Coma is a common neurological emergency seen in critically ill children. Coma is not a disease per se but instead an acute state of disordered consciousness clinically manifested due to a wide variety of medical and surgical disease processes that affect the central nervous system (CNS). It is usually described as "a state of unarousable unresponsiveness in which the eyes remain continuously closed and there is no understandable response to environmental or intrinsic stimulation."1 In contrast to the sleep state, during coma a person cannot be aroused by appropriate intense stimuli, there is no evidence of sleep–wake cycles on the electroencephalogram (EEG), and the behavioral responses mostly consist of reflex activity.
There is a lack of comprehensive large studies evaluating the overall incidence of coma in children. Most studies have a small number of subjects, are affected by the segregation of studies into traumatic and nontraumatic causes, and use a variety of definitions to define coma. This is further complicated by the fact that coma is seen in an extremely wide range of disease processes.
A number of studies report different epidemiologic rate and outcomes for coma in children. For example, a prospective, population-based, epidemiologic study from the United Kingdom of nontraumatic coma in 278 children aged between 1 month and 16 years defined coma as a Glasgow Coma Scale (GCS) score below 12 for more than 6 hours. They reported an incidence of 30.8 per 100,000 children per year, and 6.0 per 100,000 per year in the general population. In this study, age-specific incidence was significantly higher in the first year of life (ie, 160 per 100,000 children per year). CNS specific presentations became more common with increasing age, but in infants nearly two-thirds of cases presented with nonspecific systemic signs. Infection was the most common overall etiology and the etiology remained unknown in 14% of cases despite extensive investigation and/or autopsy. Mortality was highly dependent on etiology; at approximately 12 months after coma onset, overall series mortality was 46%.2 Another prospective observational study from a tertiary care teaching/referral hospital in India followed 100 children with all causes of coma from 2 months to 12 years of age. Overall mortality was 35%; CNS infection was the most common etiology followed by toxic/metabolic causes of coma in this study population.3
A recent analysis of children from 0 to 14 years of age who suffered from traumatic brain injury (TBI) in 2003 estimated that 1,565,000 TBIs in the United States resulted in 1,224,000 emergency department visits, 290,000 hospitalizations, and 51,000 deaths.4 Although many of these children sustained severe TBI (defined as GCS ≤ 8), it is not clear how many of these children were actually in coma after the injury. A previous study reported the rate of coma from TBI was 140 per 100,000 children per year in the United States.5 Kraus and associates calculated an incidence of severe TBI in children up to ...