Cranial Nerves Flashcards
What is CN I?
Olfactory
What is the path of CNI?
Olfactory nerves from roof of nasal cavity
Pass through cribiform foramina in the olfactory plate
Olfacroy bulb
Olfactory tract
Temporal lobe
What is the role of CNI?
Special sensory
What is the function of CNI?
Olfaction
How is CNI tested?
Ask about sense of smell
What is anosmia?
Loss of sense of smell
What is CNII?
Optic
What is the path of CNII?
Retinal ganglion cells
Axons form optic nerve
Exit orbit via optic canal
Fibres cross and merge at optic chiasm
What is the optic nerve?
Carries sensory fibres from one eye
What is the optic tract?
Contains sensory information from part of right and left eyes
What is the role of CNII?
Special sensory
What is the function of CNII?
Impulses generated in response to light - perceived as vision in primary visual cortex
How is CNII tested?
Visual acuity using Snellen chart
Visual fields
Pupillary responses
How can CNII be visualised?
Opthalmoscope
- seen as optic disc
Where do CNI and CNII originate from?
Forebrain
Where do CNIII and CNIV originate from?
Midbrain
What is CNIII?
Occulomotor
What is the path of CNIII?
Midbrain
Lateral wall of cavernous sinus
Superior orbital fissure
What is the role of CNIII?
Motor
Autonomic - carries parasympathetic fibres
What is the motor function of CNIII?
Innervates extra-ocular muscles
Innervates muscle of eyelid
What is the autonomic function of CNIII?
Innervates sphincter pupillae
Innervates ciliary muscle
What is the clinical relevance of CNIII?
Vulnerable to compression by raised ICP between tentorium cerebelli and temporal lobe
- sign = blown pupil
How is CNIII tested?
Inspecting eyelids and pupil size
Testing eye movements
Testing pupillary reflexes
What is a sign of CNIII pathology?
Pupillary dilation
‘Down and out’ position + ptosis
What causes ‘down and out’ position of CNIII?
Unopposed action of CNIV and CNVI
What can cause pathology of CNIII?
Raised ICP
Aneurysm of PCA
Cavernous sinus thrombosis
Vascular (secondary to diabetes/HTN)
What is CNIV?
Trochlear
What is the path of CNIV?
Midbrain
Cavernous sinus
Superior orbital fissure
What is the role of CNIV?
Motor
What is the optic tract?
Contains sensory information from part of right and left eyes
What is the role of CNII?
Special sensory
What is the function of CNII?
Impulses generated in response to light - perceived as vision in primary visual cortex
How is CNII tested?
Visual acuity using Snellen chart
Visual fields
Pupillary responses
How can CNII be visualised?
Opthalmoscope
- seen as optic disc
Where do CNI and CNII originate from?
Forebrain
Where do CNIII and CNIV originate from?
Midbrain
What is CNIII?
Occulomotor
What is the path of CNIII?
Midbrain
Lateral wall of cavernous sinus
Superior orbital fissure
What is the role of CNIII?
Motor
Autonomic - carries parasympathetic fibres
What is the motor function of CNIII?
Innervates extra-ocular muscles
Innervates muscle of eyelid
What is the autonomic function of CNIII?
Innervates sphincter pupillae
Innervates ciliary muscle
What is the clinical relevance of CNIII?
Vulnerable to compression by raised ICP between tentorium cerebelli and temporal lobe
- sign = blown pupil
How is CNIII tested?
Inspecting eyelids and pupil size
Testing eye movements
Testing pupillary reflexes
What is a sign of CNIII pathology?
Pupillary dilation
‘Down and out’ position + ptosis
What causes ‘down and out’ position of CNIII?
Unopposed action of CNIV and CNVI
What can cause pathology of CNIII?
Raised ICP
Aneurysm of PCA
Cavernous sinus thrombosis
Vascular (secondary to diabetes/HTN)
What is CNIV?
Trochlear
What is the path of CNIV?
Midbrain
Cavernous sinus
Superior orbital fissure
What is the role of CNIV?
Motor
What is the function of CNIV?
Innervates superior oblique
How is CNIV tested?
Eye movements
Where do CNV and CNVI originate from?
Pons
What is CNV?
Trigeminal
What are the branches of CNV?
Va = ophthalmic
Vb = maxillary
Vc = mandibular
What is the path of CNVa?
Pons
Trigeminal ganglion
Cavernous sinus
Superior orbital fissure
Orbit
What is the path of CNVb?
Pons
Trigeminal ganglion
Cavernous sinus
Foramen rotundum
Pterygopalatine fossa
What is the path of CNVc?
Pons
Trigeminal ganglion
Foramen ovale
Infratemporal fossa
What is the role of CNV?
General sensory
Motor
What is the general sensory function of CNV?
Skin of face Scalp Paranasal air sinuses Nasal cavity Oral cavity Anterior tongue Meninges
What is the motor sensation of CNV?
Muscles of mastication - Vc
How is CNV tested?
Sensation in dermatomes
Corneal reflex
Muscles of mastication
What are the branches of CNVb?
Infraorbital nerve
Superior alveolar nerve
Where does the infraorbital nerve lie?
Through floor of orbit - susceptible to orbital floor fractures
What does the infraorbital nerve supply?
Sensory from cheek and lower eyelid
What is the role of the superior alveolar nerve?
Carries sensory fibres from upper teeth and gums
How is CNVII tested?
Muscles of facial expression
Corneal reflex
Where does the inferior alveolar nerve lie?
Runs through bony canal in mandible exiting as the mental nerve - susceptible in mandibular fractures
What is the role of the inferior alveolar nerve?
Sensory from mental protuberance, lower lip and gum
What is the role of the lingual nerve?
General sensory from anterior tongue
What is the role of auriculotemporal nerve?
General sensory from part of ear, temple area, scalp and TMJ
What is CNVI?
Abducens
What is the path of CNVI?
Lower pons
Runs upwards into cavernous sinus
Superior orbital fissure
What is the role of CNVI?
Motor
What is the function of CNVI?
Innervates lateral rectus muscle
How is CNVI tested?
Eye movements
Where do CNVII and CNVIII originate from?
Pons
What is CNVII?
Facial
What is the path of CNVII?
Pons
Enters petrous bone via internal acoustic meatus
Gives off
- greater petrosal nerve
- chorda tympani
- nerve to stapedius
Exits base of skull via stylomastoid foramen
What are the branches of CNVII?
Frontal Zygomatic Buccal Mandibular Cervical
What is the role of CNVII?
Special sensory
Autonomic
Motor
General sensory
What is the special sensory function of CNVII?
Taste in anterior 2/3 tongue
What is the autonomic function of CNVII?
Parasympathetic from
- lacrimal glands
- mucosal glands
- salivary glands
What is the motor function of CNVII?
Muscles of facial expression
Stapedius
What is the general sensory function of CNVII?
Small area of external area
What is CNVIII?
Vestibulocochlear
What are the general sensory functions of CNX?
Lower pharynx
Larynx
What is the role of CNVIII?
Special sensory
What is the function of CNVIII?
Hearing and balance
How is CNVIII tested?
Hearing test
Weber’s + Rinne’s
Balance test
What is presbyacusis?
Old-age related hearing loss
What is an acoustic neuroma?
Benign tumour involving vestibulocochlear nerve
- tumour of schwann cells
Symptoms
- unilateral hearing loss
- tinnitus
- vertigo
- numbness/pain down one side of face
Where do CNIX and CNX originate from?
Medulla
What is CNIX?
Glossopharyngeal
What is the path of CNIX?
Medulla
Tympanic branch
Carotid body
What is the role of CNIX?
General sensation
Special sensory
Autonomic
Motor
What is the general sensory function of CNIX?
Tonsils + oropharynx
Middle ear + tympanic membrane
Carotid body + sinus
What is the special sensory function of CNIX?
Taste poster 1/3 tongue
What is the autonomic function of CNIX?
Parasympathetic to parotid gland
What is the motor function of CNIX?
Innervates stylopharyngeus
How is CNIX tested?
Gag reflex
Tested with CNX
What is CNX?
Vagus
What is the path of CNX?
Medulla
Jugular foramen
Carotid sheath
Through neck into thorax + abdomen
What is the role of CNX?
General sensory
Motor
Autonomic
What are the motor functions of CNX?
Muscles of soft palate
Muscles of pharynx
Muscles of larynx
What are the autonomic functions of CNX?
Parasympathetic to thoracic and abdominal viscera
How is CNX tested?
Test speech, cough and swallow
Gag reflex
Where do CNXI and CNXII originate from?
Medulla
What is CNXI?
Spinal accessory
What is the path of CNXI?
Medulla
Emerges through jugular foramen
Passes deep to SCM and gives off motor supply
Runs posterolaterally across posterior triangle
Enters deep to trapezius
What is the role of CNXI?
Motor
What is the function of CNXI?
Motor to SCM and trapezius
How is CNXI tested?
Shrug shoulders against resistance - trapezius
Turn head against resistance - SCM
What is CNXII?
Hypoglossal
What is the path of CNXII?
Medulla
Exits via hypoglossal canal
Passes medial to angle of mandible
Crosses internal and external carotid arteries
What is the role of CNXII?
Motor
What is the function of CNXII?
Innervates muscles of tongue
How is CNXII tested?
Inspection and movements of tongue
What occurs with damage to CNXII?
Weakness and atrophy to tongue muscles on ipsilateral side