In the old days -- before doctors removed the left half of her brain -- Maranda Francisco was almost helpless. Up to 120 seizures a day, sometimes within three or four minutes of each other, discombobulated her days and threw the whole right side of her body into continual paralysis.

At the age of 4, she was forgetting how to walk, talk, eat and learn.

Then, nearly two years ago, Maranda underwent a dramatic operation called a hemispherectomy at Johns Hopkins Children's Center in Baltimore.

In 10 hours of surgery, doctors cut out the diseased left hemisphere of her brain, including all the "gray matter" on that side.

Maranda hasn't had a seizure since. She

is off all medication. She has regained much of the use of her right arm and leg, though her right hand remains weaker and less agile than her left. She speaks normally, her memory is intact and she is rapidly making up lost ground in elementary school near her home in Denver.

"She dances. She takes swimming lessons. She's in kindergarten now," said her mother, Terry Francisco. "She just tears up the place."

In short, a normal, healthy, troublemaking 6-year-old -- who happens to be missing the left half of her brain.

The cause of Maranda's seizures was a rare inflammation of the brain called Rasmussen's encephalitis, named after the Montreal doctor who discovered it more than 30 years ago.

In a patient with Rasmussen's, the damage is confined to one side of the brain, affecting primarily the opposite side of the

body (since the left side of the body is controlled mainly by the right side of the brain, and vice versa).

"It's a strange, uncommon disease that's not in the textbooks," said Dr. John M. Freeman, director of pediatric neurology at Johns Hopkins Medical Center. Doctors aren't even sure whether or not it's caused by a virus, though it "leaves footprints like a virus," he said.

Also unknown is why the inflammation remains in one hemisphere of the brain instead of spreading to the other side.

"Cutting out the hemisphere seems to cure the problem," Freeman said.

In Maranda's case, all the seizures were on the right side of her body, apparently caused by repeated electrical misfirings on the left side of her brain.

But the reason Maranda manages so well without the left half of her brain, doctors say, is a pheonomenon called "plasticity." The two halves of the brain are not as rigidly divided as once thought. Though each has distinct functions -- one side has the major responsibility for language and the other for artistic abilities and recognition of faces, for example -- there is considerable overlap, especially in a child's brain.

Even before surgery, the healthy right hemisphere of Maranda's brain had begun compensating for her illness by taking over many of the functions of the deteriorating left hemisphere. That process has continued since the operation, as the brain's plasticity enables the remaining right side of her brain to assume more and more responsibility for speech, motor control and learning.

At the time she was operated on in August 1985, Maranda was the youngest known patient to have undergone radical brain surgery for Rasmussen's disease. Since then, seven more patients have undergone the operation at Johns Hopkins, bringing the total there to 13. They have ranged in age from infancy to 20 years old.

Besides Johns Hopkins and the Montreal Neurological Institute, where Dr. Theodore Rasmussen pioneered the hemispherectomy as a treatment for severe brain inflammation, only a handful of medical centers around the world have performed the surgery in recent years.

Maranda returned to Johns Hopkins last week for the first time since her surgery, joined by eight other hemispherectomy patients and their families in what quickly became dubbed as the first "hemi reunion" at the hospital. It was the first time any of the patients had met.

The parents established a national support group, and the children underwent a battery of follow-up tests -- with time out for press conferences, socializing, a pizza party and a picnic.

Hemispherectomy itself is not a new operation. As long ago as the 1930s, it was tried on brain tumors -- with only limited success.

But a series of medical advances in recent years has made hemispherectomy "much more feasible," said Dr. Benjamin S. Carson, director of pediatric neurosurgery at Johns Hopkins, who has performed all but one of the hemispherectomies at Hopkins in the past few years.

These advances include improved diagnostic and brain-scan techniques such as CAT scanners and magnetic resonance imaging (MRI), better ways of controlling bleeding in the brain during and after surgery, and more sophisticated ways of screening patients to rule out those for whom the risk clearly outweighs the potential benefit.

"It's basically a procedure that has been swept under the rug and forgotten about," Carson said. Now, improved technology is bringing it back.

Acknowledging that hemispherectomy is "a drastic operation" that should be used only on carefully selected patients, Carson estimated that the potential number of appropriate candidates for the surgery is "in the hundreds" in the United States alone.

As more doctors become aware of the possibilities of the surgery, he said he expects that "in 10 years or so this will be a fairly common operation."

No one knows exactly how brain plasticity and the transfer of brain function from one side to the other takes place -- or even whether it's a chemical or an electrical process, Carson said.

Until recently, it was thought that such a transfer was impossible after about age 2, but the Hopkins doctors have apparently disproved that in several cases. They now believe it is possible up to about age 7 -- and even later in some cases. In one recent case at Hopkins, Freeman said, a 13-year-old

hemispherectomy patient retained the ability to speak despite the loss of brain tissue -- apparently because the speech capacity transferred to the remaining half of the brain.

The risks of the surgery are high. It usually entails six to 10 hours of surgery under anesthesia. Infection and bleeding, either of which can cause severe brain damage or even death, are the major worries. The costs of surgery and hospitalization alone range from $50,000 to $75,000, not including years of follow-up therapy, tests and rehabilitation.

But for a child whose life is wasting away because of 100 debilitating seizures a day, the risks also are high.

"What's the worst that can happen if we don't operate?" said pediatric neurologist Freeman. Children with such severe and relentless seizures usually continue to "go downhill," he said, suffering progressive paralysis, weakness, loss of muscle control, inability to swallow and, often, premature death.

"What is the worst that could happen if we operate and the operation is not successful?" Freeman asked. "Not very much different."

"These are not our success stories," Freeman said, referring to the eight patients at the reunion. "These are our kids."

Every one of the 13 patients operated on at Johns Hopkins, he said, is free of seizures and either off all medication or on "very minimal" medications.

Each has improved markedly since the operation.

"Taking out the bad part of their brain has not reduced their IQ," Freeman said. "Of our 13 children, 12 are fine and all 13 are better than they were before."

One patient remains significantly retarded with an IQ of about 50, as she was before surgery, but her seizures are under control.

Most of the "hemi" patients had Rasmussen's disease, but the radical surgery has been used in rare instances on children with tumors or developmental abnormalities restricted to one side of the brain. In general, though, it's not useful against tumors, Freeman said.

Only a parent such as Terry Francisco who has been through it can explain to another what it's like to sit in the waiting room while one's child undergoes surgery to remove half her brain. To sit there knowing the risks, knowing the child may never walk or talk again, knowing also how quickly the child's life is deteriorating without the surgery.

"I feel like this is my family," said Terry Francisco, gesturing around the room to the other patients and their families during a press conference last Thursday.

The reunion was also a chance to put the children through a series of tests last week. Those included electroencephalograms (EEGs) to detect evidence of abnormality in the remaining side of the brain, MRIs to detect bleeding or iron buildup in the brain, and extensive neuropsychological tests of brain function, learning and language. The children also were evaluated by occupational and physical therapists.

Measuring the degree of transfer of brain function, or even the effect of hemispherectomy on a child's development and mental abilities is extremely difficult, particularly in young children, Freeman said. "We have enough trouble measuring language," he said.

But no one who saw Maranda Fransisco before her surgery, as Freeman did, and looks at her now, can mistake the difference.

"Do you want to say something, Maranda?" Freeman asked her at the press conference last week. "What do you want to tell these people?"

"Nuthin'," said Maranda, turning uncharacteristically bashful as eyes and television cameras around the room zoomed in on her. Then she whispered something in Freeman's ear.

"You love who?" he asked.

"Terry Francisco," she said, giggling.

Then, at Freeman's suggestion, she recited "Humpty Dumpty" for the crowd, and then she giggled again and then she hurried back to her chair and sat down.

Seizures were the farthest thing from her mind.