Peroneal Neuropathy: Waiting for the Other Foot to Drop

Peroneal Neuropathy: Waiting for the Other Foot to Drop

A "foot-drop" is a medical term that happily doesn't mean that the foot suddenly comes off the leg. Instead, it signifies that the foot droops down at the ankle as the leg is lifted off the ground. The muscles that should hold up the foot have gotten so weak that they can't fight gravity's pull down. People with this problem have to either lift their leg higher to avoid tripping over their drooping toes or risk tripping over them.

What is causing this annoying symptom? There are several probable causes, but one of the most prevalent is damage to a nerve bundle in the leg called the peroneal nerve. A short look at the bones in the leg will help you appreciate how this nerve bundle can get into problems. The femur is the only bone that connects the hip to the knee. It is a huge bone. The knee and ankle are connected by two bones. The tibia is the bigger bone and is closer to the interior. The fibula is the thinner bone and is closer to the exterior. That's all we need to know about the bones.

The peroneal nerve is made up of nerve fibers that travel with the big sciatic nerve that travels from the buttock to the lower leg behind the femur. That's where the "common peroneal nerve" leaves the group and goes down the outside of the knee, below the head of the fibular bone (a knobby bump just past the knee), and then wraps around the neck of the fibula right below its head. The neck of the fibula makes up the floor of the fibular tunnel that the common peroneal nerve has to go through. The common peroneal nerve is especially at risk of getting hurt in this tunnel.

The common peroneal nerve also separates into two branches inside this tunnel: the "deep peroneal nerve," which is farther from the surface of the leg, and the "superficial peroneal nerve," which is closer to the surface of the leg. Injuries to one of the two branches cause different problems than injuries to the other because they relate to muscles and skin in distinct ways.

The deep peroneal nerve makes the ankle and toes move, thus if this branch is hurt, the muscles that do these things will become weak or paralyzed. There is only a small piece of skin between the big toe and the toe next to it that is related to the deep peroneal nerve. If this branch is damaged, it will only cause numbness in this small area.

The superficial peroneal nerve, on the other hand, controls sensation in the skin on much of the outside of the calf and the top of the foot. If this nerve is hurt, these areas can become numb. This branch also lifts the outside edge of the foot, thus if the superficial peroneal nerve isn't working right, this motion stops.

The problems caused by damage to the common peroneal nerve (the parent of the two branches) are the same as the problems caused by each of the branches. This means that the ankle and toes can't bend up, the outside edge of the foot can't rise, and the outside of the calf and the top of the foot are numb.

"Peroneal neuropathy" signifies that the peroneal nerve isn't working right. Peroneal neuropathies are the most prevalent type of neuropathy that only affects one nerve at a time in the lower limbs. Researchers at the Louisiana State University Health Sciences Center recently gathered 318 individuals with peroneal neuropathy who needed surgery. At the same time, Italian researchers gathered 69 more instances, some of which didn't need surgery. These two lists of instances give us a solid idea of what causes peroneal neuropathy most often.

A lot of them were caused by bodily injuries. Some of the injuries were so bad that they broke or dislocated bones, while others were only wounds in the soft tissues or a stretch or bruise. Surgery was another typical cause. Some of the procedures were on the knee that was close by, but others were on areas that were farther away, including the hip, abdomen, or even the chest.

A lot of the cases were caused by too much outside pressure on the nerve. This happened in a number of ways. For instance, when you cross your legs for a long time, the knee of the bottom leg pushes steadily against the peroneal nerve of the crossing leg. People who were bedridden and had peroneal neuropathies probably got them from resting on the fibular tunnel for too long without moving. Some patients had their nerves trapped or pinched inside the fibular tunnel, although this had nothing to do with outside pressure.

A unusually significant number of people experienced peroneal neuropathy, which is also called "slimmer's paralysis," because they lost weight. There may have been more than one reason for these situations, such as not getting enough nutrition, pressure on the nerve, or both.

Researchers and doctors have found that in some persons, what looks like an isolated peroneal neuropathy is actually the first sign of a more widespread polyneuropathy. "Polyneuropathy" signifies that peripheral nerves are damaged in a more widespread way, not just in one region at a time. In some cases of obvious peroneal neuropathy, more tests show that the person actually has polyneuropathy caused by other things, like diabetes, drinking too much alcohol, or genetic factors.

How do they look at cases? The doctor's evaluation begins with the tried-and-true methods of taking a history and doing a physical exam. The doctor makes a list of which muscles are weak (and which ones aren't) and draws a map of the areas of numbness on the skin as part of the physical exam. More tests, such electromyography and nerve conduction studies, which look at how well the nerves and muscles work electrically, can often give useful information, such as whether more nerves are impacted and how bad the problems are.

What about treatment? The treatment for peroneal neuropathy depends on what caused it in the first place, but let's look at a common example that wasn't caused by a serious injury. Before surgery, doctors frequently try nonsurgical methods such avoiding putting more pressure on the peroneal nerve, eating better, and adding vitamins to the diet. Putting a basic brace on the ankle makes it easier to walk. In a lot of situations, the nerve heals on its own without any other treatment. But if these conservative treatments don't work (and the peroneal neuropathy isn't part of a larger polyneuropathy), the fibular tunnel may need to be surgically explored. If the nerve is pinched, the surgeon will liberate it from whatever was pinching it.

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