<正>Arachnoid cysts are benign congenital malformations,making up 1% among all the space occupying lesions(SOL).~([1,2])Sylvain fissure is the most common place(50%)but it can happen in any place.~([2])Patients might complain of a headache,ataxia,seizures,dizziness,and visual changes etc.The common psychiatric symptoms are psychosis,alexithymia,attention deficit and hyperactivity disorder,paranoid delusions,obsessive religiosity,sense of guilt or ruin,hallucinations,