Carterton girl Grace Yeats underwent a rare brain operation at Auckland's Starship children's hospital yesterday in a move aimed at reducing the severe spasms she suffers.

The 10-year-old had deep brain stimulation yesterday morning, in what is believed to be a medical first for a child in New Zealand.

She slept for much of the rest of the day, with her family "happy" with how she was doing.

Grace, a St Mary's School pupil, has been unable to move since May, when she was struck down with a mystery illness hours after complaining of a sore throat.

In a two-part operation yesterday, doctors drilled into her skull and inserted electrodes in her brain.

The electrodes were then wired to a pacemaker, which was implanted in her chest.

Jonathan Tanner, spokesman for the Grace Yeats Trust, said the surgery took "multiple hours" but the family were glad it had gone ahead as planned.

"They're happy . . . the doctors were only going to do [both parts of the operation] if they were happy with how she was, so that says something."

The device will now be calibrated to stimulate and counter the section of her brain that causes the intense and painful spasms that affect Grace's body.

- © Fairfax NZ News