Case of the Week

Background:

• Idiopathic neonatal subpial hemorrhage is a rare form of hemorrhage the pathophysiology of which is not yet well understood. It was initially proposed that birth trauma may cause venous compression that results in hemorrhage in these neonates. However, more recent literature concluded that there is likely no association between birth trauma and neonatal hemorrhagic strokes. Slaughter and colleagues⁵ have previously suggested instead that thrombosis of superficial temporal veins may result in hemorrhagic infarcts of surrounding cortical regions; a similar mechanism of venous ischemia was proposed by Cain et al.²
• While the literature demonstrates a link between idiopathic neonatal subpial hemorrhage and venous infarcts, the temporal relationship between these 2 phenomena is not clear. It may be that venous compression and thrombosis result in cortical ischemia of the underlying brain parenchyma. Perhaps more convincing is that hemorrhage into the subpial space is itself responsible for compression of the venous system. Blood in the subpial space increases pressure in the tissue, resulting in thrombosis of the deep medullary system due to this congestion. In fact, one cohort study found that more than one-half of cases examined demonstrated distension of the medullary veins.

Clinical Presentation:

• Infants typically present with episodes of apnea and/or respiratory distress. Seizures may also occur.

Key Diagnostic Features:

• Larger bleeds can be detected using cranial ultrasound—seen usually in temporal lobes as an echogenic area of abnormality.
• MRI will be more sensitive for small bleeds. MRI will demonstrate a heterogeneous blood collection along the margin of the cerebral parenchyma. The most common site of involvement is the temporal lobe, as seen in this patient. The characteristic imaging finding of idiopathic neonatal subpial hemorrhage is the “yin-yang sign,” so named for the contrast between the hypointense signal of blood and hyperintense signal of the underlying cerebral cortex. The yin-yang sign is best characterized on T2-weighted and DWI sequences as seen in this patient. This blood produces a mass effect with concurrent cerebral edema. Cortical buckling can also occur, as demonstrated in these images.

Differential Diagnoses:

• Convexal subarachnoid hemorrhage is a rare subtype of subarachnoid hemorrhage in which blood is restricted to convex spaces of the brain and does not involve the parenchyma or fissures. Unlike a subpial hemorrhage, this type of hemorrhage typically does not produce cerebral edema or mass effect. Additionally, T2 FLAIR imaging of convexal subarachnoid hemorrhage produces a signal less hyperintense as compared with idiopathic neonatal subpial hemorrhage. Intraparenchymal hemorrhage should be considered but will be more easily distinguishable on imaging.

Treatment:

• This is typically conservative, aimed at symptomatic care. Resolution of seizure activity or treatment of underlying coagulopathy is indicated as the clinical picture suggests. Long-term management includes regular developmental screening as well as close monitoring for continued seizure activity. Follow-up imaging can show encephalomalacia of the brain regions where the hemorrhage occurred.