Giant Arachnoid Cyst Presenting With Transient Facial Paresthesia: A Case Report

Arachnoid cysts are benign, cerebrospinal fluid-filled lesions that are frequently discovered incidentally on neuroimaging. Although most remain asymptomatic, large cysts may occasionally be associated with neurological symptoms due to mass effect or compression of adjacent structures. We report the case of a 61-year-old man who presented with transient numbness of the left side of the face. Brain computed tomography (CT) revealed a large right parieto-occipital arachnoid cyst with cerebrospinal fluid-like density, smooth margins, and thinning of the overlying calvaria, consistent with a long-standing lesion. The patient's symptoms resolved spontaneously, and no additional neurological deficits were observed during follow-up. This case illustrates the frequent dissociation between the striking radiologic appearance of giant arachnoid cysts and their limited clinical expression. Despite its size, the lesion was associated only with mild and self-limited symptoms, supporting a conservative management approach. Giant arachnoid cysts may remain clinically silent or present with transient symptoms. Clinical management should be guided by symptom severity and evolution rather than imaging findings alone in order to avoid unnecessary interventions.