Definition
The herniated disc (also called disc hernia or prolapsus nuclei pulposi) describes the penetration of parts of the disc into the spinal canal. The fibrous cartilage ring, also known as the annulus fibrosus disci intervertebralis, tears off. Normally the fibrocartilage ring forms the outer edge of the intervertebral disc and plays a decisive role in the positioning of the central part of the spinal column, the so-called gelatinous nucleus (lat.
: nucleus pulposus). When the fibrous ring loses its function, this gelatinous core “falls” into the spinal canal in which the spinal cord is located and pushes the nerve fibres located there. The so-called protrusion of the intervertebral disc (lat.
: protrusio) is to be distinguished from a herniated disc. Here the fibrous ring remains intact and the symptoms are less frequent than in a complete herniated disc. Overall, the herniated disc is the second most common pain syndrome after headaches, with a 79% risk of suffering from a herniated disc once in a lifetime.
Causes
The main cause of herniated discs is usually an increasing damage to the intervertebral discs over a long period of time with accompanying degeneration of the fibrocartilage ring. Hyaline cartilage such as the fibrous ring, unlike most other components of the human body, is not supplied directly by vessels, but by diffusion, i.e. by the movement of substances through different layers of the body (or membranes). If these membranes are damaged over a long period of time by forces acting on them, the fibrous cartilage, which normally consists of approx.
80% water, may no longer be sufficiently supplied and begins to dry out. The loss of water reduces the elasticity of the cartilage and increases the probability of tearing. This can be promoted by poor posture, such as office work involving sitting at a desk for long periods, but also by genetic causes or incorrect strain. Other major risk factors are overweight and lack of exercise.
Symptoms
In general, the most typical and leading symptom of a herniated disc is a sudden stabbing pain in the region supplied by the affected nerve. The symptoms of a herniated disc therefore depend on the location of the herniated disc. Depending on the height of the herniated disc, the respective spinal nerve may be affected, which supplies specific muscles in relation to strength and specific skin regions in relation to sensation.
For the nerve root C6/7, pain symptoms are typical on the index, middle and ring finger as well as in the middle of the back of the hand. Alternatively or simultaneously, numbness in the described areas may also be present. If there is pain in the neck and arm, the medical term is cervicobrachialgia.
This can have other, more banal causes besides a herniated disc. The upper arm muscle Musculus triceps brachii, colloquially known as triceps, is the identification muscle of the nerve root region C6/7, which means that the doctor can determine whether nerve damage of the level C6/C7 is present by examining this muscle: If so, there would be a loss of strength in the triceps muscle. The accompanying pain can also lead to increased blood circulation in the affected skin areas.
In addition to the paralysis symptoms and sensory disturbances described above, such as formication or tingling on the skin, the pressure of the prolapsed intervertebral disc on the sensitive nerve roots causes sudden, very strong pain. This pain radiates into the areas supplied by the nerve root. But not every form of suddenly occurring pain radiating into the arms or legs is caused by a herniated disc.
Thus, tension, degenerative diseases of the spine, spatial demands such as swellings, effusions, etc. can cause pain with similar characteristics as the pain caused by a herniated disc. The central part of the disc prolapsed during a herniated disc can compress or squeeze the nearest nerve root in the spinal cord.
From these compressed nerve roots, however, nerves emerge which on the one hand control the muscles (motor nerve fibres) and on the other hand ensure the sensation of the skin (sensitive nerve fibres). The compression of the nerve root can therefore cause paralysis, which is caused by the effect on the motor nerve fibres, as well as sensitive sensations. These sensitive sensations include pain and numbness.
So-called paraesthesias such as formication or tingling can also occur. Deafness and signs of paralysis are therefore strongly in favour of a relieving operation. For almost every nerve root in the spinal cord there is an identifying muscle, which is only or mostly innervated by nerves from this root.
Therefore, if such identification muscles fail, there is a strong suspicion of an injury at the level of the specific nerve root. The identifying muscle for segment C6 is the brachioradialis muscle, which is located on the thumb-side of the forearm and, in addition to weak flexion in the elbow joint, enables rotation of the wrist. The reflex for testing the brachioradialis muscle is the radial periosteal reflex, which the doctor can test with a reflex hammer The characteristic muscle for the segments C7/8 is the triceps brachii muscle, colloquially called triceps. The triceps is located on the rear upper arm and is mainly responsible for the extension in the elbow joint. The associated reflex is the triceps reflex.
