Magnetic Resonance Imaging (MRI) is a valuable tool for investigating pinched nerves. This imaging technique helps identify the underlying causes of nerve compression.
Understanding Pinched Nerves
A pinched nerve, medically termed radiculopathy or nerve compression, occurs when surrounding tissues like bones, cartilage, muscles, or tendons apply too much pressure to a nerve. This compression disrupts the nerve’s normal function. These issues often arise in the spine, affecting nerve roots that branch out from the spinal cord, or in other areas like the wrist, elbow, or arm.
Common causes include a herniated or “slipped” disc, where the soft cushioning between vertebrae protrudes and presses on a nerve root. Bone spurs, which are bony growths, can also narrow the space around nerves, leading to compression. Spinal stenosis, a narrowing of the spinal canal, or inflammation from injuries or repetitive motions, can also contribute to nerve impingement. Symptoms often include pain, numbness, tingling sensations like “pins and needles,” or muscle weakness in the affected area.
How MRI Scans Work
Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic technique that creates detailed images of internal body structures. Unlike X-rays or CT scans, MRI does not use ionizing radiation. Instead, it employs powerful magnets and radio waves.
The MRI machine generates a strong magnetic field that causes the protons within the water molecules in your body to align. Radiofrequency currents are then pulsed, temporarily knocking these protons out of alignment. When the radiofrequency field is turned off, the protons realign, releasing energy signals that are detected by the MRI scanner. A computer processes these signals to generate precise, cross-sectional images of organs and soft tissues, including nerves, muscles, ligaments, and discs.
What an MRI Reveals About Pinched Nerves
An MRI is highly effective in visualizing the soft tissues and structures that can cause a pinched nerve. It provides detailed images of the spinal cord and nerve roots, allowing medical professionals to identify the specific location and cause of nerve compression. For instance, an MRI can clearly show if a herniated or bulging disc is pressing on a nerve root. The displaced disc material, which might appear misshapen on the scan, can indicate narrowing of the space around the nerve.
Furthermore, an MRI can detect bone spurs that might be impinging on nerves, revealing their size and exact position. It can also visualize spinal stenosis, showing the narrowing of the spinal canal that can exert pressure on the spinal cord and nerve roots. Beyond structural issues, an MRI may also reveal inflammation or swelling around the nerve, which can contribute to the compression and symptoms. While the nerve itself isn’t directly “seen” in terms of its electrical function, the MRI effectively shows the physical conditions and surrounding tissues that are causing the nerve to be compressed or irritated.
When an MRI Might Not Be Enough
While MRI is a powerful diagnostic tool for pinched nerves, it has limitations and is not always the sole diagnostic indicator. Minor nerve compressions, especially those caused by repetitive motions or subtle inflammation, may not be clearly visible on an MRI. An MRI provides a static image, meaning it captures a moment in time and cannot show intermittent compression that might only occur during specific movements.
Moreover, an MRI primarily shows structural abnormalities and does not assess how well nerves are transmitting electrical signals. This means that while it can identify what might be pressing on a nerve, it doesn’t directly measure nerve function or the extent of nerve damage. Therefore, a physical examination, the patient’s symptoms, and medical history are crucial for a comprehensive diagnosis. Other diagnostic tests, such as electromyography (EMG) and nerve conduction studies (NCS), are often used to complement MRI findings. These tests measure the electrical activity of muscles and the speed of nerve signals, providing insights into nerve function and helping to confirm the presence and severity of nerve damage, even if an MRI appears normal.