The pathophysiology of infant subdural haematomas

The widely accepted theories concerning the pathophysiology of infant subdural haematoma (SDH) were formulated in the pre-computed tomographic (CT) scan era. Violent shaking is considered to be a crucial cause of SDH in non-accidentally injured infants. This theory has been re-examined in a clinical and CT scan review, and our findings have been correlated with results of recent head injury research. A retrospective review was conducted of all head injured infants (up to 18 months old) treated at Atkinson Morley's Hospital over a recent 20-year period (n = 100). Twenty-eight infants with a SDH were identified. CT scans were reviewed and each SDH greater than 0.5 cm thick was morphometrically analysed. Seventeen infants were Caucasian, 10 were non-Caucasian and one was of mixed race. A race-dependent pattern of SDH pathophysiology was noted, with non-Caucasian infants with a head injury more likely to have a SDH than Caucasian infants (67 v 21%, p < 0.01). All had a history of, or radiographic and clinical findings most consistent with, an impact injury, and non-Caucasian infants were significantly more likely to have a normal scalp examination despite the impact injury (p < 0.05) and to have developed the SDH after a relatively trivial fall (p < 0.01). They were also more likely to have a large (> 0.5 cm thick) SDH (p < 0.05), and to suffer post-traumatic seizures (p < 0.05). Our findings do not support shaking as the only cause of infant SDH formation and also suggest that non-accidental injury is a less common cause of SDH than it is believed to be.