Vince Neil of Motley Crue performs as part of the 4th Annual Sunset Strip Music Festival on the Sunset Strip in West Hollywood, Calif. in August, 2011.Corbis

Motley Crue singer Vince Neil has played concerts through broken bones and torn ligaments, but crippling pain recently forced him off the stage after just a few songs. The culprit? Kidney stones. It's one of the most painful medical conditions humans endure, pain experts say -- although some are worse.

In general, neuropathic pain -- pain produced by damage to nerves rather than tissue -- produces the most excruciating pain, according to Allan Basbaum, chair of the anatomy department at University of California, San Francisco, and former editor of PAIN, the Journal of the International Association for the Study of Pain. And because many of these conditions come and go, patients often live in trepidation of their next attack. "The unknown is terrifying," Basbaum said.

While a definitive ranking is impossible, here's a look at a few of the most debilitating maladies, the kind Basbaum says patients rank as a 15 on a scale of 1-10.

Cluster headacheGetty Images

1. People who suffer from cluster headaches describe them as worse than childbirth without anesthetics, worse than gunshot wounds, head injuries, or a burned hand. "They'll find the worst thing they can think of and tell you it's worse," said neurologist Dr. Peter Goadsby, director of UCSF's Headache Center. "It always causes me to stop and draw a breath."

Part of the affliction of cluster headaches is that few people know what they are.

"People will say, Why don't you take a Tylenol?" Goadsby said.

While migraines affect about 15 percent of the population, cluster headaches only afflict 0.1 percent of the U.S. population. Still, that's about the same rate as the better known multiple sclerosis, Goadsby said.

Treatments include 100 percent oxygen treatments, injections, nasal sprays and preventive drug treatment. But the current National Institutes of Health research funding for the condition is zero.

"I personally just don't get it," Goadsby said.

A CT scan of the abdomen of a 55-year-old man at the level of the kidneys, revealing kidney stones.Getty Images

2. Severe pain in the side and back, spreading to the lower abdomen and groin, plus nausea, vomiting and foul-smelling urine? No thanks.

The good news is that treatment -- from flushing your system by drinking lots of water to using shock waves to break up the stones to surgery -- should work. Neil, for example, had surgery and returned to the stage.

Trigenanal neuralgia affects sensory information from your face to your brain.Wikipedia/Gray's Anatomy

3. If you've heard of the nervous system disorder trigenanal neuralgia (and that's a big if), you've probably heard it described as the world's worst pain.

This condition affects a nerve that sends sensory information from your face to your brain, resulting in stabbing pain to the face. Patients always remember where they were and what they were doing the first time they're afflicted with the excruciating pain, Basbaum said.

Some patients respond to drugs; surgery is reserved as a last possible resort, and is not always successful. If patients aren't correctly diagnosed, they sometimes get their teeth pulled out, believing the pain is coming from their mouth. "Partners often want to hug them and they can't get near them" because it makes the pain worse, Basbaum said.

An X-ray of the human spine.iStockPhoto

4. Although someone may be paralyzed and in a wheelchair, 70 percent of those with spinal cord injuries experience terrible phantom limb pain, Basbaum said. "The experience of pain is in the brain," he said. "Just because there's no input doesn't mean that brain doesn't have a representation."

Burns are considered among the most painful conditions.iStockPhoto

5. Burns cause ongoing pain that worsens when skin is stretched or just lightly touched, due to the damaged nerves underneath the burned skin. Plus, the regular cleansings required usually involves additional pain.

An X-ray showing a so-called porcelain gallbladder. Corbis

6. Sudden pain that lasts one to five hours, accompanied by fever and vomiting, can signal a gallbladder attack. Similar symptoms to kidney stones, but gallstones are made of cholesterol, as opposed to calcium. A 2011 study published in the Journal of Urology noted that people who have one seem to have a heightened risk of the other, although the cause is unclear. You can decrease your chances of both by maintaining a healthy weight and diet.

Childbirth is painful but the outcome usually makes it worth the pain.Getty Images

7. Every experience of child birth is so different that it's especially hard to classify, but labor is often used as the barometer by which all other pain is measured.

"The first time I had a gallbladder attack, I was on the floor screaming," Basbaum said. A nurse told him it was the worst pain she'd had -- apart from having a baby.

Unlike every other condition here, however, childbirth has a major upside.