The Anatomy of the Intervertebral Foramen

The intervertebral foramen, also called the neural foramen, is the opening between the vertebrae through which spinal nerve roots travel and exit to other parts of the body. The word "foramen" is the singular form, while "foramina" is the plural form.

If the foramina narrow, they can put pressure on the nerve roots near them, causing pain. This is called neuroforaminal stenosis.

Anatomy

The vertebrae are the building blocks of the spinal column. Their purpose is to protect and support the spinal cord and also bear the majority of the weight put upon the spine.

Structure

The large, round portion of bone that makes up each vertebra is called the body. The body of each vertebra is attached to a bony ring. When the vertebrae are stacked one on top of the other, this ring creates a hollow tube through which the spinal cord passes.

The intervertebral foramen is the opening between every two vertebrae where the nerve roots exit the spine. The nerve roots travel through the foramen to reach the rest of the body. There are two neural foramina between each pair of vertebrae—one on each side.

Function

The intervertebral foramina are essentially "exit routes" from which the nerve roots leave the spine and branch out to all parts of the body.

Without the foramen, nerve signals could not travel to and from the brain to the rest of the body. Without nerve signals, the body would not be able to function.

Associated Conditions

A common problem that can affect the neuroforamina is spinal stenosis. Stenosis is a medical term that means narrowing. Spinal stenosis is usually, but not always, an age-related disorder associated with arthritis.

Spinal stenosis can occur in two places: the spinal canal (in which case it's called central canal stenosis) and the foramina.

With pain due to neuroforaminal spinal stenosis, arthritis-related bone growth (also known as bone spurs or osteophytes) that are present in one or more foramen "bump into" the nerve root that passes through that space, causing radicular pain in one leg or arm. Pain accompanied by other sensations such as tingling or numbness is called radiculopathy.

The main symptom of neuroforaminal stenosis is pain. Numbness and/or tingling can occur as well. Neurogenic claudication occurs as a result of ischemia (a lack of blood flow) to the nerves and usually presents with a heaviness in the legs. It is typically associated with central stenosis rather than foraminal stenosis. Most people with spinal stenosis feel better when they flex (bend forward at) the trunk and worse when they arch their backs. Other symptoms include weakness and/or difficulty walking more than short distances.

Treatment

Treatment for stenosis usually is aimed at relieving pain and preventing nerve symptoms from occurring or getting worse. Conservative treatments are often effective enough. These include nonsteroidal anti-inflammatory drugs (NSAIDs), physical therapy, regular exercise, and cortisone injections.

Complementary treatments such as acupuncture, massage, and chiropractic may also be helpful.

Although surgery is not commonly recommended for spinal stenosis, a doctor may suggest it for someone who is experiencing:

• Radiculopathy comprised of pain, pins and needles, electrical sensations, and/or weakness going down one arm or leg
• Neurogenic claudication in the low back
• Myelopathy in the neck and/or upper or mid-back (myelopathy symptoms are spinal cord related and occur in central canal stenosis) 
• Incapacitating pain

There are different surgical techniques for treating spinal stenosis. One such technique is called decompression laminectomy, which entails removing the buildup of bone in the spinal canal. Spinal fusion surgery is performed when there is spinal instability or severe foraminal stenosis. Most cases of stenosis don't require a fusion.