Fig 1.The patient has reddish-brown patchy pigmentation on the left upper eyelid, forehead, and crown, with scattered blisters on the skin of the crown. Blurred vision and photophobia in her left eye. VAS score:8-9.

2 | CASE PRESENTATION

The patient was a female, 74 years old. More than 20 days ago, there was no obvious inducement，but there was red herpes on the left forehead and top. It was diagnosed as ”herpes zoster” in the local hospital. Antiviral, nerve nourishing and analgesic drugs were given intravenously to her. During the course of the disease, blurred vision and photophobia gradually appeared in the left eye. One week later, the herpes subsided, but the left forehead and orbit were still painful, with unclear vision and photophobia in the left eye (Fig 1.). He was hospitalized in our department and diagnosed as ”postherpetic neuralgia”. At admission, the patient complained of paroxysmal pain in the left frontal top and orbit , which was electric shock like. VAS score: 8-9 points, about 5 minutes each time, with an interval of 1-2 hours. SF-36 score^[3-5]: physiological function (PF): 65, physiological function (RF): 0, Body pain (BP): 22, general health status (GH): 57, energy (VT): 30, social function (SF): 22.22, emotional function (RE): 0, mental health (MH): 44, health change (HT): 25; Pittsburgh sleep quality index scale^[6,7]: 19. Patchy-like dark red pigmentation can be seen in the distribution area of the first branch of the left trigeminal nerve, local tactility is normal without obvious tenderness, photophobia in the left eye, visual acuity is 0.2, no obvious abnormality in the right eye, visual acuity is 0.5. After admission, they were given ketochromate tromethamine 30mg bid, esmeprazole 40mg bid, acyclovir 0.25g tid, Mecobalamin 500 ug qd intravenously, and vaccinated with cowpox vaccine, rabbit inflammatory skin extract 6ml qd; Oral pregabalin 75mg bid had poor pain control, and there was no significant change in attack and pain degree.With the consent of the patient, low temperature plasma nerve conditioning in the distribution area of the first branch of the trigeminal nerve was performed (Fig 2.). After entering the operating room, the patients were routinely opened venous access and ECG monitoring. The appropriate surgical position was selected according to the pain site, the pain site was fully exposed, and the local routine disinfection and towel laying were carried out. 20ml of 2% lidocaine + 20ml of 0.9% normal saline were prepared into 1% local anesthetic (without adrenaline) for subcutaneous local infiltration anesthesia. After the pain of local infiltration anesthesia disappears, enter the needle with the No. 12 puncture needle inclined 15 ° with the skin. After reaching the subcutaneous area, take out the puncture needle core, insert the plasma knife head, connect the knife head with the plasma RF machine, adjust the ablation intensity of the RF machine at level 3, and the ablation time at each point is electric cutting for 5S and electric coagulation for 5S. At the same time, swing the needle tail left and right to increase the ablation range. Every 0.5cm is an ablation point, and ablation is performed while withdrawing the needle until all the painful parts are ablated. Due to the large pain area of the patient, the first operation is mainly in the most obvious areas of supraorbital foramen, subcutaneous prefrontal and top pain on the affected side. The next day, the operation is performed again, mainly in the most obvious areas above the hairline to the top pain. The operation site was kept clean and dry for 48h. Two operations completely covered the pain area of the patient.