Intervertebral Disc Infection: Discitis and How it Affects Children

Discitis, or disc space infection, is an inflammation of the intervertebral disc—the "cushion" in between the vertebrae of your spine. It can occur in adults, but it is more common in children.This article focuses on discitis in children.

Cause
The exact cause is the subject of debate, but most researchers believe that discitis is caused by infection. The infection probably begins in one of the vertebral end plates. These end plates are on the top and bottom of each vertebra, and they give nutrition to the disc. The end plate can become infected, and then the infection can spread into the disc.

It's also possible that the infection begins elsewhere and travels to the disc. This is called transient bacteremia. Ear infections and skin infections are two examples of infections that could lead to transient bacteremia and perhaps discitis.

Once the disc becomes infected, it's difficult for it to fight the infection. The disc is the largest avascular organ in the body; avascular means that they do not have their own blood supply. That's why the discs have to get their nutrition and blood supply—including white blood cells to fight infection—from diffusion through the vertebral end plates. This is an inefficient way to fight infection.

Symptoms
Symptoms usually first appear around age 7, and the most common symptom of discitis is back pain. However, it can be difficult to diagnose discitis because the back pain isn't limited to one region; it's just general (or, as doctors say, "non-specific") back pain.

A child may refuse to walk or stand up—that's a possible sign of discitis. The infection can make it very painful to walk or stand, so some children will simply avoid those activities.

Some children may also adjust their posture so that they avoid painful positions. For example, it can be more painful to bend forward (to flex the spine), so they may refuse to do that.

Even though discitis is an infection, that doesn't necessarily mean that there will be a fever. It is a possible symptom, though.

Diagnosis
As previously mentioned, it can be difficult to diagnose discitis. Even blood work—generally a good indicator of infection—isn't always helpful. Children with discitis may have a higher white blood cell count, and they may have a higher erythrocyte sedimentation rate (that's a specific test that looks at how fast red blood cells fall to the bottom of a tube. The faster they fall, the more likely it is that there's inflammation somewhere in the body).

The doctor may also order x-rays to look for decreased disc height: is the disc shrinking? That can be an indication of discitis. X-rays can also show if the vertebral end plates have eroded—another discitis indication.

The doctor may also order CT scans or MRIs to help with the discitis diagnosis.

Treatment
The body has its own treatment for discitis—autofusion. Over time, the disc inflammation can cause the body to release chemicals that actually harm the surrounding soft tissues. Damaged tissue is then replaced by scar tissue, which is the body's attempt to heal and protect itself. That scar tissue can then harden and fuse the bones—that's autofusion.

Autofusion essentially "cures" discitis by immobilizing the intervertebral disc that's been causing pain. In other words, that new bone growth (the autofusion) removes motion at the painful segment, and that reduces pain.

In terms of medical treatments—not just the body's treatment—the usual treatment for children with discitis is rest (not always an easy thing for children).

After a rest period (usually just a few weeks), the child will have a plaster cast or brace. The brace or cast will immobilize the area and actually help the vertebrae fuse in a good position—a position that won't cause pain. Without the cast, the vertebrae will still fuse, but they may be out of alignment, causing more pain.

Some patients—especially ones with an elevated white blood cell count—may need an antibiotic. These antibiotics generally target Staphylococcus aureus because that is the most common type of infection found in patients with discitis.