Natural course of pineal cysts—a radiographic study

BACKGROUND: Pineal cysts (PCs) are a benign lesion of the pineal gland that have been known to the medical community for a long time. With a prevalence rate of approximately 1% in the general population, PC is often a reason for medical counseling. The natural course of PC morphology has not been well described. In this study, we present a longitudinal magnetic resonance imaging (MRI) study of patients with PCs, with special focus on those who showed an increase or decrease in PC size. METHODS: We enrolled all patients with a PC who were referred to our department between January 2000 and January 2018. Each patient underwent a clinical examination, and the patient’s age, sex, and presenting signs and symptoms were noted. MRI was performed during periodic examinations, and a clinical and radiological course was reassessed. RESULTS: In total, 133 patients (99 women, 34 men) were enrolled. The mean maximum diameter was 12.7 ± 5.2 mm (range 7–35 mm). PCs increased in size during the follow-up in seven patients (5.3%) and decreased in size in 10 (7.5%). The remaining cysts (n = 116, 87.2%) were stable over the follow-up period. Analyzing patients according to cyst size change, we found a significant difference in the mean age between the PC progression group and PC regression group (p = 0.01). The mean size of the PCs at the time of diagnosis did not differ significantly between the two groups (p = 0.81). We diagnosed two cases of pineal apoplexy. CONCLUSION: We found that PCs are a dynamic structure that may change in size during the patient’s lifetime. Patients with an increase in PC size were significantly younger than patients with a decrease in size. Therefore, PC growth in the first, second, and third decennium is normal and does not justify medical intervention. Surgery is indicated in cases of hydrocephalus and Parinaud’s syndrome or in atypical cysts when neoplasia is suspected. The size of a PC does not predict PC behavior in terms of a future increase or decrease in size.