| A "foot-drop" is a medical term | | | | collected a series of 318 patients with peroneal |
| which--thankfully--does not mean that the foot | | | | neuropathy who required surgery, while Italian |
| suddenly disconnects from the leg. Rather, it means | | | | researchers collected another 69 cases that included |
| that when the leg is lifted from the ground, the foot | | | | those who didn't need surgery. From these two |
| droops downward at the ankle. The muscles that are | | | | tabulations of cases a good picture emerges of the |
| supposed to prop up the foot have become so | | | | more common causes of peroneal neuropathy.Many |
| weakened that they cannot overcome gravity's | | | | were due to physical traumas. Some of the traumas |
| downward pull. When people with this problem try to | | | | were severe enough to break or dislocate bones, |
| walk, they have to either hike the leg higher to clear | | | | while others involved deep cuts in the soft tissues, |
| their drooping toes or else risk tripping over | | | | and still others involved just a stretch or bruise. |
| them.What is to blame for this inconvenient | | | | Another common cause was surgical operations. |
| symptom? In truth, there are multiple possible | | | | Some of the surgeries were to the nearby knee, but |
| causes, but one of the most common culprits is | | | | others were performed on more distant structures, |
| injury to a nerve-bundle in the leg known as the | | | | like the hip, the abdomen or even the chest.Many |
| peroneal nerve. To understand how this nerve-bundle | | | | cases were due to excessive external pressure being |
| can get in trouble, a quick review of the bones of | | | | applied to the nerve. This occurred in different ways. |
| the leg is helpful. There is just one bone, a big one, | | | | For example, in prolonged leg-crossing the knee of |
| that connects the hip to the knee, and that is the | | | | the bottom leg pushes steadily against the peroneal |
| femur. There are two bones that connect the knee | | | | nerve of the crossing leg. Peroneal neuropathies seen |
| to the ankle. The tibia is the larger one and lies more | | | | in bedridden patients were presumably due to lying |
| to the inside, while the fibula is the thinner one and | | | | on the fibular tunnel for too long without a shift in |
| lies more to the outside. That's the extent of the | | | | position. Other patients had entrapment or pinching of |
| bony anatomy we need to know.The nerve-fibers | | | | the nerve within the fibular tunnel unrelated to |
| constituting the peroneal nerve travel with the huge | | | | external pressure.A surprisingly large group of |
| sciatic nerve that runs behind the femur from the | | | | patients had peroneal neuropathy due to weight loss, |
| buttock to the lower thigh. That's where the | | | | also known as "slimmer's paralysis." More than one |
| "common peroneal nerve" splits out from the pack | | | | factor might have been at play in these cases, |
| and runs along the outside of the knee, tucking | | | | including lack of nutrients, pressure on the nerve, or |
| behind the head of the fibular bone (a knobby | | | | both.Researchers and clinicians find that in some |
| protrusion just beyond the knee) and then snaking | | | | people an apparently isolated peroneal neuropathy is |
| around the neck of the fibula just below its head. | | | | actually the leading edge of a more widespread |
| The neck of the fibula forms the floor of the fibular | | | | polyneuropathy. "Polyneuropathy" means that |
| tunnel that the common peroneal nerve must pass | | | | peripheral nerves are impaired in a more diffuse |
| through. Within this tunnel the common peroneal | | | | pattern--not just single nerves in single places. So in |
| nerve is particularly vulnerable to injury.Also within this | | | | some cases of apparent peroneal neuropathy further |
| tunnel the common peroneal nerve splits into two | | | | investigations turn up polyneuropathy due to other |
| branches, the "deep peroneal nerve" (farther from | | | | causes, for example, diabetes, excessive alcohol |
| the leg's surface) and the "superficial peroneal nerve" | | | | consumption or genetic factors.How are cases |
| (closer to the leg's surface). Because the two | | | | evaluated? The physician's evaluation starts with the |
| branches have different connections to muscles and | | | | time-honored methods of history-taking and physical |
| skin, injury to one produces different impairments | | | | examination. As part of the physical examination the |
| than are produced by injury to the other.The deep | | | | doctor inventories which muscles are weak (and |
| peroneal nerve is responsible for cocking up the ankle | | | | which are not) and maps out areas of numbness |
| and toes, so injury to this branch produces weakness | | | | affecting the skin. Additional testing with |
| or paralysis of the muscles responsible for these | | | | electromyography and nerve conduction studies, |
| actions. There is just a tiny patch of skin, located | | | | which check on electrical functions of the muscles |
| between the big toe and the toe next to it, | | | | and nerves, often provides valuable information, |
| connected to the deep peroneal nerve, so damage | | | | including whether additional nerves are affected and |
| to this branch produces numbness limited to this small | | | | how bad the impairments are.How about treatment? |
| area.The superficial peroneal nerve, by contrast, is | | | | Treatment varies according to what caused the |
| responsible for skin sensation on most of the outside | | | | peroneal neuropathy in the first place, but let's |
| of the calf and top of the foot, so these areas can | | | | consider a typical case unrelated to severe trauma. |
| become numb when the superficial peroneal nerve is | | | | Nonsurgical approaches are usually tried first, including |
| injured. This branch is also responsible for lifting the | | | | avoidance of further pressure on the peroneal nerve, |
| outside edge of the foot, so this action is gone when | | | | improved nutrition and supplementation of the diet |
| the superficial peroneal nerve is not functioning | | | | with vitamins. A simple brace applied to the ankle |
| properly.Impairments due to injury of the common | | | | improves walking. In many cases the nerve recovers |
| peroneal nerve (the parent of the two branches) are | | | | without anything more drastic being done. But if |
| the sum of the impairments associated with each of | | | | these conservative treatments fail (and the peroneal |
| the branches. So this means that the ankle and toes | | | | neuropathy is not part of a more widespread |
| cannot cock upwards, the outside edge of the foot | | | | polyneuropathy) then surgical exploration of the |
| cannot lift, and there is numbness on the outside of | | | | fibular tunnel is often indicated. If the nerve is |
| the calf and top of the foot."Peroneal neuropathy" | | | | pinched, then the surgeon frees up the nerve from |
| means impairment of the peroneal nerve. Peroneal | | | | whatever was pinching it.(C) 2005 by Gary |
| neuropathies are the most common neuropathies (of | | | | CordingleyGary Cordingley, MD, PhD, is a clinical |
| the kind that affects just one nerve at a time) in the | | | | neurologist, teacher and researcher who works in |
| lower extremities. Investigators at the Louisiana | | | | Athens, Ohio. |
| State University Health Sciences Center recently | | | | |