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Cranial Nerve I
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Olfactory Nerve Clinical Notes and Interpretation
  • A patient will not typically report loss of olfactory sense unless both olfactory bulbs are involved.
  • Sense of smell may be altered by nasal or sinus problems.
  • Sense of smell may be lost post-trauma secondary to tearing of the olfactory stria from the cribriform plate of the ethmoid bone.
  • Loss of smell should alert the clinician to examine the patient for other signs of possible frontal lobe injury, such as changes in personality or unexplained visual loss.
  • Unilateral loss is more significant, as it represents a more localized presentation of olfactory dysfunction.
  • Sudden loss of smell (anosmia) is common with severe traumatic brain injuries secondary to damage of the olfactory nerve or with infections that damage olfactory receptors.
  • Gradual loss of smell may indicate a tumor that is typically located at the base of the cranial fossa or may also be an early indicator of Alzheimer's.
  • With non-organic anosmia the patient typically fails to react to ammonia.
  • With true anosmia, ammonia should be sensed by the patient because ammonia acts by stimulating the pain endings of the trigeminal nerve.
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Section: Cranial Nerve I
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