The Facial Nerve: Anatomy and Pathology.

The facial nerve is the seventh cranial nerve and consists of motor, parasympathetic and sensory branches, which arise from the brainstem through 3 different nuclei (1). After leaving the brainstem, the facial nerve divides into 5 intracranial segments (cisternal, canalicular, labyrinthine, tympanic, and mastoid) and continues as the intraparotid extracranial segment (2). A wide variety of pathologies, including congenital abnormalities, traumatic disorders, infectious and inflammatory disease, and neoplastic conditions, can affect the facial nerve along its pathway and lead to ​​weakness or paralysis of the facial musculature (1,2). The knowledge of its complex anatomical pathway is essential to clinical and imaging evaluation to establish if the cause of the facial dysfunction is a central nervous system process or a peripheral disease. Both computed tomography (CT) and magnetic resonance imaging (MRI) are the modalities of choice for facial nerve assessment, each of them providing complementary information in this evaluation (1).

Optic pathway gliosarcoma: A very rare location for a rare disease.

Gliosarcoma, a variant of glioblastoma, is a rare and aggressive tumor of the central nervous system (CNS) composed of glial and sarcomatous tissues. Up to now, there are only 2 reported cases of gliosarcoma of the optical pathway. We report a case from March 2018 of a 53-year-old male patient presented with 6 months' of right fronto-orbital pulsatile headache, behavior changes, and visual loss. The MRI study showed an expansile optic pathway lesion involving the chiasm and right optic nerve. The diagnosis of gliosarcoma was obtained by open brain biopsy and immunohistochemical analysis. Although gliosarcoma is rare, it should be considered a differential diagnosis even in optic pathway tumors in older patients. The experience of the neuropathologist with a trained eye can be the differential in the accurate diagnostic process. Optic pathway, Gliosarcoma, Glioblastoma, Magnetic resonance imaging.