Diagnosis and surgical management of a type IVb dermoid sinus in a Cavalier King Charles Spaniel

Abstract

A 6-year-old, male, neutered Cavalier King Charles Spaniel dog was referred with a 4-year history of an intermittently draining fistula on the midline of the frontal bones of the skull. Magnetic resonance imaging and computed tomography scan of the head demonstrated an extra-axial mass in the midline between the frontal lobes, contacting the meninges and extending rostrally through a defect in the frontal bones. The mass was surgically excised via a frontal craniotomy. Histopathology of the mass demonstrated stratified squamous and keratinising epithelium with adnexal structures, consistent with the diagnosis of a dermoid sinus. Previous reports have documented dermoid sinuses in the nasal region in dogs and cats with intracranial extension. This case report documents a dermoid sinus in the frontal region with intracranial extension in a dog, confirmed by advanced diagnostic imaging, histopathology, and successfully treated surgically.