I wake up due to a sleep apnea which triggers an arrhythmia. Specifically, I can wake up calmly, know I am not breathing, no have any pain at that time, and choose consciously to take a breathe and the whole thing kicks off on that breath. This is called Cyclic Variation of Heart Rate, CVHR. CVHR requires two things, an apnea event and bradycardia , slow heart rate. At which point the blood flows to my head and I feel a throbbing at the base of my skull. Like two fingers pulsing up into my head. It starts out no pain and then quickly accelerates in severity. There are variations where I feel no pain or I feel a stead mild pain throughout but worst case is it elevates to the point I feel like they are about to pop. And then it spreads out like s sponge and dissipates. This can go on to my right temple where it does the same thing, a sharper more migraine like pain. If I were to get up right then I would be fine. If I go back to sleep I am likely to wake again and repeat it. It would get more severe and eventually cause a headache. IT can go on enough that it will happen even as I stand up and walk around. Melatonin 5mg set me off and had it happen starting at 10pm at night and go all night, but low dose of 1mg was fine, did not help with attack though, just with getting to sleep.

These attacks usually happen at around 630am. If I look at my heart rate using a fitbit Im in bradycardia around that time. I also have had vivid dreams every single night for a year. These things tend to happen during dreams.

I have spent a year at doctors. Pulminologist, rheumatologist ( to look for arteritis), neurologist, cardiologist, and now a second sleep study. None of these doctors had a clue. In the end I self diagnosed with CVHR mixed with Hypnic Headache. As it happens I also stopped drinking caffeine a year ago so these "headaches" spiked to happening every other night. So I took 100mg of caffeine at bed, 10pm, on an empty stomach. I havent hade an issue in two months, not even the throbbing which would indicate more pressure from the faster heart rate.

I have a kidney stone so a year ago I stopped drinking sodas and I dont drink coffee. I had these attacks before, its why Im on a cpap, but they just figured it was CO2 build up due to apnea. When I got off of caffeine the attacks started happening every other night. They usually happen around 5-6am. I dont know who decided to call these headaches, they are nothing like it. These are attacks.

For me, because mine are triggered from CVHR and CVHR requires a slow heart rate at night, I was also able to stop these attacks by working out so hard during the day that at 10pm at night I still had a heart rate off 95bpm. So it takes all night to slow down and I never have bradycardia. But this is not 100%. So far caffeine, liquid is best, at night before bed has been perfect. I am still with a sleep specialist so they can actually diagnose me. So far Ive had to figure it out.

Neurologist (not Mayo based) didnt have a clue and just randomly gave me Amnitryptoline. It didnt help. Well, I had one night where I had the attacks, felt the pulsing, and had zero pain along with it. But while the pain is a big deal, I worry more about the pressure and damage. The drug gave me severe side effects. He wouldnt try anytihng else and wanted me to go to a cardiologist who found no issue. HE just wanted to give me a drug, have me try it for three months (with the danger of these attakcs every other night) and follow up with an appointment (so he could get paid). Thats when I did one last google due to issues I had with hypnic flinches or ticks developing. Ticks have gone away now too.

IF caffeine does not work and if bradycardia is in the mix for you, try working out. I do not know if CVHR is always involved in hypnic headaches. If you are experiencing them, have you also looked at why you wake, is it an apnea. I also wonder if these things are rare because most people have caffeine of some form throughout the day and maybe more would have them if they didnt.