Neurography is a medical imaging technique used to create detailed pictures of the peripheral nervous system, which includes all nerves outside the brain and spinal cord. This method provides images that allow healthcare providers to identify and diagnose various nerve-related conditions. By making nerves appear bright, it becomes easier to distinguish between normal and abnormal nerve tissue.
What Neurography Detects
Neurography is a diagnostic tool for conditions affecting the peripheral nerves, particularly in identifying areas of nerve compression or entrapment. Common examples are carpal tunnel syndrome, where the median nerve is squeezed at the wrist, or sciatica caused by piriformis syndrome. The detailed images can pinpoint the exact location and severity of such compressions.
The technique is also valuable for assessing traumatic nerve injuries from accidents or falls. It can visualize nerve stretching, partial tears, or complete severance, providing information that helps guide treatment. Neurography can be performed within hours or days of an injury, offering a timely diagnosis over other tests that require a waiting period.
Beyond injuries and compression, neurography can detect nerve-related tumors and show a mass’s relationship to the surrounding nerve structure. It can also identify nerve inflammation (neuritis) from autoimmune diseases or infections. The imaging can reveal nerve damage caused by radiation therapy, helping to distinguish it from tumor recurrence.
The Neurography Procedure
A patient’s experience with neurography is similar to a standard MRI scan. Before the procedure, individuals must remove any metal objects, such as jewelry and watches, as the machine uses a strong magnetic field. It is important to inform the technologist about any medical implants, as some may not be safe in an MRI environment.
During the scan, the patient lies still on a table that slides into a large, tube-shaped MRI machine. The process is non-invasive and painless, though the machine produces loud knocking and buzzing noises, so patients are given earplugs or headphones. The scan lasts between 30 and 90 minutes, depending on the area being imaged.
In some cases, a gadolinium-based contrast agent may be injected into a vein to enhance the images. This substance helps to highlight areas of inflammation or disruption to the blood-nerve barrier, making certain abnormalities more visible. After the procedure, patients can resume their normal activities immediately.
Types of Neurography
The most common form is Magnetic Resonance Neurography (MRN), which uses advanced MRI technology. Specific software and imaging sequences are used to suppress the signal from surrounding tissues like fat and muscle. This suppression makes the water signal within the nerves appear bright and clear. This technique is effective for visualizing nerves located deep within the body, like the brachial or lumbosacral plexus.
Another type is High-Resolution Ultrasound Neurography. This method uses high-frequency sound waves to produce real-time images of nerves. A small, handheld transducer is placed on the skin over the area of interest, and it emits sound waves that bounce off the nerves to create an image on a monitor.
Ultrasound is excellent for examining superficial nerves, such as those in the wrist or elbow, and it allows for dynamic assessment where the nerve is observed as the patient moves. It is also a quicker and more accessible procedure than MRN. The choice between MRN and ultrasound depends on the nerve’s location and the information the clinician needs.
Comparison with Other Nerve Tests
Neurography provides different information compared to other common nerve diagnostic tools. While neurography and a standard MRI use the same machine, their applications are distinct. A standard MRI shows general anatomy, like bones and organs, whereas neurography uses specialized protocols to make nerves stand out, detecting subtle abnormalities that might be invisible on a conventional MRI.
The distinction between neurography and electrodiagnostic tests like electromyography (EMG) or nerve conduction studies (NCS) is also important. Neurography provides an anatomical picture, showing the physical structure of the nerve in high detail. It can reveal swelling, compression, or physical disruption.
In contrast, EMG and NCS are functional tests. They measure the electrical activity of muscles and the speed at which electrical signals travel along nerves, assessing how well the nerves are working. If neurography is a photograph of a wire, EMG and NCS are tests an electrician would perform to check the current. The two types of tests are often used together to provide a comprehensive diagnosis.