Neurology | Optic Nerve | Cranial Nerve II: Visual Pathway and Lesions

Video Description

Official Ninja Nerd Website: https://ninjanerd.org Ninja Nerds! Join us in this lecture, in which Professor Zach Murphy will discuss the optic nerve and cranial nerve II, focusing on the visual pathway and common lesions. We begin by tracing the journey of visual information from the photoreceptor cells in the retina through the ganglion cell axons that converge to form the optic nerve. From here, we follow the fibers as they pass through the optic canal, reach the optic chiasm where nasal retinal fibers decussate, and continue via the optic tracts to the thalamus's lateral geniculate nucleus (LGN). From the LGN, we track the optic radiations through the temporal and parietal lobes, ultimately terminating in the primary visual cortex of the occipital lobe. In the second part of the lecture, we break down how lesions at different points along this pathway produce distinct visual field deficits. These include monocular blindness from optic nerve lesions, bitemporal hemianopia from optic chiasm damage, homonymous hemianopia from optic tract injury, and quadrantanopias from selective optic radiation involvement. We also explain the difference between lesions involving Meyer’s loop in the temporal lobe and those involving parietal lobe optic radiations, emphasizing clinical localization through visual field testing. We conclude by integrating the optic nerve’s role into the broader sensory system and discussing its importance in neurological examination. We also discuss how pathologies such as multiple sclerosis, pituitary tumors, and stroke can impact this pathway. Enjoy the lecture and support us below! 🌐 Official Links Website: https://www.ninjanerd.org Podcast: https://podcast.ninjanerd.org Store: https://merch.ninjanerd.org 📱 Social Media https://www.tiktok.com/@ninjanerdlectures https://www.instagram.com/ninjanerdlectures https://www.facebook.com/ninjanerdlectures https://x.com/ninjanerdsci/ https://www.linkedin.com/company/ninja-nerd/ 💬 Join Our Community Discord: https://discord.gg/3srTG4dngW #ninjanerd #OpticNerve #CranialNerves