Itching and perception JUN 24 2008
I try not to miss any of Atul Gawande's New Yorker articles, but his piece on itching from this week's issue is possibly the most interesting thing I've read in the magazine in a long time. He begins by focusing on a specific patient for whom compulsive itching has become a very serious problem. (Warning, this quote is pretty disturbing...but don't let it deter you from reading the article.)
...the itching was so torturous, and the area so numb, that her scratching began to go through the skin. At a later office visit, her doctor found a silver-dollar-size patch of scalp where skin had been replaced by scab. M. tried bandaging her head, wearing caps to bed. But her fingernails would always find a way to her flesh, especially while she slept.
One morning, after she was awakened by her bedside alarm, she sat up and, she recalled, "this fluid came down my face, this greenish liquid." She pressed a square of gauze to her head and went to see her doctor again. M. showed the doctor the fluid on the dressing. The doctor looked closely at the wound. She shined a light on it and in M.'s eyes. Then she walked out of the room and called an ambulance. Only in the Emergency Department at Massachusetts General Hospital, after the doctors started swarming, and one told her she needed surgery now, did M. learn what had happened. She had scratched through her skull during the night -- and all the way into her brain.
From there, Gawande pulls out to tell us about itching/scratching (the two are inseparable), then about a recent theory of how our brains perceive the world ("visual perception is more than ninety per cent memory and less than ten per cent sensory nerve signals"), and finally about a fascinating therapy initially developed for those who experience phantom limb pain called mirror treatment.
Among them is an experiment that Ramachandran performed with volunteers who had phantom pain in an amputated arm. They put their surviving arm through a hole in the side of a box with a mirror inside, so that, peering through the open top, they would see their arm and its mirror image, as if they had two arms. Ramachandran then asked them to move both their intact arm and, in their mind, their phantom arm-to pretend that they were conducting an orchestra, say. The patients had the sense that they had two arms again. Even though they knew it was an illusion, it provided immediate relief. People who for years had been unable to unclench their phantom fist suddenly felt their hand open; phantom arms in painfully contorted positions could relax. With daily use of the mirror box over weeks, patients sensed their phantom limbs actually shrink into their stumps and, in several instances, completely vanish. Researchers at Walter Reed Army Medical Center recently published the results of a randomized trial of mirror therapy for soldiers with phantom-limb pain, showing dramatic success.
Crazy! Gawande documents and speculates about other applications of this treatment, including using virtual reality representations instead of mirrors and utilizing multiple mirrors for treatment of M.'s itchy scalp. Anyway, read the whole thing...highly recommended.