Debra Meyerson was hiking near Lake Tahoe 15 months ago when a stroke destroyed part of the left side of her brain, leaving her literally speechless. It happens to more than 150,000 Americans a year.

Things just didn’t smell right to Allison Woyiwada and this wasn’t just a passing odour, it was the disgusting, intense stink of garbage. The smell filled her nose when no one else could detect it, so ...