Osteoporosis is a serious effect of neuromuscular disease, but one that can be managed
A 27-year-old woman with limb-girdle muscular dystrophy breaks a hip after tripping over a pair of shoes and falling onto a carpeted floor...
A 6-year-old boy with Duchenne muscular dystrophy is found to have low bone density while undergoing routine testing to enter a clinical trial...
A middle-aged woman who's been taking medication for an inflammatory myopathy for many years steps off a curb and fractures her ankle...
In addition to having neuromuscular disorders, these three people have something else in common: osteoporosis (OP), an invisible, progressive loss of bone that, if left untreated, can lead to further disability.
Although OP isn't rare in people with neuromuscular disorders, especially if they're taking certain medications, it's one of the more treatable — and even preventable — complications of these conditions. Unfortunately, some people have misconceptions about what OP is and what can and can't be done about it. Getting the facts is the first step in solving most problems, and OP is no exception.
Osteoporosis means a curved back or "dowager's hump."
The "hump" on the backs of many elderly women and some elderly men is the result of OP, but isn't the disorder itself.
The curved back that sometimes goes along with OP results from the destruction of the vertebrae in the spine, as they thin and collapse, tipping the spine forward.
The word osteoporosis comes from two Greek words meaning "passages in bones," a fairly accurate description of what happens in the disorder as the framework inside bones is gradually eaten away.
The process leaves gaps in the structure that weaken it, allows fractures to occur with little force and changes the shape of the vertebrae.
Two kinds of cells are always at work in bones — the osteoblasts, the bones' "construction crew," which works to lay down new bone; and the osteoclasts, the "demolition crew," which works in the opposite direction, to destroy old bone. Osteoporosis happens when the demolition cells get ahead of the construction cells, which can occur for a variety of reasons.
As bone weakens under the influence of the demolition cells, fractures occur. Hot spots for fractures are the wrists, hips and vertebrae.
Osteoporosis only affects elderly women.
Osteoporosis can affect people of both sexes and all ages. Major risk factors for people with neuromuscular disorders include prolonged lack of weight-bearing exercise and taking corticosteroid medications. These are added to the usual risk factors, such as menopause and aging.
We think of middle-aged and elderly women as the prime candidates for osteoporosis, and this is certainly true in the general population — although beyond about age 65, OP affects both sexes. Women in their late 40s to early 60s, unless they take preventive steps, usually develop OP associated with menopause. (African-American women, for reasons that aren't completely understood, have an advantage over white women when it comes to OP associated with menopause. The extent to which this advantage persists in other bone-destructive situations isn't clear.)
At menopause, the production by the ovaries of a group of female hormones known as estrogens (usually just called estrogen) and another group, the progestins (usually referred to by the main one, progesterone), ceases.
It's the lack of estrogen at menopause that tips the balance of bone building and bone destruction toward the latter. When women with neuromuscular disorders experience menopause, this risk factor for OP is added to other factors they may already have.
Aging itself seems to contribute to OP in both sexes beginning in the late 60s. Complex biochemical processes again tip the balance toward bone destruction. For those with neuromuscular disorders, aging adds another OP risk factor.
Weight-bearing exercise — specifically, standing, walking, running, jumping and probably lifting — puts stress on the bones that helps them stay strong. For those whose muscle weakness has greatly limited these activities, OP is always a risk.
Of all the risks for OP to which people with neuromuscular disorders are exposed, taking corticosteroid medications is perhaps the most serious.
|Standing, even while leaning on something, such as a walker, can help slow the course of bone loss.|
These drugs have names like prednisone (brand names Deltasone, Orasone and others); prednisolone (Prelone); dexamethasone (Decadron); deflazacort (Calcort); and triamcinolone (Aristocort).
They're used to treat inflammatory myopathies, such as polymyositis, dermatomyositis and sometimes inclusion-body myositis; myasthenia gravis and Lambert-Eaton myasthenic syndrome; and often Duchenne muscular dystrophy.
"With patients on prednisone [probably the most commonly prescribed oral corticosteroid in the United States], osteoporosis is a huge problem," says neurologist Richard Barohn, who treats patients at the MDA clinic at the University of Kansas Medical Center in Kansas City, Kan. If steps aren't taken to prevent bone loss, Barohn says, fractured vertebrae are too often the result.
"Every time I put a patient on prednisone, I put them on a prophylactic regimen for osteoporosis," he says. (See Calcium and Vitamin D.) "Prednisone is a great drug for some of these diseases. It's still the best drug we have, and it works more quickly than other drugs, but it has so many side effects. Doctors using prednisone have to become experts on the side effects, because they're putting patients at risk."
Until recently, most doctors didn't think diseases of the nerves or muscles directly caused bone loss, assuming that OP associated with these disorders came from immobility or drug treatment. But now, says Richard Henderson, a pediatric orthopedist at the University of North Carolina School of Medicine in Chapel Hill, that concept has been challenged.
In a recent study conducted at Henderson's medical center, boys with DMD who were still active and not on corticosteroids were found to have low density in their thigh bones, despite predictions to the contrary.
"What we expected to find was that bone density would be good early on and then would drop when they stopped walking," Henderson says. "But that's not really what we found. When we looked at bone density, it was already very poor when the children were still walking and playing, and then it went down from there."
Henderson's group found that bone density in the lumbar (lower) spine was (as expected) normal during the children's active years and then deteriorated as they became less mobile. The surprise was that bone density in the femur (thigh bone) was low long before lack of mobility became a factor.
"What it tells me is that poor bone in Duchenne dystrophy is not as simple as lack of weight bearing," says Henderson, who plans to do further studies on these findings.
If you don't have any symptoms, and X-rays show normal bones, you probably don't have to worry about osteoporosis.
By the time osteoporosis is visible on an ordinary X-ray, the problem is well advanced. Better tests are now available to detect OP earlier, when treatment can make a real difference. There are few warning signs of osteoporosis, other than broken bones or collapsed vertebrae, which occur when bone loss is well advanced.
OP doesn't usually hurt, although chronic back pain can be a warning sign that vertebrae are collapsing from within.
Ordinary X-rays usually aren't reliable indicators of bone density, but other tests, which are often covered by insurance, are much better. The standard test for OP now is the dual-energy X-ray absorptiometry, or DEXA, test, which is painless and noninvasive and scans the body at the hip or lumbar spine. It's usually done in the radiology department of a hospital or in a specialized clinic.
Newer tests use ultrasound (sound waves) to measure bone density at the heel. The device for the heel test is small and portable and fits nicely into a doctor's office or clinic, so these tests are gaining in popularity. Whether they'll prove to be as reliable as the DEXA scan remains to be seen.
You can't do anything about osteoporosis.
There's a great deal you can do to treat or prevent OP, ranging from dietary changes and adapted exercises to new, highly effective medications.
Virtually all milk sold in the United States is fortified with vitamin D at 100 international units (IU) per cup. Many cereal products are also vitamin-D-fortified, so together, these make a good source of both vitamin D and calcium.
One caveat: High-fiber cereals can interfere with calcium absorption, so milk added to these shouldn't be your only source of calcium.
A first step in preventing or treating OP is a dietary evaluation to see whether you're taking in enough calcium and vitamin D. A dietitian or nutritionist associated with an MDA clinic can help with this.
People usually get enough vitamin D, which is needed to absorb calcium from the intestines into the bones and to prevent excess excretion of it in the urine. Our bodies manufacture it from a "previtamin" hormone that, when exposed to sunlight through the skin, makes vitamin D.
The vitamin is also added to almost all milk sold in the United States, and to other products, including some cereals.
The National Academy of Sciences, through its National Institute of Medicine/Food and Nutrition Board, recommends that children and young adults take in 200 international units (IU) of vitamin D per day; adults age 51 and older, 400 IU; and adults 71 and older, 600 IU. Most people can meet this standard.
But residents of sunlight-poor areas, and people who keep their bodies completely covered at all times (for example, for religious reasons), or who almost never go outside, are at risk of vitamin D deficiency, as are people taking corticosteroids.
However, the vitamin is easily taken as a supplement in a variety of preparations. In fact, most major calcium preparations on the market are now sold either with or without added vitamin D.
Dietary calcium deficiency, by contrast, is a common problem. The academy says an adequate intake of calcium for adults is 1,000 to 1,200 milligrams a day; for children and teens ages 9 to 18, 1,300 milligrams; for children ages 4 to 8, it's 800 milligrams. Some experts recommend an intake of 1,500 milligrams a day for men and women over 65 and for postmenopausal women after age 50 who aren't taking estrogen.
These guidelines aren't so easy to meet.
Many diets don't provide enough calcium to prevent OP, especially for people who are on corticosteroids or have other risk factors. There are plenty of supplements to choose from, but it's also possible (and, some say, preferable) to increase calcium intake through the diet.
|Many types of calcium supplements, some with added vitamin D, are sold over the counter. Ask your doctor, nutritionist and digestive system what works best for you.|
"The first thing is to point out how to increase the dietary intake of foods high in calcium," says registered dietitian Judith Trautlein, a nutritionist at Children's Clinics for Rehabilitative Services in Tucson, Ariz., where she sees many children with neuromuscular disorders.
About risk factors for OP, Trautlein says, "When they're not weight bearing, that's a big one. The other thing is, once they're in a wheelchair, calorie needs go down, so it's harder to get all the nutrients you need in your diet. A lot of times they want to eat plenty, but to keep their weight under control, they can't."
It's hard enough to get adequate calcium when calories are plentiful, Trautlein says, but when calories are severely restricted to avoid weight gain, getting calcium from the diet can be a real problem.
Then, too, not everybody likes calcium-rich foods.
"Some kids are really into milk, so it's not a problem," Trautlein says. "But once they're in their teenage years, very often they'd rather have soda. Some eat yogurt, but not very many."
That's where supplements come in.
"We use Tums a lot," she says. "They're cheap, and kids will chew Tums. They come in mint and fruit flavors. But they're not the best absorbed. Calcium citrate gives the best absorption."
Neurologist Richard Barohn routinely prescribes vitamin D and calcium for patients taking corticosteroids.
"Everybody on prednisone gets supplemental calcium, either calcium citrate or calcium carbonate," he says. "Calcium citrate is a little better absorbed. Those are over the counter.
"Then I put patients on an additional tablet that's a vitamin D supplement. It's usually not enough to put them on calcium tablets with vitamin D. It's not enough if you're on prednisone. You have to use a separate vitamin D pill."
He often prescribes calcifediol (Calderol), an "activated" form of vitamin D that's available by prescription. This compound has gone through additional chemical processing during its manufacture that allows the body to use it more quickly and easily.
See Drugs to Prevent or Treat Osteoporosis, for a listing of calcium and vitamin D supplements. When other drugs for OP are prescribed, calcium and sometimes vitamin D are usually recommended, too.
|If standing is difficult, leaning on a kitchen counter or on a tall piece of furniture a few times a day is better for your bones than not standing at all.|
Until recently, most women experiencing menopause-related problems, including bone loss, were reassured by their doctors that taking hormones to replace those that were lost was a safe and reliable strategy.
But new evidence has shown that taking estrogens alone increases the risk of cancer of the lining of the uterus (endometrial cancer), and taking estrogen in combination with a progestin greatly reduces that risk. For women who've had a hysterectomy, the progestin isn't necessary.
However, even more recent evidence complicates the picture. Estrogen taken alone poses a small increase in a woman's risk of breast cancer, but estrogen taken with a progestin — the combination prescribed to reduce the risk of endometrial cancer — significantly increases a woman's risk of developing breast cancer.
At this time, the solution to postmenopausal therapy in general is still uncertain. Postmenopausal women with neuromuscular diseases should discuss all risk factors with their doctors before deciding on a course.
There are dozens of hormone replacement preparations on the market (see Drugs to Prevent or Treat Osteoporosis below). Fortunately, when it comes to treating and preventing osteoporosis, there's an increasing number of choices in addition to hormone therapy with estrogens and progestins.
A new class of medications called selective estrogen receptor modulators, or SERMs, has been developed to act the way estrogen does with respect to bone but not to have estrogenlike effects on other tissues, such as the breasts or uterus. The drug raloxifene (brand name Evista) is a SERM that's on the market to prevent and treat osteoporosis in women past menopause. It has to be taken with adequate amounts of calcium and vitamin D.
For men with low testosterone, replacement preparations of this hormone can be prescribed to treat or prevent osteoporosis.
Another medication that's technically a hormone but isn't a sex hormone is calcitonin (Miacalcin). The calcitonin that's marketed for osteoporosis treatment (but not prevention) is derived from salmon. It interferes with the work of osteoclasts, the cells that break down bone.
A new class of medications called bisphosphonates shows great promise in preventing and treating OP. These medications actually become part of the bone tissue and in so doing interfere with the efforts of the osteoclasts to break down bone.
Alendronate (Fosamax) and risedronate (Actonel) are examples of bisphosphonates that have U.S. Food and Drug Administration approval to treat and prevent postmenopausal osteoporosis and to treat osteoporosis in patients taking corticosteroid medications.
One problem with these drugs is that they can severely irritate the esophagus, the tube that goes from the mouth to the stomach. To minimize this risk, the drugs have to be taken in an upright position (sitting or standing), and the person taking them has to remain sitting or standing for at least 30 minutes. They can't be taken by people who have trouble swallowing or who can't remain in a sitting or standing position for at least 30 minutes.
Despite these concerns, these drugs show great promise in treating osteoporosis without the use of hormones. "These drugs work," says Chester Oddis, a rheumatologist at the University of Pittsburgh who treats patients with inflammatory myopathies, which often require corticosteroids.
"Steroid therapy weakens the framework [of bone]," Oddis says. "It reduces new bone formation, increases bone loss and decreases calcium absorption — everything you don't want." Oddis likes to start treating patients with a bisphosphonate early in their corticosteroid therapy course.
"With many patients, if they're young and starting on steroids, I give them 70 milligrams of Fosamax once a week or 5 milligrams a day. I'm treating them earlier than I did before." He says he thinks he's seeing fewer bone fractures in these patients, but he doesn't yet have the data to prove it.
If you can't do strenuous, weight-bearing exercise, you might as well forget about trying to exercise to prevent osteoporosis.
Standing a few times a day, even while leaning on something, provides bones with at least some stress that is probably helpful.
|A standing device (stander) can be a good solution to provide some weight bearing. Photo courtesy of Altimate Medical, Morton, Minn.|
"Weight bearing generally means standing up," says Robert McMichael, a neurologist and MDA clinic director in Arlington, Texas, who has limb-girdle muscular dystrophy and occasionally uses a wheelchair.
Not standing or bearing weight is a risk factor for osteoporosis, McMichael says. "When you put stress on the long bones by standing, that helps to maintain their strength."
McMichael doesn't see many arm fractures in his neuromuscular disease patients and suspects that daily arm use may be adequate to prevent these.
"Some people can't walk but can stay supported on a piece of furniture," McMichael says. "Some people get a standing frame to stand in, and that's good, too."
McMichael is all for standing and weight bearing where practical, but he doesn't think people should become "fanatical" about it when weakness prevents much exercise. Medications, he says, can compensate for lack of weight bearing when it comes to osteoporosis.
Carol Marulic, a physical therapist at University of Arizona Medical Center in Tucson, who has had a long association with the MDA clinic there, says weight-bearing activities help strengthen bones. But compromises and alternatives to full weight bearing also help bones stay strong.
For those unable to stand independently, leaning on something, such as a kitchen counter or walker, can help put pressure on joints in the spine, legs and arms. Being on the hands and knees can also put some pressure on the bones in a way that strengthens them.
Even standing and exercising in a pool, although it doesn't allow for as much weight bearing as being on land, is better than nothing, Marulic says. "For those who are somewhat unstable on their feet, it's a great way to exercise," Marulic says. "This still allows the weight bearing but in a safer medium."
If weakness prevents much exertion of any kind, Marulic recommends passive exercise — in which the work is performed by another person. A therapist or other helper (after being instructed by a professional) can apply intermittent, gentle pressure to compress joints and simulate weight bearing.
|DRUG OR SUPPLEMENT
Generic Name (Brand Name)
|HOW IT WORKS|
|Calcium (Tums, Os-Cal, Citracal, CalBurst, others)||Calcium can be used by the body to build bone.|
|Vitamin D; also called ergocalciferol and cholecalciferol||Vitamin D helps the body absorb calcium from intestines and prevents its excessive excretion in urine.|
|Activated forms of vitamin D, such as calcitriol (Rocaltrol) and calcifediol (Calderol)||Vitamin D has to be activated by enzymes in the liver and kidneys. Some experts believe the activated forms may be better than "plain" vitamin D.|
|Combined calcium and Vitamin D (Citracal + D, Os-Cal 500 + D, others)||Vitamin D is often combined with calcium because it helps with the absorption of calcium and prevents excessive excretion of the mineral.|
|Estrogens (Cenestin, Estinyl, Estrace, Premarin and others are pills; Alora, Estraderm, FemPatch and others are patches applied to the skin; Estrace and others are skin creams; and Estring is a vaginal ring)||Estrogens help to keep bone destruction from outpacing bone formation.|
|Progestins (Amen, Cycrin, Prometrium and Provera are pills or capsules; Crinone is a vaginal gel)||Adding a progestin to estrogen protects against the development of cancer of the endometrium (uterine lining).|
|Combinations of estrogens and progestins (Estratest, Femhrt and others are pills; CombiPatch is a skin patch)||Adding a progestin to estrogen protects against development of cancer of the endometrium.|
|Raloxifene (Evista)||Raloxifene, a selective estrogen receptor modulator, or SERM, is used by postmenopausal women because it has positive effects on bone with minimal effects on the breasts or uterus.|
|Testosterone (Androderm, Testoderm skin patches)||Testosterone is a male hormone that works to build and maintain bone in men much the way estrogen does in women.|
|Calcitonin (Miacalcin, others)||Calcitonin is a hormone derived from salmon that's similar to a hormone made in the human thyroid gland. Calcitonin impairs the activity of the bone-destroying osteoclasts. It's usually taken as a nasal spray but can also be given by injection.|
|Alendronate (Fosamax)||Alendronate is a bisphosphonate that interferes with the activity of osteoclasts, the bone-destroying cells.|
|Risedronate (Actonel)||Risedronate is a bisphosphonate that interferes with the activity of osteoclasts, the bone-destroying cells.|
There are a lot of high-calcium choices.