Arachnoid cysts are benign, thin-walled cavities filled with cerebrospinal fluid that arise along the craniospinal axis. Such cysts are quite rare, accounting for only 1% of all lesions occurring in the intracranial space.
The neurological symptoms associated with arachnoid cysts include headache, ataxia, ophthalmic disturbances, dizziness, seizures, and other physical abnormalities; these vary according to the function of the structures adjacent to the cyst. There are rare cases of comorbidity of arachnoid cysts with psychiatric disease, which manifest as cognitive impairment, delusional ideation, hallucinations, pseudologia fantastica, and catatonia.
Although the nature of the relationship between arachnoid cysts and psychosis is not well understood, the location of the lesion influences the specific pattern of the illness. To the best of our knowledge, comorbid cases of schizophrenia and arachnoid cysts are rare. Here, we present a case of clozapine-resistant schizophrenia associated with a large arachnoid cyst in the left Sylvian fissure. Notably, 8-week treatment regimens with high-dose risperidone or clozapine did not effectively attenuate the psychotic symptoms. The patient and his family provided informed consent for publication.