LDS Church President Ezra Taft Benson remained in serious but stable condition but was "awake and responsive" Thursday at LDS Hospital, a day after undergoing surgery to remove blood clots on each side of his brain.

His neurosurgeon Wednesday said the 2 1/2-hour surgery went well and his patient was "resting comfortably." But it was too early to determine if the 91-year-old church president has suffered brain damage." He tolerated the surgery very well. For a man of 91, he is very strong," Dr. Bruce F. Sorensen said during a press conference following the surgery.

President Benson, prophet and president of The Church of Jesus Christ of Latter-day Saints, was admitted to LDS Hospital Tuesday after a CT scan revealed bilateral subdural hematomas (collections of fluid) on both sides of his brain.

President Benson had experienced difficulty swallowing and earlier this week had suffered from severe headaches, Sorensen said.

After consultation with family members, physicians involved in President Benson's care determined the clots should be removed.

During the "commonly performed" procedure, Sorensen said, he removed clots on each side of President Benson's brain. Both were 1 1/2 to 2 centimeters thick and covered "a significant portion of his head."

"They had compressed the brain, and this may have been a reason he was having trouble swallowing."

Sorensen said the clot on the right side was easily drained through a 1-centimeter burr hole, about the size of an index fingernail, drilled in the skull. "That clot came out quite easily."

But removal of the "slightly larger" left-side clot required a craniotomy, or removal of a piece of the cranium, Sorensen said.

Sorensen said the clots had "an acute" component, meaning they had formed recently. "We know that because he had a CT scan in June which did not reveal any evidence of any clots."

But family members said they knew of no falls or injuries that might have caused them. Neither did President Benson have symptoms typical of hematomas, including paralysis and convulsions. However, according to Sorensen, the Benson family said they had noted a bit of speech trouble.

"Why they (the clots) were there, we don't know," Sorensen said.

The development of hematomas is not uncommon among older persons. At LDS Hospital, surgeons remove from two to six a month in older people.

Former LDS President Spencer W. Kimball underwent the surgery three times in two years. Sorensen also treated President Kimball, who died Nov. 5, 1985, at age 90.

Former President Ronald Reagan also underwent similar surgery recently.

If the clots are not removed, eventually they can cause death, Sorensen said.

President Benson is expected to remain hospitalized in intensive care for seven to eight days if things go well, Sorensen said.

When asked if the church president will be able to attend the church's general conference on Oct. 6 and 7, the physician said, "I would think not." During his hospitalization, President Benson will be sedated and kept still until the drains in each side of his head are removed. The drains were inserted to remove saline solution used to irrigate the areas where the clots were located.

Sorensen said his main concern is that new clots could accumulate before President Benson is scheduled to leave the hospital. Several CT scans are planned to monitor clotting.

"We hope he doesn't reaccumulate these. But we have no way of knowing that at this point."

If there's reoccurrence, the new clots will be drained through the same holes, Sorensen said. If the clots become chronic, doctors will insert a shunt, which drains the fluids into the jugular vein or another body cavity.

But "that's very seldom needed," Sorensen said.

The surgeon said the ailment could have a "significant" impact on President Benson's mental capacity, but that cannot immediately be determined.

"What we can hope to do is get a person back to the state they were in prior to this happening," he said. "But the ultimate outcome in a 91-year-old, we never know."

In addition to Sorensen, a pulmonary specialist and a cardiologist will monitor President Benson's progress.

On Nov. 6, 1986, the church leader received a heart pacemaker during a non-emergency operation. Physicians said President Benson had suffered "some episodes during which his heartbeat was slowing inappropriately."