Objective: Subdural bleeding (SDB) in infants is considered an essential symptom of nonaccidental head injury (NAHI). Recently, this view has been challenged by the "unified hypothesis," which claims that SDB in infants is related to hypoxia and brain swelling rather than to traumatic shearing of bridging veins. We analyzed a large series of infants' autopsies for the presence and causes of SDB, which should be a common event according to the unified hypothesis.
Methods: Autopsy, clinical, and legal information for infants <1 year of age from a single institution over 50 years were analyzed regarding cause of death, presence, morphology, and cause of SDB, and brain weight.
Results: From a total of 16 661 autopsies during the study period, 715 (4.3%) involved infants <1 year of age. Fifty (7.0%) of those had SDB. NAHI was identified in 17 patients. The most common cause of SDB was trauma (15 cases [30.0%]), with NAHI accounting for 14 cases. SDB was present in 82.4% of patients with NAHI but only 5.2% of infants with other causes of death. Four patients (8.0%) had unexplained SDB with no discernible cause of bleeding. Statistical analysis did not reveal any correlation between the presence of SDB and brain weight.
Conclusions: In the study population, unexplained SDB in infants was an extreme rarity. Moreover, a correlation between brain swelling and the presence of SDB could not be drawn. Our data argue strongly against the unified hypothesis and strengthen the association between SDB and NAHI in infancy.