Subtle signs, serious consequences: pediatric moyamoya disease presenting with seizures and behavioural regression

Abstract

Moyamoya disease (MMD) is a rare, progressive cerebrovascular arteriopathy characterized by chronic stenosis or occlusion of the terminal internal carotid arteries with compensatory development of a fragile basal collateral network. Although classically described with well-recognized presentations such as stroke, transient ischemic attacks, or seizures, its clinical spectrum in young children is remarkably varied, and early manifestations are often subtle, nonspecific, and easily overlooked or misattributed to more common childhood conditions. This diagnostic ambiguity is compounded in resource-limited settings, where ready access to vascular neuroimaging is not always available, and where a low index of suspicion for a rare cerebrovascular disorder can result in children being managed symptomatically for weeks or months before the underlying diagnosis is considered. We report a 2-year-2-month-old female who presented with a three-month history of behavioural change and regression of previously attained expressive language, followed by transient right-sided weakness, recurrent right-sided focal motor seizures, and progressive hemiparesis. Her early symptoms of irritability and language regression were initially unrecognized as neurological in origin, and even her first episode of transient limb weakness resolved without further evaluation, illustrating how easily the earliest, subtlest features of this disease can be missed. It was only with the onset of recurrent seizures and persistent motor deficits that neuroimaging was pursued. Magnetic resonance imaging demonstrated an acute infarct in the left inferior frontal and parietal regions, while magnetic resonance angiography revealed marked bilateral narrowing of the terminal internal carotid, anterior, and middle cerebral arteries with extensive basal collaterals producing the classical "puff-of-smoke" appearance. Non-contrast computed tomography additionally revealed chronic left hemispheric encephalomalacia with gyriform calcification, indicating an earlier, clinically silent ischemic insult that had gone unrecognized. Digital subtraction angiography confirmed bilateral terminal internal carotid artery stenosis, graded predominantly as Suzuki stage III. The child underwent left-sided encephaloduroarteriosynangiosis (EDAS) with good postoperative recovery of hemiparesis. This case emphasizes that Moyamoya disease must be considered even in the presence of subtle, seemingly unrelated symptoms such as behavioural change or language regression, particularly in settings where diagnostic delay due to varied age-specific presentation and limited imaging access can allow silent, cumulative ischemic injury before diagnosis, underscoring the need for heightened clinical vigilance across all pediatric age groups.