A herniated disc, incorrectly called a "slipped disc", is a medicalcondition affecting the spine, in which a tear in the outer, fibrous ring (annulus fibrosus) of an intervertebral disc allows the soft, central portion (nucleus pulposus) to herniate. This tear in the disc ring may result in the release of inflammatory chemical mediators which may directly cause severe pain, even in the absence of nerve root compression.
Some of the terms commonly used to describe the condition include herniated disc, prolapsed disc, ruptured disc and the misleading expression "slipped disc". Other terms that are closely related include disc protrusion, bulging disc, pinched nerve, sciatica, disc disease, disc degeneration, degenerative disc disease, and black disc.
The popular term "slipped disc" is quite misleading, as an intervertebral disc, being tightly sandwiched between two vertebrae to which the disc is attached, cannot actually "slip", "slide", or even get "out of place". The disc is actually grown together with the adjacent vertebrae and can be squeezed, stretched and twisted, all in small degrees. It can also be torn, ripped, herniated, and degenerated, but it cannot "slip".
Frequency of Herniated Discs
A herniated disc can occur in any disc in the spine, but the two most common forms are herniated discs in the cervical spine and herniated discs in the lumbar spine. The latter is the most common, causing lower back pain (lumbago) and often leg pain as well, in which case it is commonly referred to as sciatica.
Lumbar herniated disc occurs 15 times more often than cervical (neck) disc herniation, and it is one of the most common causes of lower back pain. The cervical discs are affected 8% of the time and the upper-to-mid-back (thoracic) discs only 1 - 2% of the time.
Most herniated discs occur when a person is in their thirties or forties when the nucleus pulposus is still a gelatin-like substance. With age the nucleus pulposus changes ("dries out") and the risk of herniation is greatly reduced. After age 50 or 60, osteoarthritic degeneration or spinal stenosis are more likely causes of low back pain or leg pain.
Herniated Disc Cervical Spine
Cervical disc herniations occur in the neck, most often between the sixth and seventh cervical vertebral bodies. Symptoms can affect the back of the skull, the neck, shoulder girdle, scapula, shoulder, arm, and hand. The nerves of the cervical plexus and brachial plexus can be affected.
Herniated Disc Thoracic Spine
Thoracic discs are very stable and herniated discs in this region are quite rare. Herniation of the uppermost thoracic discs can mimic cervical disc herniations, while herniation of the other discs can mimic lumbar disc herniations.
Herniated Disc Lumbar Spine
Lumbar disc herniations occur in the lower back, most often between the fourth and fifth lumbar vertebral bodies or between the fifth and the sacrum. Symptoms can affect the lower back, buttocks, thigh, and may radiate into the foot and/or toe. The sciatic nerve is the most commonly affected nerve, causing symptoms of sciatica.
Causes of a Herniated Disc
Herniated discs can occur from general wear and tear, such as jobs that require constant sitting, but especially jobs that require lifting. Traumatic (quick) injury to lumbar discs commonly occurs from lifting while bent at the waist, rather than lifting while using the legs with a straightened back. Minor back pain and chronic back tiredness is an indicator of general wear and tear that makes one susceptible to herniated discsf on the occurrence of a traumatic event from bending to pick up a pencil, or heavy backpack from the floor.
Herniation of the contents of the disc into the spinal canal often occurs when the front side (stomach side) of the disc is compressed while sitting or bending forward, and the contents (nucleus pulposus) get pressed against the tightly stretched and thinned membrane (annulus fibrosis) on the rear (back side) of the disc. The combination of membrane thinning from stretching and increased internal pressure (200 to 300 psi) results in the rupture of the confining membrane. The jelly-like contents of the disc then move into the spinal canal, pressing against the spinal nerves, thus producing intense and usually disabling pain and other symptoms.
Symptoms of a Herniated Disc
Symptoms of a herniated disc can vary depending on the location of the disc herniation and the types of soft tissue that become involved. They can range from little or no pain if the disc is the only tissue injured, to severe and unrelenting neck or low back pain that will radiate into the regions served by affected nerve roots that are irritated or impinged by the herniated material. Other symptoms may include sensory changes such as numbness, tingling, muscular weakness, paralysis, paresthesia, and affection of reflexes. If the herniated disc is in the lumbar region the patient may also experience sciatica due to irritation of the sciatic nerve. Unlike a pulsating pain or pain that comes and goes, which can be caused by muscle spasm, pain from a herniated disc is usually continuous.
It is possible to have a herniated disc without any pain or noticeable symptoms, depending on its location. If the extruded nucleus pulposus material doesn't press on soft tissues or nerves, it may not cause any symptoms. A small-sample study examining the cervical spine in symptom-free volunteers has found focal disc protrusions in 50% of participants, which shows that a considerable part of the population can have focal herniated discs in their cervical region that do not cause noticeable symptoms.