hierarchical link categories

<?php
$linkCats = get_terms('link_category');
$i = 1;
$catsToList;

foreach ($linkCats as $linkCat) {
    if ($linkCat->parent == 5) {
        if ($i > 1) {
            $catsToList .= ", ";
        }
        $catsToList .= $linkCat->term_id;
        $i++;
    }
}

$topLevelCatList = array(
    'category' => 5,
);
wp_list_bookmarks($topLevelCatList);

if ($catsToList) {
    $subCats = array(
        'category' => $catsToList,
    );
    wp_list_bookmarks($subCats);
}
?>