The way in which spine anatomy and the location of the back problem is typically described causes confusion for patients, and even for health care professionals who deal with back problems on a regular basis. Patients with back problems are all too often confused about what is pinching where, and how the back problem relates to their symptoms.
At Spine-health.com, we frequently get questions such as:
- "Is the problem at my L5 level or my L4-5 level?"
- "What does S1 mean?"
- "What is a 'transitional level'?"
- "How does my sixth vertebra relate to my back problems?"
- "How is my back causing the pain shooting down my leg?"
- "Will my back problem leave me paralyzed?"
Even when spine specialists spend a great deal of time explaining the problem, it is still often hard to understand.
This is a common problem, and it's no one's fault. Simply put, back problems are difficult to describe and difficult to understand. The goal of this article is to explain in detail how spinal anatomy is commonly described and typical sources of confusion. Importantly, this article discusses how terminology used for spinal anatomy relates to common diagnoses and sources of back problems for patients.
Back Problems Usually do Not Involve the Spinal Cord
First, it is important to explain that the spinal cord does not usually cause back problems. Conditions that involve damage to the spinal cord (which can cause paralysis) usually involve trauma or disease in the cervical spine or thoracic spine, and this is different from the majority of back problems that cause pain.
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The spinal cord originates at the base of the brain and runs down through the cervical and thoracic spinal canal and ends just before the lumbar segments begin. This means that there is no spinal cord in the low back. While some problems in the cervical spine (such as cervical stenosis) can impinge on the spinal cord and produce symptoms such as difficulty with coordination, it is far more common for back problems to affect the nerve roots rather than the spinal cord.
Nerve roots exit through holes in the bone of the spine at each level. It is common for back problems to affect the nerve roots as they exit the spine and cause pain and other symptoms that radiate to the extremities (called a radiculopathy). In the low back, the way the nerve roots exit and branch off from the lumbar spine and sacral region looks like a horse's tail (cauda equina). They exit to each side between the bones in the spine, and travel down through the low back, across the back of each buttock, down into the lower extremities. See Figure 1.
The way that back problems are described is often a source of confusion. This article provides in-depth information about two issues that are often difficult to understand:
- Nerve root impingement - A lot of confusion occurs when a herniated disc or other back problem compresses a nerve root and the problem is described both by the intervertebral level (where the disc is) and to the nerve root that is affected. Depending on where the disc herniation or protrusion occurs, it may impinge upon either the exiting nerve root or the traversing nerve root.
- Spinal abnormalities - Approximately one in ten adults has a structural low back abnormality that exists from birth. A typical abnormality is having an extra lumbar vertebra. Having a sixth lumbar vertebra rarely causes back problems, but it can create some confusion with how the spinal anatomy is described.
Before providing a detailed explanation of the above two anatomical issues, it is helpful to first review spinal terminology used to describe the normal spinal anatomy.