Neuroimaging Studies in Carbon Monoxide Intoxication

CO is a tasteless, odorless and colorless gas. The existence of endogenous CO in the human body arises from heme catabolism (Meredith and Vale 1988; Ernst and Zibrak 1998) and oxidation of organic molecules (Marilena 1997). Endogenous CO acts as a neurotransmitter for long-term potentiation, consequently playing a key role in memory and learning (Marilena 1997). It also plays a role in modulating inflammation, apoptosis, cell proliferation, mitochondrial biogenesis (Weaver 2009) and vascular relaxation (Marilena 1997). Exogenous sources of CO intoxication include smoking, forest fires, pollutants, and improper usage of heaters or furnaces (Weaver 2009; Kumar, Prakash et al. 2010). CO intoxication usually indicates exposure to exogenous sources and is considered one of the most common causes of poisoning worldwide (Prockop and Chichkova 2007; Weaver 2009), with 1000 deaths annually in Britain (Meredith and Vale 1988), and 4000-6000 deaths annually in the United States (Tibbles and Perrotta 1994; Ernst and Zibrak 1998; Weaver 1999). In Asia, the exact epidemiology remains unclear. In Japan, Hong Kong and Taiwan, a common CO etiology of intoxication is charcoal burning suicide (Lee, Chan et al. 2002). In Japan, poisoning by charcoal burning is the most lethal form of suicide and is a highly prevalent method among men aged 25-64 years of age (Kamizato, Yoshitome et al. 2009), in contrast to a high rate of drug poisoning as a method of suicide in women. In Hong Kong, the risk factors of suicide by charcoal burning are male and living alone with financial stress (Lee and Leung 2009). In Taiwan, charcoal burning was not a common method of suicide before 1998, with a rate of only 0.14 per 105 people per year (Lin and Lu 2008). With the dissemination of media and the internet, the rate of charcoal burning suicides dramatically increased by 40-fold, reaching a rate of 5.38 per 105 people per year in 2005 (Lin and Lu 2008).