Visual Pathways Lecture (PDF)

Visual Pathways • Kelly Roballo DVM, PhD • Chapter 10 and 14 Basic clinical neuroscience Visual cortex: Receptive field • Receptive field is a place where the neuron fire. • Retinotopic maps Cross section of the human eye Relationship of visual field diagrams to patient being examined. Dr...

Visual Pathways • Kelly Roballo DVM, PhD • Chapter 10 and 14 Basic clinical neuroscience Visual cortex: Receptive field • Receptive field is a place where the neuron fire. • Retinotopic maps Cross section of the human eye Relationship of visual field diagrams to patient being examined. Draw them as if they were on the wall the patient is looking at *Clinical Correlation *Clinical Correlation Overview of the visual fields Overview of the visual fields Optic Radiations: Inferior fibers (Meyer’s loop) pass through the temporal lobe. Superior fibers pass through the parietal lobe Layers of the LGN The geniculostriate pathway relays in the LGN and continues to the primary visual cortex via the optic radiations. The extrageniculate pathways by- pass the LGN via the brachium of the superior colliculus and relay in the pretectal area and superior colliculus Optic Radiations: Inferior fibers (Meyer’s loop) pass through the temporal lobe. Superior fibers pass through the parietal lobe The retinogeniculate and geniculostriate pathways in the sagittal plane *Clinical Correlation Visual field defects produced by lesions at different places in the visual pathway Ocular dominance columns and orientation columns in the cortex, and their relationship to the layers of the lateral geniculate nucleus (LGN) Cortical processing of visual information Vestibuloocular Movements Cases • A 62-year-old man comes to the physician because of persistent headaches and increased clumsiness; he cites repeated collisions into door frames. He says that he experienced decreased libido over the same period of time. After further evaluation he is diagnosed with prolactinoma (a pituitary tumor). This patient is most likely to also present with which of the following conditions? • Bitemporal hemianopsia • Dysphagia • Hydrocephalus • Right facial droop *Clinical Correlation Case • A routine magnetic resonance imaging (MRI) reveals the presence of a tumor situated in the left optic tract proximal to the lateral geniculate nucleus. The patient complained of having a reduction in his field of vision. The likely visual deficit can be characterized as • Total blindness of the left eye • Bitemporal hemianopsia • Right homonymous hemianopsia • Left homonymous hemianopsia *Clinical Correlation Cases • After suffering an infarction of the left temporal lobe (Meyers loop), a 52-yearold man develops olfactory auras that precede occasional complex partial seizures. There are no significant postictal deficits, except that the man suffers from anterograde amnesia. Neurologic testing reveals that the man also has a visual field deficit. The visual field deficit is most likely which of the following? • Bitemporal hemianopia • Left homonymous hemianopia • Right superior quadrantanopia. • Optic neuritis *Clinical Correlation