Ischemic stroke in children

Etiology: From Anemia to Moyamoya Syndrome

The absolute leader among the causes of ischemic stroke in pediatrics is sickle cell anemia (SCA). It is based on the production of defective hemoglobin, which causes red blood cells to lose their normal shape and occlude the microvasculature. The risk of ischemia increases manifold in the presence of tissue hypoxia, concurrent infections, and vaso-occlusive crises (which can even be triggered by nocturnal apnea due to adenoid hypertrophy). Up to 9% of patients with SCA under the age of twenty suffer a major stroke, and 25% experience silent cerebral infarctions.

The second most important cause is moyamoya syndrome. This is a progressive stenosis of the terminal segments of the carotid arteries, accounting for up to a third of childhood cerebral vasculopathies. The condition is accompanied by the development of fragile collaterals. The syndrome can be idiopathic or secondary—associated with SCA, type 1 neurofibromatosis, radiation therapy, Down syndrome, or previous tuberculous meningitis.

Additionally, the differential diagnosis includes:

• Post-infectious angiitis: most commonly associated with the Varicella zoster virus. It affects the internal carotid artery and the proximal segments of the middle cerebral artery, but usually has a favorable outcome with stabilization of the vessel wall within six months.
• Mitochondrial cytopathy (MELAS): manifests as extensive infarctions that do not conform to the strict boundaries of arterial territories, along with symmetric calcification of the basal ganglia.

Arterial Dissection in Pediatrics

Unlike adult practice, dissection of the head and neck arteries in children frequently occurs spontaneously, entirely without preceding trauma. This is a critical and potentially fully reversible cause of stroke.

The vertebral artery (in the segment from C2 to the foramen magnum) and the internal carotid artery (just above the bifurcation) are the most vulnerable. These spontaneous dissections are frequently caused by hereditary connective tissue dysplasias: Marfan syndrome, Ehlers-Danlos syndrome type IV, osteogenesis imperfecta, and Menkes disease.

To detect a dissection, the neuroimaging protocol must necessarily include the neck vessels starting from the aortic arch itself. Ideally, pathognomonic signs are visualized: a detached intimal flap or a double lumen. In practice, however, non-specific signs such as the "string" or "rat tail" sign—a gradual tapering of the vessel lumen—are more commonly seen.

Diagnostic Imaging and Neuroimaging

The primary objective of diagnostic imaging is not only to locate the area of necrosis but also to determine its etiology.

1. In sickle cell anemia, MRI typically reveals infarctions in watershed zones. An interesting radiological finding on skull radiographs is diffuse widening of the diploic space, which develops compensatorily due to chronic erythrocyte destruction and enhanced erythropoiesis.
2. In moyamoya syndrome, magnetic resonance angiography (MRA) reveals the "puff of smoke" appearance—a scatter of small signal-void areas of flowing blood in the projection of the basal ganglia, corresponding to proliferated collateral vessels. Leptomeningeal contrast enhancement is frequently visualized.
3. Tumor mimics: sometimes seizures in a child are caused not by a stroke, but by a dysembryoplastic neuroepithelial tumor (DNT). On MRI, it presents with a characteristic "FLAIR rim" sign, distinctly expands the cortex (often of the temporal lobe), and does not show contrast enhancement.

Surgical Intervention and Perfusion

In the event of critical blood flow deficit, neurosurgical microvascular bypass is considered. To assess the volume of viable tissue, perfusion-weighted MRI with contrast is used—it allows identification of the "diffusion-perfusion mismatch" zone.

Surgeons perform either direct bypass (superficial temporal artery to middle cerebral artery anastomosis) or indirect bypass (encephalo-dureo-arterio-synangiosis). Multiple burr holes may be placed to stimulate the growth of new vessels in the cranial vault. The success of the surgery is evaluated on follow-up MRI by an increase in cerebral blood flow (CBF) and cerebral blood volume (CBV) parameters.

Class and exam questions

What else to study on this topic

• Aneurysmal malformations of the vein of Galen (VGAM) and their endovascular treatment.
• Focal and diffuse periventricular leukomalacia (PVL) in premature infants.
• Intraventricular hemorrhage (IVH) and germinal matrix hemorrhage.
• Paraventricular hemorrhagic infarction and porencephalic cyst formation.
• The role of neurosonography (ultrasound) in the diagnosis of hypoxic-ischemic brain injuries.

Other Topics in "Pediatric Diagnostic Radiology"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.