In the past, many scientists and health care providers considered MS to be a 'painless' disease. Many people living with MS, however, might disagree with this assumption. Research conducted in the last decade has shown that pain is, unfortunately, common in MS. Recent recognition of the problem of pain in MS has increased attention to and research about pain in MS.
Prevalence of pain
While reported rates of pain have been as low as 28 percent and as high as 90 percent, the vast majority of studies that have been conducted indicate that anywhere from 43-80 percent of people with MS report MS-related pain. This variability, while confusing, may be explained by the fact that research studies use different sources for obtaining participants (for example, hospital versus outpatient clinic) and different methods for selecting which participants will be surveyed (referred to as 'sampling'). According to several European studies and at least one US study, pain problems may occur more frequently and with greater severity in people living with MS relative to the general population. Classifying MS-related pain
The World Health Organization classifies pain syndromes as nociceptive and neurogenic (or neuropathic). Nociceptive pain occurs as an appropriate physiological response transmitted to a conscious level when nociceptors in bone, muscle or any body tissue are activated, warning a person of tissue damage, and in turn, eliciting coordinated reflexes and behavioural responses, such as the quick removal of a hand from something hot.
Neurogenic pain in MS is typically initiated by a primary lesion or dysfunction in the peripheral or central nervous system, which has no biological advantage (such as warning) but causes suffering and distress. Clinical hallmarks are a burning, piercing pain, allodynia (a painful response to nonpainful stimuli), and/or hyperalgesia (an increased response to painful stimuli). In MS, some types of pain can be experienced over a long period of time or can be intense but brief. Many people living with MS experience both.
Measuring MS-related pain
Researchers and clinicians measure a number of features of MS-related pain. Pain intensity refers to how much a person hurts. This is usually assessed by asking a person to rate how intense or severe their pain has been during a specified time period on a 0-10 scale, where 0 = 'no pain' and 10 = 'pain as bad as it could be'. This type of scale is referred to as a numerical rating scale (see page 8).
| Visual analogue scales and verbal rating scales can also be used to measure pain intensity. Visual analogue scales typically have images that represent levels of pain or a straight, horizontal line with one end indicating 'no pain' and the other end indicating 'worst pain'. Individuals are then asked to mark where on the line their pain falls. With verbal rating scales, people with MS are presented with a list of words that describe various levels of pain intensity. They are then asked to circle which word best describes the intensity of their pain.
It is important to find out not only where a person feels pain (the pain location) but also what the pain physically feels like (referred to as pain quality).
These are most often assessed by simply asking an individual to describe where they hurt and what it feels like. For example, a person with MS might describe pain in their legs that is dull and aching, while another person may describe pain in their face that is sharp and stabbing.
Pain affect refers to how unpleasant or how bothersome the pain is. Pain affect taps into the emotional component of pain; in other words, how much distress or disruption the pain causes. For example, an athlete in the midst of running a marathon may rate her pain intensity as a 7 on a 1-10-point scale, but be so mentally focused on finishing the race that she rates her pain affect as a 2. Or, an air traffic controller with a mild headache may rate his pain intensity as a 3, but find it so bothersome due to the demands of his job, that he rates his pain affect as an 8. Pain affect can also be assessed using numerical rating, visual rating, and visual analogue scales.
Pain interference refers to how much pain interferes with or gets in the way of participating in daily activities. Pain interference is typically assessed by providing people with a list of common activities (such as work, sleep, leisure) and then asking them to rate how much their pain interferes with these activities on a 0-10 scale, where 0 = 'no interference' and 10 = 'unable to carry on activities'.
Conclusion
In summary the understanding and measurement of MS-related pain has grown and improved tremendously in the last decade. Continued research will help to provide the tools needed for physicians and therapists to help people with MS to manage their MS-related pain in new, effective ways.
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