From Longman Dictionary of Contemporary Englishfocalfo‧cal /ˈfəʊkəl $ ˈfoʊ-/ adjective [only before noun] MAINthe focal thing is the one that people pay most attention to → focus This issue has now become the focal centre of interest.
Examples from the Corpus
focal• The initial focal symptoms may be very brief, or they may last longer than 30 minutes. 