This delightful young lady came to see me with headaches which she was having every day while she was at school.
Interestingly, it was mainly when she was working at her desk, with her head and neck down.
In this video (below) you see how putting her head forward and down makes her shoulder weak. This weakness is occurring because in this position, she is using her neck extensor muscles (which are inhibited).
I was able to find one vertebra in her neck which was not moving properly and responded very well to a single adjustment.
She needed no further adjustments and never had another headache.
She found me again 16 years later and told me she had been fine and the headaches never returned.