Presence of Signs of Central Sensitization in Episodic and Chronic Migraine

PPT will be performed firstly at the anterior tibial muscle halfway between the most superior attachment to the tibia and its tendon in the upper one third of the muscle belly (13) and secondly at the middle of the temporalis muscle (12), using a digital algometer (Wagner FPX 50) with a 1 cm2 rubber tip. The pressure algometer will apply a perpendicular increasing pressure (1kg/s) at the different test locations until the participant reports the first feeling of pain. The PPT of 4 series of ascending stimulus intensities, with an inter-stimulus interval (ISI) of 20sec between the different stimuli and an ISI of 60sec between the 2 locations, will be measured. The first stimulus is a familiarization stimulus. Afterwards the mean of the 3 subsequent stimuli will be calculated.

The thermal tests will be performed unilateral at tibial anterior, thenar and the forehead, using a TSA-2 (Neuro Sensory Analyzer, MEDOC). At first cold and heat detection thresholds will be measured. The patient will be asked to indicate when they feel a change in temperature. Afterwards the patient will be asked to indicate when the stimulus becomes painful to determine the cold and heat pain thresholds. The thresholds of 4 series of stimuli will be measured. The first stimulus is a familiarization stimulus. Afterwards the mean of the 3 subsequent stimuli will be calculated for every location. The subject will push a button when the thresholds are reached. The baseline temperature will be 32°C and the stimuli will increase with 1°C/s (14).

The temporal summation will be assessed at the thenar eminence (19,20) using a ramp and hold protocol with the TSA-2 (Neuro Sensory Analyzer, MEDOC). Heat stimuli will be applied for a duration of 15sec. The stimulus temperature will increase from a baseline temperature of 35°C for 9sec at a sensitivity-adjusted rate of about 1,5°C/s until the HTP 5/10 of the thenar is reached. Afterwards the temperature will remain steady for the next 6 seconds. The maximal pain rating should be 50 ± 10 NRS. Subjects rate the pain intensity at the end of the ramp (9sec) and at the end of the hold procedure (15sec) using the NRS. Afterwards the ramp and hold aftersensations are measured. The subjects have to rate the pain intensity every 5sec for 30sec after the termination of the heat stimulus.

CPM will be assessed by comparing heat pain thresholds and pressure pain thresholds before and after giving a conditioning stimulus at a pain free distant zone by using a second thermode of the TSA-2 (17). The conditioning stimulus (HPT 4/10 (18) at the TA) will be applied for 120 seconds. The first test stimulus will be applied at the forehead 30 seconds after the start of the conditioning stimulus (17). The HPT will be measured twice with an ISI of 20 seconds. Immediately after the end of the application of the conditioning stimulus (120 seconds), the HPT at the forehead will be measured again twice, with an ISI of 20 seconds. Afterwards, there will be 10 minutes of rest to avoid bias.