Arachnoid cysts are fluid-filled sacs thought to be a developmental abnormality which form as a result of splitting or duplication of the arachnoid membrane. In most cases, arachnoid cysts are congenital and asymptomatic throughout an individual’s life. Rarely, arachnoid cysts develop because of head injury, intraventricular hemorrhage of prematurity, presence of a tumor, infection or surgery on the brain. Intracranial cysts are typically incidental brain imaging findings and most commonly located in the middle fossa, the suprasellar region, and the posterior fossa. In cases where the cyst enlarges significantly individuals may experience symptoms of increased intracranial pressure, mass effects, seizures, nausea and vomiting, focal neurological deficits, or hydrocephalus. This presentation compares the differing symptom presentation of two individuals with medically confirmed arachnoid cysts -- one in the middle cranial fossa region (Patient A) and the other in the posterior cranial fossa region (Patient B).

The 2 patients were referred to a private practice neuropsychological clinic for neuropsychological assessment. Patient A was a 39-year-old, right-handed, married Syrian male with 12 years if education, unemployed at the time of testing. Changes in cognition, behavior and personality were reported for Patient A approximately two years after a known cerebrovascular accident. Patient B was a 48-year-old, left-handed married Caucasian male with 16 years of education, on disability due to his medical condition. Patient B reported severe memory impairment, speech and language deficits, variable attention, executive dysfunction, impaired gait with falls, emotional dysregulation, and sleep difficulties. He was diagnosed with bipolar disorder and alcohol use disorder in remission for 9 years.

Neuropsychological testing results for Patient A were not valid, due to initiation difficulties, paranoia about the testing and consequent limited engagement in the process. Predominant symptoms were consistent with negative symptoms of schizophrenia, (i.e., avolition, abulia, and diminished emotional expression); no positive symptoms were observed or reported. His speech was limited -he lacked spontaneous speech and only responded to direct questions. His informant completed a measure assessing pre/post changes in frontal systems and there were significant increases in apathy and executive dysfunction reported. Neuropsychological results collected from Patient B revealed mild to severe impairment of aspects of executive functioning, memory, processing speed, visual attention, expressive language, and manual dexterity bilaterally and manual motor strength - more consistent with subcortical neurological disease. Self-report and informant data revealed significant difficulties with functional abilities, pre/post changes in frontal systems (apathy, disinhibition, and executive dysfunction), sleep efficiency and daytime fatigue, and psychological distress (anxiety and depressive symptoms).

The presenting case analysis illustrates the importance of neuropsychology in identifying and tracking the nature of symptoms associated with neuroimaging confirmed arachnoid cysts. This case analysis is unique as it highlights the complexities of differing symptom phenotypes of the same condition due to location of the cyst. Surgical intervention usually through draining the cyst directly or implantation of a shunt is typically recommended for symptomatic patients and that course of treatment was suggested to both patients. Treatment recommendations geared to target psychosocial and functional difficulties should also be considered.