Cranial Nerves: Difference between revisions
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'''Original Editor '''- [[User:Tarina van der Stockt|Tarina van der Stockt]] | '''Original Editor ''' - [[User:Tarina van der Stockt|Tarina van der Stockt]] | ||
'''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}} | '''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}} | ||
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== Description | == Description == | ||
[[File:Cranial_Nerves_2.png|border|right|frameless|393x393px]] | |||
Twelve pairs of nerves (the cranial nerves) lead directly from the brain to various parts of the head, neck, and trunk. Some of the cranial nerves are involved in the special senses (such as seeing, hearing, and taste), and others control muscles in the face or regulate glands. The nerves are named and numbered (according to their location, from the front of the [[Brain Anatomy|brain]] to the back). | |||
Image 1: Twelve pairs of cranial nerves emerge from the underside of the brain, pass through openings in the skull, and lead to parts of the head, neck, and trunk. The nerves are named and numbered, based on their location, from the front of the brain to the back. Thus, the olfactory nerve is the 1st cranial nerve, and the hypoglossal nerve is the 12th cranial nerve | |||
[[ | Unlike spinal nerves whose roots are neural fibers from the spinal grey matter, cranial nerves are composed of the neural processes associated with distinct [[brainstem]] nuclei and cortical structures.<ref>Sonne J, Lopez-Ojeda W. [https://www.ncbi.nlm.nih.gov/books/NBK470353/ Neuroanatomy, cranial nerve.] InStatPearls [Internet] 2019 Apr 3. StatPearls Publishing.</ref><ref>Sonne J, Lopez-Ojeda W. Neuroanatomy, Cranial Nerve.[Updated 2021 Nov 14]. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. 2022. [https://www.ncbi.nlm.nih.gov/books/NBK470353/]</ref> | ||
The names of the cranial nerves (CN) are: [[Olfactory Nerve|CN I - Olfactory]], [[Optic Nerve|CN II - Optic]], [[Oculomotor Nerve|CN III - Oculomotor]], CN IV - [[Trochlear Nerve|Trochlear]], [[Trigeminal Nerve|CN V - Trigeminal]], [[Abducens Nerve|CN VI - Abducens]], [[Facial Nerve|CN VII - Facial]], CN VIII - Vestibulocochlear, CN IX - [[Glossopharyngeal Nerve|Glossopharyngeal]], [[Vagus Nerve|CN X - Vagus]], [[Accessory Nerve Cranial Nerve 11|CN XI - Accessory]], and CN XII - [[Hypoglossal Nerve|Hypoglossal]]. <ref name="Ana">McKinley M, O'Loughlin VD. Human Anatomy. 2nd ed. New York: McGraw-Hill, 2008fckLRfckLRHill C. Practical guidelines for cystic fibrosis care. Edinburgh: Churchill Livingstone, 1998.</ref> Link: [[Introduction to Neuroanatomy|Introduction to Neuroanatomy]] | |||
<ref>Image: Wikipedia, https://en.wikipedia.org/wiki/Trochlear_nerve (accessed 12 Oct 2016)</ref><br> | |||
== Function == | == Function == | ||
The names of the cranial nerves sometimes correspond with their individual function. | The names of the cranial nerves sometimes correspond with their individual function. Some of the cranial nerves are purely sensory, others are purely motor, and the rest have both sensory and motor components. <ref>Butler A.B. Encyclopedia of the Human Brain, Four-Volume Set. Academic Press; 2002.</ref><br> | ||
{| width="468" cellspacing="1" cellpadding="1" border="1" | {| width="468" cellspacing="1" cellpadding="1" border="1" | ||
|+ Cranial nerves and their primary functions<ref name="Ana" /><ref name="Pat">Fuller KS, Introduction to Central Nervous System Disorders. Goodman CC, Fuller KS. Pathology: implications for the physical therapist. Elsevier Health Sciences; 2014. p1371-1404</ref> | |+ '''Cranial nerves and their primary functions'''<ref name="Ana" /><ref name="Pat">Fuller KS, Introduction to Central Nervous System Disorders. Goodman CC, Fuller KS. Pathology: implications for the physical therapist. Elsevier Health Sciences; 2014. p1371-1404</ref> | ||
|- | |- | ||
! scope="col" | Cranial Nerve | ! scope="col" | Cranial Nerve | ||
! scope="col" | Sensory Function | ! scope="col" | Sensory Function | ||
! scope="col" | Somatic Motor Function | ! scope="col" | Somatic Motor Function | ||
! scope="col" | Autonomic ( | ! scope="col" | Autonomic (Parasympathetic Motor) Function | ||
|- | |- | ||
! scope="row" | CN I - | ! scope="row" | CN I - [[Olfactory Nerve|Olfactory]]<br> | ||
| Smell (olfaction)<br> | | Smell (olfaction)<br> | ||
| -<br> | | -<br> | ||
| -<br> | | -<br> | ||
|- | |- | ||
! scope="row" | CN II - | ! scope="row" | CN II - [[Optic Nerve|Optic]]<br> | ||
| Vision<br> | | Vision<br> | ||
| -<br> | | -<br> | ||
| -<br> | | -<br> | ||
|- | |- | ||
! scope="row" | CN III - | ! scope="row" | CN III - [[Oculomotor Nerve|Oculomotor]]<br> | ||
| -<br> | | -<br> | ||
| Innervates the inferior oblique muscle and medial, inferior, and superior rectus muscles of the eye (move the eye); levator palpebrae superioris muscle (elevate eyelid)<br> | | Innervates the inferior oblique muscle and medial, inferior, and superior rectus muscles of the eye (move the eye); levator palpebrae superioris muscle (elevate eyelid)<br> | ||
| Innervates the sphincter pupillae muscle (constricts the pupil), and the ciliary muscle (accomodate the eye for near vision)<br> | | Innervates the sphincter pupillae muscle (constricts the pupil), and the ciliary muscle (accomodate the eye for near vision)<br> | ||
|- | |- | ||
! scope="row" | CN IV - | ! scope="row" | CN IV - [[Trochlear Nerve|Trochlear]]<br> | ||
| - <br> | | - <br> | ||
| Innervate the superior oblique eye muscle (moves the eye inferiorly and laterally)<br> | | Innervate the superior oblique eye muscle (moves the eye inferiorly and laterally)<br> | ||
| -<br> | | -<br> | ||
|- | |- | ||
! scope="row" | CN V - | ! scope="row" | CN V - [[Trigeminal Nerve|Trigeminal]]<br> | ||
| Conducts touch, temperature and pain sensation from the face, nose, mouth, nasal and oral mucosa, | | Conducts touch, temperature and pain sensation from the face, nose, mouth, nasal and oral mucosa, anterior two-thirds of tongue, and anterior scalp; part of auricle of the ear<br> | ||
| Innervate the muscles of mastication, mylohyoid, digastric (anterior belly), tensor veli palatini, and tensor tympani<br> | | Innervate the muscles of mastication, mylohyoid, digastric (anterior belly), tensor veli palatini, and tensor tympani<br> | ||
| - <br> | | - <br> | ||
|- | |- | ||
! scope="row" | CN VI - | ! scope="row" | CN VI - [[Abducens Nerve|Abducens]]<br> | ||
| - <br> | | - <br> | ||
| Innervate the lateral rectus muscle of eye (abducts the eye)<br> | | Innervate the lateral rectus muscle of eye (abducts the eye)<br> | ||
| -<br> | | -<br> | ||
|- | |- | ||
! scope="row" | CN VII - [[ | ! scope="row" | CN VII - [[Facial nerve|Facial]]<br> | ||
| Taste from anterior two-thirds of tongue<br> | | Taste from anterior two-thirds of tongue<br> | ||
| Innervate muscles of facial expression, digastric (posterior belly) and stapedius muscle<br> | | Innervate muscles of facial expression, digastric (posterior belly), stylohyoid and stapedius muscle<br> | ||
| Increase secretion from the lacrimal (tear glands) and nasal mucosal glands; [[ | | Increase secretion from the lacrimal (tear glands) and nasal mucosal glands; [[Dry Mouth|submandibular and sublingual<br>salivary glands]]<br> | ||
|- | |- | ||
! scope="row" | CN VIII - | ! scope="row" | CN VIII - [[The Vestibulocochlear Nerve (CN VIII)|Vestibulocochlear]]<br> | ||
| Hearing (cochlear branch); linear and angular acceleration, or head position in space/equilibrium<br>(vestibular branch)<br> | | Hearing (cochlear branch); linear and angular acceleration, or head position in space/equilibrium<br>(vestibular branch)<br> | ||
| -<br> | | -<br> | ||
| -<br> | | -<br> | ||
|- | |- | ||
! scope="row" | CN IX - | ! scope="row" | CN IX - [[Glossopharyngeal Nerve|Glossopharyngeal]]<br> | ||
| Touch and taste from the posterior 1/3 of the tongue; visceral sensory from the carotid bodies<br> | | Touch and taste from the posterior 1/3 of the tongue; visceral sensory from the carotid sinus and bodies<br> | ||
| Innervate the pharyngeal muscle<br> | | Innervate the pharyngeal muscle Stylopharyngeus<br> | ||
| [[ | | [[Dry Mouth|Increase secretion from the parotid salivary gland]]<br> | ||
|- | |- | ||
! scope="row" | CN X - | ! scope="row" | CN X - [[Vagus Nerve|Vagus]]<br> | ||
| Visceral sensation (excluding pain) from heart, lungs, abdominal organs, bronchi, trachea, larynx, pharynx, gastrointestinal<br>tract to level of descending colon | | Visceral sensation (excluding pain) from heart, lungs, abdominal organs, bronchi, trachea, larynx, pharynx, gastrointestinal<br>tract to level of descending colon. | ||
General sensation from the external acoustic meatus, eardrum, and pharynx<br> | General sensation from the external acoustic meatus, eardrum, and pharynx<br> | ||
| Innervates pharyngeal and laryngeal muscles and muscles at base of tongue<br> | | Innervates pharyngeal and laryngeal muscles and muscles at base of tongue<br> | ||
| Innervates smooth | | Innervates smooth muscles and glands of the heart, lungs larynx, trachea, and most abdominal organs<br> | ||
|- | |- | ||
! scope="row" | CN XI - | ! scope="row" | CN XI - [[Accessory Nerve Cranial Nerve 11|Accessory]]<br> | ||
| - <br> | | - <br> | ||
| Innervates the trapezius and sternocleidomastoid muscle<br> | | Innervates the trapezius and sternocleidomastoid muscle<br> | ||
| -<br> | | -<br> | ||
|- | |- | ||
! scope="row" | CN XII - | ! scope="row" | CN XII - [[Hypoglossal Nerve|Hypoglossal]]<br> | ||
| - <br> | | - <br> | ||
| Innervates intrinsic and extrinsic tongue muscles<br> | | Innervates intrinsic and extrinsic tongue muscles<br> | ||
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<br> | <br> | ||
{{#ev:youtube|FtJtYMRVw7A}}<br> | {{#ev:youtube|FtJtYMRVw7A}}<ref>Youtube Video: MEDZCOOL - How to Remember the Cranial Nerves (Mnemonic) https://youtu.be/6ENCJkXJvio (accessed 12 Oct 2016)</ref><br> | ||
== Dysfunction of Cranial nerves == | |||
Dysfunction of certain cranial nerves may affect the eye, pupil, optic nerve, or extraocular muscles and their nerves; thus, they can be considered cranial nerve disorders, neuro-ophthalmologic disorders, or both. | |||
== Clinical Relevance and Assessment <ref name="Ed">O'Sullivan SB, Neuromuscular Physical Therapy. In: O'Sullivan SB, Siegman RP. National Physical Therapy Examination Review & | Cranial nerve disorders can also involve dysfunction of smell, vision, chewing, facial sensation or expression, taste, hearing, balance, swallowing, phonation, head turning and shoulder elevation, or tongue movements (see table below). One or more cranial nerves may be affected. | ||
These disorders can result from tumors, inflammation, trauma, systemic disorders, and degenerative or other processes, causing such symptoms as vision loss, diplopia, ptosis, pupillary abnormalities, periocular pain, facial pain, or headache<ref>MSD manauls Overview of Neuro-ophthalmologic and Cranial Nerve Disorders Available from: https://www.msdmanuals.com/professional/neurologic-disorders/neuro-ophthalmologic-and-cranial-nerve-disorders/overview-of-neuro-ophthalmologic-and-cranial-nerve-disorders (accessed 4.2.2021)</ref>. | |||
Treatment of neuro-ophthalmologic and cranial disorders depends on the cause. | |||
== Clinical Relevance and Assessment <ref name="Ed">O'Sullivan SB, Neuromuscular Physical Therapy. In: O'Sullivan SB, Siegman RP. National Physical Therapy Examination Review & Study Guide. 19th edit. Evanston: TherapyEd, 2016. p121-184</ref><ref name="Fun">Chui KK, Schmitz TJ. Examination in Sensory Function. In: Physical Rehabilitation. 6th Edit. Philadelphia: O’Sullivan SB, Schmitz TJ, Fulk GD F.A. Davis Company, 2014. P87-121</ref> == | |||
{| width="200" cellspacing="1" cellpadding="1" border="1" | {| width="200" cellspacing="1" cellpadding="1" border="1" | ||
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! scope="col" | Involvement<br> | ! scope="col" | Involvement<br> | ||
|- | |- | ||
! scope="row" | CN I - | ! scope="row" | CN I - [[Olfactory Nerve|Olfactory]]<br> | ||
| - Test sense of smell | | - Test sense of smell by closing the other nostril and using non-irritating odors like coffee, lemon oil, etc<br> | ||
| - Inability to detect smells (Anosmia) = | | - Inability to detect smells (Anosmia) = temporal lobe lesions<br> | ||
|- | |- | ||
! scope="row" | CN II - | ! scope="row" | CN II - [[Optic Nerve|Optic]]<br> | ||
| - Test visual acuity using a Snellen chart, test central and peripheral vision<br> | | - Test visual acuity using a Snellen chart, test central and peripheral vision<br> | ||
| - Blindness, impaired vision: far (myopia) and near (presbyopia) <br> | | - Blindness, impaired vision: far (myopia) and near (presbyopia) <br> | ||
|- | |- | ||
! scope="row" | CN II – | ! scope="row" | CN II – [[Optic Nerve|Optic]]<br>CN III – [[Oculomotor Nerve|Oculomotor]]<br> | ||
| - Test pupil equality, size and shape<br>- Test pupil constriction by shining a light in the eye<br> | | - Test pupil equality, size and shape<br>- Test pupil constriction by shining a light in the eye<br> | ||
| - Absence of pupil constriction<br>- Unequal pupils (anisocoria)<br>- Horner’s syndrome<br>- CN III paralysis<br> | | - Absence of pupil constriction<br>- Unequal pupils (anisocoria)<br>- Horner’s syndrome<br>- CN III paralysis<br> | ||
|- | |- | ||
! scope="row" | CN III – | ! scope="row" | CN III – [[Oculomotor Nerve|Oculomotor]]<br>CN IV – [[Trochlear Nerve|Trochlear]]<br>CN VI - [[Abducens Nerve|Abducens]]<br> | ||
| - Test extraocular movements<br>- Observe eye position, presence of strabismus (loss of ocular alignment) or ptosis of eyelid<br>- Test pursuit eye movement without head movement<br> | | - Test extraocular movements<br>- Observe eye position, presence of strabismus (loss of ocular alignment) or ptosis of eyelid<br>- Test pursuit eye movement without head movement<br> | ||
| - Strabismus and impaired eye movement<br>- CN III: Ptosis, pupil dilation<br>- CN IV: Eye cannot look down when adducted<br>- CN VI: Eye pulled inward, eye cannot look out<br> | | - Strabismus and impaired eye movement<br>- CN III: Ptosis, pupil dilation<br>- CN IV: Eye cannot look down when adducted<br>- CN VI: Eye pulled inward, eye cannot look out<br> | ||
|- | |- | ||
! scope="row" | CN V - | ! scope="row" | CN V - [[Trigeminal Nerve|Trigeminal]]<br> | ||
| - Pain and light touch sensation of face (forehead, cheeks, jaw)<br>- Open and close jaw against resistance<br>- Test corneal and jaw jerk reflex<br> | | - Pain and light touch sensation of face (forehead, cheeks, jaw)<br>- Open and close jaw against resistance<br>- Test corneal and jaw jerk reflex<br> | ||
| - Loss of facial sensation and numbness<br>- Loss of ipsilateral corneal reflex<br>- Weakness and wasting of mastication muscles<br>- Jaw deviation when opened to ipsilateral side<br> | | - Loss of facial sensation and numbness<br>- Loss of ipsilateral corneal reflex<br>- Weakness and wasting of mastication muscles<br>- Jaw deviation when opened to ipsilateral side<br> | ||
|- | |- | ||
! scope="row" | CN VII - [[Facial nerve| | ! scope="row" | CN VII - [[Facial nerve|Facial]]<br> | ||
| - Test motor function of the facial muscles and look for asymmetry: raise eyebrows, frown, smile, close eyes tightly, puff cheeks, etc.<br> | | - Test motor function of the facial muscles and look for asymmetry: raise eyebrows, frown, smile, close eyes tightly, puff cheeks, etc.<br> | ||
| - Ipsilateral paralysis of facial muscles: unable to close eye, mouth corner droops, difficulty with speech articulation<br>= peripheral nerve injury (PNI) Bell’s Palsy ([[Facial Palsy|CN VII]]); or facial paralysis due to stroke<br> | | - Ipsilateral paralysis of facial muscles: unable to close eye, mouth corner droops, difficulty with speech articulation<br>= peripheral nerve injury (PNI) Bell’s Palsy ([[Facial Palsy|CN VII]]); or facial paralysis due to stroke<br> | ||
|- | |- | ||
! scope="row" | CN VIII - | ! scope="row" | CN VIII - [[The Vestibulocochlear Nerve (CN VIII)|Vestibulocochlear]]<br> | ||
| - Test balance<br>- Gaze instability with head rotations <br>- Test auditory acuity with a tuning fork placed in the middle on top of the head and check if the sound is equal or louder in one ear (Weber’s test)<br>- Vibrating tuning fork place on mastoid bone, then near the ear canal and note hearing acuity (Rinne’s test)<br> | | - Test balance<br>- Gaze instability with head rotations <br>- Test auditory acuity with a tuning fork placed in the middle on top of the head and check if the sound is equal or louder in one ear (Weber’s test)<br>- Vibrating tuning fork place on mastoid bone, then near the ear canal and note hearing acuity (Rinne’s test)<br> | ||
| - Vertigo and disequilibrium<br>- Nystagmus<br>- Deafness, tinnitus and hearing loss<br>- Unilateral conductive loss<br>- Sensorineural loss: sound heard in good ear<br>- Conductive loss: sound heard through bone is longer or equal than air<br>- Sensorineural loss: sound heard longer through air<br> | | - Vertigo and disequilibrium<br>- Nystagmus<br>- Deafness, tinnitus and hearing loss<br>- Unilateral conductive loss<br>- Sensorineural loss: sound heard in good ear<br>- Conductive loss: sound heard through bone is longer or equal than air<br>- Sensorineural loss: sound heard longer through air<br> | ||
|- | |- | ||
! scope="row" | CN IX – | ! scope="row" | CN IX – [[Glossopharyngeal Nerve|Glossopharyngeal]]<br>CN X - [[Vagus Nerve|Vagus]]<br> | ||
| - Listen to voice quality<br>- Test for difficulty swallowing<br>- Let the patient say “ah” and observe the soft palate elevating and that the uvula remain in midline<br>- Examine the gag reflex<br> | | - Listen to voice quality<br>- Test for difficulty swallowing<br>- Let the patient say “ah” and observe the soft palate elevating and that the uvula remain in midline<br>- Examine the gag reflex<br> | ||
| - Dysphonia<br>- Dysphagia<br>- With paralysis the palate does not elevate (lesion CN V), unilateral paralysis there is asymmetrical elevation<br>- Absent gag reflex (lesion CN IX, possibly X)<br> | | - Dysphonia<br>- Dysphagia<br>- With paralysis the palate does not elevate (lesion CN V), unilateral paralysis there is asymmetrical elevation<br>- Absent gag reflex (lesion CN IX, possibly X)<br> | ||
|- | |- | ||
! scope="row" | CN XI - | ! scope="row" | CN XI - [[Accessory Nerve Cranial Nerve 11|Accessory]]<br> | ||
| - Examine muscle bulk <br>- Test Trapezius and Sternocleidomastoid muscles against resistance<br> | | - Examine muscle bulk <br>- Test Trapezius and Sternocleidomastoid muscles against resistance<br> | ||
| - Atrophy, fasciculations, weakness PNI: shoulder droops and unable to shrug ipsilateral shoulder<br>- Unable to turn the head to the contralateral side<br> | | - Atrophy, fasciculations, weakness PNI: shoulder droops and unable to shrug ipsilateral shoulder<br>- Unable to turn the head to the contralateral side<br> | ||
|- | |- | ||
! scope="row" | CN XII - | ! scope="row" | CN XII - [[Hypoglossal Nerve|Hypoglossal]]<br> | ||
| - Examine protruded tongue: rapid side-to-side movements<br>- Examine the tongue’s resting position<br>- Listen to the patient’s word articulations<br> | | - Examine protruded tongue: rapid side-to-side movements<br>- Examine the tongue’s resting position<br>- Listen to the patient’s word articulations<br> | ||
| - Movement impairment: deviation to weak side<br>- Atrophy or tongue fasciculations<br>- Dysartrhia (CN X or XII lesions)<br> | | - Movement impairment: deviation to weak side<br>- Atrophy or tongue fasciculations<br>- Dysartrhia (CN X or XII lesions)<br> | ||
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== See also == | == See also == | ||
*[[ | *[[Moebius Syndrome|Moebius Syndrome]] | ||
*[[ | *[[Bell's Palsy|Bell's Palsy]] | ||
*[[ | *[[Temporomandibular Disorders|Temporomandibular Disorders]] | ||
*[[ | *[[Acoustic Neuroma|Acoustic Neuroma]] | ||
*[[ | *[[Migraine Headache|Migraine Headache]] | ||
*[[ | *[[Ramsay Hunt Syndrome|Ramsay Hunt Syndrome]] | ||
*[[ | *[[Trigeminal Neuralgia|Trigeminal Neuralgia]] | ||
*[[Sturge-Weber Syndrome|Sturge-Weber Syndrome]] | *[[Cervicogenic Headache|Cervicogenic Headache]] | ||
*[[Synkinesis|Synkinesis]]< | *[[Sturge-Weber Syndrome|Sturge-Weber Syndrome]] | ||
*[[Synkinesis|Synkinesis]] | |||
*[[Accessory Nerve Cranial Nerve 11|Accessory Nerve Cranial Nerve XI]] | |||
*[[Abducens Nerve|Abducens Nerve Cranial Nerve VI]]<div class="researchbox"></div> | |||
== References == | == References == | ||
<references /> | <references /> | ||
<br> | |||
[[Category:Anatomy]] | |||
[[Category:Brain]] | |||
[[Category:Brain - Anatomy]] | |||
[[Category:Brain - Nerves]] | |||
[[Category:Nerves]] | |||
[[Category:Neurology]] | |||
[[Category:Neurological - Assessment and Examination]] | |||
[[Category:Head]] | |||
[[Category:Head - Anatomy]] | |||
[[Category:Head - Nerves]] |
Latest revision as of 12:43, 23 July 2023
Original Editor - Tarina van der Stockt
Top Contributors - Tarina van der Stockt, Lucinda hampton, Innocent Abugu, Kim Jackson, Donald John Auson, Evan Thomas, Areeba Raja, Wendy Walker, Kehinde Fatola, Ahmed M Diab, 127.0.0.1, Daniele Barilla and WikiSysop
Description[edit | edit source]
Twelve pairs of nerves (the cranial nerves) lead directly from the brain to various parts of the head, neck, and trunk. Some of the cranial nerves are involved in the special senses (such as seeing, hearing, and taste), and others control muscles in the face or regulate glands. The nerves are named and numbered (according to their location, from the front of the brain to the back).
Image 1: Twelve pairs of cranial nerves emerge from the underside of the brain, pass through openings in the skull, and lead to parts of the head, neck, and trunk. The nerves are named and numbered, based on their location, from the front of the brain to the back. Thus, the olfactory nerve is the 1st cranial nerve, and the hypoglossal nerve is the 12th cranial nerve
Unlike spinal nerves whose roots are neural fibers from the spinal grey matter, cranial nerves are composed of the neural processes associated with distinct brainstem nuclei and cortical structures.[1][2]
The names of the cranial nerves (CN) are: CN I - Olfactory, CN II - Optic, CN III - Oculomotor, CN IV - Trochlear, CN V - Trigeminal, CN VI - Abducens, CN VII - Facial, CN VIII - Vestibulocochlear, CN IX - Glossopharyngeal, CN X - Vagus, CN XI - Accessory, and CN XII - Hypoglossal. [3] Link: Introduction to Neuroanatomy
Function[edit | edit source]
The names of the cranial nerves sometimes correspond with their individual function. Some of the cranial nerves are purely sensory, others are purely motor, and the rest have both sensory and motor components. [5]
Cranial Nerve | Sensory Function | Somatic Motor Function | Autonomic (Parasympathetic Motor) Function |
---|---|---|---|
CN I - Olfactory |
Smell (olfaction) |
- |
- |
CN II - Optic |
Vision |
- |
- |
CN III - Oculomotor |
- |
Innervates the inferior oblique muscle and medial, inferior, and superior rectus muscles of the eye (move the eye); levator palpebrae superioris muscle (elevate eyelid) |
Innervates the sphincter pupillae muscle (constricts the pupil), and the ciliary muscle (accomodate the eye for near vision) |
CN IV - Trochlear |
- |
Innervate the superior oblique eye muscle (moves the eye inferiorly and laterally) |
- |
CN V - Trigeminal |
Conducts touch, temperature and pain sensation from the face, nose, mouth, nasal and oral mucosa, anterior two-thirds of tongue, and anterior scalp; part of auricle of the ear |
Innervate the muscles of mastication, mylohyoid, digastric (anterior belly), tensor veli palatini, and tensor tympani |
- |
CN VI - Abducens |
- |
Innervate the lateral rectus muscle of eye (abducts the eye) |
- |
CN VII - Facial |
Taste from anterior two-thirds of tongue |
Innervate muscles of facial expression, digastric (posterior belly), stylohyoid and stapedius muscle |
Increase secretion from the lacrimal (tear glands) and nasal mucosal glands; submandibular and sublingual salivary glands |
CN VIII - Vestibulocochlear |
Hearing (cochlear branch); linear and angular acceleration, or head position in space/equilibrium (vestibular branch) |
- |
- |
CN IX - Glossopharyngeal |
Touch and taste from the posterior 1/3 of the tongue; visceral sensory from the carotid sinus and bodies |
Innervate the pharyngeal muscle Stylopharyngeus |
Increase secretion from the parotid salivary gland |
CN X - Vagus |
Visceral sensation (excluding pain) from heart, lungs, abdominal organs, bronchi, trachea, larynx, pharynx, gastrointestinal tract to level of descending colon. General sensation from the external acoustic meatus, eardrum, and pharynx |
Innervates pharyngeal and laryngeal muscles and muscles at base of tongue |
Innervates smooth muscles and glands of the heart, lungs larynx, trachea, and most abdominal organs |
CN XI - Accessory |
- |
Innervates the trapezius and sternocleidomastoid muscle |
- |
CN XII - Hypoglossal |
- |
Innervates intrinsic and extrinsic tongue muscles |
- |
Dysfunction of Cranial nerves[edit | edit source]
Dysfunction of certain cranial nerves may affect the eye, pupil, optic nerve, or extraocular muscles and their nerves; thus, they can be considered cranial nerve disorders, neuro-ophthalmologic disorders, or both.
Cranial nerve disorders can also involve dysfunction of smell, vision, chewing, facial sensation or expression, taste, hearing, balance, swallowing, phonation, head turning and shoulder elevation, or tongue movements (see table below). One or more cranial nerves may be affected.
These disorders can result from tumors, inflammation, trauma, systemic disorders, and degenerative or other processes, causing such symptoms as vision loss, diplopia, ptosis, pupillary abnormalities, periocular pain, facial pain, or headache[8].
Treatment of neuro-ophthalmologic and cranial disorders depends on the cause.
Clinical Relevance and Assessment [9][10][edit | edit source]
Cranial Nerve |
Examination |
Involvement |
---|---|---|
CN I - Olfactory |
- Test sense of smell by closing the other nostril and using non-irritating odors like coffee, lemon oil, etc |
- Inability to detect smells (Anosmia) = temporal lobe lesions |
CN II - Optic |
- Test visual acuity using a Snellen chart, test central and peripheral vision |
- Blindness, impaired vision: far (myopia) and near (presbyopia) |
CN II – Optic CN III – Oculomotor |
- Test pupil equality, size and shape - Test pupil constriction by shining a light in the eye |
- Absence of pupil constriction - Unequal pupils (anisocoria) - Horner’s syndrome - CN III paralysis |
CN III – Oculomotor CN IV – Trochlear CN VI - Abducens |
- Test extraocular movements - Observe eye position, presence of strabismus (loss of ocular alignment) or ptosis of eyelid - Test pursuit eye movement without head movement |
- Strabismus and impaired eye movement - CN III: Ptosis, pupil dilation - CN IV: Eye cannot look down when adducted - CN VI: Eye pulled inward, eye cannot look out |
CN V - Trigeminal |
- Pain and light touch sensation of face (forehead, cheeks, jaw) - Open and close jaw against resistance - Test corneal and jaw jerk reflex |
- Loss of facial sensation and numbness - Loss of ipsilateral corneal reflex - Weakness and wasting of mastication muscles - Jaw deviation when opened to ipsilateral side |
CN VII - Facial |
- Test motor function of the facial muscles and look for asymmetry: raise eyebrows, frown, smile, close eyes tightly, puff cheeks, etc. |
- Ipsilateral paralysis of facial muscles: unable to close eye, mouth corner droops, difficulty with speech articulation = peripheral nerve injury (PNI) Bell’s Palsy (CN VII); or facial paralysis due to stroke |
CN VIII - Vestibulocochlear |
- Test balance - Gaze instability with head rotations - Test auditory acuity with a tuning fork placed in the middle on top of the head and check if the sound is equal or louder in one ear (Weber’s test) - Vibrating tuning fork place on mastoid bone, then near the ear canal and note hearing acuity (Rinne’s test) |
- Vertigo and disequilibrium - Nystagmus - Deafness, tinnitus and hearing loss - Unilateral conductive loss - Sensorineural loss: sound heard in good ear - Conductive loss: sound heard through bone is longer or equal than air - Sensorineural loss: sound heard longer through air |
CN IX – Glossopharyngeal CN X - Vagus |
- Listen to voice quality - Test for difficulty swallowing - Let the patient say “ah” and observe the soft palate elevating and that the uvula remain in midline - Examine the gag reflex |
- Dysphonia - Dysphagia - With paralysis the palate does not elevate (lesion CN V), unilateral paralysis there is asymmetrical elevation - Absent gag reflex (lesion CN IX, possibly X) |
CN XI - Accessory |
- Examine muscle bulk - Test Trapezius and Sternocleidomastoid muscles against resistance |
- Atrophy, fasciculations, weakness PNI: shoulder droops and unable to shrug ipsilateral shoulder - Unable to turn the head to the contralateral side |
CN XII - Hypoglossal |
- Examine protruded tongue: rapid side-to-side movements - Examine the tongue’s resting position - Listen to the patient’s word articulations |
- Movement impairment: deviation to weak side - Atrophy or tongue fasciculations - Dysartrhia (CN X or XII lesions) |
See also[edit | edit source]
- Moebius Syndrome
- Bell's Palsy
- Temporomandibular Disorders
- Acoustic Neuroma
- Migraine Headache
- Ramsay Hunt Syndrome
- Trigeminal Neuralgia
- Cervicogenic Headache
- Sturge-Weber Syndrome
- Synkinesis
- Accessory Nerve Cranial Nerve XI
- Abducens Nerve Cranial Nerve VI
References[edit | edit source]
- ↑ Sonne J, Lopez-Ojeda W. Neuroanatomy, cranial nerve. InStatPearls [Internet] 2019 Apr 3. StatPearls Publishing.
- ↑ Sonne J, Lopez-Ojeda W. Neuroanatomy, Cranial Nerve.[Updated 2021 Nov 14]. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. 2022. [1]
- ↑ 3.0 3.1 McKinley M, O'Loughlin VD. Human Anatomy. 2nd ed. New York: McGraw-Hill, 2008fckLRfckLRHill C. Practical guidelines for cystic fibrosis care. Edinburgh: Churchill Livingstone, 1998.
- ↑ Image: Wikipedia, https://en.wikipedia.org/wiki/Trochlear_nerve (accessed 12 Oct 2016)
- ↑ Butler A.B. Encyclopedia of the Human Brain, Four-Volume Set. Academic Press; 2002.
- ↑ Fuller KS, Introduction to Central Nervous System Disorders. Goodman CC, Fuller KS. Pathology: implications for the physical therapist. Elsevier Health Sciences; 2014. p1371-1404
- ↑ Youtube Video: MEDZCOOL - How to Remember the Cranial Nerves (Mnemonic) https://youtu.be/6ENCJkXJvio (accessed 12 Oct 2016)
- ↑ MSD manauls Overview of Neuro-ophthalmologic and Cranial Nerve Disorders Available from: https://www.msdmanuals.com/professional/neurologic-disorders/neuro-ophthalmologic-and-cranial-nerve-disorders/overview-of-neuro-ophthalmologic-and-cranial-nerve-disorders (accessed 4.2.2021)
- ↑ O'Sullivan SB, Neuromuscular Physical Therapy. In: O'Sullivan SB, Siegman RP. National Physical Therapy Examination Review & Study Guide. 19th edit. Evanston: TherapyEd, 2016. p121-184
- ↑ Chui KK, Schmitz TJ. Examination in Sensory Function. In: Physical Rehabilitation. 6th Edit. Philadelphia: O’Sullivan SB, Schmitz TJ, Fulk GD F.A. Davis Company, 2014. P87-121