Author: Don Stader, M.D. Educational Pearls Cluster headaches are usually intense, unilateral,  and involve the periorbital area. CN V (Trigeminal) provides sensory and autonomic innervation the face and eyes, which play roles in headache pathology. Cluster headaches can be treated with high flow oxygen, but a new treatment involves blocking the sphenopalatine ganglion (SPG) with lidocaine. Because sensory and autonomic branches of the trigeminal traverse the SPG, lidocaine will effectively treat a cluster headache. To block the ganglion, intranasal lidocaine may be used, or a Q-tip soaked in 4% lidocaine can be applied to the most posterior aspect of the pharynx for 10-15 minutes. References: https://www.aliem.com/2017/03/trick-sphenopalatine-ganglion-block-primary-headaches/