Cranial Nerves Flashcards
Which two cranial nerves are extensions of the forebrain?
Olfactory and optic nerves (I and II)
What is cranial nerve I responsible for?
Special sense of smell (Olfactory nerve)
Which area of bone does the olfactory nerve run through to innervate the nose?
Cribiform foramina of ethmoid bone
What is cranial nerve II responsible for?
Sense of sight (optic nerve)
Some relation to pupillary size and response to light
Visual acuity
How would a patient with damage to the optic nerve present?
How could you confirm this
Blurred or absent vision in one eye
Abnormalities in pupillary reflexes
Poor visual acuity
Opthalmoscope - swollen optic disc
What occurs at the optic chiasm?
Mixing of sensory fibres from left and right optic nerves - so both sides contain information from both eyes
What is a common cause of bitemporal hemianopia?
Pituitary tumour
What is cranial nerve III responsible for?
Movement of extraocular muscles (Oculomotor nerve)
Movement of levator palpabrae superioris (retracts eyelid)
Movement of sphincter pupillae (constricts pupil)
What common signs are found in Oculomotor nerve defect?
Double vision (diplopia)
Drooping of eyelid (ptosis)
“Down and out” eye position
What would cause pupil sparing injury of the Oculomotor nerve?
What would cause pupil involving injury?
Microvascular ischaemia: diabetes, hypertension cause pupil sparing
Posterior communicating artery aneurysm, head injury, herniation cause pupil involving
What is cranial nerve IV responsible for?
Movement of superior oblique - movement of the eye downwards (Trochlear nerve)
How would a person with injury to the Trochlear nerve present?
Diplopia
Abnormal eye position (often raised)
Head tilt
What is cranial nerve VI responsible for?
Movement of lateral rectus - moves eyes laterally (Abducens nerve)
What is the false localising sign in Abducens nerve injury? What causes it?
Commonly damaged by a raise in ICP even when nothing directly compresses the nerve, due to stretching of the nerve fibres leaving the pons before entering the cavernous sinus
Which three cranial nerves share a commonality in route through the cavernous sinus and enter the orbit via the superior orbital fissure?
Occulomotor
Trochlear
Abducens
What are the functions of the trigeminal nerve?
Sensory supply to skin of face and scalp
Sensory information to anterior 2/3 of tongue
Motor innervation to muscles of mastication
Corneal reflex
What are the three branches of the trigeminal nerve?
Va -Opthalmic
Vb - Maxillary
Vc - Mandibular
What is the corneal reflex?
What use is this clinically?
Touching the surface of the eye causes both eyes to blink
Can be used to assess trigeminal nerve function alongside other tests
What pathologies are associated with the trigeminal nerve?
Trigeminal herpes zoster - shingles
Trigeminal neuralgia - shooting pains
What structures do each of the branches of the trigeminal nerve pass through respectively?
Opthalmic - cavernous sinus - superior orbital fissure
Maxillary - cavernous sinus - foramen rotundum
Mandibular - foramen ovale
What does the frontal nerve branch of the Opthalmic division of the trigeminal nerve give rise to?
The supraorbital and supratrochlear nerves that supply the forehead
Which nerve is responsible for hutchingsons sign?
Nasociliary nerve (branch of Va)
What is hutchingsons sign?
Shingles rash on tip of the nose - likely indicates eye involvement in future and therefore severity of disease
Which nerve carries general sensation to the anterior 2/3 of the tongue?
Lingual nerve (branch of Vc)
Which nerves supply the upper teeth and gums?
Superior alveolar nerves (branches of Vb)
Which nerves supply the lower teeth and gums?
Inferior alveolar nerve and mental nerve (extension of inferior alveolar nerve that passes through mental foramen)
What are the target tissues of the facial nerve?
Muscles of facial expression
Anterior 2/3 tongue (taste)
Lacrimal glands, salivary glands (excluding parotid) and mucosal glands
What sign indicates facial nerve damage?
How is this different to what is seen in a stroke?
Unilateral face droop,
Strokes are forehead sparing, whereas facial nerve lesions are not
What is Ramsay-Hunt syndrome?
Unilateral facial droop with shingles rash found in external ear
What structure does the facial nerve pass through to get into the petrous bone?
From which foramen does it emerge from the base of the skull?
Internal acoustic meatus.
Stylomastoid foramen.
Which three branches does the facial nerve give off inside the petrous bone?
Greater petrosal - lacrimal, nasal and oral mucosal glands
Nerve to stapedius - stapedius in the ear
Chorda tympani - tongue
What is the vestibulocochlear nerve responsible for?
Balance and hearing (CN VIII)
What symptoms would a person with CNVIII damage present with?
How would we test nerve function?
Hearing loss, dizziness, tinnitus.
Whisper or finger rub, tuning fork testing.
Why might an acoustic neuroma present with numbness down one side of the face as well as CNVIII dysfunction?
May also compress the trigeminal nerve.
Why are the glossopharyngeal and vagus nerves often examined together?
Very similar routes through posterior cranial fossa, jugular foramen and carotid sheath, so pathologies are more likely to affect both.
What does the Glossopharyngeal nerve supply?
Sensory supply to oropharynx, tonsils and posterior 1/3 tongue,
Parasympathetic innervation to parotid glands,
Afferent from carotid sinus and body
What does the Vagus nerve broadly supply?
Motor and sensory to larynx/pharynx and split palate.
Parasympathetic innervation to multiple tissues around the body eg heart, neck, abdomen
What do patients with damage to cranial nerves IX and X present with?
How would we test nerve function?
Difficulty swallowing, weak cough, change in voice.
Test speech, swallowing and coughing. Asses soft palate and uvula position and gag reflex
What is often a source of damage to the recurrent laryngeal nerve (branch of CNX)?
Thyroid pathology or surgery
Damage to superior thorax
What is the Hypoglossal nerve responsible for?
How is damage to it assessed?
Tongue movement and protrusion.
Ask patient to protrude tongue, if deviation to one side, that Hypoglossal nerve is damaged.
What is the Spinal accessory nerve (CN XI responsible for?)
How do we test its action?
Motor supply to sternocleidomastoid and trapezius.
Test actions of these muscles (turn head and shrug shoulders against resistance).
Which cranial nerves may be damaged with pathology or surgery within the carotid sheath?
IX - Glossopharyngeal,
X - Vagus,
XI - Accessory,
XII - Hypoglossal.
