As a multiple national and world champion powerlifter, Robert Herbst bench presses more than 300 pounds and lifts more than 400 pounds from the floor. He was nominated for the 2013 Sullivan Award for America's top amateur athlete.

But since his nomination, Herbst has been dogged by debilitating injuries. In November 2013, Herbst, age 56, of Larchmont, NY, underwent an initial procedure to remove bone spurs in his elbow. "They resulted from living an athletic life with lots of punishment on the elbow, including being a collegiate wrestler. The heavy lifting certainly contributed," he says.

As a result, scar tissue formed around and compressed his ulnar nerve, which runs from the collection of nerves under the collarbone to the hand, causing what is known as nerve entrapment neuropathy. He underwent a second surgery in late January to decompress and free the nerve near the inside of his elbow, an area that is sensitive to pressure, dubbed the funny bone.

"The doctors explained that I had a 'kink' in the nerve, like a garden hose," Herbst says.

Diagnosis of nerve entrapment usually begins with a physical examination and may include an X-ray, an electromyogram (which records the electrical activity of muscles), and a nerve conduction study (which evaluates how quickly electrical signals move through that nerve).

Treatment may include injecting anesthetics, steroids, or anti-scarring materials at the entrapment points. In some cases, surgery can be performed on the affected area. In addition, avoiding the repetitive behaviors that cause the entrapment can help.

Currently doing rehabilitation for his fingers, which are still numb, Herbst says he now has very weak "pinch strength" and lacks fine motor coordination.

"The doctor tells me it may take more than a year to get back to normal," Herbst says.

Nerve entrapment can affect anyone. "Any nerve anywhere can potentially become entrapped. When it does, patients will usually experience pain, numbness, and weakness, in that order, depending on the severity of the entrapment," says Aaron Filler, MD, PhD, a neurosurgeon at Cedars-Sinai Medical Center in Los Angeles.

The term "entrapment" is used to convey any number of problems occurring at a particular point along a nerve, according to Dr. Filler. "The nerve becomes irritated—pinched, squeezed, narrowed, or stuck on something, a condition called an adhesion."

Nerves may slide freely between soft, fatty tissues along most of their course but become pinched or squeezed through tight spots, according to Dr. Filler. Swelling can occur in these areas, increasing compression of the nerve.

"For example, nerves are often very close to the skin or rest against a bony structure," says Ahmet Hoke, MD, PhD, director of the neuromuscular division and a neurology professor at Johns Hopkins Medicine in Baltimore, MD, and member of the American Academy of Neurology (AAN).

In some cases, nerve entrapment doesn't cause pain, or consistent pain. "Nerve entrapment usually isn't a serious condition if it doesn't cause pain or weakness," Dr. Hoke says. "On the other hand, some people have extreme pain, even though the actual compromised nerve measured by nerve conduction studies is only mildly entrapped," he says.

The Dangers of Overuse

As the first chief medical officer of the National Collegiate Athletic Association (NCAA), Brian Hainline, MD, usually sees sudden acute nerve injuries caused by serious trauma.

"A person can fall down and break a leg, injuring the nerve, or get a penetrating wound that shears the nerve," says Dr. Hainline, who is a clinical professor in NYU Langone Medical Center's neurology department, Fellow of the AAN, and vice-chair of the AAN's sports neurology section.

"Most of the time, however, nerve entrapment occurs because of chronic overuse, asking the body to do something repetitively when it's simply not prepared to do so," Dr. Hainline says.

It can occur at any age, but is especially common when an athlete specializes in a sport instead of doing a variety of sports, according to Dr. Hainline. Weightlifters, for example, often overdevelop one area of the body, causing a nerve to become entrapped. But other athletes are at risk as well. "A baseball pitcher who repeats the same motion over and over might not have the correct muscle balance in the arm to support all he's asking that arm to do, especially around the elbow. Then the elbow can become lax or not be well supported, and the natural sliding mechanism of the nerve within the canal can cause scar tissue to build up around that nerve," he explains.

Surgery doesn't always fix the problem. "If you don't correct the overuse phenomenon or the imbalance that led to the problem, it will recur," Dr. Hainline points out.

Dr. Hainline says he worries when the condition develops in children or adolescents, as it was formerly seen predominantly in patients in their 20s and 30s. "All the best evidence tells us that sports specialization should not take place before puberty. It not only impedes overall athletic performance, but that performance won't peak the way it should," he says.

However, nerve entrapment doesn't just affect athletes; in fact, it's more common than many people realize, according to Allan Belzberg, MD, director of the Peripheral Nerve Center and associate professor of neurological surgery at Johns Hopkins in Baltimore, MD. Leaving a leg crossed for too long can cause tingling or weakness in the peroneal nerve territory (called a "crossed leg palsy"), while a person who drinks too much and stays asleep in the same position for a long time can pinch the radial nerve in the arm, which is called "Saturday night palsy."

Misdiagnosis

Pain syndromes often generate heated discussion among doctors and patients, in part because of the challenges in diagnosis, according to Dr. Belzberg. "Many of us are researching better ways to more accurately differentiate types of nerve problems," he says.

For example, piriformis syndrome—a type of nerve entrapment that affects the small piriformis muscle situated deep in the buttock—is often misdiagnosed as sciatica. Piriformis syndrome (also called false sciatica) causes pain in the buttock and leg by pinching the sciatic nerve, whereas true sciatica is usually caused by a pinched nerve in the low back. "In a small percentage of patients, a spinal examination may not show the true cause of pain," Dr. Belzberg says.

"A very high risk exists for misdiagnosing nerve entrapment due to piriformis syndrome as a lumbar disc problem, resulting in unnecessary surgery," says Dr. Filler.

Pelvic nerve entrapments such as piriformis syndrome, along with pudendal nerve entrapment and ilioinguinal nerve entrapment, may affect millions of people a year in the U.S., according to Dr. Filler.

Pudendal nerve entrapment can cause genital and rectal pain, sexual dysfunction, and bladder problems, according to Dr. Filler. Ilioinguinal nerve entrapment that affects a branch of the first lumbar nerve can be mistaken for an inguinal hernia, which is when contents of the abdomen—usually fat or part of the small intestine—bulge through a weak area in the lower abdominal wall.

The Earlier, the Better

An anesthetic delivered with the help of MRI can also help resolve harder-to-identify diagnoses, as with meralgia paresthetica, also called Bernhardt-Roth syndrome, a nerve entrapment syndrome that causes a severe burning sensation on the skin of the outer thigh.

"Meralgia paresthetica can be seen in people who are overweight, pregnant, or have diabetes," says Dr. Belzberg. "With the patient in the MRI machine, we guide a needle directly to the nerve's location to block it with minimal local anesthesia. The syndrome needs to be differentiated from lumbar spine problems, which can be done with these cutting-edge imaging techniques."

In addition to treating what's more apparent, doctors can now better predict who might develop nerve entrapment, according to Dr. Belzberg.

"Patients with an underlying disorder of peripheral nerves, such as metabolic or peripheral neuropathy, are at a higher risk for nerve entrapment," says Dr. Belzberg. Metabolic neuropathies are nerve disorders that occur with diseases that disrupt the chemical processes in the body—a common form of metabolic neuropathy is diabetic neuropathy. Peripheral neuropathies damage the peripheral nervous system, the vast communications network that transmits information from the brain and spinal cord or central nervous system to every other part of the body.

"Think of a nerve as a fancy electric cable," Dr. Belzberg says. "When injured by trauma, repetitive motion, or a metabolic problem, the nerve may be more susceptible to another injury. In addition, everybody basically has sites where there's just more of a pinch."

For many people, diagnosing and treating nerve entrapment can improve neuropathy, according to Dr. Belzberg. "Just because a patient has neuropathy doesn't mean that the pain results from the neuropathy itself—perhaps the patient is more susceptible to entrapment, which can send pain over the top. Also, nerve entrapment doesn't have to be terribly severe to cause symptoms," he explains.

In other words, a patient who has a neuropathy can have pain associated from an entrapment that would have been otherwise asymptomatic, or showing no symptoms. "The entrapment may be a second hit to a nerve already damaged by the neuropathy," Dr. Belzberg says.

Because such a significant portion of the population is aging, neuropathy is becoming more common, as is the need to accurately identify pain sources and treat them, Dr. Belzberg says.

What is Nerve Entrapment?

The term "nerve entrapment" typically refers to compression of nerves in the arms and legs, while ulnar nerve entrapment refers to the resulting dysfunction affecting the fourth and fifth fingers and muscles of the hand. The most common nerve entrapment syndrome is carpal tunnel syndrome (CTS), which affects the median nerve in the wrist.

Types of Nerve Entrapment 

Distal nerve entrapment syndromes are those that affect the arm or leg.

• Carpal tunnel syndrome: The most common nerve entrapment syndrome, carpal tunnel occurs when the median nerve that runs from the forearm to the palm and the first three and half of the fourth digits become entrapped at the wrist.
• Cubital tunnel syndrome: A compression of the ulnar nerve at the elbow causes this second most common syndrome, which involves a weak hand and pain, numbness and tingling in half of the fourth and the entire fifth digit.
• Guyon's canal syndrome: The ulnar nerve becomes entrapped while passing through a wrist tunnel called Guyon's canal. This condition sometimes mimics cubital tunnel syndrome.
• Peroneal nerve entrapment at the fibular head: The fibula joins the tibia to form the knee joint. The peroneal nerve is a branch of the sciatic nerve that supplies movement and sensation to the lower leg, foot, and toes. Entrapment can cause pain, make lifting a foot difficult, or even cause a "foot drop."
• Tarsal tunnel syndrome: The tibial nerve becomes trapped in the tarsal tunnel on the inside of the ankle. This nerve supplies movement and sensation to the sole of the foot and the muscles that flex the toes.
• Plantar nerve entrapment: Nerve branches at the inner arch of the foot are compressed.
• Posterior interosseous nerve entrapment: Affecting a nerve in the forearm, it may result in weakness of finger extension or cause dropped fingers or thumb.