Yelena Bonner, wife of Nobel Peace Prize laureate Andrei Sakharov, has been given permission to leave the Soviet Union for medical treatment, a well-known Soviet journalist said here today, as another dissident allowed to leave yesterday arrived in the Netherlands.

Irina Grivnina, 40, a Jew who was a member of a group investigating Soviet use of psychiatric hospitals to confine dissidents, arrived with her family in Amsterdam.

Grivnina's efforts to emigrate have received considerable attention in the Netherlands. Her departure comes just three days before the Dutch government is to announce on Friday its decision on deployment of U.S. medium-range missiles, a move that the Soviet Union has opposed vigorously.

The Bonner and Grivnina initiatives are seen here as related Soviet efforts to show flexibility on human rights issues as the Nov. 19-20 summit meeting of Soviet leader Mikhail Gorbachev and President Reagan approaches.

The announcement on Bonner came from Victor Louis, an accredited correspondent for the London Sunday Express, who said he understood Bonner could leave any time on an exit visa that is "normally" good for two or three months.

Louis said Bonner would be granted only a temporary visa to seek the eye treatment she cannot obtain in Gorki, a city east of Moscow to which she was banished last year. Sakharov, a physicist famous for his role in the human rights movement here, was banished to Gorki in 1980, although he has never been tried. That city, east of Moscow, is off-limits to foreigners.

"It doesn't mean she is allowed to come back to Moscow," said Louis. "It has nothing to do with that."

Allowing Bonner to go abroad for treatment would be "a significant gesture," said one western diplomat today. "But there is a point at which you want to see substance."

Grivnina's case reportedly had been raised at the meeting in Paris earlier this month of Gorbachev and French President Francois Mitterrand, and it had become something of a cause in the Netherlands. She was convicted in 1981 of slandering the U.S.S.R. Her five-year prison term later was reduced to two years. Later, she wrote articles for Dutch publications.

Louis said he did not know when Bonner was leaving or where she would go. She went to Italy on two previous trips abroad to treat glaucoma. Her mother and two children by a previous marriage live in Boston, making the United States another possible destination.

The case of Sakharov and Bonner has headed the list of human rights complaints raised at practically every meeting between western Allowing Bonner to go abroad for treatment would be "a significant gesture." -- A western diplomat heads of state and Soviet officials. It came up in Paris and it is likely to be raised at the summit next month in Geneva.

Louis' story, which first appeared yesterday in the West German daily Bild Zeitung, could not be checked with other sources here today, and some diplomats cautioned against treating the report as fact.

Since the late summer, Sakharov and Bonner have been in infrequent contact with friends in Moscow, causing new worries about the state of the 64-year-old scientist's health.

Sakharov went on a hunger strike early last year to press Soviet authorities to give his wife permission to go abroad for medical treatment, but his fast ended and no visa was granted.

Sakharov, who is still a member of the prestigious Soviet Academy of Sciences, has never applied to go abroad, Louis said today. Louis has been a conduit of information about Sakharov and Bonner in the past, and in July provided western television with a film of the couple.

"I am the source," said Louis, when asked where the information about Bonner had come from. "You have the story firsthand."

If the Soviets allowed Bonner to go abroad for medical treatment, they would have dealt with only one aspect of the Sakharov case. For human rights activists here and and abroad, the key issue has been the physicist's banishment to Gorki in 1980, not long after he issued a statement opposing the Soviet invasion of Afghanistan.

Bonner, who married Sakharov in 1970, traveled for four years between Moscow and Gorki, acting as her husband's spokesman. In August 1984, she was tried and sentenced to five years' internal exile.