What is Cauda Equina and Conus Medullaris Syndromes?
Cauda equina syndrome and conus medullaris syndrome are conditions that share similarities in structure and symptoms. So, we will discuss them together, highlighting key differences. The conus medullaris is the lower end of the spinal cord, usually situated at a point equivalent to the first lower backbone (L1 vertebral level) in an average adult. Conus medullaris syndrome develops when there is a pressure-induced injury to the spinal cord between the 12th thoracic vertebrae (T12) and the second lumbar vertebrae (L2).
On the other hand, the cauda equina is a bundle of nerves and nerve roots that come from the lower part of the spinal cord, usually between the first and fifth lower backbone levels (L1-L5). This area contains nerve fibers that control movement and sensation in the legs, bladder, rectum, and the region between the genitals and the rectum (perineum). Cauda equina syndrome happens when there is pressure on, and interruption of these nerves’ functions. It often affects nerves from the third to the fifth lower backbone levels (L3-L5), and may also involve the conus medullaris.
Both syndromes are considered medical emergencies because they can cause symptoms such as back pain radiating to the legs, problems with movement and feeling in the lower limbs, bladder or bowel issues, sexual problems, and lack of sensation in the buttocks area (saddle anesthesia). Both conditions pose a high risk of legal action if not diagnosed and treated promptly because delays can result in permanent, serious disability.
What Causes Cauda Equina and Conus Medullaris Syndromes?
Cauda equina syndrome and conus medullaris syndrome are conditions caused by pressure on the spinal cord and nerves that come from the lower part of the spine (L1-L5 levels). The most common reason for this pressure, in 45% of cases, is a slipped disc in the lower part of the spine. Other things that can cause this pressure include an abscess (a collection of pus) around the spine, blood clot around the spine, infection of the disc in the spine, a tumor (which could be from a cancer that started somewhere else in the body or one that started in the nervous system), injury (especially if bone fragments are pushed back into the spinal canal), narrowing of the space inside the spine, and blockage of the main blood vessel in the body. There are also rare instances where cauda equina syndrome was linked with chiropractic treatments, placement of medical devices between the spinous processes, and a blood clot in a large vein in the body.
Risk Factors and Frequency for Cauda Equina and Conus Medullaris Syndromes
Cauda equina syndrome and conus medullaris syndrome are rare conditions, affecting 1 in 30,000 to 100,000 people every year. There are usually about 1.5 to 3.4 reported cases per million people each year. These conditions are often seen in 3% of all disc herniations and are most commonly found in young men. This may be due to the fact that this group is more likely to experience injuries to the thoracic and lumbar regions of the spine. Based on current estimates, the U.S. would see approximately 1016 new cauda equina syndrome cases and 449 new cases of conus medullaris syndrome every year.
- Cauda equina syndrome and conus medullaris syndrome are rare, affecting 1 in 30,000 to 100,000 people per year.
- The annual incidence is between 1.5 to 3.4 cases per million people.
- These syndromes occur in 3% of all disc herniations.
- They are most common in young men, possibly because this group is more prone to spinal injuries.
- In the U.S, approximately 1016 new cases of cauda equina syndrome and 449 new cases of conus medullaris syndrome are reported each year.
Signs and Symptoms of Cauda Equina and Conus Medullaris Syndromes
For a thorough diagnosis, the doctor will need a detailed history about recent falls, injuries, usage of blood-thinning drugs, any spinal treatment received, history of drug injections, any past cancer diagnosis, or chiropractic adjustments. Also, any overall signs of illness like chills or fever would be relevant.
Patients might report problems like:
- Back pain and sciatica (seen in as many as 97% of patients)
- Weakness and changes in feeling in the legs
- Bladder control issues (causing either unintentional holding of urine or incontinence in up to 92% of patients)
- Bowel control issues (causing either unintentional holding or incontinence in up to 72% of patients)
- Reduced sensation in the buttocks area (in up to 93% of patients)
- Sexual issues (difficulty in maintaining an erection in men)
The symptoms listed above may not always specifically point to a Conus Medullaris Syndrome (CMS) or Cauda Equina Syndrome (CES). But, if several of these symptoms are presented together, doctors may suspect these conditions. It’s interesting to note, that these symptoms lack strong predictive abilities, particularly in the early stages of these syndromes. However, decreased sensation in the buttocks area associated with bladder problems are usually the first signs of CES and are indicators of potentially severe outcomes of CMS/CES.
After the doctor suspects such conditions based on your history, he/she will conduct a detailed neurological examination. The doctor will look for:
- Motor or sensory problems in the legs – usually affecting both sides but can also impact one side more than the other
- Signs of nerve damage in the legs – weakened reflexes, low muscle tone, muscle shrinkage
- Loss of sensation in the buttocks area
- Decreased or absent rectal tone
- Decreased or absent contraction of pelvic muscles
- A swollen bladder indicating the inability to pass urine
In cases of isolated Conus Medullaris Syndrome, problems with the legs often appear on both sides and are symmetric. There may also be signs of nerve damage, such as muscle stiffness and excessive reflexes.
Testing for Cauda Equina and Conus Medullaris Syndromes
If you’re a patient suspected to have a medical condition called Cauda Equina syndrome (CES), your doctor may advocate for an emergency MRI scan. This type of scan is considered the best method to assess the condition. The goal is to perform this scan within one hour from when you first see the doctor. This is because early diagnosis and consultation with a neurosurgeon or orthopedic specialist is crucial.
For patients who can’t have an MRI (like those with metallic implants), a CT myelogram can be done instead. This type of imaging has some limitations, as it requires the injection of a special dye through a spinal tap to visualize the spinal cord and its structures.
In addition to these imaging tests, your doctor may perform a bladder scan to measure the amount of urine left in your bladder after you’ve urinated. This is especially critical as it assesses the bladder for any signs of urinary retention, a common symptom of CES.
Treatment Options for Cauda Equina and Conus Medullaris Syndromes
If you have cauda equina syndrome or conus medullaris syndrome, it’s important to see a neurosurgeon or orthopedic specialist quickly. These conditions require a specific type of surgery called decompression surgery. The two common methods used are laminectomy and sequestrectomy, sometimes followed by a discectomy.
In simple words, in a laminectomy, a part of the bone in your spine is removed to relieve pressure on your spinal cord or nerves, while in a sequestrectomy, specific pieces of your herniated disk, which could be pressing onto your nerves causing pain, are removed. A discectomy, which may follow these procedures, is where part or all of an intervertebral disc (acting as a cushion between your spinal bones) is taken out.
What else can Cauda Equina and Conus Medullaris Syndromes be?
When trying to understand what’s causing problems with the spinal cord, doctors consider several possibilities. They focus on conditions that can’t be relieved by reducing pressure on the spinal cord. These conditions include:
- Spinal cord infarction, a stroke that happens in the spine
- HIV-related myelopathy, a nerve disease related to HIV
- Transverse myelitis, an inflammation of the spinal cord
- Multiple sclerosis, a disease that affects the brain and spinal cord
- Syringomyelia, a disorder in which a cyst forms within the spinal cord
- Spinal arteriovenous malformation, a complex tangle of blood vessels in the spine
What to expect with Cauda Equina and Conus Medullaris Syndromes
Research suggests that timing is crucial when it comes to treating conditions like conus medullaris and cauda equina syndromes with surgical decompression. This simply means that operating early to relieve pressure on these parts of the spinal cord leads to better outcomes for patients. This is particularly true if the surgery takes place within 48 hours of the first symptoms appearing.
Longer periods of compression can lead to more severe and permanent damage to the structures and functions of the spine, and this means a worse outcome for patients. Importantly, if a patient has been having bladder problems before the surgery, this has been linked to worse outcomes, no matter when the decompression takes place.
However, doctors still recommend early decompression surgery for a better prognosis, regardless of the patient’s initial clinical conditions. So, the general rule is the earlier the surgery is performed, the better.
Possible Complications When Diagnosed with Cauda Equina and Conus Medullaris Syndromes
A large number of people diagnosed with cauda equina syndrome and conus medullaris syndrome may experience ongoing complications. A study reviewed the outcomes over a 63-day period focusing on bladder control, bowel control, numbness in the ‘saddle’ area (around the buttocks), sexual function, and sciatica (nerve pain in the lower back and legs). It showed that many patients still had lingering symptoms, even if they had undergone surgical decompression.
For example, almost half of the patients (47.7%) continued to deal with bladder control issues, needing to use self-catheterization or having a permanent catheter. Bowel control issues improved significantly following the surgery, but still remained a problem for over 41.8% of patients 63 days after the surgery. Ongoing sexual dysfunction was reported by 53.3% of patients and numbness in the ‘saddle’ area was still a problem for 56.6%.
Sciatica remained an issue for 47.5% of patients. The most influential factors on the outcomes were the neurological state of the patient when they were diagnosed and the severity of the injury, with less severe injuries leading to better outcomes.
Simplified explanation of complications:
- Continued bladder control issues (47.7% of patients).
- Persistent bowel control problems in over 41.8% patients, even after surgery.
- Lingering sexual dysfunction (53.3% of patients).
- Numbness in the ‘saddle’ area (56.6% of patients).
- Ongoing sciatica issues (47.5% of patients)
The data indicates that the patient’s neurological state at diagnosis and the severity of the injury are crucial factors in predicting the end results. It was also observed that patients with less severe injuries tended to recover better.
Preventing Cauda Equina and Conus Medullaris Syndromes
If you come to the doctor with sciatica, but show no other signs of CES/CMS, also known as Cauda Equina Syndrome and Conus Medullaris Syndrome, the doctor will warn you about other symptoms that may appear. These symptoms may include issues with bladder or bowel movement, impotence, and numbness in the areas on the body that would touch a saddle while riding a horse, often referred to as ‘saddle anesthesia’. If you start to experience any of these symptoms, it’s important you return to the doctor immediately.
If the doctor thinks you might have CES/CMS, they will keep you informed about your tests, such as MRI shold you went through a bladder scan, and any upcoming meetings with surgeons. Once the condition is confirmed, the doctor will discuss possible complications and give you a realistic picture of what to expect based on the severity of your situation.
CES/CMS syndromes have significant impact on a person’s life and often result in legal cases. Therefore, it’s very important for the doctor to take a detailed history, carry out a thorough physical examination, and reach a conclusion as quickly as possible.
In legal cases about CES, there is a connection between surgical decompression (a type of surgery used to relieve pressure on the spinal cord) being carried out more than 48 hours after diagnosis, and a negative outcome for the doctor involved. Interestingly, the extent of loss of bodily function did not impact the legal judgement in the cases studied.
