When faced with severe pain in the lower back, a person can be desperate for relief, even if it means surgery.
But surgery to alleviate low back pain shouldn't be performed unless other treatments have been tried for at least six weeks and have failed, according to Jack Wilberger, chairman of the department of neurosurgery at Allegheny General Hospital.
There is one big exception to this rule, he said.
"Only in the case of the horsetail do you absolutely have to have surgery, and you have to have it right away," Dr. Wilberger said.
The "horsetail" is cauda equina syndrome (using the term in Latin). It develops when the nerve roots at the lower end of the spinal canal, which provide motor and sensory function to the legs and the bladder, are compressed or pinched so much that sensation and movement are impaired or cut off altogether. If the pressure isn't relieved right away, CES can cause incontinence and paralysis.
"Surgery for CES is twice as likely to be successful if it is performed within 48 hours of symptom onset," said Jack Stern, a spine surgeon in White Plains, N.Y., and an assistant professor of medicine at Yale University. "Results will be favorable for about two-thirds of patients who undergo surgery within that time frame; only about one-third of patients who are operated on after 48 hours will do well."
Ideally, surgery should be conducted within 12 hours of diagnosis, according to a 2009 British study.
Cauda equina got its name because the nerves that extend from the spinal cord down the back of each leg look like a horse's tail. Among all the causes of low back pain, it's the only true medical emergency, Dr. Wilberger said.
It's hard to diagnose. The chief symptoms are weakness or numbness in the legs and feet, loss of sensation -- or a strange sensation -- in the buttocks, inner thighs and sacral region (the sacrum is a triangular-shaped bone between the spine and the tailbone), urinary or bowel incontinence, a sharp stabbing pain in the leg, or lower back pain. Symptoms may vary in intensity, come on suddenly or develop slowly over time.
Cauda equina syndrome is caused most often by a massive herniated disk. Disks (round, spongy pads of cartilage) between the vertebrae (bones) of the spine, act as shock absorbers. In a herniated or slipped disk, the center portion of the disk pushes out and puts pressure on the nerve roots.
Typically, a herniated disk is caused by injury. The older we get, the more likely we are to have one because as we age, the spinal disks tend to dry out, which makes them less flexible, more prone to tearing or rupturing from even a minor strain.
Other causes of CES are spinal infections, tumors or bleeding, spinal stenosis (a narrowing of the canal in the spine through which nerves pass), and complications from severe injuries to the lumbar (lower) spine such as a fall, car crash, gunshot and stabbing wounds. Another cause is arteriovenous malformation, a birth defect in which arteries and veins are tangled and not connected by capillaries.
Cauda equina syndrome is very rare. A study of U.S. military medical records for the years 2001-10 found an average of just seven cases per 100,000 person-years. A herniated disk will lead to CES no more than 6 percent of the time, according to studies published in medical journals in 2008 and 2004.
In about 70 percent of the cases in which a herniated lumbar disk does lead to cauda equina syndrome, the patient had a history of chronic low back pain. Males in their 30s and 40s are most prone.
There are two other sources of low back pain for which surgery may be the best means of providing relief, Dr. Wilberger said.
As we get older, the soft tissues and bones in the spine tend to harden and become overgrown, narrowing the space for the spinal nerves. Spinal stenosis occurs most often in those older than 60, but degenerative changes in the spine are detectable in 95 percent of us by the time we're 50. It's equally common in men and women, but women are more likely to display symptoms. Arthritis is the most common cause.
Spinal stenosis also can be treated with medication, and in some cases, its effects eased by improved posture, and exercise. So surgery should be considered only when its effects are severe, and other means to alleviate pain have failed, Dr. Wilberger said.
Surgery sometimes also is the best way to treat spondylolisthesis, he said. It occurs when the pars interarticularis (a small piece of bone which connects one facet joint in the spine to the one below it) fractures, causing one vertebral body to slip forward over the other.
The pars interarticularis (Latin for "bridge between two joints") is thin and has a poor blood supply, which makes it susceptible to fractures. It's most likely to occur in children and adolescents, but symptoms usually don't develop until we're older.
Fracture of the pars interarticularis doesn't always result in spondylolisthesis. Up to 7 percent of the population may have one or the other, but most will never display symptoms. Of those who do, only about 20 percent will ever need surgery.
New minimally invasive techniques have reduced the risk of back surgery and speeded recovery from it.
"Recuperation is very quick," Dr. Wilberger said. "We can probably do 50 percent of routine spine surgeries as outpatient."
The primary reasons for hospital stays for his back surgery patients now is because they have travelled a considerable distance to have the surgery, or they experience nausea or other side effects from anesthesia, Dr. Wilberger said.
Still, he said, surgery should be performed "in no more than 20 percent" of cases where surgery is an option and is essential only in the case of the horsetail.
An alternative to surgery for some is an epidural spinal injection, in which a steroid and a local anesthetic are injected directly into the area from which the pain is coming.
In one recent study, 80 percent of patients suffering from persistent sciatica (pain affecting the sciatic nerve, which extends from the lower back down each leg) caused by a herniated disk reported relief. In another, 75 percent of patients suffering from lumbar spinal stenosis reported significant reduction of pain.
But pain reduction from steroidal injections usually is temporary, and there are risks and side effects. A study conducted at Johns Hopkins University last year indicated that patients suffering from sciatica -- especially those who were overweight -- got more pain relief from exercise.
Jack Kelly: firstname.lastname@example.org or 412-263-1476. First Published September 16, 2013 4:00 AM