LOWER EXTREMITY NERVE COMPRESSION IN HYPERMOBILE AND EHLERS DANLOS (EDS) PATIENTS

Dr. Matthew C. Oseto, MD

Ericson Hand and Nerve Center

425-776-4444

Presented January, 15, 2023

What is Collagen?

Collagen is the basic building block for everything in the body. It’s found in ligaments, tendons, skin, and nerves. The scaffolding of those tissues is made of collagen.  Collagen starts as molecules, they coalesce into filaments and then get woven into ligaments.  A good example would be a rope versus steel cable.  Collagen is the fiber and ligaments are the rope.  The fibers of the rope are more stretchy than the wire in the steel cable.  If you have a collagen disorder, you’ll have loose joints and therefore less stability in your joints.  Also, your nerves will be softer and less resistant to compression and stretch.

Nerve Compression in Hypermobile/EDS Patients

Everyone has nerve compression sites; the most common is carpal tunnel of the wrist.  These are spots in the body where nerves run between muscles/tendons, fit in tight tunnels of connective tissue, or make abrupt turns at joints.  Most people tolerate it pretty well. If you have repetitive motion, soft nerves, or inflammation of the nerve then you could have carpal tunnel symptoms or symptoms of other nerve compression. Compression symptoms are more common if you’re hypermobile.  If you are hypermobile you have soft, compressible nerves and loose joints which stretch your soft nerves (examples: rolling your ankle, joint dislocations, instability).  A tight spot in someone with healthy collagen might be no problem if their nerves can handle it or handle the pressure on it but soft nerves are unlikely to handle it.

Managing Nerve Compression

Posture is important. By improving your posture for neck and shoulder, it can help decompress the nerves up high and possibly relieve symptoms down the arm, even if there is a secondary compression further down.  Similarly, in the legs, avoiding slouching, crossing the legs, leaning the ankle or leg against a desk or chair can help minimize nerve compression.

Why do Hypermobile/EDS Patients Seem to Have More Falls?

The hypermobile/EDS population tends to have a lot of falls due to loose joints, POTS (postural orthostatic tachycardia syndrome), and weakness in ankles, knees, and hips due to nerve compression. The compression makes it much harder to correct a misstep or fully lift the toe to clear a step causing you to catch your toe and trip. Numbness and loss of proprioception (where your joint is in space) can also cause falls. Much of the body’s ability to know where your joint is in space by skin stretch. Researchers numbed the skin over the wrist but left the deeper nerves alone and patients couldn’t tell where their joint was (wrist pulled back or flexed down). If you have stretchy skin, you aren’t going to be able to tell where the joint is until you get significant stretch where it may be past the point where you can save your fall or sublux your joint.

Nerve Compression and Injury From Falls

There is a vicious cycle where you can have nerve compression that leads to pain, weakness, and numbness that leads to falls. Then when you fall, you can directly bruise nerves if you hit them on a stair or furniture.  Also, nerves can have stretch injury. When you roll your ankle, you’re going to stretch the nerves (common peroneal nerve) that run all the way down your leg from the outside of the knee to the base of the tops of the toes. There’s a tight spot on the outside of your knee where the nerve is relatively tethered so that when you roll your ankle you’re stretching it and it’s stuck at the outside of the knee and can get damaged and form scar tissue and swell. This swelling and stretch can then cause more nerve compression and pain.

Other Causes of Nerve Compression

Nerves in the lower extremities have natural tight spots.  For example, as the sciatic nerve divides into the tibial and common peroneal nerve behind the knee, the tibial nerve enters the soleus muscle through a tight area of fascia.  In similar fashion, the common peroneal nerve wraps around the outside of the knee and is secured in a tight fascia tunnel.  These are two areas that can be predisposed to compression.  Some compression is positional.  Poor posture (crossing legs, etc.), tight clothes, shoes, and braces can also contribute. Inflammation and swelling of nerves due to diabetes, viral infection, and excessive alcohol consumption can aggravate nerve compression by increasing the size of the nerve relative to the fixed size of the compression area.   When you have diabetes, your cells take in sugar. When it breaks down that sugar into sorbitol, the sorbitol can’t leave the cell. It’s stuck, it doesn’t have a transporter to get out and it causes an osmotic gradient. The sorbitol wants to hold onto water and that leads the cell to swell and your body doesn’t have a good way to break that down.

What Can Be Done About Nerve Compression?

Conservative management – what do we do about lower extremity nerve compression? The big one is avoiding compression of the nerves of the back and legs. So that core strength, posture, and avoiding crossing legs. You can also look at vitamin and mineral deficiency. If you’re iron deficient it can affect your nerves.

What Are The Symptoms of Lower Extremity Nerve Compression?

Many patients describe it as an aching, gnawing, deep, hard-to-describe pain. It can be intermittent depending on position or activity. Some people have numbness and/or foot and ankle weakness. Lower extremity nerve compression can contribute to Restless Leg Syndrome. For restless legs, people will say they have unpleasant sensations inside the legs. They feel like it’s deep, not on the skin’s surface.   Patients describe a crawling, creeping, pulling, throbbing, aching, itching, electric, and intermittent feeling in their legs. Most of the time people say it’s an urge to move the legs, especially at night when they’re lying down. It’s mostly relieved by moving the legs, but only temporarily. There is no real single cause but it can be associated with things like peripheral neuropathy, iron deficiency, or a dopamine imbalance.

Surgical Management of Lower Extremity Nerve Compression

If we look at the lower extremity, you see the sciatic nerve running down and just above the knee it splits into two nerves. On the front of the leg, you have the femoral nerve. The two main nerves we are concerned about are the tibial and peroneal nerves. The tibial nerve is the one that runs down the back behind the knee. (where two tight spots are). This would tend to cause symptoms of aching down the back of the leg, behind the knee, and down towards the inside of the ankle and into the bottom of the foot. This can also cause numbness in the bottom of the foot and a weak ankle as well. As the tibial nerve runs down the leg, it sends off branches to all the muscles that raise your arch, bring your toes down, and push off. The other branch of the sciatic nerve is the common peroneal nerve that runs from behind the knee to the outside of the lower leg. This is the nerve that wraps around the outside of the knee. Compression can cause pain and aching over the outside of the shin down toward the top of the foot. This nerve sends the branches down that keep you from rolling your ankle.

If symptoms persist in spite of conservative treatment, surgery to release the tight tissue that is pushing on the nerves can help. After surgery, you’ll need to be non-weight bearing to allow swelling to subside. When you put weight through your leg, you’re pressurizing your foot and that makes the incisions want to open. Another reason is gravity causes fluid to pool and that increases swelling which causes the wounds to stretch and have poor healing. It typically takes one to three weeks for the incisions to heal. You’ll want to keep your leg elevated for the first three to five days. Recovery is variable and depends on many factors. These include how much and how long the nerves have been compressed, the tendency for patients to form scar tissue, and level of hypermobility. Nerve recovery can take up to a year or more.

Summary

Nerve compression in the lower extremities can have symptoms ranging from nagging, intermittent discomfort to debilitating pain, weakness, and numbness.  Nerve compression is more likely in hypermobile/EDS patients because of joint laxity and “soft nerves.”  Improving posture, avoiding compression (crossing legs), and changing positions when sitting can help improve symptoms.  If conservative measures fail, surgery to decompress the tight spots around the nerves can help.