What is Disc Sequestration?
Disc sequestration is the most severe degree of disc herniation, in which the nuclear material of the disc spills out and completely separates with the disc. A herniated disc, also called a disc prolapse, slipped disc, or ruptured disc, is a tear or rupture of a disc in the spine. These discs are located between each two vertebrae and serve to cushion the movements of the vertebrae. Discs are composed of a tough fibrous layer called the annulus fibrosis that surrounds a gel-like substance called the nucleus pulposis. When a disc herniates, the annulus fibrosis suffers a tear that lets the nucleus pulposis squeeze out.
Symptoms of a ruptured disc range depending on how severe the herniation is and where the offending disc is located. Disc herniations are classified based on the posterior longitudinal ligament (PLL) and the degree of the rupture. The posterior longitudinal ligament runs vertically along the spine and passes each disc at its posterior, or back, side. The PLL separates the posterior side of the disc from the epidural space, which surrounds several spinal nerve roots. The three classifications of a herniated disc are disc protrusion, disc extrusion, and disc sequestration.
Disc protrusion entails a bulge in the disc and tearing of the annulus fibrosis, but no PLL damage, so that the nuclear material is contained. Protrusion may present with no pain or severe pain, depending on whether or not the bulge affects the nerves. Disc extrusion implies a complete tear in the annulus fibrosis, allowing nuclear material to seep out into the epidural space. Disc extrusion presents a similar range of symptoms to disc protrusion, severity depending on whether nerves are compressed.
Disc sequestration means that the nucleus pulposis has leaked out of the disc entirely and has separated with the disc due to a breach of the PLL. The nuclear material can then travel into the epidural space and is considered a free fragment. Disc sequestration is often severely painful, exhibiting sciatica, or pain down the back down the back and leg. In severe cases, the patient may develop cauda equine syndrome, which can cause loss of bowel control and numbness in the legs. This is considered a medical emergency in need of immediate surgery and can lead to permanent neurological damage if left untreated.
Disc sequestration happens most frequently in older patients, because the integrity of the disc degrades over time, making it more susceptible to herniation. Gradual strain on the disc, an acute strain, or a combination of both can cause a rupture to occur. Though most disc herniations do not require surgical treatment, a disc sequestration usually requires decompressive surgery. Candidates for surgery are those with cauda equine syndrome, muscle atrophying, and those for whom non-surgical treatments have failed.
The surgery is called a discectomy and may be performed differently depending on the individual case. During a discectomy, the surgeon removes part or all of the disc and sometimes inserts mesh to reinforce the disc or a prosthetic disc. The patient may have the option of a traditional open discectomy, a microdiscectomy, or an endoscopic discectomy. A doctor will discuss with the patient which course of action is best for each particular case.
Written by Caitlin Kenney
