Peripheral Neuropathy and Sjögren's
This discussion of peripheral neuropathy is taken from a talk given by Elaine Alexander, MD, PhD, Arena Pharmaceuticals, Inc. at the Foundations April 2001 meeting, "Laughter is the Best Medicine." This article provides a definition of peripheral neuropathy and discusses the types and causes. Part II addresses treatment.
The Moisture Seekers, Vol. 20, Issues 7 and 9, October 2002, Summer 2002
Peripheral Neuropathy and Sjögren's Syndrome: Pts 1 & 2
Peripheral neuropathy - a set of disorders resulting from damage to nerves or to
their protective coating - occurs more often in people with Sjögren's syndrome
than in the general population.
"The Moisture Seekers" Newsletter. Vol. 20, Issue 9, October 2002 pages 1 & 12
"The Moisture Seekers"
Newsletter. Vol. 20, Issue 7, Summer 2002 pages 1 - 4
Peripheral neuropathy - a set of disorders resulting from damage to nerves or to their protective coating - occurs more often in people with Sjögren's syndrome than in the general population. Although the total number of people who suffer from peripheral neuropathy is not known, it is suspected that at least 10-20% of people with Sjögren's syndrome have it.
The peripheral nervous system comprises nerve fibers bundled together to serve as messengers for sensations from the brain and spinal cord to organs, muscles, and skin and back to the brain. The fibers are coated with a protective membrane known as the myelin sheath. Peripheral neuropathy occurs when either the nerve fiber or the myelin sheath is injured and the ability to send messages or impulses is affected. Sometimes the brain responds to these abnormal transmissions by translating them as pain or numbness. Other times, a muscle or organ sends back a response such as decreased movement. Because there are many types of both nerve fibers and injuries, peripheral neuropathy can be difficult to diagnose. It is not a single disease with a single set of symptoms, but a number of ailments with different symptoms and consequences.
There are five ways to characterize peripheral neuropathy. First, physicians look at the number of nerves that are affected:
- mononeuropathies are those in which one nerve is affected; a well-known example is carpal tunnel syndrome.
- polyneuropathies involve many nerves, often symmetrically so that both feet or hands are affected. Polyneuropathies can be external, which are injuries to the nerve itself, or demyelinating, which are injuries to the protective myelin sheath, or mixed, involving both types of injuries.
A second important way to classify neuropathies is by the fiber type that is injured. There are three types of fibers:
- sensory - involved with feeling and touching; sensory neuropathies cause abnormal sensations such as pain, cold, heat or burning sensations, tingling, or numbness.
- motor - necessary for all our voluntary or intentional movements, such as walking, stretching, or making a fist; motor neuropathies may result in weakness or spasms.
- autonomic - concerned with involuntary functions including dilation and constriction of pupils and blood vessels and the functioning of our digestive system and bladder; autonomic neuropathies (also known as entrapment neuropathies) can cause changes in these functions and include decreased perspiration, bowel and bladder problems, and sexual dysfunction.
The size - as well as type - of fiber is also a determining factor in the type of neuropathy:
- small fiber neuropathy can cause decreased sensation to pinpricks or temperature; discomfort or burning sensation in lower extremities; autonomic problems with bowel, bladder, or sweating abnormalities; but usually does not affect strength, motor function, and balance.
- large fiber neuropathy may result in loss of reflexes and motor dysfunction such as weakness, unsteadiness, and balance problems.
In making a diagnosis of peripheral neuropathy, physicians also want to know how quickly the symptoms occurred. If they occurred quickly, over a matter of days, the neuropathy is considered acute. Those that occurred less quickly but still in a relatively short time, generally over a few weeks, are considered sub-acute. Chronic neuropathies develop slowly, usually over a six-month or longer period. Most of the neuropathies suffered by people with Sjögren's are either sub-acute or chronic.
It also is important to determine whether the neuropathy is (1) pure (or parasympathetic) or (2) sympathetic. Recent studies indicate that Sjögren's patients have a primary defect in parasythetic enervation resulting in the failure of lacrimal and salivary glands to make tears and saliva. Antibodies against receptors on these ganglia nerves may actually be involved in decreasing the function of the nerves, and similarly the lacrimal and salivary glands in the case of primary Sjögren's.
Diabetes is perhaps the most common cause of peripheral neuropathy. Other diseases, including rheumatoid arthritis, leukemia, AIDS and HIV, are also implicated as causes. So too are chemicals, toxins, poisons, vitamin deficiencies, and repetitive activities. During the past 35 years neurologists and other researchers have discovered that certain neuropathies occur frequently with Sjögren's syndrome. Much of this research occurred at Johns Hopkins University and the Mayo Clinic. Physicians at both centers now recommend that anyone diagnosed with a peripheral neuropathy should be evaluated for Sjögren's syndrome.
"The Moisture Seekers" Newsletter. Vol. 20, Issue 9, October 2002 pages 1 & 12
The peripheral nervous system can repair itself, particularly if the cause of damage is removed or alleviated. Many of the symptoms of peripheral neuropathy can be treated. And, particularly when diagnosed early, before they are more severe, peripheral neuropathies can be treated.
What treatment should be used and how well it will work depends to some extent on the cause of the neuropathy. Stopping repetitive motions that cause carpal tunnel syndrome should help stop the neuropathy. Keeping diabetes in close control or restoring better kidney function through dialysis may help control neuropathies caused by diabetes or by kidney dysfunction.
However, when the cause of neuropathy is not clear or seems to be due to an autoimmune disease such as Sjögren's syndrome, treatment will more likely alleviate the pain rather than cure or treat the underlying cause. Pain relief of neuropathy includes medication, physical therapy, and improved nutrition. There is no single medication that works for everybody with neuropathies. Those commonly used include over-the-counter and prescription drugs approved for pain relief, antidepressants, and antiseizure.
Among the antidepressant pain relievers are amitriptyline (Elavil) and nortriptyline (Pamelor). According to their manufacturers, these products can cause sleepiness and dry mouth. Thus, these drugs, which are also used to treat headaches and depression, may not be appropriate for most people with Sjögren's. A newer pain medication - tramadol (Ultracet) - may help control burning or stabbing pain. Side effects reported by the manufacturer include constipation, sleepiness, and increased sweating. Additionally, there may be an increased risk of seizures if Ultracet is taken with selective serotonin reuptake inhibitors, tricyclic antidepressants, or opioids.
Antiseizure medications that have been used with some success in treating neuropathy include gabapentin (Neurontin) and carbamezepine (Tegretol, Carbatrol). The manufacturers report that common side effects of both products include drowsiness, balance problems, dizziness, and nausea. Gabapentin also can cause heartburn, increased appetite and weight gain and irritability. Carbamezepine also can result in temporary blurred vision, dry mouth, and difficulty passing urine.
Researchers are examining both capsaicin cream and gamma globulin as treatments for neuropathy. Capsaicin appears to offer relief for pain from osteoarthritis, rheumatoid arthritis, and neuralgia by reducing substance P, which is found at nerve endings and is involved in transmitting the pain signal to the brain. Gamma globulin is believed to either alter or stop the immune response that causes injury to the myelin sheath (or protective coating around nerve fibers). Steroids also may be used to suppress the immune response causing injury to the myelin sheath.
Physicians writing for www.neurologychannel.com recommend that physical therapy for peripheral neuropathy "should include caring for your feet, massage, and exercise." They suggest hand and foot massage, which will increase circulation, and avoiding things that will bother your feet if they are affected. These include avoiding standing for too long and not wearing tight shoes or socks.
Finally, a healthy, nutritious diet is not only essential for normal nerve function but also can help heal damaged nerves. Nutrients known to help proper nerve function include:
- thiamin (B1), found in whole grains, seeds, beans, peas, pork, and brewer's yeast;
- B12, found in dairy products, meat, poultry, and eggs - known to help proper nerve function;
- calcium, found in dairy products, leafy vegetables, and tofu; and
- potassium, found in spinach, squash, bananas, orange juice, milk, and other fruits and vegetables.
A special thanks to the Sjogren's Syndrome Foundation for allowing Sjogren's World to reprint this article online. For more information on the Sjogren's Syndrome Foundation, please visit their website: