In clinical practice, olfactory nerve is not used as a routine screening.
The following patients should be carefully examined for damage to the olfactory nerve
Head injury (the olfactory nerve is torn from the cribriform plate), Extraparenchymal brain tumors at the base of the frontal lobe (olfactory groove meningiomas) or Nasal intraepithelial tumors (neurosensory blastoma), Vitamin B12 deficiency , Kalmann Patients with syndrome (ovarian agenesis) and neurodegenerative diseases such as multiple system atrophy, Parkinson's disease , Alzheimer's disease and other diseases.
How to do
(1) First, ask the patient whether he has subjective olfactory disorders such as olfactory hallucinations, and first check whether the patient's nasal cavity is unobstructed to rule out local lesions in the nasal cavity itself. This test cannot be done when there is inflammation or obstruction in the nasal cavity.
(2) Instruct the patient to close his eyes . The examiner presses or blocks one nostril of the patient with his fingers, selects several substances with identifiable odors, puts them into several bottles with the same appearance, and places them in the patient's nostril under examination. Ask the patient to name the odor he or she smells. After testing one side, check the opposite side in the same way.
* In the "DeMyer Neurological Examination", it is recommended that when changing the other nostril for testing, the corresponding stimulation should not be provided first. This is used to test the patient's suggestibility and attention.
Options include: lemonade, perfume, mint water, soap, toothpaste, tea, camphor , turpentine, etc.
Inspection findings
Loss of smell: When the sense of smell is normal, the smell of various test items can be correctly distinguished. Otherwise, it is a loss of smell, which can be divided into unilateral or bilateral loss of smell. The differential diagnosis of hyposmia/loss of smell is as follows:
Hyperolfactory: is more common in hysteria.
phantom smell: Irritating lesions of the olfactory center can cause phantom smell attacks, such as temporal lobe epilepsy . Also seen in schizophrenia, hysteria, ethanol withdrawal, and Alzheimer's disease.
Supplementary knowledge
. Simple methods and quantitative inspection methods
Simple method: Take something beside the bed, such as a piece of fruit, an orange or a bottle of juice, and let the patient identify whether the smell is normal.
Quantitative detection method: If careful measurement or comparison is required, an olfactometer can be used to measure the minimum amount of gas that produces the sense of smell. The method is to use a syringe to fill a predetermined gas, and then slowly inject it into the olfactometer. When the patient can identify the type of odor, the amount of gas required is recorded.
. Regarding irritating substances
The sensory fibers of the olfactory epithelium come from two pairs of cranial nerves: I olfactory nerve and V trigeminal nerve . Among them, only the I olfactory nerve is related to the sense of smell.
Irritating substances such as ammonia, acetic acid, ethanol and formaldehyde solution can stimulate trigeminal nerve endings. Most textbooks believe that these should not be used for olfactory examination.
However, in "Easy Nervous System Examination", ammonia is used in the olfactory examination, and the examination method is the same as before. The examination findings are as follows:
- patients can properly identify various odors - normal sense of smell;
- patients cannot identify odors, but can identify ammonia - anosmia.
- The patient was unable to identify any odor, including ammonia—considering that the loss of smell may not be entirely organic.
. Some nouns
Anosmia: no sense of smell.
Hyposmia: Reduced perception of smells.
Hyperosmia: Overly sensitive to smells.
Osmia: Impaired or impaired perception of smells.
Parosmia: An inverted or distorted perception of smells.
Phantom smell: being able to sense smells that do not exist.
Olfaction aging: loss of sense of smell due to aging.
Odor hallucination: A very unpleasant smell.
Fecal hallucination: the stench of excrement.
Olfaction: The inability to identify or identify perceived odors.
