Aetiologies and Epidemiology of Subdural Haematoma in Infancy

Abstract: According to scientific studies, subdural haematoma (SDH) in combination with retinal haemorrhage and encephalopathy (usually denoted as the triad) during infancy is highly specific for abusive head trauma/shaken baby syndrome, if a fall from over one meter, a traffic accident and certain medical conditions have been excluded. Other studies have challenged this notion since there are witnessed falls from less than one meter which has caused acute SDH, birth-related SDH which have been confirmed to develop into chronic SDH, and external hydrocephalus that can be complicated by a spontaneous SDH or an SDH from minor trauma.These aetiologies have not been taken into consideration in prior studies on abusive head trauma. An independent review on infant abusive shaking from the Swedish Agency for Health Technology Assessment concluded that there was insufficient evidence for determining the specificity of the triad for isolated shaking. The aim of this thesis was to increase the understanding of the aetiologies and the epidemiology of infant SDH. This was accomplished by studying registry data (Paper I and II), descriptive reviews of infants with SDH (paper I, III and IV) and infants subjected to witnessed or spontaneously admitted shaking (paper V).The maximum incidence of fatal AHT in Sweden, 0.6/100 000, was at least 10 times lower than in other Western countries and the risk of unreported fatal AHT was low (Paper I). A majority of the deceased infants had neonatal conditions, several were twins and/or preterm, one had a cerebral vascular condition, and one signs of metabolic disorder (Paper I). Approximately 12 infants every year are diagnosed with SDH beyond the first week of life and the case-fatality rate for all SDH diagnosis categories is 6.2% (Paper II). Males, preterm born and twins have a higher risk to develop SDH in general, and those having an abuse diagnosis had increased odds of being born preterm and small-for-gestational age (Paper II). Chronic SDH has a higher freqency of male and premature infants and a lower mortality rate than acute SDH (Paper III). Infants with chronic CSDH, but not with acute SDH, tend to have findings on neuroimaging and a head circumference that are suggestive of external hydrocephalus complicated by spontaneous SDH or SDH from minor trauma (Paper IV). Intracranial and ocular findings in infants subjected to abusive shaking were rare, seen in 2 out of 36 infants, both with pre-existing intracranial pathology, and of non-specific character (Paper V).In conclusion this thesis provides evidence that non-abusive aetiologies for SDH in infancy may have been overlooked in previous research.