Abstract
BACKGROUND: Spontaneous regression is relatively rare in meningiomas. Since meningiomas are known to have a relationship with sex-related hormones, spontaneous regression cases related to sex hormones have been reported. OBSERVATIONS: A 66-year-old man with a petroclival meningioma was radiologically followed up for 13 years. The tumor initially measured 2.535 cm3 and 2.521 cm3 on gadolinium-enhanced magnetic resonance imaging (MRI) and fast imaging employing steady-state acquisition MRI, respectively. However, the measurements decreased in the follow-up period to 0.977 cm3 and 0.98 cm3, respectively, demonstrating spontaneous regression of an asymptomatic meningioma located in a petroclival area. Continuous meticulous long-term follow-up revealed this phenomenon. LESSONS: It is important to retain the option of conservative treatment for patients ineligible for surgery for reasons such as advanced age and coexisting diseases. https://thejns.org/doi/10.3171/CASE24416.