Cranial nerves Flashcards
What is the primary function of Cranial Nerve I (CN I)?
Smell
* Sensory in function
Responsible for the sense of smell (olfaction)
How is the integrity of Cranial Nerve I tested?
Have the patient close their eyes and occlude a nostril, present an aromatic agent, and ask for identification
Repeat the process with the other nostril using a different aromatic agent
What substances are commonly used to test olfaction?
- Vanilla
- Mint oil
- Coffee
- Chocolate
The aromatic substances should not be irritating
What can cause a unilateral loss of olfaction?
Meningiomas
These tumors affect the olfactory nerve
What factors may lead to bilateral loss of olfaction?
- Obstruction of the nasal passage
- Heavy smoking
- Rhinitis (stuffy nose)
- Hay fever
- A cold
These conditions can affect the sense of smell
What is the primary function of Cranial Nerve II (CN II)?
Vision
* Sensory in function
Responsible for vision
How can the integrity of the optic nerve be assessed?
- Testing visual acuity
- Testing visual fields
Visual acuity is tested monocularly, while visual fields can be assessed using confrontation or counting finger methods
What is the method for testing visual acuity?
Performed monocularly, at distance and near, with the patient’s best correction in place
This ensures accurate measurement of vision
What methods can be used to test visual fields?
- Confrontation method
- Counting finger method
These methods are performed without correction in place to avoid interference
What should be done if a defect is noted in visual fields during testing?
Further quantify via automated visual field testing
This provides a more detailed assessment of visual field defects
What is the purpose of red cap desaturation testing?
To compare the level of saturation of a red target between the eyes
This test helps in assessing the integrity of the optic nerve.
How is red cap desaturation testing performed?
With one eye occluded, a red object is presented to each eye, and saturation levels are compared
The test should be conducted in a fully illuminated room.
What perceived difference in saturation indicates a likely afferent pupillary defect (APD)?
A perceived difference of 20% or more
This suggests abnormalities in the optic nerve.
What is assessed during the observation of the optic nerve?
The overall integrity and health of the optic nerve
This includes techniques such as ophthalmoscopy and fundus lenses.
Where is the nucleus of Cranial Nerve III located?
In the midbrain
CN III is also known as the oculomotor nerve.
What muscles does the oculomotor nerve supply?
- Medial rectus
- Superior rectus
- Inferior rectus
- Inferior oblique
- Levator palpebral muscles
It is also involved in pupil and accommodative innervation.
What should patients not be wearing during the pupillary reaction assessment?
Glasses
This ensures accurate assessment of the pupillary response.
What is considered a normal pupillary reaction to light compared to near response?
More brisk
The pupillary reaction to light should be quicker than that associated with near response.
What is the purpose of extraocular motility testing?
To assess any restrictions or asymmetries in eye movement
Patients are asked to fixate on a target moved into the nine fields of gaze.
What should happen to both pupils when a near stimulus is presented?
Both pupils should constrict equally
This indicates a normal accommodative response.
What is the function of Cranial Nerve IV (CN IV)?
Motor in function
Where is the nucleus of Cranial Nerve IV located?
In the midbrain
What muscle does Cranial Nerve IV innervate?
Superior oblique muscles
How is the integrity of CN IV tested?
Assessing extraocular motility for any deficits
* superior oblique
What are the main functions of Cranial Nerve V (CN V)?
Motor and sensory functions
In which part of the brain is the nucleus of Cranial Nerve V located?
In the pons
What are the three main divisions of the trigeminal nerve?
- Ophthalmic (V1)
- Maxillary (V2)
- Mandibular (V3)
What are the subdivisions of the ophthalmic division (V1) of CN V?
- Nasociliary
- Frontal
- Lacrimal
NFL!!!
Which subdivision of V1 is most commonly affected by herpes zoster ophthalmicus?
Frontal division
What are the subdivisions of the nasociliary division of V1?
LINE
* Long ciliary
* Infratrochlear
* Nasal
* Posterior Ethmoid
What areas does the ophthalmic portion of CN V supply?
- Eyes
- Nose
- Forehead
- Temples
- Paranasal sinuses
- Nasal mucosa
What areas does the maxillary division of CN V supply?
- Teeth
- Cheeks
- Lips
- Upper jaw
- Maxillary sinuses
- Hard palate
- Nasal mucosa
What areas does the mandibular division of CN V supply?
- Teeth
- Lip
- Lower jaw
- Tongue
- Buccal mucosa
- External ear
- Auditory meatus
- Meninges
*sensory innervation to lower face
*motor innervation to muscles of mastication
What muscles do the motor fibers of CN V supply?
- Muscles responsible for mastication
- Mylohyoid muscle
- Anterior belly of the digastric
- Tensor veli palatini
- Tensor tympani
What is the method for testing the corneal reflex?
Patient’s gaze is directed away while the clinician touches the corneal surface with a cotton wisp
True or False: The reaction of each eye is compared during corneal reflex testing.
True
What is the function of Cranial Nerve V (CN V)?
Sensory and motor functions
CN V is also known as the Trigeminal Nerve and is responsible for sensation in the face and motor functions such as biting and chewing.
What are the three divisions of CN V?
- Opthalmic division
- Maxillary division
- Mandibular division
Each division is responsible for sensation in different areas of the face.
How can CN V be assessed via superficial stimulation?
By brushing the jawbone, base of nostrils, and forehead with a cotton-tipped applicator
The patient should be able to locate where they were brushed.
What does palpation of masseter muscles assess in CN V?
Muscle clenching, asymmetries, and resistance to closure
Any irregularities may suggest a neurological defect.
What is the function of Cranial Nerve VI (CN VI)?
Motor function
CN VI is also known as the Abducens Nerve.
Where does the nucleus of CN VI lie?
In the pons
The pons is a part of the brainstem.
What muscle does CN VI supply?
Lateral rectus muscle
This muscle is responsible for moving the eye laterally.
How can CN VI be tested?
By assessing extraocular motility
This tests for any potential restrictions or deficits in eye movement.