A fancy way of referring to the weird stinging pains and itches that linger after a bout of shingles. My PHN isn't terribly severe, although I do catch myself scratching my head fairly frequently. But once in a while it'll feel like someone suddenly stabbed a hypodermic needle into my scalp where the lesions broke out over a month ago. From what I read about PHN, it's a good thing my healthcare provider prescribed Valtrex so quickly, because it can reduce the severity of PHN or even prevent it from occurring.
The nerve damage resulting from an attack of herpes zoster is the culprit behind PHN. Some researchers did MRIs on people with shingles and found that about half of them had visible lesions on nerve tissue after a HZ attack.
Weird, weird virus.