Anosmia: Classification of Types and Effect on Quality of Life

Topics: Olfaction, Olfactory system, Anosmia Pages: 5 (1841 words) Published: November 15, 2010
Anosmia is characterised as the loss of the ability to perceive smell, also known as a lack of olfactory function (Parker &Parker, 2004). Anosmia is said to be caused by an underdevelopment or absence of the olfactory bulbs and tracts (Dallago, Abech, Pereira-Lima, Leaes, Batista, Trarbach & Oliveira, 2008). It has been shown that approximately 1 in 10 000 males and 1 in 15 000 females are affected by this condition (Vowles, Bleach & Rowe-Jones, 1997). There are various disturbances that can cause an individual to suffer from anosmia, including exposure to dangerous chemicals, nasal obstruction/ inflammation, head trauma, neurological diseases and surgical intervention (Mackay-Sim, Grant, Owen, Chant & Silburn, 2004). No matter which type of anosmia an individual suffers from it always has an effect on the quality of life experienced by the individual. One way of contracting anosmia is that of congenital anosmia where the individual has inherited a reduction or total lack of the sense of smell. A study by Assouline et al (1998) regarding two patients suffering from congenital anosmia found that growth regarding the olfactory fila seems to have been arrested prematurely between 7 to 16.5 weeks of gestation. It is considered to be extremely rare with only a small minority of approximately 0.01% suffering from congenital anosmia (Feldmesser, Bercovich, Avidan, Halbertal, Haim et al, 2007). To have congenital anosmia occur in a single member of a family is considered extremely rare and usually presents late (Vowles, et al, 1997). A case study done on a 5 year old girl by Vowles et al. (1997) demonstrated a case of congenital anosmia. While she showed an inability to differentiate between various concentrations of PEMEC sniff bottles, she showed no physical indication to explain her defective ability to smell. It is also shown in congenital anosmia that there is a absence or severe decrease in the individuals olfactory receptors, those that remained present however appeared to be normal (Jafek, Murrow, Michaels, Restrepo & Linschoten, 2002). Another type of anosmia is known as specific anosmia, this is defined as a failure to perceive a certain odour at ten times the mean normal threshold (Griff & Reed, 1995). There has been up to 89 different variations of specific anosmias identified so far, each being linked to a particular odour. The more common variants of this are those who cannot detect the odours of isobutyric acid or sweat with up to 2 to 3% of the population suffering (Venstrom, & Amoore, 2006). Another major example of specific anosmia was studied by Wysocki, Dorries & Beauchamp (1989) with regards to the chemical andronstenone, with 40 to 50% of adults being unable to detect it. There have been various human twin studies performed that support the belief that specific anosmias stem from a genetic basis (Griff et al, 1995). For example, in relation to detection of androstenone and isoamyl actetate, it has been shown to have a greater affiliation in monozygotic twins compared to dizygotic twins (Wysocki & Beauchamp, 1984; Wysocki et al, 1989). Kallmanns Syndrome is a rare genetic disorder that is characterised by hypogonadism, which is a decreased functioning of the glands that produce sex hormones (Hardelin, 2001). Kallmanns has also been linked to the development of anosmia due to the abnormal migration of olfactory axons and gonadotropin releasing, hormone producing, neurons (Kulkarni, Balaji, Kulkarni, Sushanth, & Kulkarni, 2007). The Kulkarni et al (2007) study follows a case study of a 19 year old boy suffering from Kallmann’s Syndrome. They tested the presence of anosmia through a series of serial dilutions of multiple odorants and found that the anosmia was due to hypoplasia or aplasia of the olfactory bulbs and tracts. The subject of the study was found to have an absence of olfactory bulbs and hypoplastic olfactory sulci when a magnetic resonance imaging was performed (Kulkarni, et al, 2007; Quinton, Cheow,...
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