Complex sentence: The cardinal symptoms of the cluster headache attack are the severe or very severe unilateral orbital, supraorbital and/or temporal pain lasting 15--180 minutes, if untreated, attack frequency of one to 8 attacks every 24 hours.
Split into simpler sentences: The cardinal symptoms of the cluster headache attack are severe or very severe unilateral orbital, supraorbital and/or temporal pain lasting 15--180 minutes. If untreated, attack frequency will range from one to 8 attacks every 24 hours.