The day after a 15-year-old girl had half of her brain removed to stave off debilitating seizures, she began showing the first tentative but encouraging signs of movement and speech.

Doctors at Johns Hopkins Children's Center upgraded Amber Ramirez, a freckled Lincoln, Neb., teenager suffering from a rare form of epilepsy, from critical to fair condition yesterday morning. Doctors said that a groggy Amber, who had undergone a nine-hour operation Tuesday, opened her eyes, groaned and even brushed them away after they tickled her to test motor functions.

Amber's responses yesterday prompted her neurologist, John M. Freeman, to deliver an optimistic prognosis despite previous concerns that the teenager might be too old to have a full recovery. Freeman predicted that Amber would be able to walk within a month and, most likely, regain her ability to talk after many months of rehabilitation.

"Amber is doing exceedingly well," Freeman said. "I am very optimistic about her state right now, and I am optimistic about her future. But I don't have a crystal ball, and I don't like to predict things I can't control."

Just as important: Since the surgery, Amber has not suffered one of the violent seizures that sometimes struck a dozen times a day. To stop them and the relentless disintegration of her brain that is a symptom of her disease, known as Rasmussen's encephalitis, Amber opted for a radical surgical procedure performed 30 to 40 times a year in the United States.

Teams of doctors and nurses, headed by neurosurgeon Benjamin Carson, removed the left half of Amber's brain Tuesday in a procedure known as a hemispherectomy. The brain's left side controls speech and delicate motor skills, but Amber's reactions yesterday and earlier tests suggested that some of those abilities had transferred to her right hemisphere before surgery.

Before the operation, Freeman tried to determine how much speech had moved to the right side of Amber's brain. While she extended her right arm and spoke, he injected her with a tranquilizer that numbed the left side of her brain. She was still talking when her right arm went limp, though not with the same skill.

Doctors once believed the ability to speak would not migrate to the right brain after the second year of a child's life. While that has been proved incorrect, Freeman said, Amber will likely have a more difficult time recovering her speech than if she had undergone surgery at an earlier age.

One of Amber's best friends, Kaci Caves, had the same surgery in November 1996 and is in the process of regaining her speech. The two met four years ago when they had appointments at Johns Hopkins on the same day. Kaci, who was 13 when she had her surgery, is a junior at Jenks High School in Tulsa, where she attends regular classes.

"The older you are, the harder it is to develop, and the longer it takes," Freeman said. "It is a very frustrating time for Kaci, and it will be for Amber and her family. We expect Amber's speech will return."

Both Kaci and Amber were diagnosed with Rasmussen's encephalitis, a degenerative brain disorder that acts with the vigor of a virus and can lead to paralysis, mental retardation and death. Doctors estimate that only 1,000 people worldwide suffer from Rasmussen's; half of the 80 hemispherectomies conducted at Johns Hopkins have been done on those with the disease.

When Amber learned she had the disease, she was a 9-year-old who loved softball and other outdoor activities. Her symptoms started with numbness in her right leg that gradually became so severe that she needed a wheelchair.

She has had three less drastic operations since then, but none have stopped the seizures that require more than a dozen disorienting pills a day to calm.

Since Kaci had the surgery, she and her mother, Regina Caves, worked to persuade Amber to have the operation. But Amber and her mother, Sheri Ramirez, put it off out of fear they might never have another conversation. First Amber was too scared. Then it was her mother's turn.

Caves has been keeping Ramirez updated on Kaci's recovery, which doctors say has been quite successful. Caves talked with Sheri Ramirez Tuesday afternoon by telephone as the surgery neared conclusion.

"I was amazed at how calm she was," Caves said yesterday after checking on Amber's condition. "You can . . . remove parts of the brain. But much to our distress, you realize they have to take out half the brain."

Caves said that her daughter walks with a limp and that her right arm has not recovered fully, but "you'd never know she has had half of her brain removed."

"And her speech is coming back more and more every day," Caves said.

It took nine months for Kaci to regain enough of her speech to hold a conversation, and she still becomes confused at times. Often, her mother said, she thinks of the word she wants to use but says a different one--and immediately knows it's wrong.

Kaci sometimes spells words to ensure she says the one she selected in her mind. Recently, her mother said, she spelled "butterfly" after feeling uncertain she could say it. But Caves said that she knows she made the right decision to proceed with the surgery, and that Sheri Ramirez will, too.

"It will be worth it," Caves said. "Amber will be able to live a life independent of her mother. Both these girls wanted that, that they could live a life and not always having to be with Mom. Amber will be able to do that, and it gets better and better every day."

Brain Surgery

During a nine-hour surgical procedure called hemispherectomy, surgeons removed the left hemisphere of Amber Ramirez's brain. Amber suffers from a rare disease that destroys brain tissue and causes seizures. Here's how the surgery was conducted:

A large C-shaped incision was made behind Amber's hairline, down the middle of her head and behind her ear. Her scalp was peeled back, and a similar-shaped cut was made into her skull to expose her brain.

After cutting through the brain covering, surgeons used special cauterizing "tweezers" to seal off blood vessels. The temporal lobe was removed first, followed by the frontal, parietal and occipital lobes.

The brain is normally surrounded by cerebrospinal fluid, which cushions and protects it. Once Amber's left brain was removed, this fluid -- produced naturally by brain tissue -- filled the cavity in minutes.

Surgeons then replaced the skull plate and sewed Amber's scalp in place.

SOURCE: Johns Hopkins Children's Center

CAPTION: Amber Ramirez

CAPTION: Amber Ramirez, 15, began feeling the symptoms of her disease, Rasmussen's encephalitis, when she was 9 years old.

CAPTION: Surgeon Benjamin Carson and Sheri Ramirez, Amber's mother, at news briefing.