A pinched nerve, medically termed a compressed nerve or radiculopathy, describes a condition where excess mechanical pressure is applied to a nerve by surrounding anatomical structures. This compression can originate from various tissues, including rigid bone or cartilage, as well as softer muscle or tendon sheaths. When a nerve sustains this pressure, its normal function is disrupted, leading to symptoms like pain, a burning sensation, tingling, numbness, or muscle weakness in the area the affected nerve supplies.
Understanding Nerve Impingement
Peripheral nerves often travel through narrow, confined passageways, and any encroachment on this limited space can quickly cause problems. This physical pressure acts similarly to a hose being stepped on, interrupting the flow of signals and restricting the nerve’s internal blood supply. The mechanical force on the nerve restricts the flow of oxygen and nutrients, a condition known as ischemia, which causes the nerve fibers to malfunction. Continued pressure can affect the nerve’s insulating layer, leading to demyelination that slows signal transmission. This reduced blood flow and resulting inflammation can also make the nerve more sensitive.
Structural Changes Leading to Compression
The most common long-term causes of nerve compression stem from degenerative and structural changes within the spine and joints.
One frequent cause involves the intervertebral discs, which act as cushions between the spine’s vertebrae. A herniated disc occurs when the soft, gel-like center pushes through a tear in the tougher outer layer, causing the displaced material to press directly onto a nearby nerve root. Alternatively, a bulging disc happens when the outer wall weakens and expands outward, which can also irritate and compress the nerve.
Age-related wear and tear, particularly osteoarthritis, can lead to the formation of bony outgrowths called osteophytes, or bone spurs. These irregular growths develop as the body attempts to stabilize a degenerating joint and often reduce the size of the openings through which nerves exit the spinal column.
Another structural issue is spinal stenosis, defined by the narrowing of the spinal canal itself, the central channel housing the spinal cord and nerve roots. This narrowing is typically caused by a combination of thickened ligaments, bone spurs, and bulging discs that collectively crowd the space. The reduced diameter of the canal can put sustained pressure on the nerves, resulting in pain that often worsens with walking or standing.
External and Positional Causes
In contrast to chronic structural changes, other causes of nerve compression are related to acute events, repetitive actions, or systemic inflammation.
Acute trauma, such as a fall, car accident, or sports injury, can lead to immediate nerve compression. These sudden impacts can cause fractures or joint dislocations that physically misalign bone fragments against a nerve. The rapid swelling and bruising that follow trauma can also cause soft tissue to expand and exert pressure on the local nerve.
Repetitive stress and sustained poor posture are common culprits for nerve issues in the limbs. Activities requiring frequent, repeated motions, such as assembly line work or prolonged typing, can cause inflammation and thickening of tendons and ligaments. In the wrist, this leads to carpal tunnel syndrome, where swollen tissues compress the median nerve as it passes through the narrow, rigid space. Maintaining a poor posture for long periods, like slouching at a desk, can mechanically irritate nerves in the neck and upper back.
Systemic conditions that cause inflammation or fluid retention can also lead to nerve impingement by increasing the volume of soft tissue. For example, the fluid gain associated with pregnancy can lead to edema that swells nerve pathways, causing temporary compression. Underlying inflammatory conditions such as rheumatoid arthritis, or metabolic disorders like diabetes and hypothyroidism, can cause thickening of soft tissues and increased susceptibility to nerve entrapment.