Have you ever heard the expression, “don’t crane your neck?” It’s really good advice---”craning,” or straining, the neck, such as to better see a computer screen, or when accommodating to bifocal lenses, sets one up for neck pain and headaches.
These postures cause abnormal cervical stresses, and one of the common results is a superior misalignment of the posterior arch of the 2nd cervical vertebra, C2.
In my practice, about 80% of my headache patients have this misalignment.
It is corrected by precise, gentle adjustment with the Activator instrument.