Overview of Electrodiagnostic Evaluation of Peroneal Neuropathy
The fibular nerve, previously known as the peroneal nerve, is a crucial nerve in the foot region. The name was changed to avoid confusion with the similarly sounding perineal nerve. This nerve is often affected by issues like compression, direct injury, entrapment or inadequate blood supply, which lead to a condition known as fibular neuropathy. This is the most common nerve-related issue in the lower part of the body.
Fibular neuropathy affects both the deep and superficial fibular nerves in your foot. Although, it usually impacts the deep fibular nerve more than the superficial one because it’s closer to the surface and more prone to injury or compression. The area where the fibular nerve is closest to the skin, also known as the fibular neck or head, is its most common compression site.
When suffering from fibular neuropathy, some people experience an unexpected or gradual foot drop that may lead to tripping or falling. Patients may also feel a sensation like pins-and-needles—or a loss of sensation—in outer parts of the lower leg and in the top of the foot. Although foot drop is often painless, some patients do complain of pain before any signs of foot drop appear. When checked meticulously, these patients may only have a slight weakness when lifting their foot upward. Not all patients with fibular neuropathy will show abnormal nerve testing results; in fact, around one-third of them will likely have normal results.
This nerve can get injured due to certain behaviors or conditions, such as crossing the legs for long durations, improper position during surgery, significant weight loss, incorrect application of casts, remaining in a crouched position for prolonged periods (carpet installers, builders and farmworkers are especially susceptible), and diabetes. Foot drop can also be mistaken for another condition known as L5 radiculopathy, which affects the fifth lumbar nerve in the lower spine. However, a simple physical examination can help your doctor tell the difference between the two.
Problem in the deep fibular nerve can be due to injuries (like ankle sprains or fractures), narrow or high-heeled footwear, growth of bony spurs, cysts or fat lumps, or even conditions within the foot where the nerve passes under a band of fibrous tissue at the front of the ankle joint. The superficial fibular nerve can also get damaged through trauma, ankle sprains, or fat lumps.
Anatomy and Physiology of Electrodiagnostic Evaluation of Peroneal Neuropathy
The common fibular nerve, which helps us control and feel our leg, is connected to the nerve roots from L4-S1 which are part of your lower spine. A small part of the nerve also connects to the L2 nerve root, a little higher up on your back. This nerve is created in the group of nerves at the lower part of your spine, known as the lumbosacral plexus. It travels within a larger nerve, the sciatic nerve.
The sciatic nerve has many smaller parts that are separated but bundled together. Just above an area behind the knee known as the ‘popliteal fossa,’ these bundles form into two primary nerves: the common fibular nerve and the tibial nerve.
A branch from the fibular part of the sciatic nerve gives the command to contract to a muscle called the short head of the biceps femoris muscle. In case of any problem with the fibular nerve at the fibular neck, this muscle will remain unharmed. The skin on the side of your knee is controlled by the lateral cutaneous nerve, which is a part of the common fibular nerve. Following this branch of nerves, the common fibular nerve takes a turn around the fibular neck and goes between the bone and a muscle, the peroneus longus muscle by passing through a sort of tunnel.
The muscles tibialis longus and brevis, which help us lift and turn our foot, get their signals from the superficial fibular nerve. This nerve also sends signals to the skin on the side of the lower part of the leg and on the top of your foot and toes, except the area between the first and second toe.
The deep fibular nerve, also known as the anterior tibial nerve, controls various other muscles that help the movement of our toes and foot including the tibialis anterior, extensor digitorum longus, extensor hallucis longus, peroneus tertius, and extensor digitorum brevis muscles. This nerve also sends signals to the skin between the first and second toe.
Interestingly, between 15 and 25% of people also have an extra fibular nerve that comes from the superficial fibular nerve. This extra nerve provides unique control to the extensor digitorum brevis muscle, a muscle in your foot.
Why do People Need Electrodiagnostic Evaluation of Peroneal Neuropathy
If a person is suffering from a common type of nerve damage called fibular nerve neuropathy, they might be experiencing weakness in certain foot muscles. This might cause their foot to drop or slap against the ground when they walk. They could also lose some feeling in certain areas of their leg and foot. If they tap the outside of their knee (a test known as Tinel’s sign), they might fee a tingling sensation or pain, indicating nerve damage. They might also find it hard to flex their ankle or extend their big toe, due to weakened muscles.
If a person has fibular neuropathy that is affecting the deeper nerves in their foot, they might experience pain, muscle weakness, or a waste away (atrophy) of their foot muscles, especially a muscle located on the top of the foot called the EDB muscle. They could also feel numb or have a prickling “pins and needles” feeling between their first and second toes. They may feel pain on the top of their foot, which gets better when they move their foot around.
For people with a specific type of fibular neuropathy that affects the superficial (closer to the skin) nerves, they might experience pain, numbness, a prickling feeling, or a loss of sensation in the calf and top of the foot. However, the area between the first two toes is usually not affected. If the nerve damage is near to where the nerves supply certain muscles, these people could also experience weakness when they try to move their foot outward. This can be problematic as it affects the normal movement and balance of the foot.
When a Person Should Avoid Electrodiagnostic Evaluation of Peroneal Neuropathy
There are very few reasons why someone with fibular neuropathy, which is a nerve disorder in the leg, should not have an electrodiagnostic test. This is a type of test that uses small electric shocks to see how well your nerves are working. However, one of these tests, called electromyography (EMG), should not be done if you have serious bleeding disorders. Also, needles for EMG shouldn’t be used in areas where there is an active infection in the skin or the tissues underneath.
Another type of electrodiagnostic test, called nerve conduction studies, shouldn’t be done on patients who have external or implanted devices to help control their heart rhythm, like a cardiac defibrillator. Before these nerve tests are done, doctors will check if you have a pacemaker, a device that helps to regulate your heart beat. It’s very important that the electrical stimulation from these tests doesn’t come close to these heart devices.
Equipment used for Electrodiagnostic Evaluation of Peroneal Neuropathy
An EMG/NCS machine is a device that doctors use to check the health of your nerves and muscles. It’s kind of like a very specific computer set up by a medical professional just to check on these parts of your body.
The machine uses special sensors called electrodes to pick up electrical signals from your nerves and muscles. These electrodes come in two types: needle and surface. Needle electrodes are thin, sharp sensors that the doctor inserts into your muscle. Surface electrodes, on the other hand, are placed on top of your skin.
The machine also has components known as amplifiers and filters. Amplifiers are parts of the machine that increase the strength of the electrical signals picked up by the electrodes. This lets the doctor see the signals more clearly. Filters are parts of the machine that remove unnecessary noise or interference, giving a clean, clear signal for the doctor to examine.
Who is needed to perform Electrodiagnostic Evaluation of Peroneal Neuropathy?
A technician and a physiatrist, known also as a rehabilitation physician, play key roles in healthcare. A technician is a professional who assists with tests and procedures. Their work can range from taking blood samples to operating medical machines. On the other hand, a physiatrist is a medical doctor who specializes in physical medicine and rehabilitation. They focus on improving the overall quality of life for patients with physical impairments or disabilities. They do this through various therapies, helping patients regain their strength and movement capabilities.
How is Electrodiagnostic Evaluation of Peroneal Neuropathy performed
Before having an electric nerve test, your doctor will first thoroughly review your medical history, including any relevant health events and physical exams you’ve had. They will sit down with you and any family members involved in your care to explain why you need the test and what will happen during it. This conversation is an important part of the process, so don’t be afraid to ask any questions you have.
A complete electric nerve test may involve a number of steps. One of these is testing the nerve pathways to your extensor digitorum brevis (EDB) muscle, located in your foot. This is done both above and below the knee to check if there’s any problem with nerve messages getting blocked near your fibula (part of the lower leg). If they can’t get a good reading from the EDB muscle, they may take measurements from the anterior tibialis muscle in your shin instead.
Your doctor may also test your superficial fibular sensory nerve, which helps control sensation in your leg and foot. If the test shows a low signal strength, it could mean that the nerve is damaged ‘distal to the dorsal root ganglion’, or, in other words, damage has happened further down the nerve away from where it connected to the spinal cord.
Additionally, the test may also look at the muscles that are controlled by the sciatic nerve. This includes the short head of the biceps femoris muscle, which is a part of your hamstring. This part of the test helps doctors tell the difference between problems with the fibular nerve or issues closer to the hip. It’s very important to test both sides so that doctors can compare the results and get a clearer picture of what’s happening.
Finally, the doctors may also look for an extra fibular nerve. This is done by stimulating a point behind the bony bump on the outside of your ankle (the lateral malleolus) and recording response at the EDB muscle.
Possible Complications of Electrodiagnostic Evaluation of Peroneal Neuropathy
Tests that study your body’s electrical activity, known as electrodiagnostic studies, generally have few complications or risks. These could include:
- A tiny chance of bleeding
- A minimal risk of causing an infection where the testing device is inserted
- Some possible discomfort during the test
What Else Should I Know About Electrodiagnostic Evaluation of Peroneal Neuropathy?
Fibular neuropathy, a nerve condition that mainly affects the sensation and muscle movement in your leg, can be identified through different studies and tests. These check the state of your nerves and muscles.
We need to check two types of nerves, sensory and motor, to understand this condition better. Imagine sensory nerves as messengers taking information from your body to your brain, and motor nerves do the opposite, bringing commands from your brain to your muscles, making them move or do a particular action.
Here’s how we do it:
Sensory Nerve Studies
Gauging your ‘sensory’ nerves (nerves that help you feel things like touch, heat, or pain), we check if your fibular nerve is responding well. This nerve is located near the surface of your leg. If it’s healthy, you’ll get good responses. But if it has any damage, the responses will be low or completely absent.
Motor Nerve Studies
Here, we look at your ‘motor’ nerves (nerves that help your muscles move). If you’ve experienced a slowdown or block in nerve messages, it points to an issue with the nerve’s outer covering. Think of it as a weakened insulator on a wire, hampering the smooth flow of electricity.
One important thing to note is that if your muscles get smaller or atrophy, we may need to test a different muscle. Sometimes, muscle atrophy can be due to simple reasons like wearing tight shoes, not a disease. If needed, we compare the result with the other leg, and we may also need to check other muscles unrelated to the fibular nerve.
An accessory (additional) fibular nerve can sometimes come into play, improving the muscle responses. To test this, we stimulate an area behind your outer ankle bone.
Sometimes we also check ‘late responses’ or F-wave responses. These are nerve messages that bounce back from the muscle after an initial stimulus, much like an echo. If these are slow or absent, it could point to fibular neuropathy. But keep in mind, they aren’t very specific. We use other tools such as H-reflexes, which exclude fibular nerve involvement, to rule out other possible conditions.
Needle Electromyography
This test involves inserting very fine needles into your muscles. It is used to diagnose nerve and muscle conditions. It can show specific details of diseases damaging your axons, the core wire within the nerve transmitting electrical impulses.
In a healthy condition, your muscles will have normal firing frequency and motor unit action potential (the ‘work orders’ your brain sends through the nerves). For patients with mostly damaged outer nerve covering, we note decreased activity of these ‘work orders’ but no change in how they look.
It’s important to rule out other nerve diseases. So we also test muscles that are far from the troubled area and the paraspinal (near the spine) muscles.
Looking at the ‘firing pattern’ of the short head of the biceps femoris muscle (muscle on the back of your thigh) can help us identify the exact location of nerve trouble. This is crucial when there are injuries at two sites, i.e., the buttock and the fibular head areas.
In summary, diagnosing fibular neuropathy involves a series of careful and meticulous tests and comparisons across the muscles in your leg.
