Causes and Diagnosis of Subdural Hemorrhage in 3-Month-Old Infants

Primary Causes by Frequency

Subdural hemorrhage in 3-month-old infants most commonly results from non-accidental trauma, followed by coagulation disorders, particularly vitamin K deficiency, and rarely from vascular malformations or birth trauma 1, 2
Vitamin K deficiency is a specific concern at this age, with documented cases of 3-month-old infants developing subdural and intraparenchymal hemorrhage from congenital vitamin K deficiency 1, 2, 3
Maternal use of warfarin, phenytoin, or barbiturates during pregnancy can cause vitamin K-dependent coagulation factor deficiencies requiring higher postnatal vitamin K doses 2
Severe coagulation deficiencies are more likely to cause spontaneous hemorrhage, while milder deficiencies typically require trauma as a trigger 1, 2

Other coagulation defects include factor VIII deficiency, factor XIII deficiency, and thrombocytopenia, though thrombocytopenia risk is low with platelet counts >20,000/mm³ 1, 2, 3

Arteriovenous malformations and arteriovenous fistulas can present in neonates and young infants, though they more commonly cause high-output cardiac failure in this age group 2, 3

Birth trauma can cause subdural hemorrhage, though this typically presents immediately after delivery rather than at 3 months of age 2

Subdural hemorrhage in a non-mobile 3-month-old infant is highly concerning for child abuse and requires immediate evaluation 4, 5
The American Academy of Pediatrics recommends that all 3-month-old infants with subdural hemorrhage require evaluation for bleeding disorders unless independently witnessed or verifiable significant trauma exists or other findings definitively consistent with abuse are present 4
Essential laboratory evaluation includes PT, aPTT, platelet count, and consideration of von Willebrand disease and factor XIII testing 4
The American College of Radiology guidelines recommend non-contrast CT as first-line for acute diagnosis, while MRI provides superior detection of small hemorrhages, subacute blood products, and associated injuries 5

Do not miss vitamin K deficiency—specifically ask about maternal medications during pregnancy and adequacy of postnatal vitamin K administration 1, 2