A report stating that your conus terminates at T12-L1 means your spinal cord ends at a completely normal level. The conus medullaris is the tapered, cone-shaped tip where your spinal cord ends, and T12-L1 refers to the junction between your twelfth thoracic vertebra and first lumbar vertebra. This is a standard finding that radiologists note on MRI reports as a routine anatomical landmark, not as a sign of a problem.
What the Conus Medullaris Actually Is
Your spinal cord doesn’t run the entire length of your spine. It tapers to a point well above your lower back, and that tapered endpoint is called the conus medullaris. Below it, a bundle of individual nerve roots fans out like a horse’s tail (called the cauda equina) and continues down through the lower spinal canal to reach your legs, bladder, bowel, and pelvic area.
The conus itself gives rise to nerves that control some critical functions. The lowest spinal nerves, originating from segments S3 through S5, provide both motor and sensory signals to the lower extremities, bowel, bladder, perineum, and sexual organs. This is why radiologists always note the conus position: if it were abnormally low or compressed, those functions could be at risk.
Why T12-L1 Is a Normal Finding
In adults, the conus most commonly ends around the L1 vertebral body, with the average position at the upper portion of L1. The normal range spans from T12 down to roughly the upper L3 level, following a bell-curve distribution across the population. A T12-L1 termination sits right in the middle of that range, slightly above the average. Studies using MRI have found that no one in their samples had a conus positioned above T12, so your result is well within expected territory.
The position varies naturally from person to person. About half the population has a conus that ends at or above the L1-L2 disc space. A small percentage, around 6%, have a conus that extends as low as L2-L3. Your T12-L1 level is unremarkable and requires no follow-up on its own.
Why Radiologists Report This Level
Even though a normal conus position isn’t clinically exciting, radiologists document it on every lumbar or thoracic MRI for two practical reasons.
First, it confirms the spinal cord isn’t abnormally low. A conus that sits below L2 in an adult raises concern for a condition called tethered cord syndrome, where the spinal cord is anchored by tissue that prevents it from sitting at its normal height. Noting a normal conus level rules that out at a glance.
Second, the conus level matters for spinal procedures. Lumbar punctures (spinal taps) and epidural injections are typically performed at L3-L4 or L4-L5 precisely because those levels are safely below where the spinal cord ends. Knowing exactly where the cord terminates helps clinicians plan any future procedures without risk of needle injury to the cord itself.
When the Conus Position Would Be Concerning
A conus that terminates below L2 in an adult is considered low-lying and may point to tethered cord syndrome. In this condition, the spinal cord is pulled downward by an abnormal attachment, often a thickened filum terminale (the thin strand that anchors the cord’s tip to the tailbone area) or sometimes a fatty mass called a lipoma. Diagnosis typically requires both the low conus position on MRI and a thickened filum.
Symptoms of a tethered cord in adults can include lower back pain that worsens with activity, numbness or weakness in the legs, difficulty with bladder or bowel control, and changes in sexual function. These symptoms tend to develop gradually and may worsen during growth spurts in children or with physical stress in adults. None of this applies to a conus at T12-L1, which is a normal, healthy position.
How the Conus Reaches Its Final Position
In early fetal development, the spinal cord fills the entire length of the spinal canal. As the fetus grows, the bony spine elongates faster than the cord itself, so the cord’s endpoint gradually “ascends” relative to the surrounding vertebrae. By birth, the conus typically sits around L3. It continues to rise during infancy and early childhood, reaching its adult position by roughly age two. The final resting level, whether that’s T12, L1, or somewhere in between, stays essentially fixed for the rest of your life.
This is also why a conus that remains too low can signal a problem: it may not have ascended properly during development, suggesting it was held in place by an abnormal tether.
What to Take Away From Your Report
If your MRI report states “conus terminates at T12-L1,” it’s a one-line confirmation that your spinal cord ends exactly where it should. It’s not a diagnosis, not an abnormality, and not something that needs treatment. Radiologists include it the same way they note that your kidneys are a normal size or your liver looks unremarkable. It’s a checkbox confirming normal anatomy, and you can move on to whatever else the report actually flagged, if anything.