Sheridan, who played in the 2007 World Cup final and toured with the British and Irish Lions two years later, has a long-standing issue in the neck/shoulder area and suffered a fresh setback during Toulon's Top 14 match against Perpignan last month.
Now Laporte has revealed that the 34-year-old former Sale player has been ordered to rest for four weeks, after which doctors will assess whether he can return or have to retire.
"He has always had a problem between his neck and his shoulder," Laporte told French radio station RMC.
Rugby
'Devastating' injury blow for Wade
03/12/2013 AT 04:37
"The surgeon has told him it's not necessary to have a new operation.
"He will now have a month of complete rest and, if the pain does not go away, he will have to stop playing."
Top 14
France scrum-half Tillous-Borde extends Toulon deal
14/02/2015 AT 11:54
Top 14
All Black Conrad Smith moving to France after World Cup
06/02/2015 AT 01:56