Nerve damage, known medically as peripheral neuropathy, occurs when nerves outside the brain and spinal cord are injured, compressed, or deteriorate. It affects roughly 2.4% of the global population, rising to 8% in older adults. The damage can range from a temporary loss of function that heals in days to permanent destruction that requires surgery.
How Nerves Get Damaged
Your peripheral nerves are made of two key components: the axon, which is the long fiber that carries electrical signals, and the myelin sheath, a fatty coating that insulates the axon and speeds up those signals. Nerve damage can target either one or both.
When an axon is physically cut or crushed, the portion separated from the nerve cell body goes through a predictable breakdown. Within hours, calcium floods the injured segment. Over the next day or so, the internal structure of the axon collapses, and the fiber fragments. Cleanup cells then arrive about three days later to clear the debris. This process, called Wallerian degeneration, is the body’s way of preparing the ground for potential regrowth.
In other cases, the myelin sheath breaks down while the axon itself stays intact. The insulation splits apart, develops tiny bubbles, or peels away in segments. Without that protective coating, nerve signals slow dramatically or misfire. If the damage is limited to myelin, the body can rebuild it, though the new segments tend to be shorter and thinner than the originals.
Common Causes
Diabetes is the leading cause of peripheral neuropathy in the United States. About two-thirds of people with diabetes develop mild to severe nerve problems, typically starting with tingling or burning in the feet. Chronically elevated blood sugar damages nerves both directly and by restricting the blood supply that keeps nerve tissue alive.
Physical trauma is the second major category. Car accidents, falls, sports injuries, and even prolonged pressure from a cast can crush or sever nerves. Repetitive strain, like the kind that causes carpal tunnel syndrome, narrows the passageways nerves travel through and gradually compresses them. Broken or dislocated bones can press on neighboring nerves, and herniated discs in the spine can pinch nerve fibers where they exit the spinal cord.
Other well-established causes include autoimmune diseases (where the immune system attacks nerve tissue directly), kidney and liver disease (which allow toxins to build up in the blood), alcoholism, and certain medications, particularly chemotherapy drugs. Chemotherapy-induced neuropathy can persist long after treatment ends. Nutritional deficiencies also play a significant role, particularly low vitamin B12, which is essential for building and maintaining the myelin sheath. Low B1 (thiamine) can cause a condition called beriberi, characterized by symmetrical weakness and tingling. Interestingly, too much vitamin B6 can also cause nerve damage, with evidence suggesting that excess B6 is actually a more common culprit than deficiency.
Symptoms Depend on Which Nerves Are Affected
Your body has three types of peripheral nerves, and the symptoms you experience depend on which type is damaged.
Sensory Nerve Damage
Sensory nerves carry information about touch, temperature, and pain. When they’re damaged, you may feel tingling, numbness, burning, or stabbing pain, often starting in the hands and feet. Some people become hypersensitive to touch, finding even bedsheets painful. Others lose sensation entirely, which is dangerous because you can injure yourself without realizing it.
Motor Nerve Damage
Motor nerves control your muscles. Damage here causes weakness, cramping, twitching, and eventually muscle wasting. You might drop things, have trouble with buttons, or find it hard to walk. Over time, muscles that lose their nerve connection shrink in size. This is especially common in the feet, lower legs, and hands, and can lead to visible deformities.
Autonomic Nerve Damage
Autonomic nerves control functions you don’t consciously think about, and damage here produces some of the most surprising symptoms. Your heart rate may respond sluggishly to changes in position, causing lightheadedness when you stand up. Digestive problems like bloating, nausea, constipation, and nighttime diarrhea are common. Bladder control can become unreliable. Men may develop erectile dysfunction, and women may experience reduced sensation and difficulty with arousal. Even your sweat glands can malfunction, leaving some parts of your body drenched while others stay completely dry. Your pupils may respond slowly to light changes, making night driving difficult.
Three Grades of Nerve Injury
Not all nerve damage is equal. Clinicians classify injuries into three main grades, and the distinction matters because it determines whether you’ll recover on your own.
The mildest form is a temporary conduction block where the myelin is disrupted but the underlying nerve fiber stays intact. This is the most common response to blunt trauma. Think of a limb “falling asleep” from pressure, but lasting longer. Recovery typically takes a few days to 12 weeks as the myelin repairs itself.
The middle grade involves actual loss of the axon while the connective tissue tubes surrounding the nerve remain intact. Because the tubes are still there, the regenerating axon has a pathway to follow. Recovery is possible but slow.
The most severe form is a complete severing of the nerve. No recovery is expected without surgery to reconnect the cut ends. Even with surgical repair, outcomes depend on the location and extent of the injury. In some cases, a mass of disorganized, regenerating nerve fibers forms at the injury site, creating a painful lump called a traumatic neuroma.
How Nerve Damage Is Diagnosed
Two tests form the backbone of diagnosis. A nerve conduction study measures how fast and how strongly electrical signals travel through your nerves. Electrodes placed on your skin deliver a mild electrical pulse, and recording electrodes on a nearby muscle measure the response. A damaged nerve produces a slower, weaker signal than a healthy one.
An electromyography (EMG) test checks the electrical activity in your muscles. A small needle electrode is inserted into the muscle, and the machine records signals while you relax and while you contract the muscle. A healthy muscle at rest produces no electrical signals. If it does, that suggests the nerve supplying it is damaged. Together, these two tests can pinpoint where along a nerve the damage has occurred and how severe it is.
How Fast Nerves Can Recover
Peripheral nerves can regenerate, which sets them apart from nerves in the brain and spinal cord. But the process is slow. Axons regrow at a relatively constant rate of about 1 millimeter per day, or roughly one inch per month. You can estimate recovery time by measuring the distance between the injury site and the muscle or skin area the nerve supplies. An injury in your upper arm that needs to reach your fingertips may take many months to heal.
This timeline applies to cases where the nerve’s outer structure is intact and the axon has a clear path to follow. When a nerve is completely severed, surgical repair is needed first, and the regenerating fibers still have to cover the full distance afterward. The new myelin that forms during recovery is thinner than the original, so signals may remain slightly slower even after healing is complete.
Treatment and Management
Treatment starts with addressing whatever is causing the damage. For diabetic neuropathy, that means better blood sugar control. For nutritional deficiencies, supplementation with B12 or other vitamins. For compression injuries, relieving the pressure through splinting, physical therapy, or surgery.
Managing nerve pain itself typically involves medications that calm overactive nerve signals. The American Academy of Neurology recommends thinking about treatment in terms of medication classes: if one type of pain-relieving drug isn’t working or causes intolerable side effects, switching to a different class is more effective than trying another drug in the same category. Opioids are specifically not recommended for diabetic nerve pain. Topical treatments and non-drug approaches like physical therapy are also part of the toolkit.
What Happens if Nerve Damage Goes Untreated
Unmanaged nerve damage tends to get worse over time, and the complications extend well beyond pain. Loss of sensation in the feet is particularly risky. Without pain signals, small cuts and blisters go unnoticed and can develop into serious infections and ulcers, especially in people with diabetes. This is one of the leading causes of foot amputations.
Motor nerve damage leads to progressive muscle wasting. Muscles that lose their nerve supply shrink and weaken, sometimes causing visible deformities in the feet and hands. Balance also deteriorates because your brain relies on constant sensory feedback from your feet and legs to keep you upright. Without those signals, falls become more frequent, particularly in the dark when you can’t compensate with vision. Autonomic damage can mask the warning signs of other serious events, including heart attacks and dangerously low blood sugar, making these conditions harder to catch in time.