Hopkins doctor will help separate Siamese twin girls in South Africa

March 19, 1994|By Jonathan Bor | Jonathan Bor,Sun Staff Writer

Dr. Benjamin Carson, a Johns Hopkins neurosurgeon, will travel to South Africa next month to join a team of doctors in the delicate separation of Siamese twins who are attached at the back of the head.

The girls, who are 6 months old, appear to have separate brains and a shared major blood vessel.

The operation will be further complicated because one girl's brain encroaches into the other's skull.

Most likely, surgeons will have to split the shared vein and reconstruct the halves so that each child has an independent and fully functioning vessel.

Dr. Carson said there is a slim chance that surgeons will find separate vessels that merely appear as one on X-rays.

Dr. Carson, 42, chief of pediatric neurosurgery at Hopkins, said separations of "complexly joined" twins -- sharing brain tissue or blood vessels inside the skull -- have been tried about 60 times but never successfully.

In each case, the children have either died or survived blind, retarded or otherwise impaired.

If the girls survive surgery, they will face several perils in the days and months that follow.

Problems include infection, swelling and hydrocephalus, a fluid buildup that causes excessive pressure and enlargement of the skull.

Any of these can cause brain damage.

But Dr. Carson said the sisters' condition -- looking in opposite directions, unable to crawl, sit up or perform most physical activities -- leaves them little hope of a bright future without surgery.

The girls, Mahlatse and Nthabiseng Makwaeba, are daughters of a homemaker and an employee of the Department of Agriculture of Lebowa, one of the black "homelands." The family has four other daughters -- including twins -- and lives in a rural village in the Northern Transvaal.

The operation, occurring around the time of South Africa's first multiracial election, resounds with symbolism.

Dr. Carson, who is black, will join a biracial team of doctors at Ga-Rankuwa Hospital, about 30 miles north of Pretoria. The girls are black.

The hospital is part of the Medical University of Southern Africa, which trains most of the nation's black doctors.

First black neurosurgeon

Dr. Carson said he was invited to participate by Dr. Sam Mokgokong, an acquaintance who is the hospital's chief neurosurgeon.

In his mid-30s, Dr. Mokgokong is the first black neurosurgeon in that racially divided nation.

"The doctors involved have done me a great honor by inviting me because, frankly, I think they could do it without me," Dr. Carson said yesterday at a news briefing at Johns Hopkins Hospital.

The operation, which could last as long as 24 hours, will involve about 20 doctors.

Although the physicians are donating their time, an appeal for $145,000 is being made to the South African public to defray Dr. Carson's travel expenses and the cost of the girls'

post-operative care.

Because Dr. Carson is black, his visit probably would have been impossible just a few years ago, said John H. Chettle, legal adviser to the medical university. Mr. Chettle, a South African expatriate, works with a law firm in Washington.

1987 operation

The operation is similar to one performed at Johns Hopkins in 1987, when a 70-member team separated twin boys from Germany who were joined at the back of the head. Patrick and Benjamin Binder were returned to Germany and are believed to be mentally retarded.

Dr. Carson, who participated in that operation, said he has tried to contact the family over the years to learn of the boys' conditions, but his letters have gone unanswered.

Two years after the operation, another Hopkins doctor visited the twins while traveling. Patrick was still hospitalized and showed little neurological function; Benjamin, although also apparently retarded, was sitting up and taking feedings by mouth.

Yesterday, Dr. Carson blamed the Binders' mental condition primarily on brain infections after surgery.

In the Makwaebas' case, doctors hope to avoid infection by transplanting sheets of dura -- the leathery material that envelopes the brain -- over exposed tissue once the sisters are separated. This should provide a protective membrane between brain and scalp.

Dura, obtained from cadavers, was not available when the Binders were separated because a moratorium had been placed on its use.

In at least one case, infection had spread from the grafted dura to a patient's brain.

The ban was lifted when better methods of sterilization were developed.

Suspended animation

Surgeons will probably stop the girls' hearts and lower their body temperatures -- placing them in a state of suspended animation -- before they divide and reconstruct the blood vessel.

This is done to prevent excessive bleeding, which can also injure the brain. The vein, called the sagittal superior sinus, is the brain's major blood drainage system.

The girls can remain in a suspended state for about an hour before their brain cells demand more nourishment.

Once the girls are separated, doctors will restore body temperature and blood flow, cover the exposed brain tissue with dura, then close the scalp with flaps of skin from the girls' backs.

High quality of life

At a later date, surgeons will use titanium mesh to replace the circular piece of skull removed from each girl's head.

Dr. Carson did not rate the girls' survival chances or their prospects for a high quality of life.

He acknowledged that sacrificing one girl would enhance her sister's chance for a healthy life, but said he would be opposed to such a decision on ethical grounds.

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