Physiology and Pathophysiology of Sneezing and Itching: Mechanisms of the Symptoms
Sneeze is a coordinated protective respiratory reflex which arises due to stimulation of the upper respiratory tract, particularly the nasal cavity. Actually, activation of the central and peripheral nervous system plays a major role in the pathophysiolog
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Murat Songu and T. Metin Onerci
Keywords
Sneeze reflex • Sneezing • Itching • Physiology • Pathophysiology
Core Messages
• Despite its being such a commonplace phenomenon suffered the world over, little is known about the sneeze reflex action, which sometimes becomes a sign associated to a series of different medical conditions. • The sneezing reflex may be divided in two phases. The first is a nasal or sensitive phase, following stimulation of the nasal mucosa by chemical or physical irritants. The efferent or respiratory phase consists of eye closing, deep
inspiration, and then a forced expiration with initial closing of the glottis and increasing intrapulmonary pressure. The sudden dilatation of the glottis gives rise to an explosive exit of air through the mouth and nose, washing out mucosal debris and irritants. • Clinical studies using positron emission tomography indicate that there is no isolated itching center in the brain but that there are different cortical centers which are involved in the processing of the itch. • The factors that play role in the etiology of sneeze reflex are rhinitis, photic sneeze reflex, physical stimulants of the trigeminal nerve, central nervous system pathologies, psychogenic sneezing, snatiation reflex, and sexual ideation.
M. Songu, MD (*) Department of Otorhinolaryngology, Izmir Katip Celebi University Ataturk Research and Training Hospital, Polat Caddesi 353 Sokak No: 53 Karabaglar, Izmir 35360, Turkey e-mail: [email protected] T.M. Onerci, MD Department of Otorhinolaryngology, Faculty of Medicine, Hacettepe University, Ankara, Turkey T.M. Önerci (ed.), Nasal Physiology and Pathophysiology of Nasal Disorders, DOI 10.1007/978-3-642-37250-6_11, © Springer-Verlag Berlin Heidelberg 2013
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M. Songu and T.M. Onerci
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Sneeze is a coordinated protective respiratory reflex which occurs due to stimulation of the upper respiratory tract, particularly the nasal cavity (Songu and Cingi 2009). Apparently, activation of the central and peripheral nervous system plays a major role in the pathophysiology of this process. Sensory nerves of the afferent trigeminal system including myelinated Aδ-fibers and thin, nonmyelinated C-fibers of the nasal mucosa transmit signals generating sensations, including itching and motor reflexes, such as sneezing. These nerves can be stimulated by various reasons. Sneeze reflex frequently accompanies rhinitis of allergic or nonallergic origin. Sneeze can also arise due to bright light or sun (ACHOO syndrome), physical stimulants of the trigeminal nerve, psychogenic or central nervous system pathologies, and even due to a full stomach (snatiation reflex) or a sexual ideation. In this chapter, we aimed to review the physiology, pathophysiology, etiology, diagnosis, treatment, and complications of sneezing and itching.
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Historical Perspective
Sneezing has always been a remarkable sign and a noteworthy occurrence throughout the history. In Asia and Europe, the sneezing superstition extends through a wide range of race, age, and countr
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