When NOT to put the needle where it hurts!

Allodynia and hyperalgesia – may be signs of central sensitisation…

Although the terms “wind up” and central sensitisation are often used synonymously, although they are not strictly equivalent. Wind up will occur in response to any painful stimulus and would normally resolve over time. Central sensitisation can be thought of as wind up that has not wound down and represents a chronic pain state.
http://en.wikipedia.org/wiki/Pain_wind-up

In practical terms central sensitisation may be identified in our patients by the presence of allodynia and, to a lesser extent hyperalgesia. Allodynia refers to when a normally non-noxious stimulus (touch for example) is perceived as pain. Hyperalgesia is an exaggerated response to a painful stimulus, and is therefore rather harder to be certain about.

Allodynia will be missed if the examination of the patient involves immediate firm palpation, such as grasping a limb and manipulating the joint – all the examiner will discern is pain, although it will not necessarily correlate with the movement of the joint and may therefore be confusing.

A light touch over the whole patient prior to deeper palpation will reveal suferficial allodynia by a sharp or shrinking movement away from the touch, fasiculations and tremor, as well as other more obvious pain responses.

Needling an area of superficial allodynia will generally be resented and is likely to make the pain condition worse. If the area is localized, then the following approaches can be tried:

• Segmental (needle another area innervated by the same spinal nerve as the area affected)
  
• Peri- segmental (needle around or either side of the area affected)
  
• “Mirror point” (where the pain affects a limb the same points on the opposite leg can be needled)
  
• Heterosegmental (needling some general points away from the area of allodynia in the hope that the heterosegmental effects will be potent enough to give pain relief).
  

If the whole patient is too painful to needle then it is often advisable to use medication to help reduce central sensitisation to a level whereby needling can be used without aggravating the problem.

In practice, those patients who just seem to get worse with acupuncture and do not improve may have central sensitisation, and their pain condition should be reviewed with this in mind.