Transverse myelitis is caused by inflammation that damages the spinal cord, specifically the protective coating (myelin) around nerve fibers. In roughly 68% of cases, no specific trigger is ever identified. When a cause can be pinpointed, it typically falls into one of several categories: infections, autoimmune disorders, or, very rarely, vaccinations. The condition affects 1 to 8 people per million each year, with no significant differences across ethnic or geographic populations.
How Spinal Cord Inflammation Causes Damage
The spinal cord relays signals between your brain and the rest of your body. Nerve fibers in the cord are wrapped in myelin, a fatty insulation that allows electrical signals to travel quickly and efficiently. In transverse myelitis, the immune system attacks this myelin in a localized segment of the spinal cord. The resulting inflammation disrupts or blocks signals passing through that segment, which is why symptoms appear below the level of the injury. If the inflammation hits the mid-back area, your legs and lower body are affected. If it strikes higher up in the neck, your arms can be involved too.
The word “transverse” refers to the inflammation extending across the width of the cord, often affecting both sides of the body equally. In some cases, though, only one side is damaged, producing symptoms on just one half of the body.
Infections That Can Trigger It
Viral infections are the most commonly identified trigger. The spinal cord inflammation sometimes develops during the infection itself, but more often it appears days or weeks afterward. In these post-infectious cases, the virus doesn’t directly invade the spinal cord. Instead, the immune response it provokes misfires and attacks the body’s own nerve tissue.
Viruses linked to transverse myelitis include herpesviruses (such as varicella-zoster, the virus behind chickenpox and shingles), enteroviruses, West Nile virus, Zika virus, and influenza. Respiratory and gastrointestinal infections are also common preceding events. Bacterial infections, including Lyme disease and tuberculosis, can occasionally cause the condition as well, though this is less frequent.
Autoimmune and Inflammatory Conditions
Transverse myelitis can be the first sign of a broader autoimmune disorder, or it can appear in someone already diagnosed with one. Lupus and sarcoidosis are among the systemic conditions that can cause spinal cord inflammation. In these cases, the same immune dysfunction attacking joints, skin, or lungs also targets the spinal cord.
Two neurological autoimmune conditions deserve special mention. Multiple sclerosis (MS) involves recurring episodes of demyelination throughout the brain and spinal cord, and transverse myelitis can be its initial presentation. Neuromyelitis optica spectrum disorder (NMOSD) is a rarer condition in which the immune system produces antibodies that specifically attack the spinal cord and optic nerves. Distinguishing transverse myelitis from an early episode of MS or NMOSD is one of the most important tasks during diagnosis, because the long-term treatment strategies differ significantly.
Vaccines: Rare but Documented
Transverse myelitis following vaccination has been reported, though the numbers are extremely small relative to the billions of doses administered worldwide. The hepatitis B vaccine, approved in 1986, was linked to 13 reported cases of transverse myelitis over a roughly seven-year period, making it the most commonly associated vaccine during that era. The oral polio vaccine has a known, though very rare, ability to cause a form of poliovirus infection that can itself lead to spinal cord inflammation.
More recently, 593 cases of transverse myelitis were reported to the Vaccine Adverse Event Reporting System following COVID-19 vaccination, out of approximately 11.7 billion doses given globally. Other vaccines occasionally linked to TM include those for influenza, diphtheria-pertussis-tetanus (DPT), and rabies. It’s worth noting that reporting a case to a surveillance system does not confirm the vaccine caused it. These databases capture temporal associations so researchers can investigate patterns.
Most Cases Have No Known Cause
Despite thorough testing, about 68% of transverse myelitis cases are classified as idiopathic, meaning no underlying infection, autoimmune condition, or other trigger is found. This is a frustrating reality for many patients and their families. The leading theory is that these cases still involve an immune system misfire, possibly triggered by an infection that was too mild to notice or that cleared before symptoms began. The immune system’s response lingers and turns against spinal cord tissue even after the original threat is gone.
How Symptoms Develop
Transverse myelitis can come on in two distinct patterns. The acute form develops over minutes to a few days. The subacute form builds more gradually, typically over one to four weeks. Both types share a core set of symptoms that reflect the disrupted communication through the spinal cord.
Pain is usually the first thing people notice. It often starts as sudden lower back pain, then radiates outward as sharp, shooting sensations down the legs or arms, or in a band-like pattern around the chest or abdomen. Abnormal sensations follow or appear alongside the pain: burning, tingling, prickling, numbness, or an unusual coldness in the legs. Some people become hypersensitive to light touch, temperature changes, or the feel of clothing against their skin. Sensory changes in the torso and genital area are also common.
Weakness typically appears in the legs and can worsen rapidly. Some people first notice their legs feeling heavy or that they’re dragging a foot. Others progress to partial paralysis (paraparesis) or, in severe cases, complete paralysis requiring a wheelchair. When the upper spinal cord is involved, arm weakness develops as well. Bladder and bowel dysfunction is frequent because the nerves controlling these functions travel through the spinal cord.
How It’s Diagnosed
Diagnosis centers on confirming that the spinal cord is inflamed and ruling out other explanations for the symptoms, such as a compressed disc, tumor, or stroke affecting the spinal cord’s blood supply. An MRI of the spine is the primary imaging tool, showing the location and extent of inflammation. Blood tests help screen for autoimmune markers, and a spinal tap (lumbar puncture) can reveal elevated white blood cells and protein levels in the spinal fluid, both signs of active inflammation.
Doctors also test for antibodies associated with MS and NMOSD, because identifying these conditions early changes the treatment approach and outlook. The diagnostic workup can feel extensive, but distinguishing a one-time episode of transverse myelitis from a relapsing condition is critical for long-term care.
Treatment and Recovery Outlook
Initial treatment focuses on reducing the spinal cord inflammation as quickly as possible. High-dose steroids given through an IV are the standard first step. For people who don’t improve with steroids, plasma exchange (a procedure that filters the blood to remove the immune proteins causing damage) is sometimes used. After the acute phase, rehabilitation becomes the focus: physical therapy, occupational therapy, and management of pain, bladder issues, and muscle spasticity.
Recovery varies widely. About one-third of people recover well, with only minor lingering symptoms. Another third have a moderate outcome, retaining some degree of weakness, sensory changes, or bladder problems. The remaining third experience significant long-term disability, including the need for mobility aids. Recovery, when it happens, typically begins within one to three months and can continue for up to two years. Early, aggressive treatment and a less severe initial presentation are generally associated with better outcomes.
People whose transverse myelitis turns out to be linked to MS or NMOSD face a different trajectory, because those are relapsing conditions requiring ongoing treatment to prevent future episodes. For idiopathic transverse myelitis, recurrence is uncommon but not impossible, with some studies estimating repeat episodes in a small percentage of patients.