Neurosurgeons are using a noninvasive brain surgery to treat essential tremor, depression and other conditions. Here’s how it works.

Undergoing clinical trials around the world is a brain surgery that doesn’t need an incision or produce any blood yet drastically improves the lives of people with essential tremor, depression and more. The procedure, known as a focused ultrasound, aims sound waves at parts of the brain to disrupt faulty brain circuits causing symptoms.