Amputation and phantom pain

My grandma had her leg amputated as a palliative measure last week, and it got me thinking.

She says that she still feels pain from where the ulcers on her leg were before the operation. To me that’s plain weird. I’d heard that you can still feel a limb once it’s gone - that was strange enough, but still feeling wounds on a leg that isn’t there is to my mind very strange. So I have some questions:

  1. Why can you still feel the limb that’s gone?
    1a. Why can you still feel wounds on the limb that’s gone?
    1b. Why, although you can still feel the limb and wounds does it not hurt as much as it did before?
  2. Do you ever stop feeling the limb and/or wounds?
  3. Is it just me or is it plain weird?

Seems pretty obvious to me, not weird at all.

The brain knows that nerve x goes to spot y, so any signal received along that nerve is interpreted as coming from that spot.

If a limb is amputated the nerves still go up to the amputation site. Any stimulation along their path will be felt as if the limb were still there.

This also happens without amputation being involved. Nerve damage in the lower back is often felt as referred pain in the legs, for instance, as it’s the nerves going to the legs that are affected.

Yes, I would expect the effect would fade over time, but no idea how long.

This site has some info on it.

I had always thought that it was caused by the same mechanism the above poster mentioned. Reading through this site though, it seems that it is not as simplistic as that.

  1. Damaged nerves send signals that the brain interprets as coming from a limb.
    1a. Damaged nerves send signals to the brain that the brain interprets as pain.
    1b. Sometimes the pain hurts less, sometimes more.
  2. Not necessarily.
  3. Yup.

I don’t think any more precise reasons for phantom limb pain are known.

A good book to read about Phantom Limb and some treatment methods for it is Phantoms in the Brain by V.S. Ramachandran.

I think alot of it is psychological. I remember years and years ago watching a special on this. One of the cases they were working on was someone who had her arm amputated, at the elbow I believe. She had the sensation that the phantom hand was clenched into a fist, so tightly that the fingernails were digging it the palm and that was causing pain. To relieve it the doctor made a box with two holes in the bottom and a mirror runing diagonally from the top left to the bottom right. She put the phantom hand in the hole on the left (under the mirror, and the real hand (clenched in a fist) in the right hole. Looking down on the box it looked like both of her hands (because of the mirror), the doctor had her unclench her real hand and imagine that she was unchlenching the phantom one as well. IIRC that did the trick and the pain was gone.