Background: The general use of radiation therapy and radiosurgery as first-line or adjuvant treatment of central nervous system (CNS) lesions has been associated with several harmful effects. Case Description: We report the case of a 16-year-old male patient, submitted at the age of seven to surgical removal of a world heath organization (WHO) grade II diffuse astrocytoma and referred for adjuvant radiosurgery after three further surgeries due to local recurrences. Seven years after radiosurgical treatment, he presented with symptoms of intracranial hypertension. Magnetic resonance imaging (MRI) at the time showed a cavernous malformation in the tumor bed, histologically confirmed, without tumoral recurrence. Conclusion: This case report emphasizes the relation between radiosurgery and the appearance of the novo cavernous malformations, only described previously in one adult patient.