Retinal Hemorrhages Are the Most Likely Additional Finding
In a 2-month-old previously healthy infant presenting with subdural hematoma and seizure, retinal hemorrhages are the most likely additional finding, as this clinical triad strongly suggests abusive head trauma (AHT), which is the leading cause of subdural hematomas in this age group.
Clinical Context and Epidemiology
The presentation described is classic for non-accidental trauma in infancy:
- Non-accidental injury accounts for 55% of subdural hematomas in children under 2 years of age, making it the most common etiology in this population 1
- Subdural hematoma is the most commonly seen intracranial abnormality in abusive head trauma, particularly when multiple, involving the convexity, interhemispheric fissure, or posterior fossa 2
- AHT is responsible for the majority of severe traumatic brain injury in children under 2 years of age, with case fatality rates above 20% 2
The Diagnostic Triad
Retinal Hemorrhages: The Key Distinguishing Feature
Retinal hemorrhages are present in the vast majority of abusive head trauma cases and are the most discriminating finding:
- All 26 patients in one series of infantile acute subdural hematoma had retinal and preretinal hemorrhage 3
- Retinal hemorrhages show a significantly higher incidence in the abuse group compared to accidental trauma, making this the most important clinical feature for distinguishing abusive from accidental injury 1
- The presence of retinal hemorrhages, along with subdural hematoma and seizures, forms the classic triad of shaken baby syndrome 4
Why Not the Other Options?
Disruption of the middle meningeal artery:
- This causes epidural hematoma, not subdural hematoma
- Epidural hematomas are uncommon in infants and typically result from high-impact trauma with skull fractures
- The middle meningeal artery runs between the skull and dura, not in the subdural space 2
Elevated INR:
- While coagulopathy can cause subdural hematomas, the question specifies a "previously healthy infant"
- Coagulopathy would be a pre-existing condition, not an "additional finding" discovered during workup
- In the absence of systemic disease history, coagulopathy is unlikely 5
Thrombocytopenia:
- Similar to elevated INR, this would represent a pre-existing hematologic disorder
- The infant is described as "previously healthy," making underlying thrombocytopenia unlikely
- Thrombocytopenia is not characteristically associated with the acute presentation of traumatic subdural hematoma 5
Clinical Pitfalls and Important Caveats
External Hydrocephalus Exception
One important caveat: Infants with external hydrocephalus (benign enlargement of subarachnoid spaces) can develop subdural hematomas and retinal hemorrhages from minor trauma:
- External hydrocephalus with arachnoidomegaly can predispose to subdural hematomas from minimal trauma 5, 6
- Retinal hemorrhages can occur in this setting even with minor injury, which may lead to false accusations of abuse 6
- However, spontaneous subdural hematoma in infants is rare and cannot be diagnosed unless non-accidental injury has been questioned thoroughly 5
- Positive elements like macrocrania, arachnoidomegaly, or severe dehydration are necessary for the diagnosis of spontaneous subdural hematoma 5
Mandatory Evaluation Steps
When subdural hematoma is identified in an infant:
- Fundoscopic examination is mandatory to identify retinal hemorrhages 5, 3
- Skeletal survey should be performed to identify associated long bone and rib fractures, which are significantly more common in abuse cases 1
- All cases must be evaluated for possible non-accidental injury before considering alternative diagnoses 5
- Head growth curves should be reconstructed to differentiate idiopathic from symptomatic macrocrania if considering benign causes 5
Age-Specific Vulnerability
The 2-month age is particularly high-risk:
- Non-accidentally injured children are significantly younger than accidentally injured children with subdural hematomas 1
- Most cases of infantile acute subdural hematoma occur between 7-10 months, but younger infants are at higher risk for abuse 3
- Young age of the infant, combined with subdural hematoma and retinal hemorrhages, strongly suggests child abuse as the most likely cause 1