What is the difference between primary and secondary pain syndromes?
In primary pain syndromes, the pain itself is the disease. Examples include migraine, trigeminal neuralgia, and cluster headache. A secondary pain syndrome is due to an underlying (often structural) cause—for example, trigeminal neuralgia due to a tumor pressing on the cranial nerve. One of the major issues in any primary pain syndrome is to exclude an underlying destructive cause (tumor or infection).