Neuropathy is a generic term that refers to damage to the peripheral nerves which normally transmit messages from the central nervous system to the muscles, glands, and organs, as well as sensory information from the skin and special senses to the brain. When there is injury to a single nerve, it is called a mononeuropathy, as seen in carpal tunnel syndrome, a disorder where the median nerve is compressed by a tendon at the wrist. When it occurs to multiple nerves, it is called polyneuropathy. Nerve diseases can be classified as “demyelinating” when they affect the protective layer covering the nerve fibers and help them conduct impulses more quickly, or “axonal” when they involve the nerve fibers (axons) themselves. The damage can also be specific to motor nerves that control the muscles, sensory nerves, or autonomic nerves.

There are many causes for neuropathy including metabolic conditions like diabetes, autoimmune diseases, toxins, vitamin deficiencies, and inherited genetic disorders like Charcot-Marie-Tooth disease. Diabetes is one of the most common causes of neuropathy and usually causes numbness, tingling, and pain in the feet. There are a number of medications, particularly cancer chemotherapy, which can also cause neuropathy.

Medications for neuropathy can help with symptoms such as burning and pain associated with neuropathy. Treating the cause of neuropathy, such as improving control of blood sugar for diabetic neuropathy, stopping toxic exposures, or vitamin supplements for vitamin-deficient neuropathies can help prevent further nerve damage. Autoimmune neuropathies may require immune therapy with medications such as infusions.

Myasthenia gravis (MG) is an autoimmune condition that causes weakness that worsens with increasing effort or activity and improves with rest. It often presents with droopy eyelids (ptosis), double vision, and trouble with swallowing or talking. Generalized weakness can also occur.

This condition is due to a problem at the neuromuscular junction where one’s own immune system prevents chemical signals from passing from the nerves to the muscles. This results in fluctuating muscle weakness. MG is caused by an autoimmune response, which occurs when the immune system targets a part of our own bodies rather than foreign bacteria or viruses. The immune system creates antibodies against the receptors on the muscles for the chemical acetylcholine, which prevents the signals from activating the muscles. These antibodies can be detected in the blood in about 90% of people who have MG with generalized weakness, and about 50% of people where MG affects only their eye muscles.

Electroneuromyography (EMG) can also help with the diagnosis, showing decreased muscle responses with repetitive stimulation. A special technique called single fiber EMG is a very sensitive test to assess for the presence of myasthenia gravis and is sometimes used to make the diagnosis of MG. It is not clear what triggers the autoimmune response, but it has been associated with tumors of a gland called the thymus in the chest, as well as certain medications. Your doctor may order a CT scan of the chest to find out if you have an enlarged thymus or a thymus tumor (thymoma), and if so, an operation to remove it may lead to better control of MG.

A number of medications have been used for long term control of MG. These often include a steroid (prednisone) or other immune-suppressing medicine like azathioprine (Imuran®), sometimes together with a medication that helps improve chemical communication between the nerves and muscles such as pyridostigmine (Mestinon®). Some patients may require other medications to be infused intravenously to control their condition such as eculizumab (Soliris).

MG can be life-threatening if it causes weakness of the respiratory muscles. You should let your neurologist know if you develop shortness of breath. If symptoms are mild, a pulmonary function test may be helpful to track your breathing. If you suddenly become severely short of breath, you should call 911 to be taken to a hospital, as symptoms can progress rapidly into an acute “myasthenic crisis” which requires admission to the hospital. Sometimes a ventilator is needed to keep you breathing while special treatments are given. These include intravenous immunoglobulin (IVIG) which downregulates the immune response to the MG antibody, or plasma exchange in which the antibodies are removed from the blood in a “blood-washing” dialysis machine, usually every other day for 5 treatments. MG crisis can sometimes occur in the setting of pregnancy, infections or medication changes.

Our myasthenia gravis program offers the latest diagnostic testing and treatments for MG.

Electroneuromyography (EMG) is a series of tests that measure how the nerves and muscles are working and how well the nerves communicate with the muscles. This testing can tell us where a nerve or muscle problem is located and often the nature of the problem based on the abnormalities discovered. EMG is most often done in the outpatient setting and is performed by neuromuscular specialists who have specialized training in performing and interpreting this test.

There are two main components to the test, which usually takes 30 to 60 minutes. The first part consists of nerve conduction studies, which are performed by giving electrical stimulations to the nerves and then measuring how fast the nerve conducts and how big of a signal is produced a fixed distance away. The doctor or technician may use heated towels to warm your arms or legs before testing. With motor nerves, an electrode is placed on a specific muscle, and the electrical stimulation to the nerve causes a small muscle twitch which is detected by the electrode. If the signal takes longer than expected to reach the muscle, there may be a problem with the myelin cells that cover and insulate the nerves, suggesting a “demyelinating neuropathy.” If the muscle twitch is smaller than expected, it could be a problem with the axon nerve fibers that make up the nerve, suggesting an “axonal neuropathy,” or it could also be a problem with the muscle itself. With sensory nerves, the electrode picks up a tiny signal in the sensory nerve. Other tests may look at the signals that go up to the spinal cord and back down the nerve. Together, these tests show how the nerves are working. If you have weakness, the doctor may give a rapid series of electrical stimulations to the nerve which tests whether there is a problem with the chemical signals from the nerves going to the muscles. This occurs with diseases like Myasthenia gravis.

The second part of the test involves inserting a small needle electrode into specific muscles. This can be uncomfortable but most patients tolerate it well, and your doctor will monitor how you are doing at all times. This part of the test shows whether the muscles are “irritable” due to loss of nerve connections, whether the nerve has partially grown back to contact more muscle fibers, and whether there might be a problem in the muscles themselves. Your doctor may ask you to move a single muscle by increasing amounts gradually. These tests provide important information that can lead to diagnosis of a wide variety of nerve and muscle diseases, including common conditions like carpal tunnel syndrome and rare conditions such as inflammatory muscle disease. EMG can also be used by your neurologist to select specific muscles for botulinum toxin injections.

Motor-neuron disease (MND) is a class of disorders that affect the motor neurons and results in marked muscle weakness, loss of muscle bulk (atrophy), and often tiny muscle twitches known as fasciculation. The cause of MND is not known, but these conditions selectively attack motor neurons, the nerve cells that control muscle movement, while sparing the sensory systems. There are two main types of motor neurons. The “upper motor neurons” live in an area of the brain just in front of a major groove called the central sulcus, and send their axon fibers down the spinal cord. These fibers send information to the “lower motor neurons” that directly contact the muscles. Loss of the lower motor neurons causes weakness and atrophy of the muscles and twitches called fasciculation. Loss of the upper motor neurons leads to decreased coordination for skilled tasks, stiffness, and spasticity, and increased (“brisk”) spinal reflexes.

The most widely known MND is amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, in which both upper and lower motor neurons are affected. Other forms include primary lateral sclerosis (PLS), which affects primarily the upper motor neurons and often has a less severe course than ALS, and progressive muscular atrophy (PMA), which primarily affects the lower motor neurons. MND is considered neurodegenerative with gradual progression and severe disability, often leading to death in a few years. If an MND is suspected, you should see a neuromuscular specialist who will order or perform an EMG which can confirm or exclude the diagnosis. Sometimes other conditions can mimic MND. If you have MND, regular visits to your neuromuscular specialist are important. Since the disease can progress rapidly, changes in breathing, speech and swallowing function can occur and require supportive treatments. Although this is a progressive and incurable disease at the present time, there have been significant improvements in survival and quality of life, mostly associated with better supportive treatments such as gastrostomy tubes and non-invasive ventilation. Riluzole and edaravone are medications FDA approved for the treatment of MND and are associated with a modest extension of life expectancy. There are many ongoing clinical trials being conducted around the world to find new treatments for this condition.

Muscular dystrophy (MD) is a group of neurological conditions with defects in structural proteins in the muscles causing progressive muscle weakness. There are many different types of MD. The best known are Duchenne MD and the milder Becker MD, both caused by defects in the muscle protein called dystrophin found on the X chromosome. Emery-Dreifuss MD causes wasting and weakness of the shoulders and upper arms and the calf muscles of the legs, as well as contractures in the elbows, neck and heels, and a heart rhythm problem known as conduction block. Facioscapulohumeral (FSH) MD begins in the teenage years and causes progressive weakness in muscles of the face, shoulders, and chest with lesser involvement of the arms and legs. Limb-girdle muscular dystrophy (LGMD) affects the large muscles of the shoulders and hips. Myotonic dystrophy presents in adulthood with muscle spasms, cataracts, cardiac abnormalities, and endocrine problems. Oculopharyngeal muscular dystrophy (OPMD) predominantly affects the eye movement muscles and those associated with speech and swallowing. Diagnosis of these MD syndromes is made by a neuromuscular specialist based on the pattern of weakness, changes in serum CK (a muscle enzyme that is increased in the blood due to muscle breakdown), muscle biopsy, EMG and genetic testing. Since the heart is a muscle that is affected in several forms of MD, we often obtain an EKG, echocardiogram, and x-rays. While there is no specific treatment for most MD, physical therapy, supportive deceives and other supportive measures are used to improve function and quality of life. A few medications are under investigation for specific MD types.

Inflammatory muscle disease is a group of muscle diseases where there is inflammation and breaks down of muscles. Many of these conditions are autoimmune diseases in which one’s own immune system “attacks” the muscles causing muscle and weakness. These include dermatomyositis which is an autoimmune muscle disease that is associated with both muscle weakness and skin changes and rashes. Necrotizing myopathies are associated with exposure to certain cholesterol medications or anti-signal recognition particle antibodies (SRP) and can be very severe. Overlap myositis is a group of autoimmune inflammatory muscle disease associated with different antibodies or other rheumatological diseases. These autoimmune muscles disease can be treated with a variety of medications that suppress or change the immune system to prevent further attack on the muscles. Another type of inflammatory muscle disease includes inclusion body myositis (IBM). This condition causes muscle degeneration and inflammation and tends to affect the thigh muscles and handgrip muscles early in the disease. There are no known treatments for this condition yet, but physical therapy can help to improve daily function.