Photic Sneeze Reflex - Pathophysiology

Pathophysiology

There is much debate about the true cause and mechanism of the sneezing fits brought about by the photic sneeze reflex. Sneezing occurs in response to irritation in the nasal cavity, which results in an afferent signal propagating through the ophthalmic and maxillary branches of the trigeminal nerve to the trigeminal nerve nuclei in the brainstem. The signal is interpreted in the trigeminal nerve nuclei, and an efferent signal goes to different parts of the body, such as mucous glands and the diaphragm, thus producing a sneeze. The most obvious difference between a normal sneeze and one caused by the photic sneeze reflex is the stimulus - normal sneezes occur due to irritation in the nasal cavity, while the latter can result from a wide variety of stimuli. Some of the theories regarding the mechanism of a sneeze resulting from an unusual stimulus are below.