Dynamic nature of choroid fissure cysts

Choroidal fissure cysts (CFCs) are considered benign, static lesions within the brain's choroidal fissure. However, their behavior over time remains incompletely understood.

To investigate longitudinal changes in CFC size and morphology and assess associated hippocampal mass effect.

This retrospective longitudinal study included patients with CFCs measuring ≥2 mm on initial magnetic resonance imaging (MRI) who also had follow-up MRI. Changes in cyst size were categorized as increase, decrease, or no change, with significant change defined as ≥0.2 mL from baseline. To account for the confounding effects of rapid brain growth, patients younger than 5 years were analyzed separately from those aged 5 years and older.

A total of 42 patients with 43 cysts were included. Among 35 patients aged ≥5 years (mean age, 18 years; range, 5-54 years), mean cyst volume was 1.1 mL, with diameters ranging from 3 to 31 mm. Appreciable hippocampal mass effect was present in 21 cases (60%). Mean follow-up interval was 5.7 years (range, 1 month to 23.6 years). Cyst size increased in 2 cases (6%), decreased in 11 (31%), and remained stable in 22 (63%). In patients younger than 5 years (7 patients, 8 cysts), cysts increased in 3 (38%), decreased in 3 (38%), and remained unchanged in 2 (25%).

CFCs can demonstrate significant interval size changes, challenging the traditional view of these lesions as static. More than one-third of cysts in patients aged ≥5 years changed over time, and appreciable hippocampal mass effect was common.