A “pinched nerve” is a general term describing nerve compression or nerve entrapment. This condition occurs when undue pressure is exerted on a nerve by surrounding tissues, which can include bone, cartilage, tendon, or muscle. This mechanical pressure disrupts the nerve’s ability to transmit signals, leading to characteristic symptoms. The resulting discomfort often presents as pain, a burning or prickling sensation, tingling, or numbness in the area the affected nerve supplies. Identifying the precise anatomical location where the nerve is compressed is a primary step in diagnosis and treatment.
Pinched Nerves in the Spinal Column
The most common presentation of nerve compression occurs at the spine, where nerve roots branch out from the spinal cord. This condition is medically termed radiculopathy. Compression happens as the nerve roots exit the spinal column through small openings called foramina. Spinal radiculopathy is categorized based on the region involved: the neck (cervical spine) and the lower back (lumbar spine).
Cervical Radiculopathy
In the neck, nerve root compression often results from a herniated disc, where the inner material bulges out and presses directly on the nerve. It can also be caused by degenerative changes like bone spurs, which develop as the discs narrow. Compression in this area typically causes pain, tingling, or weakness that radiates down the shoulder and into the arm, forearm, and hand.
Lumbar Radiculopathy
The lower back is the site of lumbar radiculopathy, which is a frequent cause of sciatica. This condition involves compression of the large sciatic nerve roots (L4 to S3) as they exit the spine. The pressure is often mechanical, stemming from a lumbar disc herniation or from spinal stenosis, a narrowing of the spinal canal. Symptoms manifest as sharp, shooting, or burning pain that travels from the buttock down the back of the leg and into the foot.
Compression Sites in the Upper Body and Arms
Nerve entrapment also occurs frequently in the peripheral nervous system, away from the spinal column. This typically happens in narrow anatomical tunnels created by ligaments and bone. These peripheral neuropathies are often due to inflammation or tissue swelling rather than disc or bone changes. The two most common sites in the upper body are the wrist and the elbow.
Carpal Tunnel Syndrome
In the wrist, Carpal Tunnel Syndrome involves the compression of the median nerve as it passes through the carpal tunnel. This narrow passageway is formed by carpal bones and roofed by the transverse carpal ligament. Compression often arises from swelling of the synovium, the tissue surrounding the flexor tendons that share the tunnel space. This swelling reduces the limited room available for the nerve, leading to numbness and tingling in the thumb, index, middle, and half of the ring finger.
Cubital Tunnel Syndrome
At the elbow, Cubital Tunnel Syndrome is the second most common compression neuropathy of the upper extremity. Here, the ulnar nerve is compressed as it travels behind the medial epicondyle, a bony prominence on the inside of the elbow. The compression is most common where the nerve passes beneath the fibrous arch formed by the flexor carpi ulnaris muscle. Symptoms typically affect the little finger and the ulnar half of the ring finger.
Lower Extremity and Pelvic Nerve Entrapment
Peripheral nerve compression in the lower body can cause symptoms often mistaken for lumbar spine issues, but the cause is locally restricted to muscles or connective tissue. One such condition is Piriformis Syndrome, which is a non-spinal cause of sciatica-like pain. The piriformis muscle is located deep in the buttock.
Piriformis Syndrome
The sciatic nerve, the largest nerve in the body, typically passes directly underneath the piriformis muscle as it exits the pelvis. If the piriformis muscle spasms, becomes inflamed, or is hypertrophied, it can constrict the sciatic nerve. In a small percentage of the population, the nerve may even pass directly through the muscle, making it susceptible to compression during muscle contraction.
Tarsal Tunnel Syndrome
Another common entrapment site is the ankle, which is affected by Tarsal Tunnel Syndrome. This condition involves the posterior tibial nerve as it travels through the tarsal tunnel, a narrow space located on the inside of the ankle behind the medial malleolus. The tunnel is roofed by a thick band of tissue called the flexor retinaculum. Compression occurs when the volume of the tunnel contents increases, such as due to fluid swelling, space-occupying lesions, or foot deformities. This compression results in pain, numbness, and tingling across the sole of the foot.