Imaging: CT and MRI
On computed tomography, blood collections appear differently depending on the stage: hyperdense in acute, isodense in subacute, and hypodense in chronic. A diagnostic pitfall exists: hypodense fluid is easily mistaken for normal widening of the subarachnoid spaces.
Magnetic resonance imaging has significantly higher sensitivity. It easily differentiates cerebrospinal fluid (CSF) from chronic subdural hematomas and better visualizes small collections invisible on CT. T2* and SWI sequences clearly demonstrate torn or occluded bridging veins (cerebral bridging veins). Specific markers of such thrombosis include the tadpole sign (tadpole sign) or lollipop sign (lollipop sign). MRI also detects thrombosis of deep intramedullary veins.
How to distinguish abusive from accidental trauma
The key factor is the localization of the hemorrhage.
- In abusive head trauma (AHT), bilateral lesions are typical. Blood closely abuts the falx cerebri (falx), layers onto the tentorium cerebelli (tentorium), or is located directly within the falx itself. This is a strict predictor of abuse, especially in the presence of cerebral edema. Involvement of the posterior fossa is also typical for AHT.
- In accidental trauma, hematomas are predominantly located over the cerebral convexity surfaces (cerebral convexities).
It is important to consider that precise dating of hematomas is practically impossible. The signal changes not only due to the natural evolution of the hemorrhage, but also due to meningeal tears with CSF-blood dilution (CSF-blood dilution) and the formation of hematohygromas. For this reason, it is extremely difficult to visually differentiate repeated trauma from spontaneous rebleeding into a primary hematoma.
Overdiagnosis pitfall: benign macrocrania
The mere presence of a subdural collection is not absolute proof of abuse. Some infants exhibit benign macrocrania — a physiological widening of the transitional subarachnoid spaces. As a result, cortical veins are constantly stretched and can be easily injured.
To avoid misdiagnosing AHT, a sudden increase in head circumference must be correlated with the presence of parenchymal lesions.
Signs of accidental hematomas in the setting of macrocrania:
- Collections are consistently homogeneous.
- No hemosiderin deposits.
- No cortical vein thrombosis.
- Brain parenchyma and clinical presentation are normal.
The main challenge is that without prior imaging confirming baseline macrocrania, proving the connection between an acute hematoma and this condition is extremely difficult.
Associated injuries and clinical prognosis
Abusive trauma is rarely limited to hematomas alone. Pseudocystic parenchymal tears are frequently identified, which may contain fluid levels (fluid-fluid levels). Multiple non-hemorrhagic subcortical lesions and cerebral lacerations (lacerations) negatively impact the prognosis and subsequent neurodevelopment of the child.
Shear stress leads to diffuse axonal injury. Such foci should be sought in the centrum ovale (centrum ovale), subcortical region, corpus callosum (corpus callosum), and cerebral peduncles (cerebral peduncles). Most of them are non-hemorrhagic, making MRI using FLAIR, T2, and DWI sequences critically important for diagnosis. Assessment of regional brain anisotropy on DWI reveals occult structural abnormalities.
Briefly: answers to topical questions
What metabolic diseases and coagulopathies must be included in the differential diagnosis of subdural hematomas in infants?
Differential diagnosis of subdural hematomas in infants must be performed with various coagulopathies and specific congenital metabolic disorders.
Metabolic conditions that require exclusion include:
- Glutaric aciduria type I (glutaric aciduria type I) — an inherited metabolic disorder.
- Menkes disease (Menkes disease) — an inherited metabolic disorder.
The differential diagnosis also includes subdural collections following acute dehydration or meningitis.
What other types of hemorrhage, besides subdural hematomas, are part of the shaken baby syndrome classic triad?
The classic triad of shaken baby syndrome includes only one additional type of hemorrhage besides subdural hematoma.
The complete triad includes the following pathologies:
- Subdural hematoma (SDH) — an accumulation of blood beneath the dura mater.
- Retinal hemorrhage (retinal haemorrhage) — detected by ophthalmoscopic examination or MRI.
- Encephalopathy — brain injury (the third component of the triad, which is not a hemorrhage).
What characteristics of skull fractures (location, type) are most specific for abusive trauma?
Complex skull fractures are most specific for abusive trauma, whereas simple linear fractures occur frequently but have low diagnostic value.
Comparison of specificity for various types of skull fractures:
| Skull fracture type | Specificity for abusive trauma |
|---|---|
| Complex fractures | Moderate specificity (Moderate specificity) |
| Linear fractures | Low specificity (Common but low specificity) |
The tadpole sign or lollipop sign on MRI is a specific radiological clue indicating signal loss within occluded bridging veins in abusive trauma.
Class and exam questions
Why are bridging veins specifically injured in abusive trauma?
Specific trauma biomechanics cause sharp tension and shear, leading to rupture or thrombosis of bridging veins connecting the cortex to the venous sinuses.
Can the exact date of hemorrhage be established from MRI or CT scans?
No, precise dating is extremely difficult. The picture is distorted by CSF dilution of blood due to meningeal tears, formation of hematohygromas, and the risk of repeated, overlapping injuries.
Which MRI sequence is most effective for detecting torn veins?
T2* or susceptibility-weighted imaging (SWI) sequences best visualize blood breakdown products and allow identification of thrombosed veins.
What else to study on this topic
- Dating subdural hemorrhages: challenges in neuroimaging
- Diffuse axonal injury in shaken baby syndrome
- Pseudocystic brain tears: formation mechanisms and outcomes
- Differential diagnosis of subdural collections and benign macrocrania
Master the entire topic in the "Diagnostic Radiology" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on «Subdural hematoma in abusive head trauma» and 2,199 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 10 video lessons on the subject
Other Topics in "Pediatric Diagnostic Radiology"
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.