material. The large disc herniation compresses all of the nerve roots hanging below the end of the spinal cord, also known as the conus madullaris this is located at L1, 2.
The collection of nerve roots hanging from the end of the conus madullaris is known as a cauda equina meaning horses tail. Cauda Equina syndrome can also be caused by an epidural abscess, a hematoma, tumor, or collapsed bone compressing the lumbar thecal sac. Please note though, that it's unusual for common degenerative spinal stenosis alone to present as cauda equina syndrome.
In assessing for cauda equina syndrome, start your evaluation by taking a good history, ask about the onset of symptoms. Patients usually experience rapidly progressive back and bilateral leg pain, urinary incontinence or retention, bilateral lower extremity numbness, progressive bilateral lower extremity weakness and bilateral numbness in the groin, some cases may have a slower more insidious onset, however.
Ask about a history of cancer, infection, osteoporosis, a steady progression of neurological deficits and recent trauma. Ask specifically about numbness in the groin, known as saddle anesthesia, this is very common in cauda equina syndrome, it refers to loss of sensation in the perineum. Also asked specifically about urinary hesitancy, urinary incontinence, and fecal incontinence.
Urinary retention is actually the most common sign of cauda equina syndrome. Note though, that it's very unusual to have urinary incontinence or retention without accompanying weakness or reflex loss in the distal muscle groups of the legs. It can happen however, early in the syndrome or with a very low disc herniation that came to lie below the S1 nerve roots.
Bowel incontinence without bladder incontinence or retention or without associated weakness is extremely rare, and other ideologies need to be considered. Make sure you do a complete physical and neurological examination. Focus in on the lower extremities but realize if the upper extremities are involved, it's not a cauda equina syndrome.
Assess strength in the hip flexors, the hip abductors and adductors, the knee extensors and flexors, check ankle dorsiflexion and plantar flexion. Most cases of cauda equina syndrome will affect the distal muscles that is the feet, dorsiflexor and plantar flexors and possibly the knee extendors, as most big disc herniations occur L 4 5 or L 5 S 1, thus more proximal muscles may not be affected.
Muscle weakness should be relatively symmetric, and will involve muscles innervated by the nerves leaving the canal below the level of the compression. For example, a compression at L 4 5 will not affect hip function and may not affect the knee extensors, but it should result in weakness of the ankle dorsi and plantar flexors.
Weakness of hip flexors generally points to a problem above the cauda equina. Note, the patient may not have much in the way of weakness early in the syndrome, but it usually rapidly progresses. Also note that if you find weakness only in one leg, even if it involves the whole leg, this is not cauda equina syndrome. You're going to have to consider other pathologies.
We've actually seen femoral artery occlusions, hip fractures, aseptic necrosis of the hip and other pathologies miss diagnosed as cauda equina syndrome. On sensory exam, check sharp sensation with a broken tongue depressor in the anterior, medial and lateral thigh, and the lateral and medial leg and the top and the bottom of the foot. Also, make sure you check sharp sensation in the saddle region that is the groin and the perirectal region, sensory loss here is very concerning for cauda equina syndrome.
Make sure you also check sensation over the torso and the arms. Loss of sensation over the torso or in the arms indicates a problem above the cauda equina. It's important to check reflexes in cauda equina syndrome, therefore check the patellar and the Achilles reflexes. It would be very rare to have well preserved Achilles reflexes and have a bonafide cauda equina syndrome. In a similar light, if the reflexes are hyper, consider a problem in the spinal cord in the cervical or thoracic regions.
Make sure you check rectal tone, generally in cauda equina syndrome, it's going to be diminished or absent. Bulbocavernosus and cremasteric reflexes are often also lost in cauda equina syndrome, their preservation argues against the diagnosis. Next, evaluate the post void bladder for retention with bedside ultrasound, or via straight catheterization.
Empty the bladder at full, note that retention does not clinch the diagnosis however, due to the fact that pain, various medications such as analgesics and muscle relaxants, and a very distended bladder can cause retention. With any suspicion of cauda equina syndrome, obtain an emergent MRI of the lumbar spine without contrast.
If an MRI is not available, order an emergent CT myelogram of the lumbar spine. On MRI, look at T 2 sagittal and axial images of the lumbar spine, recognize that the very common entity of degenerative stenosis can result in tremendous narrowing of the thecal sac, but rarely presents with cauda equina syndrome. This is because compression of the nerve roots developed over an extended period of time and the nervous system adapted to it.
So you're really on the lookout here for large disc herniations and other acute causes of cauda equina compression. To cause cauda equina syndrome a herniation or any other pathology will need to take up almost the entire cross sectional area of the spinal canal, half a canal will not do it. The disc herniation in this image is not nearly large enough to cause cauda equina syndrome, even if it's declared a very large herniation by the radiologists.
In a patient with suspected cauda equina syndrome, if the lumbosacral spine does not explain your findings look higher up in the spinal canal. This MRI demonstrates a metastatic tumor compressing the spinal cord in the lower thoracic region, resulting in bilateral leg weakness and incontinence and was mistaken initially for a cauda equina syndrome. Treatment of cauda equina syndrome is almost always surgical. Surgery involves the removal of materials that may be compressing the nerves of the cauda equina.
Most commonly this is affected via decompressive laminectomy, in which portions of the posterior elements of the vertebrae are removed, then the spinal canal is entered and disc herniations, bone spurs, overgrown ligaments and any other material that's compressing the cauda equina are drilled or cut away. There really is no adequate conservative management of cauda equina syndrome. You can start some steroids, dexamethasone 4 to 10 milligrams every six hours, but this is just in preparation for surgery. Cauda Equina syndrome can be rapidly progressive and devastating, so please if you're considering it, call your neurosurgeon immediately.