Zones of the body

Zones of the body

Posted by AskNurseLinda on Feb 12, 2018 11:15 am

We often hear about zones of the body when discussing spinal cord injury. These are areas of nerves that control movement and sensation of the body usually called dermatomes or levels of injury. These zones indicate where your injury is and where function might be preserved below your documented level of injury or zone of partial preservation.

9f787d9ee5d43673b112836039eaae00-huge-zoThe spine is divided into sections for anatomical definition. If the spine was just counted by number from top to bottom, it would become very confusing to figure out what part you are trying to identify. Nerves from the spine control movement and sensation. Each nerve controls a section and side of the body. A section is called a dermatome. This is easily seen when a person is on hands and feet. The dermatomes are like slices of bread but through the body. When a person is standing, it is a little more difficult to visualize.

The cervical (C) spine are located from the skull to just above the start of the rib cage. There are eight cervical vertebrae which have nerves exiting from each side. These nerves control breathing, neck mobility, and much of arm and hand function.

Vertebrae that have ribs attached to them are called thoracic (T). The ribs are clear anatomical landmarks that make these vertebrae easy to recognize on an X-ray or MRI. There are twelve thoracic vertebrae. You can measure on the outside of your body to tell which thoracic area you are identifying. The natural nipple line coordinates with nerves from thoracic level 4. The natural position of the umbilicus or belly button coordinates with thoracic level 10.  If you start at the nipple line, thoracic level 5 will be two finger widths below. Every two finger widths will coordinate with another thoracic level until you reach thoracic level 10 which will be the belly button.

The nerves exiting from each side of the thoracic vertebrae control some arm movement and the trunk. Assessment of the trunk is difficult because there is little movement there except for the jobs of helping to hold up our bodies and to be able to correct ourselves if we lean. One of the main jobs of the trunk of the body is to hold ourselves upright. This is a big job which has little recognition for importance as it is usually taken for granted until it is missing or not functioning at optimum.

The lumbar (L) vertebrae start after the last vertebrae with a rib attached and go down the spine until the sacrum is reached. There are five. If you look at someone’s back, you can see the lumbar vertebrae as that little sway in the lower back. The lumbar vertebrae are important for lower abdominal, hip and leg function.

The sacral (S) vertebrae consist of a bone that looks like a shield in pictures or x-rays. The vertebrae of the sacral spine are fused together. There are also five of these levels. This section is called the cauda equina or horse’s tail because it looks like a bunch of nerves that resemble an internal tail. These nerves control the back of the legs, bowel, bladder and sexual function. The interesting thing about these nerves is that they are actually peripheral nerves.

Each of the pairs nerves that exit from either side of the spinal cord, control that same side of the body. Since we are all individual humans with slight differences and discrepancies from one another, the nerve control might not be precisely and exactly the same on each side or might be very slightly different from one person to another. However, these differences are so slight that measuring can be done without error.

Each of the levels is labeled with the first letter of the boney level followed by the number of the vertebrae in that section. For example C4 is the cervical section at the 4th vertebrae. T10 is the thoracic level at the 10th vertebrae. Communication will consist of these terms.

Your healthcare professional will assess your level of spinal cord injury which can be caused from disease or trauma. Each level is assessed for movement and sensation. Every time you have an examination of level of injury, all dermatomes should be assessed. Because the body is always attempting to heal itself, you may find a random nerve that is working or starting to work. Finding this nerve can be used effectively to provide therapy to possibly increase function.

The highest nerve with full function is the level of your spinal cord injury. However, the body is not truly identical on both sides. Spinal cord injury is not typically exact on both sides, either. The last nerve with full function is the official diagnosis but you could have partial function or even a lower level on the opposite side of your body. In this case, your diagnosis is the last fully functioning nerve, but you could also have a zone of partial preservation (ZPP) indicated at a lower level across the body or even on just one side.

A diagnosis with a ZPP will give healthcare professionals information to work with that area of the body for functional improvement. Occasionally, this area can be treated to create increased movement and strength which will lead to enhanced function.

Individuals with spinal cord injury become very adept, very quickly at understanding the levels of the spinal cord. Not always to they understand why or the entire picture of the diagnostic process. Taking your time to have your entire body assessed and mapped for function and sensation can be tedious but when understanding the value of capturing any movement or sensation can be critical to improvement in function.

Nurse LindaI'm online in this community every Wednesday from 8-9 PM ET to answer your SCI and paralysis related questions.

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