The Effect of Interventional Procedures on Serum CGRP and PACAP-38 Levels in Chronic Migraine

Preoperative Visit:

During the preoperative visit, patients' additional illnesses, demographic data, and medication use will be recorded. The patients' NRS (Numerating Rating Scale) score will be recorded. Antebrachial venous blood samples will be taken along with routine samples requested after the outpatient examination.

Intraoperative Nerve Block Procedure:

All procedures were planned to be performed under sterile conditions with ultrasound guidance while the patient was in the prone position.

GON Block: The ultrasound probe was placed in a transverse plane 2-3 cm lateral to the Protuberantio Ocipitalis Externa. After visualizing the occipital artery, it was targeted medial to the GON artery. After local anesthesia with 1% lidocaine (skin-subcutaneous), a 21 Gauge 5 cm long needle tip was guided from lateral to medial using an in-plane approach to precisely place it in the center of the nerve for the block (Figure 2). After negative acission, the block was performed with 3 ml of 2% Prilocaine. Supraorbital/supratrochlear nerve block: The ultrasound probe is placed along the supraorbital notch, through the medial third of the supraorbital border. The supraorbital nerve (SON) and the supratrochlear nerve (STN) are located just above its medial border. 2 cc of 2% prilocaine is injected into the target using a 5 cm, 21 gauge needle and inplane technique.

Intraoperative Pulse Radiofrequency procedure:

For radiofrequency, a 5 cm long RF cannula with a 5 mm active tip is placed in the target under ultrasound guidance, and the needle tip is guided from laterally to medially using an inplane approach to precisely center the nerve. To induce a congruent paresthesia response in the occipital nerve distribution, 50 Hz 1v sensory and 2 Hz 2v motor electrical stimulation was performed with an SMK (Select RF StraightCannula, 100mm, 22G, 10mm active tip SMK-S1010-22) RF electrode. Pulsed radiofrequency (Neurotherm NT1100 / 13001-12) will be applied at 42°C for 240 seconds.

Patients will be observed after the procedure. Patients who do not experience postoperative complications and are mobile will be discharged at 2 hours. Patients may withdraw from the study at any time.

Patients meeting the eligibility criteria will be informed in detail about the procedure. Written and verbal consent will be obtained from the patients.

Post-operative visits:

Venous blood sampling will be performed one month after the procedure, along with routine samples requested after the outpatient examination.

Samples were collected between 9 and 11 a.m. to avoid the influence of circadian rhythms on CGRP levels. Subjects were required to discontinue any anti-inflammatory or analgesic medication in the previous 48 hours. Blood samples were taken from the non-dominant forearm to measure interictal serum CGRP levels using commercial ELISA kits (Novus Biologicals Inc., USA) following the manufacturer's instructions. Absorption levels were measured with a spectrophotometer at a wavelength of 450 nm to 2 nm. The detection limit of the test was considered to be 9.3 pg/ml for CGRP.

For PACAP 38, blood samples were collected into ice-cold glass tubes containing the anticoagulant ethylenediaminetetraacetic acid (EDTA, 12 mg) and the protease inhibitor aprotinin (Trasylol, 1200 IU) and kept at 4°C until centrifuged (2000 rpm for 10 minutes at 4°C). Plasma samples will be stored at -80°C until measured by PACAP-38.

Pain intensity will be assessed using the NRS (Numerical Rating Scale) at 1, 3, and 6 months post-procedure.

The NRS is a pain intensity assessment system based on a system where the individual describes their pain on a scale of 0 (none) to 10 (unbearable pain).