Dropdown menu with descriptions only in sub-menu elements in Drupal 7? I'm trying to implement a dropdown menu in my custom theme. At the moment, this means I have a region for the primary and another region for the secondary menu. 

According to the design I would like implement, the description of a menu element should be visible - but only for sub-menu elements, like in this menu:


My problem is the following:

I can't find a way to handle different levels of menus accordingly, i.e. to add the markup of the descriptions only where necessary and the different classes on ULs.

How should I implement this kind of menu?

[I've installed the Menu Block module for some help with this. It adds several new hooks that might be useful, but we will see...]

Thanks for checking out this question!
Within your theme's template.php, you can override the theme_menu_link() function. 

Target the $variables['element']['#original_link']['depth'] variable to check for the depth of the current menu item. 

The variable $variables['element']['#original_link']['localized_options']['attributes']['title'] holds the "description" value entered on the menu item's edit page.