Photic sneeze reflex: Difference between revisions
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===Mechanism=== |
===Mechanism=== |
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The probable cause is a congenital malfunction in [[ |
The probable cause is a congenital malfunction in [[deadly]] signals in the [[trigeminal nerve nuclei]]. The fifth [[cranial nerve]], called the trigeminal nerve, is apparently responsible for sneezes.{{Citation needed|date=July 2010}} Research suggests that some people have an association between this nerve and the nerve that transmits visual impulses to the brain. Overstimulation of the [[optic nerve]] triggers the [[trigeminal nerve]], and this causes the photic sneeze reflex.{{Citation needed|date=July 2010}} |
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On the other hand, some people with the trait feel that it is advantageous.{{citation needed|date=October 2010}} In the event that nasal discomfort occurs, but to an extent that is insufficient to induce a sneeze, intentionally seeking and finding a light source facilitates the sneezing process and is in turn a mode of relief.{{citation needed|date=October 2010}} |
On the other hand, some people with the trait feel that it is advantageous.{{citation needed|date=October 2010}} In the event that nasal discomfort occurs, but to an extent that is insufficient to induce a sneeze, intentionally seeking and finding a light source facilitates the sneezing process and is in turn a mode of relief.{{citation needed|date=October 2010}} |
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Revision as of 17:41, 25 April 2011
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Autosomal Dominant Compelling Helioophthalmic Outburst (ACHOO) Syndrome is a genetic autosomal dominant disorder that results in uncontrollable sneezing in response to numerous stimuli, such as looking at bright lights or periocular injection. The condition affects 18-35% of the population, and its exact mechanism of action is not well understood.[1]
Overview
Photic sneeze reflex, also known by the backronym Autosomal Dominant Compelling Helioophthalmic Outburst Syndrome (ACHOO Syndrome),[2] and the "Peroutka Sneeze Gene", is an autosomal dominant hereditary trait which causes sneezing, possibly many times consecutively (due to naso-ocular reflex [3]) when suddenly exposed to bright light. The condition affects 18-35% of the human population.[4]
The first mention of the phenomenon is probably in the later work attributed to Aristotle (Problems, book XXXIII).[5] (between the third century BC to the 6th century AD).
Mechanism
The probable cause is a congenital malfunction in deadly signals in the trigeminal nerve nuclei. The fifth cranial nerve, called the trigeminal nerve, is apparently responsible for sneezes.[citation needed] Research suggests that some people have an association between this nerve and the nerve that transmits visual impulses to the brain. Overstimulation of the optic nerve triggers the trigeminal nerve, and this causes the photic sneeze reflex.[citation needed]
On the other hand, some people with the trait feel that it is advantageous.[citation needed] In the event that nasal discomfort occurs, but to an extent that is insufficient to induce a sneeze, intentionally seeking and finding a light source facilitates the sneezing process and is in turn a mode of relief.[citation needed]
This sneeze reflex can also be brought on by sudden inhalation of cold air or exposure to strong flavors.[citation needed] This implies an overstimulation of any nerve close to the trigeminal nerve can cause the sneeze reflex.
Management
While this phenomenon is poorly understood, recent research has shown that antihistamines being used to treat rhinitis due to seasonal allergies may also reduce the occurrence of solar sneezes in people affected by both conditions.[6]
Symptoms
ACHOO syndrome manifests itself in the form of uncontrollable sneezing in response to a stimulus which would not produce a sneeze in people without the disorder. The sneezes generally occur in bursts of 1 to 10 sneezes, followed by a refractory period that can be as long as 24 hours.
Photic Sneezing
A photic sneeze is the most common manifestation of ACHOO syndrome. A photic sneeze is a sneeze that results from exposure to a bright light. Photic sneezes are hypothesized to occur in response to light with a specific wavelength of 430 nm, which corresponds to the wavelength of a cloudless blue sky.[1] Photic sneezes are harmless annoyances for the most part, but can pose physical risk to people who are operating vehicles or machinery, which involves precise movement and reactions.
A study conducted by the School of Optometry at the University of Alabama at Birmingham, found that females represent sixty-seven percent of photic sneezers. Ninety-four percent of those were caucasian. The study also found no correlation between photic sneezing and the presence of a deviated septum, and a non-significant association with tobacco use. The study also showed that photic sneezing is more likely to be acquired than inherited.[7]
Response to Periocular Injection
During surgeries in and around the eye, such as corneal transplant surgery, the patient often requires injection of a local anesthetic into the eye. In patients with ACHOO syndrome, an injection into the eye, such as that undergone in a retrobulbar or peribulbar block can often elicit a sneeze from the patient. During these procedures, the patient may be sedated prior to the periocular injection. The patient begins to sneeze just as the needle is inserted into the eye, often resulting in the anesthesiologist having to remove the needle before injecting the local anesthetic in order to avoid damaging the patient's eye.[8]
Response to Fullness after Eating
Stomach fullness is another example of a stimulus that causes uncontrollable sneezing that may be linked to ACHOO syndrome. People who exhibit this symptom undergo uncontrollable fits of 3-15 sneezes immediately after eating large meals which completely fill the stomach. The so-called snatiation reflex occurs independently of the choice of food eaten, and is not believed to be an allergic reaction of any kind.[9] Although even less well-understood than photic sneezing and sneezing in response to periocular injection, the trait appears to be inherited in an autosomal dominant fashion.[10]
Pathophysiology
There is much debate about the true cause and mechanism of the sneezing fits brought about by ACHOO syndrome. 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.[11] The most obvious difference between a normal sneeze and an ACHOO syndrome related sneeze is the stimulus - normal sneezes occur due to irritation in the nasal cavity, while ACHOO sneezes 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.
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 sneezing. 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 sneeze could result instead of photophobia.[11]
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 sneezing are also activated, due to the generalization. This could lead to a sneeze in response to a stimulus other than nasal irritation.[11]
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 with ACHOO syndrome, even this direct stimulation can lead to a photic sneeze.[11]
Propofol-Induced Inhibitory Suppression
Uncontrollable sneezing during a periocular injection while sedated by propofol is likely caused by the propofol. Propofol has been shown to temporarily suppress inhibitory neurons in the brainstem, which is also where the trigeminal nucleus - the "sneeze 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 sneeze in the unconscious patient.[12]
Risks
Sneezing generally does not present any particular risks to the individual, and is usually more of an annoyance than a risk of injury. The fits of sneezing brought about by ACHOO syndrome can, however, have dangerous implications during certain scenarios and activities.
Disease Transmission
Perhaps the most universal risk of sneezing is the spread of disease. Bacterial infections can spread to susceptible uninfected people via the spread of microscopic organisms suspended in the droplets expelled by a sneeze. Bacteria which commonly spread by sneezing include bacterial meningitis, strep throat, and tuberculosis. Viral infections can also be spread by sneezing. When a virus is expelled by a sneeze, its mucous membrane evaporates, and the virus becomes a droplet nucleus which can be inhaled by another person, thus spreading the virulent infection. Examples of virulent infections that spread by sneezing include measles, mumps, rubella, and influenza.[13]
Vehicle Operation
A fit of sneezing while operating a vehicle can cause the operator to lose control of the vehicle, resulting in damage to the person, vehicle, and surroundings. In particular, photic sneezing poses a considerable risk to aircraft pilots, due to the presence of the bright sun and the precise reactions needed to successfully pilot an aircraft. For the pilot of a fighter aircraft, if an uncontrollable fit of sneezing were to occur during aerial combat, the pilot could be incapacitated when his or her situational awareness needs to be greatest. A plane landing on an aircraft carrier or shoreline also requires incredibly precise movements and quick reflexes. The reflection of the sun off of the surrounding water has a high probability of producing at least 1 photic sneeze for pilots with ACHOO syndrome. Any amount of sneezes during a critical moment during landing could cause the pilot to lose control, resulting in potential disaster.[1]
Medical Procedures
Uncontrollable fits of sneezing are common in patients under propofol sedation who undergo periocular or retrobulbar injection. A sneeze by a sedated patient often occurs upon insertion of a needle into or around their eye. The violent and uncontrollable movement of the head during a reflexive sneeze has potential to cause damage within the patient's eye if the needle is not removed before the sneeze occurs.[12]
Preventative Measures
There is currently no definitive way to cure the sneezing fits brought on by ACHOO syndrome. Photic sneezing can be combated by shielding ones eyes with hats or sunglasses. There are many remedial fixes for sneezing, such as placing a finger horizontally below the nose or holding the nose closed when the beginnings of a sneeze are felt.
The most helpful way to avoid the risks stated above is to be aware of any inclination to sneeze in response to strange stimuli. If a pilot knows he is at risk for experiencing a photic sneeze during a flight, he can wear polarized goggles to block out the sun, or at the very least be prepared for a sneeze and have measures planned to minimize the risk from such a sneeze. Any patient with a history of uncontrollable sneezing who requires periocular surgery should tell his doctor or anesthesiologist, so that they can take appropriate measures to minimize the risk of injury in case of a sneeze during the surgical procedure. People who know they have a tendency to experience sneezing fits after consuming a large meal can make an effort to reduce the size of their meals, since snatiation seems to occur only as a result of an extremely full stomach.
See also
References
- ^ a b c Breitenbach RA, "The photic sneeze reflex as a risk factor to combat pilots." Mil Med. Dec 1993, 158:806-9, PMID 8108024.
- ^ http://www.ivillage.com/sunlight-and-sneezing-there-connection/6-n-136794
- ^ http://allergies.about.com/od/fa1/f/nasoocularrefle.htm
- ^ Breitenbach, RA; Swisher, PK; Kim, MK; Patel, BS (1993). "The photic sneeze reflex as a risk factor to combat pilots". Military medicine. 158 (12): 806–9. PMID 8108024.
{{cite journal}}: Cite has empty unknown parameter:|author-name-separator=(help); Unknown parameter|author-separator=ignored (help); Unknown parameter|month=ignored (help) - ^ Looking at the Sun Can Trigger a Sneeze, Karen Schrock, ScientificAmerican.com, January 10, 2008.
- ^ "Solar Sneeze Reflex". Western Journal of Medicine. 146 (5): 20. 1 May 1987. PMC 1307391. PMID 18750225.
{{cite journal}}:|access-date=requires|url=(help) - ^ Semes, L.P., Amos, J.F. and Waterbor, J.W. "The Photic Sneeze Response: Descriptive Report of a Clinic Population." Journal of American Optometry Association June 1995, 66(6): pp 372-377
- ^ Abramson DC, "SUDDEN UNEXPECTED SNEEZING DURING THE INSERTION OF PERIBULBAR BLOCK UNDER PROPOFOL SEDATION" Canadian Journal of Anaesthesia-Journal Canadien D Anesthesie Aug 1995, 146(1):31-35.
- ^ Hall JG, "THE SNATIATION REFLEX" Journal of Medical Genetics Apr 1990, 27(4):275-275.
- ^ Teebi AS, Alsaleh QA. 'AUTOSOMAL DOMINANT SNEEZING DISORDER PROVOKED BY FULLNESS OF STOMACH' Journal of Medical Genetics Aug 1989, 26(8):539-540.
- ^ a b c d Abramson DC. "SUDDEN UNEXPECTED SNEEZING DURING THE INSERTION OF PERIBULBAR BLOCK UNDER PROPOFOL SEDATION" Canadian Journal of Anaesthesia-Journal Canadien D Anesthesie Aug 1995 42(8):740-743.
- ^ a b Ahn ES, Mills DM, Meyer DR, Stasior GO. "Sneezing reflex associated with intravenous sedation and periocular anesthetic injection" American Journal of Ophthalmology Jul 2008 146(1):31-35.
- ^ Cole EC, Cook CE. Characterization of infectious aerosols in health care facilities: an aid to effective engineering controls and preventive strategies. Am J Infect Control. 1998 Aug;26(4):453-64. Sneezing can transmit many diseases PMID 9721404