Eighty-nine patients with trigeminal neuralgia underwent 102 PRGR procedures. PRGR was conducted under fluoroscopy. After the egress of CSF, anhydrous glycerol (0.3-0.4 cc) was injected in the sitting position. In the absence of CSF flow, 0.25 mL 2% lidocaine was injected to elicit hypesthesia in the affected side. Once hypesthesia was elicited glycerol was injected. Patients were grouped as A (CSF flow present) or B (CSF flow absent), according to the egress of CSF at the time of needle placement