Subdural hematomas (SDH) in infants often result from nonaccidental head injury (NAHI), which is diagnosed based on the absence of history of trauma and the presence of associated lesions. When these are lacking, the possibility of spontaneous SDH in infant (SSDHI) is raised, but this entity is hotly debated; in particular, the lack of positive diagnostic criteria has hampered its recognition. The role of arachnoidomegaly, idiopathic macrocephaly, and dehydration in the pathogenesis of SSDHI is also much discussed.

We decided to analyze apparent cases of SSDHI from our prospective databank.

We selected cases of SDH in infants without systemic disease, history of trauma, and suspicion of NAHI. All cases had fundoscopy and were evaluated for possible NAHI. Head growth curves were reconstructed in order to differentiate idiopathic from symptomatic macrocrania.

Sixteen patients, 14 males and two females, were diagnosed with SSDHI. Twelve patients had idiopathic macrocrania, seven of these being previously diagnosed with arachnoidomegaly on imaging. Five had risk factors for dehydration, including two with severe enteritis. Two patients had mild or moderate retinal hemorrhage, considered not indicative of NAHI. Thirteen patients underwent cerebrospinal fluid drainage. The outcome was favorable in almost all cases; one child has sequels, which were attributable to obstetrical difficulties.

SSDHI exists but is rare and cannot be diagnosed unless NAHI has been questioned thoroughly. The absence of traumatic features is not sufficient, and positive elements like macrocrania, arachnoidomegaly, or severe dehydration are necessary for the diagnosis of SSDHI.