Test Your Knowledge

This submission is a "Test your knowledge" case question crafted around a specific part of the Bony Anatomy of the skull. This question is centered around the anterior cranial fossae and a pathology associated with that specific part of the skull.

Test Your Knowledge • • Walter Moore, BS, Medical Student Sponsoring faculty: Manasa Gunturu, MD & Melanie Truong-Le, DO, OD University of Mississippi Medical Center Departments of Ophthalmology and Neurology Corresponding Author: •Melanie Truong-Le, DO, OD [e-mail] NOVEL: Test Your Knowledge Collection A 34-year-old woman presents to the emergency department with progressive vision loss in her left eye over the past couple of weeks. She also has intermittent headaches, the feeling of “my left eye is going to pop out of my head,” and rhinorrhea that leaves a weird taste in their mouth. On examination, the left pupil responds normally to light but does not constrict during accommodation. There is no ptosis or diplopia. The patient’s medical history is unremarkable, and she denies any past trauma. Fundoscopy shows optic disc pallor. MRI of the brain reveals a wellcircumscribed mass near the cribriform plate, causing bony remodeling. Which of the following structures is most likely compressed by this lesion? A. Oculomotor nerve (CN III) B. Optic nerve (CN II) C. Trochlear nerve (CN IV) D. Trigeminal nerve (CN V) Anterior cranial fossae Correct Answer: B. Optic Nerve (CN II) The optic nerve runs just posterior and superior to the cribriform plate in the anterior cranial fossa. A lesion in this area (i.e., meningioma) can compress CN II, leading to monocular vision loss and a relative afferent pupillary defect. The optic disc pallor supports chronic optic nerve compromise. A. Oculomotor nerve (CN III) – Incorrect. CN III lies in the midbrain and cavernous sinus, not in the anterior cranial fossa. It may produce ptosis, mydriasis, and diplopia, not isolated vision loss. C. Trochlear nerve (CN IV) – Incorrect. CN IV innervates the superior oblique muscle and is not located near the cribriform plate. Lesions produce vertical diplopia. • D. Trigeminal Nerve (CN V)– Incorrect. Lesion of the trigeminal nerve may cause sensory changes but not vision loss OpenStax. "Figure 7.6: Cranial Fossae." Anatomy and Physiology. OpenStax, https://anatomytool.org/content/openstax-anatphys-fig76cranial-fossae-english-labels. Licensed under CC BY 4.0.AnatomyTOOL