A 39-year-old female with mechanical prosthetic heart valve, taking vitamin K antagonist therapy for 5 years. Presented with history of headache for 10 months and generalized tonicoclonic seizures. On the admission, the patient had a normal physical exam, including a complete normal neurological and cranial nerve exam, with no sensory or motor deficit We performed a computed tomography (CT) of the brain that revealed a large low-density temporal lesion, numerous low-density fat droplets were noted in the subarachnoid space. The MRI could not be performed because of the presence of the prosthetic valve. We prepared the patient for surgery; the management of the anticoagulant treatment was discussed with the cardiologists and anaesthetists because this type of medicine increases the risk of haemorrhage as an operator and after surgery. The patient underwent a large temporal craniotomy and the tumour was exposed and totally excised without any incident, the cyst was formed with keratinaceous and sebaceous secretions. The postoperative CT scan revealed that the tumour mass had been completely removed, however, small fat droplets were spotted in the subarachnoid spaces similar to the preoperative CT scan. The histopathological examination concludes to dermoid cyst. The patient recovered well from surgery, showing no motor or sensory deficit with correct consciousness. The anticonvulsant has been administrated to prevent seizures and the oral anticoagulant treatment has been restarted 1 month after surgery.