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Sensory cranial nerves


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Sensory cranial nerves

  1. 1. the first cranial nerve, or simply CNI, carries the sensory information for the sense of smell. Derived from the embryonic nasal placode, the olfactory nerve is capable of regeneration. The olfactory nerve is sensory in nature and originates on the olfactory mucosa in the anterosuperior nasal cavity.
  2. 2. Smell !
  3. 3. Lesions to the olfactory nerve can occur because of blunt trauma, such as coupcontra-coup damage, meningitis, and tumors of the frontal lobe. They often lead to a reduced ability to taste and smell. However, lesions of the olfactory nerve do not lead to a reduced ability to sense pain from the nasal epithelium. This is because pain from the nasal epithelium is not carried to the central nervous system by the olfactory nerve; rather, it is carried to the central nervous system by the trigeminal nerve (cranial nerve V).
  4. 4. Anosmia |is the inability to perceive odor, or in other words a lack of functioning olfaction. Anosmia may be temporary but traumatic anosmia can be permanent. Anosmia is due to an inflammation of the nasal mucosa; blockage of nasal passages or a destruction of one temporal lobe
  5. 5. Damage to this nerve impairs the sense of smell. To test the function of the olfactory nerve, doctors block one of the patient's nostrils and place a pungent odor (such as damp coffee essence) under the open nostril. The test is then repeated on the other nostril. If the patient can smell the coffee, not necessarily identify what it is, the patient’s olfactory nerve is functioning.
  6. 6. The optic nerve, also known as cranial nerve II, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve does not regenerate after transection.
  7. 7. Vision !
  8. 8. Damage to the optic nerve typically causes permanent and potentially severe loss of vision, as well as an abnormal pupillary reflex, which is diagnostically important. The type of visual field loss will depend on which portions of the optic nerve were damaged. In general: Damage to the optic nerve anterior to the optic chiasm causes loss of vision in the eye on the same side as the damage. Damage in the optic chiasm causes loss of vision laterally in both visual fields (bitemporal hemianopsia). It may occur in large pituitary adenoma. Damage to the optic tract posterior to the chiasm causes loss of vision in the visual field on the side opposite to the damage. Injury to the optic nerve can be the result of congenital or inheritable problems like Leber's Hereditary Optic Neuropathy, glaucoma, trauma, toxicity, inflammation, ischemia, infection (very rarely), or compression from tumors or aneurysms. By far, the three most common injuries to the optic nerve are from glaucoma, optic neuritis (especially in those younger than 50 years of age), and anterior ischemic optic neuropathy (usually in those older than 50). Glaucoma is a group of diseases involving loss of retinal ganglion cells causing optic neuropathy in a pattern of peripheral vision loss, initially sparing central vision.
  9. 9. Optic neuritis is inflammation of the optic nerve. It is associated with a number of diseases, the most notable one being multiple sclerosis. Anterior Ischemic Optic Neuropathy is a particular type of infarct that affects patients with an anatomical predisposition and cardiovascular risk factors. Optic nerve hypoplasia is the underdevelopment of the optic nerve causing little to no vision in the affected eye. Ophthalmologists and optometrists can detect and diagnose some optic nerve diseases but, those sub-specialists that are neuroophthalmologists, are often best suited to diagnose and treat diseases of the optic nerve. The International Foundation for Optic Nerve Diseases (IFOND) sponsors research and information on a variety of optic nerve disorders and may provide general direction.
  10. 10. known as the eighth cranial nerve, transmits sound and equilibrium (balance) information from the inner ear to the brain. The vestibulocochlear nerve is derived from the embryonic otic placode.
  11. 11. Balance & Audition !
  12. 12. Damage to the vestibulocochlear nerve may cause the following symptoms: 1- hearing loss 2- vertigo 3- false sense of motion 4- loss of equilibrium (in dark places) 5- nystagmus 6- motion sickness 7- gaze-evoked tinnitus.