Acute Onset of Psychosis in a Patient with a Left Temporal Lobe Arachnoid Cyst

Arachnoid cysts are considered a rare neurological tumor, few of which exhibit any symptomatology. A 38-year-old Haitian American female with no past psychiatric history presented with rapid onset of psychosis. Workup for medical etiology proved to be within normal limits, with the exception of a left temporal lobe arachnoid cyst. The purpose of this paper is to add to a number of existing case reports that suggest a relationship between such lesions and psychiatric illness. 1. Introduction Arachnoid cysts are considered to be a relatively rare neurological tumor, accounting for roughly 1% of intracranial space occupying lesions [1]. Of patients undergoing a brain MRI, only 1.4% are identified to have an arachnoid cyst. Most of these (34%) are found to be in the mid cranial fossa, the majority (70%) being left sided. Even more rare are patients who become symptomatic (5%); among the most common complaints are headache, ataxia, seizures, dizziness, and visual changes [2]. Numerous articles have also reported patients with intracranial arachnoid cysts presenting with psychiatric illness as their main symptom [3–5]. Although no clear-cut mechanism has yet been identified, there are copious instances of patients being cured of their psychiatric symptoms following neurosurgical intervention [6–9]. Meanwhile, the remainder of patients were managed medically. We would like to present a case in which a middle aged female develops rapid onset psychosis and delirium. After extensive medical workup for the etiology of her condition, there were no abnormalities to be found, with the exception of a left temporal lobe arachnoid cyst. 2. Case Presentation Mrs. G is a 38-year-old Haitian American female brought into the emergency department by her family due to a sudden onset of psychotic behavior and delirium. She has no past psychiatric history and her unusual behavior started roughly one week prior to admission. The patient takes no home medications and has no family history of psychiatric illness. She works as a nurse in a nearby hospital, takes care of two children, and lives in the same apartment building as her mother, who was the original witness to the patient’s change in behavior. Her symptoms included religious and persecutory delusions as well as delusions of control. Also, she has had zero to little sleep over the past week. The patient was alert and oriented to person, place, and time. She remained cooperative during her interview, however she became irritable upon questioning of her delusions. Her thought process was linear, logical, and goal directed.