Peripheral nerves send messages from the brain and spinal cord to the rest of the body. They help do things such as move the body's muscles for walking and sense that the feet are cold. Peripheral nerves are made of fibers called axons that are insulated by surrounding tissues.

Peripheral nerves are fragile and easily damaged. A nerve injury can affect the brain's ability to communicate with muscles and organs. Damage to the peripheral nerves is called peripheral neuropathy.

It's important to get medical care for a peripheral nerve injury as soon as possible. Early diagnosis and treatment may prevent complications and permanent damage.

With a peripheral nerve injury, symptoms may range from mild to serious, limiting your daily activities. Your symptoms often depend on which nerve fibers are damaged:

• Motor nerves. These nerves regulate all the muscles under your conscious control, such as those used for walking, talking and holding objects. Damage to these nerves can cause muscle weakness, painful cramps and muscle twitching.
• Sensory nerves. Because these nerves relay information about touch, temperature and pain, you may experience a variety of symptoms. These include numbness or tingling in the hands or feet. You may have trouble walking, keeping your balance with your eyes closed, fastening buttons, or sensing pain or changes in temperature. Injury of sensory nerves also may cause pain.
• Autonomic (aw-tuh-NOM-ik) nerves. This group of nerves regulates activities that are not controlled consciously, such as breathing, heart and thyroid function, and digestion. Symptoms may include excessive sweating, changes in blood pressure, the inability to tolerate heat and gastrointestinal symptoms.

Many peripheral nerve injuries affect more than one type of nerve fiber, so you may experience a range of symptoms.

When to see a doctor

If you experience weakness, tingling, numbness or a total loss of feeling, see your healthcare professional to find out the cause. It's important to treat peripheral nerve injuries early.

Peripheral nerves can be damaged in several ways:

• Injury from an accident, a fall or sports can stretch, compress, crush or cut nerves.
• Medical conditions, such as diabetes, Guillain-Barre syndrome and carpal tunnel syndrome, can damage nerves.
• Autoimmune diseases including lupus, rheumatoid arthritis and Sjogren syndrome also can damage nerves.

Other causes include narrowing of the arteries, changes in hormone balance and tumors.

People who experience physical trauma or play sports may be at higher risk of an injury that can stretch or crush peripheral nerves. People with certain medical conditions also may be at higher risk of peripheral nerve injuries. These conditions, especially diabetes, may put nerves at greater risk of compression.

To diagnose peripheral nerve injuries, your healthcare professional reviews your medical history. You're asked about any accidents or previous surgeries you've had and about your symptoms. Your healthcare professional also conducts a physical and neurological exam. If there are symptoms of a nerve injury, you may need diagnostic tests, which may include:

• Electromyography (EMG). In an EMG, a thin-needle electrode inserted into the muscle records the muscle's electrical activity at rest and in motion. Reduced muscle activity can suggest nerve injury.
• Nerve conduction study. Electrodes placed at two different points in the body measure how well electrical signals pass through the nerves.
• Magnetic resonance imaging (MRI). MRI uses a magnetic field and radio waves to produce detailed images of areas affected by nerve damage.
• Ultrasound. Like MRI, these high-frequency sound waves produce detailed images of the area affected by nerve damage.

Many tests may be used to help diagnose the type and severity of peripheral nerve injury. When you make your appointment, be sure to ask whether you need to prepare for these tests. For instance, you may need to stop taking certain medicines for a few days or avoid using lotions the day of the test.

If possible, take along a family member or friend. Sometimes it can be difficult to absorb all the information you're given during an appointment. Someone who accompanies you may remember something that you forgot or missed.

Other suggestions for getting the most from your appointment include:

• Write down all your symptoms, including how you were injured, how long you've had your symptoms and whether they've gotten worse over time.
• Make a list of all medicines, vitamins and supplements that you take.
• Ask questions. Children and adults with peripheral nerve injuries have several options for restoring lost function. Be sure to ask about all the treatments available to you or your child. If you run out of time, ask to speak with a nurse or have your healthcare professional call you later.