ABSTRACT【Background】Vestibular schwannoma (VS) is a benign tumor, and gamma knife radiosurgery (GKS) is a treatment option for small and medium-size tumors. Radiation-induced cavernous malformation (RICM), a rare type of radiation therapy injury, is predominantly reported in pediatric brain tumor cases. We report a rare case of rapid RICM formation more than 5 years post-GKS for VS, requiring surgical treatment. 【Observations】A 73-year-old man presented with left-sided hearing loss and was diagnosed with VS, for which he underwent GKS. Follow-up magnetic resonance imaging (MRI) showed a transient tumor expansion, followed by shrinkage. However, 5 years post-GKS, the patient developed worsening left hearing loss and ataxic gait. MRI revealed a 30-mm cystic lesion in the left cerebellopontine angle, exerting brainstem compression. The lesion was surgically excised, and histopathological analysis revealed features of both VS and cavernous malformation-like lesion. 【Lessons】This case highlights the occurrence of RICM 5 years after GKS for VS, leading to rapid neurological decline. Although exceedingly rare, long-term follow-up should be considered to avoid rapid deterioration of neurological symptoms due to RICM. Surgical excision is recommended for symptomatic lesion and provides symptomatic relief.
WATANABE et al. (Wed,) studied this question.