Intracranial arachnoid cysts (IACs) are benign, slow-growing developmental anomalies. In 4–14% of cases, IACs are accompanied by seizures. Since most cysts do not cause any symptoms, many lesions remain clinically silent and are found incidentally. As these lesions are slow-growing, they can become symptomatic over time and may give rise to epileptic seizures. Since IAC localization and seizure focus do not always coincide, a unifying theory between IACs and epileptogenesis is still lacking. We present a case of a 49-year old man who presented himself as a result of a first tonic-clonic insult. No major risk factors nor antecedents in his medical history were present. MRI confirmed a voluminous cystic lesion at the transition of motor cortex and supplementary motor area. Due to the large volume (with risk of cyst rupture) and compatible clinical, radiographic, and electroencephalographic features, cyst fenestration through craniotomy was performed. Epileptic seizures were resolved completely after this procedure. IACs are not uncommon and are frequently encountered incidentally in patients who present with epilepsy. Some authors have been classifying this association as rather exceptional. However, we illustrated a case in which excellent surgical results were obtained in a patient with focal epilepsy in which both clinical and electroencephalographic features were compatible with arachnoid cyst localization. Therefore, in patients with no other identifiable causes for epilepsy, thorough evaluation should be performed and surgical intervention should be considered. We developed a flowchart in order to guide clinicians in the appropriate approach of these patients. Therefore, this summary could serve as a scaffold for future high-quality studies concerning this topic.
