Potential contribution of hypertension to evolution of chronic migraine and related mechanisms

Patients with migraine with or without aura were enrolled and were divided into two groups based on headache frequency: high frequency migraineurs (H) (≥10 days per month) and low frequency migraineurs (<10 days per month) (L). Within each group, hypertensive (H) and non-hypertensive (N) patients were selected on the basis either of hypertension history or of the result of 24-hour blood pressure monitoring in agreement with 2018 ESC/ESH Guidelines [26].

The cerebral vascular reactivity was studied monitoring the blood flow velocity in the medial cerebral artery (MCA) of both sides using two pulsed wave Doppler probes (2 MHz) positioned at the temporal acoustic windows with continuous blood pressure monitoring and recorded with a signal integrator (Poewer Lab).

All patients were free of medications known to interfere with the vascular ton.

The acquisition was carried out in a dim light room with the patient in supine position. After 10 minutes of basal recording, nitroglycerine (NTG, 0.9 mg) was administered sublingually and monitoring was carried out for a further 30 minutes. Afterwards, in off-line mode, samplings of about 20 cycles every 2 minutes were considered to determine the mean velocity at baseline, while samplings of about 40 cycles were carried out at 10, 20 and 30 minutes after drug administration. Possible artifacts were excluded from samplings.

Tilting test was carried out with a tilting bed that allowed to continuously measure blood pressure and heart rate at different degrees of inclination. In our laboratory, the patients were evaluated first in clinostatism for 10 minutes and then at an inclination of 60 degrees for a further 10 minutes. The aim of the test was to assess the activities of the sympathetic and parasympathetic nervous system, expressed as a percentage, and the sympathetic-vagal balance.

Twenty-four hours blood pressure monitoring was carried out with an automatic recorder equipped with an armlet that was applied to the non-dominant arm and that takes measurements every 15 minutes during the day and every 30 minutes during the night. This allowed to assess the circadian rhythm of pressure and, in particular, the dipping, i.e. the reduction of the pressure during sleep.