A missing limb can still hurt
After an amputation, most people feel the limb still present. Many feel pain in it. The sensation is generated by the nervous system, not by tissue that is gone.
Silas Weir Mitchell, treating Civil War amputees, described the phantom limb in the nineteenth century. Modern surveys find phantoms in a large majority of amputees, and pain in a substantial fraction. The sensations range from a mild presence to a clenched, burning hand that will not open, attached to an arm that ends above the elbow.
The mechanisms are in the stump nerves and in the cortical maps that used to serve the limb. Those maps reorganise, and the reorganisation correlates with pain. Mirror therapy — watching the intact limb move in a mirror so that the phantom appears to unclench — helps some patients. It is evidence about the map. It is not a cure that works for everyone.
Caveats
- Prevalence estimates vary with the study and the kind of loss. 'Most' is fair for the sensation of presence. Pain is common and not universal.
- A phantom is not evidence of a ghost. It is evidence that experience is constructed centrally.
Sources
- 1Ramachandran V. S., Hirstein W.. The perception of phantom limbs: the D. O. Hebb lecture. Brain 121, 1998.