There is much debate about the true cause and mechanism of the<unk> ng fits brought about by the<unk> .<unk> ng occurs in response to irritation in the nasal cavity, which results in an afferent nerve fiber 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 nerve fiber signal goes to different parts of the body, such as mucous glands and the thoracic diaphragm, thus producing a<unk> . The most obvious difference between a normal<unk>  and a<unk><unk>  is the stimulus: normal<unk> s occur due to irritation in the nasal cavity, while the<unk><unk>  can result from a wide variety of stimuli. Some theories are below. There is also a genetic factor that increases the probability of<unk> . The C allele on the rs10427255 SNP is particularly implicated in this although the mechanism is unknown by which this gene increases the probability of this response. Optic-trigeminal summation Stimulation of the ophthalmic branch of the trigeminal nerve may enhance the irritability of the maxillary branch, resulting in an increased probability of<unk> ng. This is similar to the mechanism by which photophobia develops by persistent light exposure relaying signals through the optic nerve and trigeminal nerve to produce increased sensitivity in the ophthalmic branch. If this increased sensitivity occurred in the maxillary branch instead of the ophthalmic branch, a<unk>  could result instead of photophobia. Parasympathetic generalization The parasympathetic nervous system has many neighboring fibers that respond to different stimuli. When one stimulus activates multiple nerve fibers of the parasympathetic nervous system, parasympathetic generalization is occurring. There is a possibility that sensory input from the eyes could travel to the neurons in the cortex that interpret such signals, but neighboring neurons which are involved in<unk> ng are also activated, due to the generalization. This could lead to a<unk>  in response to a stimulus other than nasal irritation. Increased light sensitivity When the trigeminal nerve is directly stimulated, there is the possibility that increased light sensitivity in the ocular nerve could result. An example of directly stimulating would be plucking an eyebrow or pulling hair. In many people who show the<unk> , even this direct stimulation can lead to a<unk><unk>  which is why we find it easier to<unk>  while looking at a bright light. Propofol-induced inhibitory suppression Uncontrollable<unk> ng during a periocular injection while sedated by propofol is likely caused by the drug. Propofol has been shown to temporarily suppress inhibitory neurons in the brainstem, which is also where the trigeminal nucleus – the<unk>  center" of the brain – lies. This chain of events leads to increased sensitivity to stimulation and reduced threshold for involuntary responses. In this hypersensitive state, the periocular injection stimulates the ophthalmic and/or maxillary branch of the trigeminal nerve, which results in summation in the trigeminal nuclei. This summation can lead to a<unk>  in the unconscious patient.
Photic sneeze reflex
Pharyngeal reflex
Snout reflex
Pressure of speech
Alaryngeal speech
Palmomental reflex
Tonic labyrinthine reflex
Chaddock reflex