SQL: using CASE, LIKE, and a variable

I'm using both CASE and LIKE on a regular basis but I can't figure out
how to use LIKE with a variable as part of a CASE expression in a
static SQL statement.

If a user enters a keyword into the keyword field, I want to do a LIKE
against a description field, something along the lines of this:

Case When keyword > ' '  Then description like '%:keyword%' else null

One problem is trimming the search token so SQL gets '%WIDGET%' and
not '%WIDGET       %'.

I can code around the situation but I have a feeling I'm missing
something...or am I?

Thanks,
Reeve