Dermoid cysts originate from embryonic tissues trapped in the cranial fusion lines and typically manifest extra-axially. However, intradiploic dermoid cysts are rare among cranial tumors, and their rupture has been sparsely documented. We present a case showcasing a remarkable phenomenon—the spontaneous rupture of an intradiploic dermoid cyst into the subarachnoid space, displaying a distinct “volcano-like” appearance on CT and MRI scans. This case represents the first documented instance of spontaneous intracranial rupture of an intradiploic dermoid cyst into the subarachnoid space. Although uncommon, this rupture poses a risk of severe complications, such as chemical meningitis and vasospasm. This extraordinary presentation of an uncommon lesion at an atypical location may contribute to a better understanding of the potential mechanisms of rupture, thereby emphasizing the importance of recognition and exploration.

Dermoid cysts originate from embryonic tissues trapped in the cranial fusion lines and typically manifest extra-axially. However, intradiploic dermoid cysts are rare among cranial tumors, and their rupture has been sparsely documented. We present a case showcasing a remarkable phenomenon—the spontaneous rupture of an intradiploic dermoid cyst into the subarachnoid space, displaying a distinct “volcano-like” appearance on CT and MRI scans. This case represents the first documented instance of spontaneous intracranial rupture of an intradiploic dermoid cyst into the subarachnoid space. Although uncommon, this rupture poses a risk of severe complications, such as chemical meningitis and vasospasm. This extraordinary presentation of an uncommon lesion at an atypical location may contribute to a better understanding of the potential mechanisms of rupture, thereby emphasizing the importance of recognition and exploration.

Dermoid cysts originate from embryonic tissues trapped in the cranial fusion lines and typically manifest extra-axially. However, intradiploic dermoid cysts are rare among cranial tumors, and their rupture has been sparsely documented. We present a case showcasing a remarkable phenomenon—the spontaneous rupture of an intradiploic dermoid cyst into the subarachnoid space, displaying a distinct “volcano-like” appearance on CT and MRI scans. This case represents the first documented instance of spontaneous intracranial rupture of an intradiploic dermoid cyst into the subarachnoid space. Although uncommon, this rupture poses a risk of severe complications, such as chemical meningitis and vasospasm. This extraordinary presentation of an uncommon lesion at an atypical location may contribute to a better understanding of the potential mechanisms of rupture, thereby emphasizing the importance of recognition and exploration.