Cranial nerve lesions, part 1 (olfactory & optic nerves) скачать в хорошем качестве

Cranial nerve lesions, part 1 (olfactory & optic nerves)

https://drive.google.com/file/d/1v0u9... This document summarizes lesions and clinical examination techniques for the Olfactory (CN I) and Optic (CN II) cranial nerves. Olfactory Nerve (CN I) Anatomy: Unmyelinated filaments pass through the cribriform plate to the olfactory bulb; it is a direct extension of the CNS. Lesion: Anosmia. Pathology: Common causes of anosmia include trauma (shearing of filaments in cribriform plate fractures) or viral infection. Clinical Exam: Test each nostril separately with non-irritating odors such as coffee or soap, and avoid ammonia, which triggers CN V pain fibers. Clinical Highlight: Foster Kennedy Syndrome (due to an olfactory groove tumor like a meningioma) is a triad of ipsilateral anosmia, ipsilateral optic atrophy, and contralateral papilledema. Optic Nerve (CN II) Examination The CN II exam is divided into four components: Acuity: Measured with a Snellen chart; establishes baseline vision sharpness and targets the macula integrity. Fields: Assessed via confrontation testing to map the visual field and localize a lesion. Neuro-Ophthalmology Golden Rule: The left side of the brain sees the right side of the world, and vice versa. Lesion Signatures: Specific field defects localize a lesion along the visual pathway. Optic Nerve: Monocular Blindness. Optic Chiasm: Bitemporal Hemianopsia (e.g., Pituitary Adenoma). Optic Tract: Contralateral Homonymous Hemianopsia. Optic Radiations (Meyer's Loop in Temporal Lobe): Contralateral Superior Quadrantanopia ("Pie in the Sky"). Optic Radiations (Parietal Lobe): Contralateral Inferior Quadrantanopia ("Pie on the Floor"). Visual Cortex: Contralateral Homonymous Hemianopsia with Macular Sparing (e.g., PCA stroke). Reflexes (Light Reflex): The afferent limb is CN II, and the efferent limb is CN III. The Relative Afferent Pupillary Defect (RAPD), or Marcus Gunn pupil, is a sign of afferent pathway dysfunction. Test: The Swinging-Flashlight Test reveals paradoxical dilation when light is swung to the affected eye. Etiology: RAPD indicates unilateral/asymmetric optic nerve pathology, such as optic neuritis (associated with MS), ischemic optic neuropathy, or compressive optic neuropathy. Differential: RAPD is distinguished from Anisocoria (efferent defect) because the pupils are typically equal at rest. Fundoscopy: Direct visualization of the fundus for: Papilledema: Swelling of the optic disc, indicating intracranial hypertension. Optic Atrophy: Pale optic disc, indicating dead nerve fibers (e.g., advanced MS or long-term compression).