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Herniated Nucleus Pulposus

There are soft-tissue discs between the bony vertebral bodies in your thoracic spine (rib cage area) that are called intervertebral discs. These discs are composed of a soft gel-like center called the nucleus pulposus, and a tough outer layer that surrounds the disc called the annulus fibrosis. The intervertebral disc creates a joint between each of the vertebral bodies that allows them to flex and extend, rotate slightly, and laterally bend. When the outer layer, annulus fibrosis tears, the soft center migrates out through the opening, creating a “herniated”, “slipped”, or “ruptured disc”. Each of these terms describes the same process.

Tears in the outer layer of the disc can be very painful by themselves. Once a tear has occurred, pressure from everyday activities, such as flexion and extension of the back, can help to push the disc’s nucleus through the ruptured annulus. When you have a tear in your annulus, but the nucleus has not been squeezed out of the center of the disc, then you will usually have pain in your back only. However, if you have torn the annulus and the ruptured nucleus is irritating a nerve root, then you can have pain radiating from your back towards your chest and even abdominal area. Disc herniations can cause different patterns of pain, numbness, and weakness in your body, depending upon where the herniation or fragments of disc are located within the spinal column.

Symptoms

When a nerve root or the spinal cord is being pinched, you may experience pain in your back, and pain or numbness radiating around your rib cage towards your chest/abdomen. In severe cases, the muscles that are controlled by the nerve root that is being compressed by the disc herniation may become weak. The pain that you feel in your back and chest/abdomen can come from a combination of a tear in the annulus fibrosis, from the pressure that the disc herniation puts on the nerve, or from irritation, inflammation and swelling within the nerve.

Diagnosis 

The diagnosis of a herniated thoracic disc begins with a complete physical examination of the back and lower extremities. Your doctor will examine your back for flexibility, range of motion, and the presence of certain signs that suggest that your nerve roots or spinal cord are affected by the disc herniation. This often involves testing the strength of your muscles and checking your reflexes to make sure that they are still working normally. You will often be asked to fill out a diagram that asks you where your symptoms of pain, numbness, tingling and weakness are occurring.

A routine set of x-rays is also usually ordered when a patient with thoracic back pain goes to see a doctor. Many times, these x-rays are normal because the disc is composed of soft-tissue which does not show up on the x-ray. Instead, in situations where a herniated disc is a likely cause of a patient’s symptoms, doctors will order an MRI or a CT scan. An MRI scan is very useful for determining where disc herniations have occurred and where the nerve roots or spinal cord are being compressed. A CT scan is often used to evaluate the bony anatomy in the thoracic spine, which can show how much space is available for the nerve roots and spinal cord within the spinal canal. The nerve roots exit the spinal canal through a bony tunnel called the neuroforamen, and it is at this point that the nerve roots are especially vulnerable to compression by disc herniations.

A CT scan or an MRI is often not ordered until a decision has been made to proceed with surgery. This is because scientific studies show many people with “normal” backs have evidence of significant disc herniations on MRI scans, and these people do not have any symptoms of back pain. Therefore, MRI’s are usually ordered only when the diagnosis is unclear, or after it becomes apparent that the patient is not going to get better with non-surgical options and the surgeon needs to determine what type of surgery is best to relieve the symptoms.

Surgery for thoracic disc herniations is offered as an early option for people who have evidence of muscle weakness that is being caused by nerve root or spinal cord compression. This is because muscle weakness is a definite sign that the nerves are being injured (more seriously than when pain is the only symptom) and relieving the pressure on the nerves is more of an urgent priority. In other situations, surgery is offered after physical therapy, rest, and medications have failed to adequately relieve the symptoms of pain, numbness and weakness.

For more information about the surgery for disc herniations, please see discectomy