Your entire body is powered by nerves, but those nerves can be damaged by injury or an illness such as diabetes. Nerve damage can affect your ability to feel and move. And exactly how your body and your movement are affected depends on where in the body the damaged nerves are located.
Neuropathy is a disorder that affects the nerves. The peripheral nerves are those that are part of the peripheral nervous system, which affects feeling and movement all over the body. The cranial nerves are those that arise directly from your brain or brainstem and often affect areas like the face and eyes.
Neuropathy can occur for many different reasons. Diabetic neuropathy is one of the most common types, and it means that it's nerve damage that is caused by diabetes. It happens if you don't control your diabetes and your blood glucose levels are unstable and jump around from high to low. Diabetic neuropathy often affects the nerves in the feet, but can also affect several cranial nerves and your vision.
Neuropathies can be classified in different ways. One type is called mononeuropathy, which means that only one nerve is damaged. Polyneuropathy means that several nerves are damaged and that many parts of the body are affected. But you can also have a condition called mononeuritis multiplex, which means that two or more individual nerves in different places in the body have been damaged.
Different types of neuropathies can cause different symptoms, based on which nerves are damaged, and where they're located. Generally, neuropathies can cause:
A tingling sensation
Skin that feels sensitive to the touch
Weak or paralyzed muscles
When a nerve located in the skull is damaged, it's called a cranial neuropathy. Several different nerves can be affected, which is called multiple cranial neuropathy (MCN).
Some of the different types of cranial neuropathies include:
Bell's palsy. This condition occurs when the facial nerve is affected. It can cause drooping of part of the face, and is often caused by a virus that causes swelling, which puts pressure on the facial nerve. It usually only affects one side of the face.
Microvascular cranial nerve palsy. This condition affects the nerves in the eye. It is most common in people who are diabetic and in those who have high blood pressure. Microvascular cranial nerve palsy can cause double vision and other problems with eyesight.
Third nerve palsy. Third nerve palsy can cause an eyelid to sag and droop, double vision, difficulty moving the eye, and a pupil that is bigger than normal. These symptoms occur because the third cranial nerve is affected, and it helps to manage the muscles that move the eye. Sometimes children are born with third nerve palsy. But it may also be caused by an injury to the head or an infection. A disorder affecting the brain, such as an aneurysm or brain tumor, may also cause third nerve palsy. Diabetes and migraines are other possible causes.
Fourth nerve palsy. Also called superior oblique palsy, this affects the superior oblique muscle. That muscle is controlled by the fourth cranial nerve. Fourth nerve palsy can cause the eye (or eyes) to turn abnormally and sometimes makes you see double. It's often a congenital birth defect, which means that a baby is born with it. But an injury to the head, or a stroke or tumor can also cause fourth nerve palsy.
Sixth nerve palsy. Also called cranial nerve VI palsy, this affects the sixth cranial nerve. The sixth cranial nerve can be damaged by some sort of infection, a stroke or tumor, increased pressure in the brain, and even migraines. Damage to the sixth cranial nerve can cause abnormal movement of the eye and double vision.
A doctor will usually perform a neurological exam along with other tests to diagnose neuropathy. Depending on the type of cranial neuropathy that is suspected, tests may include:
Electromyography, which measures the electrical activity of muscles when working and at rest
CT or MRI scan
Nerve conduction velocity tests to help identify how and where the nerve is damaged
Biopsies of the skin and nerves to find out how severely nerves are damaged
Many types of neuropathies will get better with time, without any treatment. For some types of neuropathies and in some cases, surgery may help. Other times, the nerve damage can't be treated or repaired.
But it's important to diagnose and treat any health conditions that are causing the neuropathy. Treating common causes like high blood pressure, infections, and diabetes can help to treat the neuropathy. Eating nutritious foods, avoiding smoking, and limiting alcohol are also helpful in managing neuropathy.
Neuropathy can't always be prevented. But controlling common causes can help to reduce the risk of developing neuropathy. Reducing your risk factors for stroke, managing your diabetes well, and lowering high blood pressure can all be helpful in preventing neuropathy.
If you want to find out more information about preventing, treating, and living with neuropathy, contact the National Institute of Neurological Diseases and Stroke.