Active_comparator: 1 Vagus nerve stimulation

The first group will receive cervical transcutaneous vagus nerve stimulation that will be carried out with a TENS device, using a small self-adhesive surface electrodes (1 cm diameter). The electrodes will be positioned on the surface of the neck that corresponds to the position of the left cervical branch of the vagus nerve, over the carotid pulse just medial to the sternocleidomastoid muscle (Molero-Chamizo et al., 2022) using a biphasic, asymmetrical waveform with a pulse duration that is less than 250 microseconds and a frequency of 20 hertz. Intensity is adjusted according to the sensory threshold level of each patient, each session lasts for 30 minutes (Kutlu et al., 2020). All patients will receive 3 sessions per week for a total of 12 sessions, The sessions will be carried on at Department of Rheumatology and Rehabilitation, Cairo University Hospital

Active_comparator: 2 Medical treatment

This group will receive medical treatment in the form of: Gabapentin 300 mg capsule once at night, and Duloxetine 30 mg cap once daily for 30 days.

Active_comparator: 3 Combined vagus nerve stimulation and medical treatment

This group will receive cervical t-VNS in the same protocol like the vagus nerve stimulation group, in addition to medical treatment in the form of: Gabapentin 300 mg capsule once at night, and Duloxetine 30 mg cap once daily for 30 days.