There are three basic types of pain, depending upon what physical mechanism in the body is causing the symptom: somatic, neuropathic, and visceral. A fourth kind, mixed, is a combination of the others. It’s important to know what basic kind of pain is present, because treatment differs. Myofascial pain is the most common; it’s a variation of somatic pain. Finally, certain medical illnesses can cause pain that is hard to diagnose unless they are looked for.
Somatic pain is the most common cause of physical pain
“Somatic” means pain in the skin, bones, muscles, ligaments, tendons, and joints. This includes arthritis, tendonitis, and most kinds of headaches, neck pain, and low back pain. This kind of pain is typically aching, sore, and knifelike. It often improves with aspirin or ibuprofen. Similar but sharper pain would occur if you cut or bruised yourself or broke a bone.
Acute somatic pain due to an injury or infection requires rest while the tissue heals. Chronic somatic pain usually does best with frequent gentle exercise that gradually intensifies as you become fit.
Neuropathic pain is due to disease or injury of the nervous system
“Neuropathic pain is less common than somatic pain. It’s like the burning, tingling, or electric feeling you get when you hit your “funny bone” (ulnar nerve) in your elbow. It includes carpal tunnel syndrome, various kinds of pinched nerves, and “neuropathy” or nerve damage due to diabetes or a variety of other illnesses. Another common neuropathic pain is postherpetic neuralgia that follows “shingles,” an outbreak of herpes zoster. Neuropathic pain usually responds poorly to anti-inflammatory agents like ibuprofen, but it often improves with Neurontin, Lyrica, or another antiseizure medication. (These drugs prevent seizures by stabilizing the nervous system, and they appear to help pain the same way.) Opiates like morphine or Vicodin typically aren’t helpful.
Neuropathic pain requires attention to the underlying cause of the pain, whether it be diabetes, shingles, or a pinched nerve. Often, once you’ve treated the underlying problem as best you can, frequent gentle exercise gradually reduces the pain.
Visceral pain rarely lasts a long time
Visceral pain is due to contractions in a hollow organ. Menstrual cramps and labor are visceral pain, as is pain from kidney stones and gallstones. It is a deep, crampy, boring sensation that ranges from mild to extremely severe. Many people have brief periods of visceral pain when their stomachs are upset, or during a menstrual period. (The only common chronic visceral pain is irritable bowel syndrome.) It often responds to the same medications as somatic pain, but exercise is not usually helpful.
Interestingly, all four kinds of pain often improve with antidepressant medication, whether or not the person with pain is depressed. Sometimes doctors prescribe antiseizure medications like Neurontin (gabapentin) or Lyrica regardless of what type of pain you have. Antiseizure drugs don’t work as well for somatic or visceral pain, and people may just get side effects (grogginess and mental clouding) without benefit. But occasionally people find them of enormous help.
Mixed pain is a combination of somatic and neuropathic
Sometimes pain has multiple physical causes. Someone with low back pain who has had five low back surgeries doesn’t have a simple, obvious single reason for pain. Scar tissue may be pinching nerves. Muscles are in a knot. The nervous system is on tilt. Treatment requires a combination approach.
Several medical illnesses can cause pain that may be hard to diagnose
Vitamin D deficiency is surprisingly common in people who never get any sun. Severe deficiency causes bone pain that is difficult to diagnose unless one draws a vitamin D blood level. But this critical level of deficiency is rare.
Polymyalgia rheumatica causes muscle aching and stiffness and is seen mostly in women over age 55. It is also diagnosed with blood tests.
Occasionally severe vitamin B12 deficiency causes widespread pain. It, too, can be diagnosed with a blood test.
Obstructive sleep apnea is easy to overlook but must not be missed. In addition to causing severe all-over aching and depression, sleep apnea can be the source of severe medical problems and can be fatal.
Alcoholism and drug addiction often are associated with a variety of aches and pains. Even people who take opiate drugs properly for pain relief may find that over time their pain escalates, a phenomenon called opiate hyperalgesia (“hyper” means too much and “algesia” means pain).
By far the most common type of pain is myofascial pain—achy and tender muscles. Common examples include tension headaches and the majority of neck, shoulder, and low back pain. It can be triggered by injury, illness, depression, anxiety, fear, insomnia, and stress. It’s the pain you feel if you wake up with a “wry neck,” an aching in your neck if you sleep wrong. If you have low back pain that comes and goes, suddenly producing painful spasms, this is probably myofascial as well. There is no actually pathology associated with myofascial pain: your muscles are tense and sore but not injured. Sometimes pain and spasm create a mutually reinforcing vicious cycle. Most patients are surprised at how intense myofascial pain can be, and how long it can last (years, although usually it improves on its own).
One contributing factor is that involved muscles are often bunched up and shorter than normal. Foreshortened muscles hurt. When stretched or gently worked out, the pain is apt to go away. Thus, the most important treatment for myofascial pain is exercise and stretching, including functional restoration if you are really hurting. Lack of sleep worsens myofascial pain, but so does excessive rest. You’ll start to ache all over if you spend several days in bed.
Most people don’t realize how important stress can be in causing and maintaining myofascial pain. Moreover, learning relaxation can dramatically reduce the pain you’re in, regardless of the underlying cause. Blocked anger is also a major contributor.