A 1-month-old, full-term boy is brought to the emergency department by his mother due to difficulty awakening him from sleep. The mother says that the infant was momentarily left alone this morning and rolled off a bed. Since then, he has been sleepy and less active than usual. Physical examination shows a lethargic boy with a large, full anterior fontanelle. Bilateral retinal hemorrhages are seen on funduscopic examination. Which of the following is the most likely diagnosis?
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This lethargic child with bilateral retinal hemorrhages and a large, full, anterior fontanelle has most likely experienced abusive head trauma (AHT).
Abusive head trauma (AHT), formerly known as shaken baby syndrome, is inflicted intracranial injury usually due to vigorous shaking. The resultant injuries are due to infants' unique anatomic features. Infants have larger heads, enlarged subarachnoid spaces, higher brain water content, and decreased cervical muscle tone compared to older children. These factors lead to increased movement of the immature brain in relation to the skull, shearing the bridging cortical veins that run between the dura and arachnoid mater (subdural space). This can result in multiple subdural hematomas; because AHT may occur repeatedly over weeks to months, acute on chronic subdural hemorrhages are often seen.
The shaking motion also applies shearing forces at the interface between the vitreous and the retinal vessels (vitreoretinal traction), commonly causing bilateral retinal hemorrhage. Posterior rib fractures are another frequent manifestation due to grasping of the torso during shaking.
(Choice B) Although bacterial meningitis can cause lethargy and a bulging fontanelle, patients are typically febrile and bilateral retinal hemorrhages would not be expected.
(Choice C) Idiopathic thrombocytopenic purpura (ITP), caused by platelet autoantibody formation, presents with petechiae, ecchymoses, and bleeding after minor trauma. Intracranial hemorrhage is rare, and retinal hemorrhages are not seen in patients with ITP.
(Choice D) Although vitamin K deficiency can present with intracranial bleeding, bilateral retinal hemorrhages are not typical, and patients with bleeding due to vitamin K deficiency usually come to medical attention within a week after birth. In addition, this patient's other red flags (eg, history inconsistent with development) are more concerning for AHT.
(Choice E) Retinoblastoma is the most common ocular tumor of infancy and presents with absence of the red reflex on physical examination. Lethargy, a bulging fontanelle, and retinal hemorrhage are not seen.
(Choice F) An accidental fall from bed-height would be generally insufficient to cause a large intracranial hemorrhage resulting in altered mental status, and would not explain this patient's retinal hemorrhages. In addition, the history provided by this patient's parent does not match his developmental age (rolling over is not typical before age 4 months).
Educational objective:
Abusive head trauma is classically caused by vigorous shaking of an infant and results in subdural hemorrhage (due to shearing of bridging cortical veins) and retinal hemorrhages (sheared retinal vessels). Additional red flags include injuries inconsistent with history or developmental age.