Headache prevention in a patient with hypertension

Case scenario

A 62-year-old woman has suffered from headaches all her life. When she was younger, she had experienced attacks of classic weekend migraines, with aura, nausea and photophobia, but these lasted only a couple of days. Over the years the character of the headaches changed to become a much more frequent global ache, which proved difficult to control. She was helped at last when she started taking the monoamine oxidase inhibitor (MAOI) tranylcypromine (Parnate), and she had very few headaches for the next 25 years. Because of increasing concern about her unstable hypertension and also her dislike of the dietary restrictions advised while on this drug (avoiding foods with high tyramine content and alcohol), tranylcypromine was ceased 12 months ago. She has not had a headache-free day since, despite extensive medication trials and the use of several different antidepressants. Her blood pressure is now well controlled (without calcium channel blockers). She states that her headaches sometimes clear in the evening and she has noticed that they are definitely better when she is sleep deprived.

What mechanism could be at work here? How can this patient be helped?