A 38-year-old American woman has developed an itch. Previously she had eye shingles, a painful disease in which a herpes virus infects the optic nerve. The disease was brought under control quickly, and the pain in the eye disappeared. But then the itching began.
Now she suffers continuous itching on the right side of her scalp, so unbearable that at night the woman scratches herself until she bleeds. For a whole year she wakes to red stains on her pillow from the blood. Then one morning her pillow was not red from blood as usual, but green. She goes to the emergency department of Harvard Medical School in Boston, where physician Anne Louise Oaklander is amazed to see that the woman has scratched a hole right through her skull – and has reached the brain.
Itching versus pain
Oaklander wondered how the patient had been able to do so much harm without pain stopping her. She studied the nerves of the woman’s scalp, and found that
