I am a 40 year old male and have experienced this my whole life and looked online for others every now and then. It is close to a tension head ache in that the same part of the back of the neck and head are affected however there is no muscle tension experienced during the event and it can come and go in seconds if I keep all joy in check. What is actually happening is the unprotected portion of the vertebral Artery from the spine to the basilar artery swells. the swelling can be felt just behind the ears and circling to the back of the base of the skull. The pain is extremely intense similar to a cluster headache in that vision can be affected with halos that quickly goes away with normal blood flow being returned. As a young man I did see a specialist about this issue and he was aware of the issue and sheepishly stated that it is common in serial killers. I remember being taken back by that statement. I could see how it might take someone who was already disturbed that way though as it almost feels like punishment for all of the good things in life. It''s only personal emotional happiness or extreme sadness that affects this for me. Moments of euphoria or dismay with close friends or family. Laughter sadness or excitement alone never causes it. I can go skydiving, wreck my car or get a huge tax return and it will never happen. It is the emotional tie that seems to be the trigger. I have never came across another person with this issue. I remember thinking something was seriously wrong with me as a child as know one else seemed to experience this. I have always kept it in check by limiting my sense of joy or loss with family and close friends and they understand even if I don't. I am sorry to hear that someone else has this affliction however I am glad to see that I am not alone. Even though the specialist seemed to understand the symptoms he said they do not know what causes it and can not treat it. It does not affected my productivity as it only affects my down time with family and friends and for the most part I have learned over time how to cope with that. In case this is being read by a young person experiencing this issue that not understanding what is going on I want you to know I have been successful in life in creating my own business, have a great relationship with my family, am happily married and at the time of posting this I have not started the hobby of serial killing. It sucks however it is manageable.