Mature filum terminale teratoma. Excision guided by direct stimulation of nerve roots. / Teratoma maduro del filum terminale. Extirpación guiada por estimulación directa de raíces nerviosas.

A 45-year-old male patient, with no history of interest, consulted in emergency department due to a progressive loss of strength in the lower limbs at the distal level with impossibility for dorsal flexion of the left foot, as well as neurogenic bladder. The MRI revealed a mass at the filum terminale with completed occupation of transverse diameter of the dural sac. The radiological diagnosis was lipoma of filum terminale. The patient underwent surgery with intraoperative neurophysiological monitoring using direct stimulation of nerve roots, which allowed the removal of a tumour composed of sebaceous material, fat and hair. The anatomopathological study classified it as a mature cystic teratoma. Postoperative evolution was favorable.