BALTIMORE -

Heather Sheeley-Johns can walk along a busy city street without worry. For years, cars, horns and sirens were impossible to hear.

"I think things were a little more muffled. Having a very difficult time figuring out where the sound was coming from," described Sheeley-Johns.

Sheeley-Johns was diagnosed with neurofibromatosis 2 in her late 20s. Tumors on one cranial nerve caused her hearing to get progressively worse.

"Losing hearing at that age can be very traumatic and very isolating," said Dr. Jaishri Blakeley, a neurosurgeon at Johns Hopkins University School of Medicine in Baltimore.

Blakeley is an expert in tumors of the nervous system. NFs are not cancer, but they grow relentlessly and have no effective therapies.

"Surgery is for sure the standard of care. The trouble with surgery is it's very difficult to remove the tumor, without damaging the nerve," Blakeley explained.

Blakely is studying the impact of an already FDA-approved drug on NF 2 tumors. Bevacizumab is given intravenously every three weeks for 30 to 60 minutes. The drug shrinks the blood vessels near the tumor, making the tumor smaller.

"If there was something that could prolong my hearing, there wasn't a doubt. I had to try," Sheeley-Johns said.

Thirty-six percent of the trial participants gained back hearing on the drug. Sixty percent of those patients kept their hearing, even when they were off the drug for three months.

"It has not only stopped the hearing loss, but my hearing has actually gotten better by about 30 percent," said Sheeley-Johns.

It's life-changing treatment for those in the prime of their lives.

Sheeley-Johns' hearing gains have lasted several years, but since this is an experimental treatment, doctors aren't sure if the results will be permanent.

Blakeley said the drug is not for every patient, since side-effects include an increase in blood pressure, change in ovarian function, and the possibility of kidney damage.

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