Cranial Nerves Flashcards
Name all the Cranial Nerves.
- CN I - Olfactory
- CN II - Optic
- CN III - Oculomotor
- CN IV - Trochlear
- CN V - Trigenminal (Opthalmic, Maxillary, Mandibular)
- CN VI - Abducens
- CN VII - Facial
- CN VIII - Vestibulocochlear
- CN IV - Glossopharyngeal
- CN X - Vagus
- CN XI - Accessory
- CN XII - Hypoglossal
Name Cranial Nerve I and describe its innervation. How does it exit the cranium?
Olfactory
- Special Sensory - Olfaction (smell)
- through Cribiform Plate of Ethmoid Bone
Name Cranial Nerve I and describe its innervation. How does it exit the cranium?
Olfactory
- Special Sensory - Olfaction (smell)
- through Cribiform Plate of Ethmoid Bone
What may be the complications of fractured Cribiform Plate of the Ethmoid Bone?
- Ansomnia
- Rhinorrhea
Name Cranial Nerve II and describe its innervation. How does it exit the cranium?
Optic
- Special sensory - Vision
- through Optic Canal
How may increased cranial pressure lead to blindness?
- Optic nerve is a brain tract e.g. wrapped around with meninges
- Raised ICP -> Swollen Optic Nerve
Name Cranial Nerve III and describe its innervation. How does it exit the cranium?
Oculomotor
- Somatic Motor - Extraocular muscles (except Superior Oblique & Lateral Rectus) & Levator Palpebrae Superioris
- PNS Motor - Constrictor Pupillae
- through Superior Oribital Fissure
How may a Cranial Nerve III palsy represent?
- Out and down eyeball
- Complete Ptosis
- Dilated Pupil
Name Cranial Nerve IV and describe its innervation. How does it exit the cranium?
Trochlear
- Somatic Motor - Superior Oblique
- through Superior Orbital Fissure
How do you test a Cranial Nerve IV palsy represent?
- Extorted eyeball
- Patient unable to look medially when looked down e.g. unable to read book
Name Cranial Nerve V and describe its innervation. How does it exit the cranium?
Trigeminal
- Opthalmic Br. leaves via Superior Orbital Fissure
- Opthalmic Br. - general sensory - Upper Conjunctive & Cornea & Scalp & forehead & anteriosuperior nose & Frontal + Ethmoid sinuses
- Maxillary Br. leaves via Foramen Rotundum
- Maxillary Br. - general sensory - Maxillary sinuses & Posteroinferior nose & Palate & Upper teeth & upper lip
- Mandibular Br. leaves via Forman Ovale
- Mandibular Br. - general sensory - Auricles & External Acoustic Canal & External Eardrum membrane & skin of Temples & Cheeks & Lower Teeth & Anterior 2/3 tongue
- Mandibular Br. - somatic motor - muscles of Mastication
A patient comes to you with rashes on his Upper forehead and complains about severe pain in of his eyes. What may be the diagnosis?
Varicella Zoster infection of Opthalmic Nerve (CN Vi)
What is the Corneal reflex?
irritation of cornea -> Opthalmic (CN Vi) efferent -> brain -> Facial (CN VII) afferent -> Orbicularis Oculi -> blinking
How do you test the Mandibular Nerve?
Palpate Temporalis and Masseter when patient clenches the teeth
Name Cranial Nerve VI and describe its innervation. How does it exit the cranium?
Abducens
- Somatic Motor - Lateral Rectus
- through Superior Orbital Fissure
How may an infection of Oculomotor Nerve spread to other nerves? Which nerves may be affected?
- CN IV - Trochlear
- CN Vi - Opthalmic
- CN Vii - Maxillary
- CN VI - Abducens
- all these nerves are surrounded by Cavernous Sinus
What is the Corneal reflex?
irritation of cornea -> Opthalmic (CN Vi) Afferent -> brain -> Facial (CN VII) Efferent -> Orbicularis Oculi -> blinking
Name Cranial Nerve VII and describe its innervation.
Facial Neve
- General sensory - via CN Viii, Auricle & External Acoustic Meatus
- Special sensory - Taste of anterior 2/3 of tongue
- Somatic motor - muscles of Facial Expression
- PNS - Greater Petrosal Br. - Mucous glands of oral cavity, nose, pharynx & Lacrimal glands
- PNS - Chorda Tympani Br. - Submandibular & Sublingual salivary glands
Name Cranial Nerve VIII and describe its innervation. How does it exit the cranium?
Vestibulocochlear
- Vestibular Br. - special sensory - Balance
- Cochlear Br. - special sensory - Hearing
- through Internal Acoustic Canal
Describe the course of Cranial Nerve VII.
Arise from brain with 3 nuclei:
- Facial Nucleus - motor
- Nucleus Salitarius PNS
3 roots travel within Temporal Bone first via Internal Acoustic Canal
- close to the inner ear
- also the Trochlear Nerve
Enter Facial Canal then:
- motor & sensory roots fuse to form Facial Nerve Proper
- Facial Nerve Proper & PNS fibres form the Geniculate Ganglion
They branch to give rise:
- Greater Petrosal Nerve -> PNS fibres to mucous glands
- Nerve to Stapedius
- Chorda Tympani PNS to Submandibular & Sublingual glands
Rest of fibres as Cranial Nerve exits cranium via Stylomastoid Foramen then
- 3 motor branches run posterior to the ear and neck
- main motor trunk travels through Parotid gland without innervating it, splits into 5 motor fibres to muscles of Facial expression
Compare and contrast Lower Motor Neurone Facial Nerve Palsy and Bell’s Palsy.
- Loss facial expression - Occipitofrontalis spared (caused by BILATERAL UPPER motor neurone Facial N palsy)
- Complete Ptosis
- Loss of lacrimation & secremotor function in oral and nasal mucosa
- Changes in taste & hearing
- Facial Nerve Palsy: often permanent & known causes
- Bell’s Palsy: will recover & idiopathic causes
Name Cranial Nerve IX and describe its innervation. How does it exit the cranium?
Glossopharyngeal
- General sensory - Pharynx & Middle Ear & internal surface of Tympanic Membrane & posterior 1/3 Tongue
- Special sensory - Taste of posterior 1/3 tongue
- Visceral sensory - Carotid Body & Sinus
- Somatic motor - Stylopharyngeus
- PNS - Parotid Gland
- through Jugular Foramen
Name Cranial Nerve X and describe its innervation. How does it exit the cranium?
Vagus
- General sensory - External Acoustic Canal & external surface of Tympanic Membrane
- Motor - muscles of Pharynx, Larynx & Palate
- PNS - smooth muscles & glands of Thorax (including bronchi) & Abdomen
How may the Vagus Nerve be damaged? What complication may it cause?
- Left Recurrent Laryngeal Br. is more vulnerable
- Mitral Stenosis -> enlarged LA -> lifted L. Pulmonary A. -> push L. Recurrent Laryngeal N. against Aortic Arch
- Paralysis of Vocal Cords -> hoarseness in voice
Name Cranial Nerve XI and describe its innervation. What is special about this Cranial nerve? How does it exit the cranium?
Accessory
- the only Cranial nerve arises from Spinal Cords, receives roots from C2-C4
- Somatic motor (Cranial Br.) - muscles around neck
- Somatic motor (Spinal Br. ) - Trapezius & Sternocleidomastoid
- through Jugular Foramen
Name Cranial Nerve XI and describe its innervation. How does it exit the cranium?
Hypoglossal
- Somatic motor - Tongue
- through Hypoglossal Canal
How may damages to CN III at different locations present differently?
- Distal to Ciliary Ganglion (affecting only efferent fibres): Out & down eyeball + Complete Ptosis
- Proximal to Ciliary Ganglion (affecting both efferent & PNS fibres): above + Mydriasis + loss of accommodation reflex
How may an infection of the Internal Carotid Artery spread to cranial nerves?
- Through Cavernous Sinus, affecting:
- CN III, IV, Vi, Vii, VI
How is the Opthalmic Nerve tested?
Corneal reflex
- irritation -> Opthalmic afferent -> brain -> Facial efferent -> Orbicularis Oculi
Which branches of the Trigenminal nerve are hitch-hiked by Sympathetic fibres? What may a damage to their presynaptic fibres cause?
- CN Vii Maxillary & CN Viii Mandibular
- Damage -> Harlequin Syndrome: Anhydrosis + Vasodilation of the affected sensory territories
How do you test whether the CN VII is damaged?
- Inspection of facial symmetry (forehead spared)
- Changes in taste and hearing?
- Dry mouth & nose?
- Examination of motor function:
Occipitofrontalis -> raise eyebrows
Orbicularis Oculi -> close eyes
Buccinator -> blow up cheeks
Levator Labii Inferioris -> show teeth
What are the possible causes of Facial Nerve palsy?
- Parotid pathology (Parotiditis/Parotidectomy)
- Trauma (Temporal bone fracture)
- Neurological
- Neoplasty
- Cerebrovascular disease
- often unilateral, if bilaterally: Parkinson’s Disease
Describe the anatomical course of CN VII.
- Originates from brainstem with 3 nuclei:
A. Facial Nucleus -> motor
B. Solitary Nucleus PNS - All fibres through Internal Acoustic Canal into Pterosal part of Temporal Bone (near inner ear)
- Enter Tympanic Cavity and split:
A. Greater Petrosal N (only PNS) -> Pterygopalatine Ganglion -> Constrictor Pupillae
B. Nerve to Stapedius
C. Chorda Tympani (PNS + sensory) -> Submandicular Ganglion -> hitch-hikes on Lingual Nerve (br. of CN Viii) -> Submandibular + Sublingual Glands (PNS) and Taste of anterior 2/3 tongue - Major branch of Facial Nerve exits through Stylomastoid Foramen near Mastoid process then splits:
A. hjks Auriculotemporal Br of CN Viii -> sensory to Auricles
B. Nerves to posterior belly of Digastric & Stylomastoid
C. Motor Br -> Parotid Gland and splits:
a. Temporal Br.
a. Zygomatic Br.
a. Buccal Br.
a. Mandibular Br.
a. Cervical Br.
Describe the course and targets of the Cranial nerves that has brain stem Parasympathetic nuclei.
- Edinger-Westphall nucleus -> Oculomotor N -> synapses at Ciliary ganglion -> Constrictor Pupillae
- Superior Salivatory nucleus -> Facial N -> greater Petrosal N -> synapses at Pteryogopalatine nucleus -> Lacrimal glands & Mucous glands of oral and nasal cavities
- Superior Salivatory nucleus -> Facial N -> Chorda Tympani N hitch-hikes on Lingual N (br. of CN Viii) -> synapses at Submandibular ganglion -> Submandibular & Sublingual glands
- Inferior Salivatory nucleus -> Glossopharyngeal N -> hitch-hikes on Auriculotemporal N (br. of CN Viii) -> synapses at Otic ganglion -> Parotid glands
- Inferior Salivatory nucleus -> Glossopharyngeal N -> directly -> Oropharynx glands
- Dorsal Vagal Motor nucleus -> Vagus N -> directly -> Laryngopharyngeal glands
How does the head and neck receive their Sympathetic inputs?
- Presynaptic SNS fibres synapse at Superior/Middle/Inferior ganglion
- Postsynaptic fibres travel along arteries (their main targets) to their targeting structures
Describe briefly the target of Sympathetic inputs to the head and neck?
- Superior ganglion -> Cardiac plexus + Pharyngeal plexus + C1-C4
- Middle ganglion -> Cardiac plexus + C5-C6
- Inferior ganglion -> Cardiac plexus + C7-T1
What happens if the Sympathetic Trunk is damaged?
Horner’s syndrome:
- Mitosis = constricted pupils
- Partial Ptosis = lost of Superior Tarsal Muscles
- Anhydrosis = lost of sweating
- Vasodilation - redness + temperature
The main targets of sympathetic fibres are blood vessels hence also travel along with them to other targets, through which vessels do they each travel with?
- Superior Cervical Ganglion -> Internal & External Carotid Arteries
- Middle Cervical Ganglion -> Inferior Thyroid Artery
- Superior Cervical Ganglion -> Vertebral Artery
Only the sympathetic fibres from the Superior Cervical Ganglion travel through the 4 Ganglia that Parasympathetic fibres synapse at, through which blood vessels do these sympathetic fibres each travels through? And what are each of their targets?
- along External Carotid Artery -> Middle Meningeal Artery -> Otic Ganglion -> Parotid gland
- along External Carotid Artery -> Facial Artery -> Submandibular Ganglion -> glands of Oral cavity
- along Internal Carotid Artery -> Pterygopalatine Ganglion -> Nose & Nasopharynx & Palatine
- along Internal Carotid Artery -> Opthalmic Artery -> Ciliary Ganglion -> Dilator Pupillae
In some people, the Inferior Cervical Ganglion joins the first Thoracic ganglion, what is this ganglion called?
Stallate Ganglion
Which cranial nerves are hitch-hiked by Sympathetic fibres? Describe their course and targets.
- CN III: via Internal Carotid A -> Opthalmic A -> through Ciliary Ganglion -> Dilator Pupillae
- CN Vii: via Internal Carotid A -> Pterygopalatine -> Palatine & Nasopharynx
- CN Viii Mandibular : via External Carotid A -> Facial A -> through Submandibular Ganglion -> Nose & Oral cavity
- CN IX Glosoopharyngeal : via External Carotid A -> Meningeal A -> through Otic Ganglion -> Parotid Gland
Name the branches of Mandibular Nerve (CN Viii)
- Buccal
- Auriculotemporal
- Inferior Alveolar
- Lingual
