What is Spinal Cord Ischemia?
Spinal cord ischemia and infarction, or the lack of adequate blood flow to the spinal cord, is less common than similar conditions affecting the brain. However, it’s important to note that they can still lead to severe consequences such as death, disability, and reduced quality of life for people who survive it. Thanks to advances in medical imaging and more precise diagnostic criteria, we now know more about these conditions and how they affect the spinal cord.
Quick identification and appropriate use of diagnostic tests, including imaging studies, can result in many patients recovering well. They can regain much of their normal function through thorough clinical follow-ups, occupational therapy, and rehabilitation. So, understanding this condition and reacting quickly is key to better health outcomes.
What Causes Spinal Cord Ischemia?
Acute spinal cord ischemia (ASCI), a condition where the blood supply to your spinal cord is temporarily cut off, can happen in many ways. A good number of these cases occur around the time of surgery or due to disease of the aorta (the main blood vessel supplying oxygenated blood to your body). It’s helpful to group these causes into two categories: those that occur naturally (spontaneous) and those that occur as a result of a medical procedure.
Spontaneous Causes of Spinal Cord Ischemia
Much like a stroke impacting the brain, we can use a classification system called TOAST to work out possible reasons why your spinal cord isn’t getting enough blood. These causes could include blockages of large or small vessels, blood clots from the heart, among others. The most common cause of spinal cord ischemia is disease of the aorta. In fact, about 1% of patients coming in with acute Type A aortic dissection (a serious condition where the aorta’s inner layer tears) could have spinal cord stroke. A large swelling of the aorta, with or without the aorta tearing, can also lead to spinal cord ischemia. Other common causes of ASCI include unhealthy and hardened arteries, diseases affecting the aorta, and aging changes in the spine.
Rarely, a stroke can happen due to clots travelling from damaged sections of the aorta, tumors in the heart, or infections of the heart valves. Similarly, an uncommon case of spinal cord infarction happens due to disc material moving within the body; this can occur with a sudden disc herniation. Large bony growths on the spine or spinal canal narrowings can also cause acute spinal cord ischemia, particularly with sudden movement.
Injury to the cervical vessels, the vessels supplying the spinal cord, can result in interrupted blood flow to the spinal cord. This could be due to trauma, sudden head-turning, drug misuse, and chiropractic manipulation. There are also less usual causes of spontaneous cord ischemia like blockages to the major vessel of the spinal cord, abnormal tangles of blood vessels, sickle cell anemia, lupus, blood collections outside of the blood vessels and decompression sickness.
Iatrogenic, or Doctor-Induced, Causes of Spinal Cord Ischemia
Unfortunately, a substantial number of spinal cord ischemia cases can occur during or after medical procedures. In fact, one report suggested nearly half of all recorded spinal cord infarctions were because of doctor-induced causes.
Surgery of the aorta has been known to increase the risk of spinal cord stroke for a long time now. Spinal cord ischemia can happen both while the aorta is being temporarily closed for surgery and when it’s reopened post surgery. This is due to sudden reperfusions (restoration of blood supply) causing a flood of blood to the smaller arteries coming off the aorta, which can overload the spinal cord.
Blood flow to your spinal cord can also stop after certain procedures, although this is very rare. It’s a serious complication that can happen after injecting numbing medication into the ganglion (a cluster of nerve cells), injecting steroids around the spine, placing of a special balloon in the aorta to improve blood flow, or placing a catheter (a flexible tube) into the space just outside the covering of the spinal cord. There’s also a chance for unintended blockage during procedures to stop bleeding from spinal blood vessels. Moreover, surgeries on the lower spine can also cause infarction, as there is a risk of small particles of disc material entering the bloodstream and blocking the smaller vessels.
Risk Factors and Frequency for Spinal Cord Ischemia
Spinal cord ischemia and infarction, which means less blood supply leading to damage or tissue death, are less common than stroke affecting the brain, making up only about 0.3% to 1% of all strokes. An even rarer condition called Acute Spinal Cord Ischemia Syndrome (ASCIS) is a cause of spinal cord disease in about 5-8% of cases. It is important to note that both men and women have an equal chance of being affected by these conditions. It’s also been observed that people with these conditions often have several health risks like high blood pressure, diabetes, and signs of large-vessel atherosclerosis, which is the hardening and narrowing of large blood vessels.
Signs and Symptoms of Spinal Cord Ischemia
When giving medical care, it is crucial to fully document the patient’s history, including when symptoms began and how they evolved. Regular neurologic exams are also key to tracking changes in neurologic functions. Spinal cord ischemia, or reduced blood flow to the spinal cord, can cause a variety of symptoms depending on which vessels are affected.
The standard sudden issue is a sudden and painless inability to move the legs and hold in urine. A quick drop in function (within 12 hours of the onset) with a severe neurologic deficit is a signature trait. However, some patients may show a slow onset of symptoms, which typically suggests a different cause. While rare, some patients may report having feelings of numbness or abnormal sensations beneath the injury level. Some may experience these issues after an abrupt change in body position or abdominal straining.
One of the most common manifestations is Anterior Spinal Artery (ASA) syndrome. This disorder damages two-thirds of the front of the spinal cord but generally spares nerve paths that contribute to touch sense and body position senses. A complete form of the syndrome causes symptoms like impaired movement in the legs, altered sensations of pain and temperature, and disruption of normal bowel and bladder function. If parts of the spinal cord that control muscle function are damaged, the patient might lack normal reflexes, and tests of muscle function might show abnormal results.
In some cases, symptoms might depend on which specific part of the spinal cord is affected. For example, injury to the lower parts of the neck might cause paralysis of the diaphragm. Issues in the mid-back could cause problems with blood pressure regulation or other disruptions to normal body regulation. If the bottom of the spinal cord is involved, the patient might have unresponsive bladder, bowel, and legs.
Among the other potential signatures of spinal cord ischemia is the so-called Brown-Sequard syndrome, which is usually related to traumatic injury. This condition results in weakness on one side of the body and loss of pain and position sense on the opposite side. There are also some patients who have repeated events of temporary symptoms, called spinal cord transient ischemic attacks.
Additionally, a rare syndrome known as “surfer’s myelopathy” has been described in novice surfers. It is believed to be due to prolonged prone positioning causing a type of injury to the blood supply of the spinal cord.
Testing for Spinal Cord Ischemia
If doctors suspect that blood is not reaching the spinal cord properly, an MRI or Magnetic Resonance Imaging will be done. This is a type of scan that gives a detailed image of the soft tissues in our body like our brain and spinal cord. But it’s worth noting that about a quarter of patients who have symptoms might have a completely normal-looking MRI.
When performing an MRI for this condition, doctors use a variety of techniques to get a detailed image of the spinal cord. However, even with these methods, understanding the images can be challenging.
A process called Diffusion-Weighted Imaging (DWI) can be particularly helpful. This technique is very sensitive to changes in the spinal cord caused by lack of blood supply. DWI shows high signal areas, indicating swelling and reduced water motion within the cells. This usually appears within 8 hours of injury. Even if DWI doesn’t show any signs of damage to the spinal cord, doctors won’t rule out spinal cord ischemia if other symptoms suggest it.
Gadolinium, a special dye used in MRIs, can also help doctors tell the difference between spinal cord ischemia and other conditions that might appear similar on an MRI. Normally, spinal cord damage due to lack of blood flow will take about 3 to 4 days to show up on an MRI, even with the help of Gadolinium.
MRI can also show other signs that suggest spinal cord ischemia. Certain patterns or shapes seen on the MRI, such as a “pencil-like” zone or an “owl’s eye” appearance, can suggest spinal cord ischemia. These signs must be examined carefully since they might show up in other conditions as well.
Other imaging methods like CT scans or Digital subtraction angiography (DSA) are rarely used as they are less effective at detecting spinal cord ischemia. DSA, however, might be necessary to confirm certain spinal blood vessel abnormalities.
A lumbar puncture, which is a medical procedure where a needle is inserted into the lower back to collect cerebrospinal fluid, might not be very helpful in diagnosing spinal cord ischemia. However, it can be used to rule out other conditions such as viral myelitis and neuromyelitis optica.
There are also several emerging techniques such as Diffusion tensor imaging (DTI), magnetization transfer imaging (MT), and functional MRI (fMRI), that could potentially be used in the future for detecting spinal cord ischemia. These methods can provide more detailed and accurate information of the spinal cord structure and its functionality. However, these techniques are still being researched and are not part of the standard diagnosis and treatment procedures for spinal cord ischemia.
Treatment Options for Spinal Cord Ischemia
Unlike stroke (cerebral ischemic infarction) where the guidelines for management and care are well-established, there aren’t any fixed guidelines on how to manage acute spinal cord ischemia, a deficiency in blood flow to the spinal cord, which can lead to serious complications. This is due to the condition’s rarity and inconsistency. Management strategies generally involve customizing the treatment plan to each patient’s unique circumstances, aiming to prevent any serious short-term and long-term issues.
Some cases of spinal cord ischemia can be handled through surgery, particularly if the cause is a build-up of pus (abscess) or blood (hematoma) in the spine. Immediate removal of these blockages can prevent further injury to blood vessels and lasting neurological issues. If the patient’s spinal cord ischemia follows after aortic surgery (surgery related to the main artery in the body), several other strategies have proven to be helpful. One such strategy uses a tube to drain cerebrospinal fluid (CSF), the clear fluid found in the brain and spine, typically from the lower back. This can help stabilize the pressure in the spine during the surgery. Although generally safe, this procedure does carry some risk, such as causing a subdural hematoma, or a specific kind of bleeding in the brain. Cooling techniques, called hypothermia protocols, along with CSF drainage can also help to prevent postoperative ischemia (shortage of blood flow). In addition to this, monitoring of nerve signals during surgery has proven useful in reducing ischemic events. Keeping the blood pressure steady at above 55mm Hg (mean arterial pressure) during the procedure has been shown to lower the risk of neurological problems.
Medical management of spinal cord ischemia remains a challenge due to the limited data available. There are some instances of treatment with thrombolysis, a treatment which dissolves dangerous clots in blood vessels, improving blood flow and preventing damage to tissues and organs. But, it is currently unclear how far this treatment can be applied and what risks it might entail. Early administration of corticosteroids, a type of anti-inflammatory medicine are sometimes given in cases of acute spinal cord injury as it may improve functional recovery. However, it is uncertain whether this benefit extends to patients with vascular cord ischemia. In cases where the disease is thought to be due to hardening or narrowing of the arteries (atherosclerotic), anticoagulant and antiplatelet drugs, that thin the blood, are often used. However, controlled studies in large groups of patients (prospective trials) on this treatment approach are lacking.
What else can Spinal Cord Ischemia be?
There are many other medical conditions that might look like spinal cord ischemia, meaning their symptoms and imaging results may seem similar. These can be categorised into compressive myelopathies related to backbone pressure, infectious myelopathies caused by disease-causing organisms, inflammatory myelopathies due to immune system responses, or nutritional myelopathies due to vitamin deficiencies.
- Compressive etiologies refer to conditions such as tumors, blood clots, pus pockets, or bone changes due to aging. These can be easily spotted with standard medical imaging.
- Infectious etiologies require detailed patient history and laboratory tests to diagnose. They may include infections like HTLV1, HIV, Varicella, and a complex neurological condition called PML.
- Inflammatory or autoimmune conditions include transverse myelitis and multiple sclerosis.
- Nutritional myelopathies can happen due to a vitamin B12 deficiency and impact the posterior (back) column of the spinal cord.
- Certain diseases, such as neuromyelitis optica, where elongated lesions form on the spinal cord, can also look like spinal cord ischemia.
New diagnostic criteria proposed by Zalewski and team include factors like patient history, MRI findings, analysis of cerebrospinal fluid and the likelihood of other diagnoses. According to their proposed grading, an affected patient may have ‘definite’, ‘probable’ or ‘possible’ spinal cord ischemia. These grades could be further classified as either being spontaneous (unexpectedly occurring) or periprocedural (occurring during medical procedures). The testing of these criteria on 280 patients diagnosed with non-ischemic conditions showed high specificity, as only 3.2% met criteria for possible spinal cord ischemia, and none was categorised as definite or probable.
What to expect with Spinal Cord Ischemia
Many people who experience a spinal stroke, officially known as cord ischemia or infarction, often manage to recover significant movement, though how much and how fast is often difficult to predict. In a certain study, findings showed that about 42% of patients showed noticeable improvement, while 36% improved little or not at all. This same study observed that the patients who retained their ability to extend their knee and move their hip out to the side have a better chance at recovery.
In another study, around 68% of the patients reached their most severe symptoms one hour after their injury, and the severity of this ‘low point’ was really helpful in predicting their long-term results. Another study found that, on average after 4.5 years, 41% of these patients could walk on their own, and a further 31% could walk with the help of walking aids.
Regardless of these generally reassuring numbers, the mortality rate for this group of patients is reported to be 9%.
Patients diagnosed with Anterior spinal artery (ASA) syndrome, a particular type of spinal stroke, tend to have less promising outcomes – presumably because their strokes are more extensive. Reports suggest that the older the patient is at the time of stroke and the more severe symptoms they faced at their ‘low point’ are predicative of poorer outcomes.
A more recent study, lasting an average of over 7 years, compared the recovery outcomes of patients with brain and spinal strokes. The results suggested that patients with spinal strokes had higher rates of employment and lower death rates. However, these patients also experienced higher rates of chronic pain and a decrease in their ability to live independently (as measured on the modified Rankin scale, a measure of disability).
These authors suggest that older studies, which had shorter follow-up periods, may have overestimated how much the patients’ ability to function was damaged. For instance, in this recent study, about two-thirds of their patients could walk at their final check-up, compared to only half being able to walk one week after their stroke.
Possible Complications When Diagnosed with Spinal Cord Ischemia
The main health issues after a spinal cord stroke are weakness in the lower limbs and an inability to pass urine. These can seriously impact quality of life and lifespan because they can lead to repeated bladder infections and bed sores. For those who survive, report suggests that 42% will need to use a wheelchair for the long term, while 54% will need a catheter for bladder management.
Common Health Issues:
- Weakness in lower limbs
- Inability to pass urine
- Repeated bladder infections
- Bed sores
- Long-term wheelchair use
- Need for using a catheter for bladder management
Preventing Spinal Cord Ischemia
Patients suffering from spinal cord injuries, as well as their family members, are suggested to ask for help and find companionship in groups who advocate for such individuals. Organisations like the Christopher and Diana Reeve Foundation offer useful resources. These resources provide information for those with spinal cord paralysis and their caregivers, including advice on insurance, disability, and therapy services. There is also opportunity to connect with online communities for additional support. More helpful resources can be found at Paralyzed Veterans of America (PVA.org). This site promotes advances in research, raises awareness about spinal cord injuries, provides community support, and even allows people to participate in adaptive sports competitions. The United Spinal Association website (unitedspinal.org) is another vast online platform full of resources. These resources are useful for patients and those who wish to assist spinal injury patients by donating, providing companionship, and advocating for disability rights.