There might be other options out there. This is something that worked for me once but there are no guarantees that it will work at all times.
Stop SQL Server instance -> Copy MDF and LDF files to another location -> Delete original MDF and LDF files -> Start SQL Server instance again -> Create new database with exact same name and file names -> Stop SQL Server -> overwrite newly created MDF and LDF.
After this your database should be back online. If it is then go ahead and put it into EMERGANCY mode and SINGLE USER mode.
Finally go ahead and execute DBCC CHECKDB like this
DBCC CHECKDB (databaseName, REPAIR_ALLOW_DATA_LOSS) WITH NO_INFOMSGS
More information you can dig out from resources directly connected with SQL Server databases and database corruption in MS SQL Server any version...
SQL Server Repair Toolbox