Hiding an element that contains only spaces using CSS

I am trying to hide the following element in an automatically generated HTML document:

  <p id="sitspagedesc" class="sitspagedesc">

    </p>

In some pages, the <p> tag will contain an inner value but in others it can contain only spaces as shown in the example. I need to find a way of hiding this so that it is hidden using CSS only, as changing the HTML is not an option.

I have tried to hide it using

.sitspagedesc:empty
{
display:none;
}

but this does not work, presumably on the account of the spaces the element contains.

Does anyone have any good ideas?

Thanks :)