Cannot delete Description manually. Instead, try this script:
GO
EXEC sp_dropextendedproperty
@name = N'MS_Description'
,@level0type = N'Schema', @level0name = dbo
,@level1type = N'Table', @level1name = 'tableName'
,@level2type = N'Column', @level2name = 'fieldName';
GO
source
share