Disc protrusion

What it means

Each spinal cushion has a tough, layered outer wall wrapped around a softer centre. A protrusion sits partway between two other common descriptions: it is more focal and dome-shaped than an even, all-around bulge, but the outer wall has not torn open the way it does in an extrusion. The base of the dome — where it attaches to the rest of the cushion — is still wider than the part sticking out furthest, which is exactly what separates a protrusion from a true herniation with a leaked fragment.

Why it appears on a CT or MRI report

Radiologists measure how far the tissue extends beyond the normal disc margin and describe its shape, and a focal, broad-based dome earns the label "protrusion" rather than "bulge" or "extrusion." The report will usually note the spinal level (for example L4-L5 or C5-C6), which side it favours (central, paracentral, foraminal, or far lateral), and whether it touches, displaces, or compresses a nerve root or the spinal canal. Some reports use "disc herniation" as an umbrella term and list "protrusion" as the subtype, which can be confusing if you are comparing reports from different clinics.

What it usually means

Protrusions are common and, like other disc changes, they turn up often in people who have no back or leg pain at all — imaging studies of pain-free adults regularly find them. When a protrusion does cause symptoms, it is usually because it sits close enough to a nerve root to irritate or compress it, producing pain, tingling, or numbness that radiates down an arm or leg rather than staying in the back or neck. The size of the protrusion on the scan and the severity of symptoms do not always line up — a small protrusion in the wrong spot can hurt more than a larger one that has plenty of room. Many protrusions shrink on their own over months as the body reabsorbs some of the displaced tissue.

When to follow up

Mention this finding to your doctor if you have pain radiating down an arm or leg along a specific path, numbness or tingling in a defined patch of skin, or new weakness in a hand or foot. Most protrusions respond well to physical therapy, activity modification, and time, with imaging playing a supporting role alongside your actual symptoms and a physical exam. Seek same-day care for sudden severe leg weakness, loss of bladder or bowel control, or numbness in the saddle area — these are red-flag signs that need urgent evaluation.

A plain-language way to picture it

Think of a jelly donut sat on a table with something pressing down on one side. Instead of squashing evenly all the way around, the dough bulges outward mostly in one spot, forming a rounded dome. The dough has stretched thin there, but it hasn't torn, and the jelly is still contained inside — it just occupies a spot the dough shouldn't reach. That focused dome, still attached at a wide base, is the picture of a protrusion.