Transverse myelitis develops when inflammation damages the spinal cord, and the most common trigger is an immune system that turns against the body’s own nerve tissue. About 1 in 100,000 people develop it each year. In most cases, the inflammation strips away myelin, the protective insulation around nerve fibers in the spinal cord, disrupting the signals that travel between the brain and the rest of the body. The cause falls into a few broad categories: infections, autoimmune diseases, and, less commonly, problems with blood flow to the spinal cord.
The Immune System Is the Central Player
Regardless of the specific trigger, transverse myelitis almost always involves the immune system attacking spinal cord tissue it shouldn’t. Sometimes this happens because an infection confuses the immune system. The proteins on certain viruses or bacteria look similar enough to proteins on myelin that immune cells, primed to fight the infection, accidentally target the spinal cord instead. This “friendly fire” response can occur days or weeks after you’ve already recovered from the original illness, which is why many people don’t immediately connect a recent cold or stomach bug to their neurological symptoms.
In other cases, the immune attack on the spinal cord is the first sign of a chronic autoimmune condition that was already developing silently. For some people, transverse myelitis is essentially the debut of multiple sclerosis, neuromyelitis optica spectrum disorder (NMOSD), or another condition that hadn’t been diagnosed yet.
Infections That Can Trigger It
A wide range of infections have been linked to transverse myelitis. The virus doesn’t necessarily need to infect the spinal cord directly. Often, the damage comes from the immune response the infection sets off. Viruses associated with transverse myelitis include:
- Herpes viruses, including the ones that cause chickenpox, shingles, and cold sores
- Epstein-Barr virus (the cause of mono)
- Cytomegalovirus
- Enteroviruses like poliovirus and coxsackievirus
- West Nile and Zika viruses
- Influenza
- Hepatitis B
- Mumps, measles, and rubella
Bacterial infections are less commonly involved but still well documented. Lyme disease, syphilis, tuberculosis, and certain types of bacterial pneumonia (particularly mycoplasma) have all been linked to transverse myelitis. Even everyday infections like bacterial skin infections, middle-ear infections, and gastroenteritis caused by campylobacter bacteria can precede it. Fungal and parasitic infections of the spinal cord are rare causes but do occur, particularly in people with weakened immune systems.
Autoimmune Diseases That Affect the Spinal Cord
Several autoimmune conditions can cause transverse myelitis as one of their complications. In some cases, the spinal cord inflammation is what leads to the autoimmune diagnosis in the first place.
Multiple sclerosis is one of the most important to rule out. In MS, immune cells attack myelin throughout the brain, spinal cord, and optic nerves. A single episode of spinal cord inflammation may turn out to be the first “relapse” of MS. Neuromyelitis optica spectrum disorder (NMOSD) is another key condition. It primarily affects the spinal cord and the nerves of the eyes, and it’s identified through a blood test that detects specific antibodies called AQP4-IgG. Distinguishing NMOSD from MS matters because the two conditions require different long-term treatments.
Lupus, Sjögren’s syndrome, and sarcoidosis are systemic autoimmune diseases that can also inflame the spinal cord. Spinal cord involvement occurs in 20% to 35% of people with Sjögren’s syndrome and may be the very first symptom of the disease in about 20% of those patients. In lupus, transverse myelitis is rarer, affecting only 1% to 2% of patients, but it tends to be one of the more severe complications when it does happen. Sarcoidosis causes neurological problems in roughly 5% to 13% of people with the disease, and spinal cord inflammation is one possible form.
Post-Vaccination Cases
Vaccinations have occasionally been identified as a possible trigger, though the risk is extremely small. The mechanism is similar to post-infectious transverse myelitis: the immune system, activated by the vaccine, misfires and attacks spinal cord tissue. A large pharmacovigilance study using the World Health Organization’s global database found a statistical association between COVID-19 vaccines (both mRNA and viral vector types) and transverse myelitis, with symptoms typically appearing within about 6 to 8 days of vaccination. However, the overall rate was approximately 0.28 cases per 1 million vaccine doses, making it exceptionally rare. Influenza vaccines showed a similar, very small association.
Vascular Causes That Mimic It
Not every case of sudden spinal cord dysfunction is caused by inflammation. A spinal cord stroke, where blood flow to part of the spinal cord is cut off, can produce nearly identical symptoms. This is sometimes caused by a blood vessel malformation, a blocked artery supplying the spinal cord, or complications from aortic surgery. Early MRI scans can look normal in spinal cord strokes, which makes them easy to confuse with transverse myelitis initially. Doctors typically use imaging, blood tests, and spinal fluid analysis to sort out the cause.
When No Cause Is Found
Historically, 15% to 30% of transverse myelitis cases were labeled “idiopathic,” meaning no underlying cause could be identified. More recent research suggests that number shrinks significantly with thorough testing and follow-up. A study from Finland found that after careful initial evaluation and re-assessment over time, only about 6% of cases remained truly unexplained. Many initially idiopathic cases eventually turned out to be early presentations of MS, NMOSD, or a systemic autoimmune disease that hadn’t fully declared itself yet. This is why doctors typically monitor people after a first episode, repeating blood work and imaging over subsequent months.
What the Symptoms Look Like
Transverse myelitis typically comes on over hours to a few days. It often starts with a band-like pain or tightness around the torso, back pain, or unusual sensations in the legs. Weakness, numbness, and tingling below the level of the spinal cord inflammation develop as the condition progresses. Bladder and bowel problems are common. The severity depends on how much of the spinal cord is affected and at what level. Inflammation in the upper spinal cord can affect the arms and legs, while inflammation lower down may only involve the legs.
Recovery Outlook
Recovery varies widely. A commonly cited pattern is the “rule of thirds”: roughly one-third of people recover well with little lasting disability, one-third are left with moderate problems like residual weakness or sensory changes, and one-third have significant permanent disability. How much someone recovers depends on the underlying cause, how quickly treatment begins, and how severe the initial attack was. Recovery typically begins within one to three months, but can continue gradually for up to two years. People whose transverse myelitis is linked to NMOSD or lupus tend to have a harder recovery than those with a single post-infectious episode.