An HIV-positive patient developed shingles. After the shingles healed, this patient began experiencing a very severe unremitting itch, which caused her to scratch through her own skull while sleeping one night. How is this possible, and what are the mechanics of itch that would allow a patient to feel no pain from scratching? Dr. Anne Louise Oaklander, associate professor of neurology at Harvard Medical School, reveals the pathophysiology of neurological itch. Is itch really just low-level firing of pain neurons, or is itch entirely distinct? Dr. Michael Greenberg hosts.