$categories modification

[Ssleepless]

I'm hoping I can get some suggestions about this problem which has been stalling me for a while now. I am trying working on index_nested.tpl.php, in order to display subcategory descriptions while viewing the parent category, ie:

Imagine the following category structure:
foo
-subfoo1
-subfoo2
bar
bam

If you were to view the category foo, by default it displays:
-category image, name, description
-the clustered subcategory image & name of subfoo1 and subfoo2, which are held in $categories['categories_image'] and $categories['name']

the category description is held in $category['categories_description'] but there is no $categories['categories_description']

So basically I have been unable to figure out how to add this to the array, or even where the appropriate place to do it is. Any thoughts on this?