Herniated Thoracic Disc

Each thoracic disc begins as a "pancake" with relatively even thickness from side to side and front to back. It has a rounded front and rounded sides to match the contours of the vertebral column and it is a bit concave on the back surface to accommodate the spinal canal. This results in a "kidney bean" shape. There is an outer ring of rather tough, gristly cartilage (the annulus) and an inner core of different, softer cartilage (the nucleus). As the disc becomes softer, it can collapse to a lesser thickness which allows perhaps more flexing movement than before. There is a ligament running longitudinally across the back surface of the bodies which bridges across the back side of each disc, in front of the spinal cord and exiting nerves, from the edge of one body to the next. The spinal cord is a complex neurological structure running through the spine with longitudinal nerve fiber tracts, exiting nerves and centers of nerve cells all providing important functions for parts of the body at or below the segment in question. Disc material can be displaced towards the spinal canal to cause compression of the spinal cord or nerves, either building up underneath the longitudinal ligament or even penetrating through it. Sometimes a long-standing disc herniation can take on calcium and become hard. There is much less "extra" space for the spinal cord in the thoracic spinal canal than elsewhere in the spine which makes the cord especially vulnerable here.

Cause of Thoracic Disc Herniation

Degeneration of the disc can be seen as a change in the signal on an MRI scan as the physical consistency of the nucleus becomes even softer. This naturally occurring process results in softening of the disc over many years of living. Absent some major accident, degeneration must be present for a disc herniation to happen. As the softened material becomes more fluid and deformable, the weight and forces on the spine during movements which squeeze and flex the disc between the vertebral bodies cause the nucleus to try to bulge outward. Sometimes the annulus is thinned out or pushed ahead of the deforming nucleus material. Sometimes a piece of the nucleus works its way through a crack in the annulus. I like to describe it as a jelly doughnut being squeezed and the innards coming out. In my practice, most thoracic disc herniations have less clear relationship to accidents or strain injuries than we see with cervical or lumbar disc herniations but it is certainly possible that one could occur this way. As with other portions of the spine, a herniated thoracic disc is usually the final result of movements and accumulated physical stresses of the spine over the course of many years. Occasionally, a single event seems to mark the onset of symptoms.

Treatment of Thoracic Disc Herniation

Since the thoracic spine is not subjected to the same stress as, for example, the lumbar spine, there seem to fewer problems of a "mechanical" nature. Back pain from thoracic disc degeneration or herniation is usually not severe which means very small herniations might be left alone if, in fact, they are ever detected. On the other hand, herniations that compress the spinal cord can cause neurological malfunctions which should be treated as soon as possible. The surgical approaches to the thoracic disc herniation are a little different than in other portions of the spine mostly due to the lack of "extra" space in the spinal canal. The herniation must be attacked from an angle a little to the side or from all the way in front. Surgical approach from the front means going through the chest with removal of a rib or two with rare exception of the highest segment of the thoracic spine being accessible through the neck. The front approach is often necessary if the cord is being compressed severely or across the entire canal. Smaller herniations compressing the cord can be reached by removing some of the bone along the side the canal until the front part of the canal has been reached. Disc herniations which are located to one side can then be withdrawn directly away from the spinal cord into the extra space that is created.

Outcome of Thoracic Disc Herniations

Spinal cord compression from any cause, at any segment of the spine can cause neurological malfunctions that are permanent. There is no method to absolutely determine whether a malfunction is temporary or permanent but, in general, the longer a malfunction has been present, the more permanent it is likely to become. Recovery from the effects of a thoracic disc herniation is possible, especially if the malfunctions have just recently developed. In some people, the recovery is essentially complete. Others are less fortunate, but there is always a chance of improvement unless all spinal cord function has been lost and/or the malfunction has been very longstanding. Another advantage of surgical treatment (even if neurological malfunction has been more long-standing) is the potential avoidance of future increase in neurological malfunction by eliminating the pressure on the spinal cord as soon as it is discovered. Persons who experience persisting neurological problems despite surgical treatment might need to wait several months and sometimes more than a year for all the benefit to be seen. With or without surgical decompression, malfunctions which have been present for years due to cord compression are not usually expected to improve further. Patients who only experience symptoms relating to compression of one of the exiting nerves in the thoracic spine generally do very well if, in fact, surgery is required.


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