COGNITIVE AND PSYCHOTIC SYMPTOMS IN A PATIENT WITH INFRATENTORIAL ARACHNOID CYST: CASE REPORT.

We present a case of a patient with treatment resistant hallucinatory experiences with incidental finding of an arachnoid cyst localized in the posterior infratentorial cranial fossa dorsally to the cerebellum. Psychological testing revealed significant deficit of cognitive functions to the level of mild intellectual disability in a person that had previously finished high school with good grades. A combination of clozapine and lamotrigine led to significant improvement in mood and reduction of hallucinations, but without improvement in cognitive functions. We also performed a literature review of previously published case reports or case series of co-occurring posterior fossa arachnoid cyst and schizophrenia or psychosis or psychiatric symptoms using PubMed search and discuss some controversies considering their treatment outcome.