Differences Between Subdural and Subarachnoid Hemorrhage in Children
Understanding Pediatric Brain Bleeds: Subdural vs. Subarachnoid Hemorrhage
When it comes to neurological emergencies in children, intracranial bleeding is a serious concern that requires prompt diagnosis and treatment. Two of the most commonly discussed types are subdural hemorrhage (SDH) and subarachnoid hemorrhage (SAH). While both involve bleeding within the layers surrounding the brain, they differ significantly in location, causes, symptoms, and clinical outcomes.
What Is Subdural Hemorrhage in Children?
Subdural hemorrhage occurs when blood accumulates in the space between the dura mater (the outermost protective layer of the brain) and the arachnoid membrane. This type of bleed is often categorized based on its location—supratentorial (above the tentorium cerebelli) or infratentorial (below it). In pediatric cases, subdural hematomas frequently appear at the top of the brain and are commonly bilateral, meaning they affect both sides.
Causes of subdural bleeding in infants and young children include traumatic head injury—such as from falls or non-accidental trauma—and metabolic factors like vitamin K deficiency, which impairs normal blood clotting. Newborns, especially those who have undergone difficult deliveries, are particularly vulnerable.
When significant bleeding occurs, it can lead to increased intracranial pressure, resulting in symptoms such as seizures, altered consciousness, focal neurological deficits, and in severe cases, herniation of the brain—potentially leading to death if not treated immediately.
On imaging studies like CT scans, acute subdural hemorrhages typically appear as crescent-shaped (lentiform) densities along the inner table of the skull. Early detection through neuroimaging is crucial for effective intervention and improved prognosis.
Exploring Subarachnoid Hemorrhage in Pediatric Patients
In contrast, subarachnoid hemorrhage refers to bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater, which is filled with cerebrospinal fluid (CSF). Blood enters this space when a blood vessel in the brain ruptures, either due to trauma or spontaneously.
Subarachnoid bleeds are generally divided into two categories: traumatic and non-traumatic (also known as spontaneous). Traumatic SAH often follows head injuries, while spontaneous cases may stem from underlying vascular abnormalities such as aneurysms or arteriovenous malformations—though these are rarer in children than in adults.
Symptoms and Diagnostic Clues
One hallmark of subarachnoid hemorrhage is its sudden onset. Children may present with a "thunderclap" headache—the most intense headache of their life—accompanied by nausea, vomiting (often projectile), neck stiffness (nuchal rigidity), photophobia, and signs of meningeal irritation. Altered mental status and seizures can also occur.
Diagnostically, non-contrast CT scans are highly effective in detecting SAH, usually revealing hyperdense (bright white) blood in the basal cisterns or sulci—appearing as circular or diffuse high-density areas around the brainstem and cerebral fissures. If CT results are inconclusive, a lumbar puncture may be performed to check for xanthochromia in the CSF, confirming recent bleeding.
Key Differences Summarized
The primary distinction lies in the anatomical site of bleeding: subdural hemorrhages form beneath the dura but outside the brain tissue, often from bridging vein tears, whereas subarachnoid bleeds originate within the CSF-filled space and usually stem from arterial rupture.
Clinically, subdural hematomas may develop more gradually, especially in chronic cases, while subarachnoid hemorrhages tend to present acutely with dramatic symptoms. Imaging patterns also differ—crescent shapes for SDH versus diffuse or cisternal blood distribution for SAH.
Both conditions require urgent neurosurgical evaluation and multidisciplinary care. Prompt recognition of symptoms, accurate imaging interpretation, and timely management are essential to minimizing long-term neurological damage and improving survival rates in pediatric patients.