sub_category description

After trying this on my own for quite some time now, I’m posting my problem here. Hopefully there is somebody who knows how to solve this.

On my site I have got 4 parent categories which all have a couple of child categories. Each child category has a couple of posts.
For each child category I would like a description of that category to appear above the posts as sort of a “sticky” description.
I have been trying this with a piece of code I found on this forum and some of my own additions:

<?php
if (is_tag());
else
$category = get_the_category(”);
$cat_slug = $category[0]->category_nicename;
if (file_exists(TEMPLATEPATH. ‘/cat_description/’.$cat_slug.’.php’) ) {
include (TEMPLATEPATH . ‘/cat_description/’.$cat_slug.’.php’);
echo ”?“;
} else {
echo ”;
}
?>

What is does is check the folder “…/cat_description” to see if there is a file named category-slug.php which matches the category slug of the current page. If it does, then the content of the category-slug.php file is shown, which is just plain HTML.
I have placed this piece of code in my archive.php and at first it seemed to work. But then I found out it only works for some sub-categories, while for others, there is no description shown.

As it turns out, when you get the categories name with get_the_category, you do not get the name of the current, but of the parent category. For example, I got a parent category called “Augmented Reality” and two child categories named “Augmented Anatomy” and “Augmented Subsurface”.
For one of the two I get the right category name when I get it through get_the_category, but for the other I get the parents’ category name and no description is shown.

Does anybody know a solution to the get_the_category problem for child categories?