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.