Most of elderly onset psychosis present as a consequence of one or more organic processes. We present the case of an 81-year-old patient with diagnosis of a posterior fossa meningioma. It emerged with abrupt positive symptoms of psychosis with important family and social disruption. The interest of the case lies in the low frequency of psychiatric symptoms associated to this type of tumor, given its location. Thus, these symptoms may be explained, by normal pressure hydrocephalus (NPH) secondary to the tumor.

To highlight the importance of performing a complete organic screening in elderly onset psycotic patients.

From the mentioned case, we performed a literature review of psychopathology associated with NPH.

Psychiatric examination demonstrated parasitization delusions and delusional misinterpretations; tactile and visual zoomorphic hallucinations were also present. They were compatible with Ekbom syndrome; anxiety and behavioral disorganization were prominent. We introduced treatment with risperidone 0.5mg/12h with important decrease of positive psychotic symptoms. Currently, the patient is waiting for a ventricular-peritoneal shunt.

The NPH usually presents with memory failures, psychomotor slowing, problems in calculating and writing. It may progress to a neurological impairment so intense that may be indistinguishable from Alzheimer's disease. From a psychopathological point of view, affective or psychotic symptoms and/or behavioral disorganization may also appear. In few cases, HNT onset shows with prominent psychiatric symptoms instead of neurological impairment. These symptoms may improve with pharmacological and surgical treatment. Thus, it is important to get an accurate diagnosis.