8) The Trochlear,Trigeminal & Facial nerves Flashcards
Give some key points about the trigeminal nerve
CN V Largest CN Sensory & Motor Transit for some autonomic nerves 3 branches (ophthalmic, maxillary, mandibular)
Give some key points about the ophthalmic nerve
CN Vi
Sensory only (cornea, conjunctiva, nasal cavity, forehead)
Tested via corneal reflex
3 branches
Postgang. parasymp. fibres to lacrimal gland
What are the 3 branches of the ophthalmic nerve?
Frontal
Nasociliary
Lacrimal
Give some key points about the maxillary nerve
CN Vii
Sensory only (nasal cavity, maxillary sinus, upper lip)
14 Terminal branches
Associated with parasymp. ganglion (pterygopalatine)
Give some key points about the mandibular nerve
CN Viii
Sensory (mucous memb., lower lip, chin, ant 2/3 tongue)
Motor (mastication, mylohyoid, digastric)
Associated with submandibular & otic ganglion (salivary glands)
What are the motor functions of the facial nerve?
Muscles of facial expression
Posterior belly of digastric
Stylohyoid
Stapedius
What are the sensory function of the facial nerve?
Skin close to external acoustic meatus
Taste (ant. 2/3 tongue, chorda tympani)
what are the parasympathetic actions of the facial nerve?
Pterygopalatine parasympathetic ganglion
Lacrimal gland
Submandibular gland
Sublingual gland
Describe the course of the facial nerve
- Motor cortex
- Pons
- Internal acoustic meatus
- Facial canal
- Stylomastoid foramen
- Branches to face & neck
Name the intracranial branches of the facial nerve
greater petrosal nerve
chorda tympani
nerve to stapedius
Name the extracranial branches of the facial nerve
Temporal (occipitofrontalis & superior orbicularis oculi)
Zygomatic (inferior orbicularis oculi)
Buccal (orbicularis oris, buccinator, zygomaticus)
Marginal mandibular (mentalis)
Cervical (platysma)
How would you test the occipitofrontalis?
raise eyebrows
keep them raised against resistance
How would you test the orbicularis oculi?
Scrunch up eyes
Keep them scrunched up against resistance
How would you test the buccinator?
Puff out cheeks
Keep puffed out against resistance
How would you test the levator labii superioris & depressor labii inferioris?
show teeth
Keep them shown against resistance
Name some non-traumatic causes of a facial nerve palsy
Inflammation
Infection e.g. Viral - Herpes, Parotitis - S.aureus
Compression - parotid tumour
Name some traumatic causes of a facial nerve palsy
Fractures, temporal bone Stabbing Gunshots Childbirth [Iatrogenic - surgery, parotidectomy]
How can you tell the difference between a stroke and Bell’s palsy?
Stroke:
Forehead sparing
Occipitofrontalis & orbicularis oculi not paralysed
Bilateral innervation
Bell’s palsy:
All muscles of facial expression paralysed
In relation to other CNs how big/long is the trochlear nerve?
Smallest CN (no. axons) Longest intracranial length
Describe the course of the trochlear nerve
Nucleus portion - midbrain, caudal to oculomotor nucleus, decussation of nerve
Cavernous sinus portion - lateral wall below oculomotor n. then sup. orbital fissure above oculomotor n.
Orbital portion - enters orbit, superiomedial to LPS & SR
Which muscle does CN IV innervate and what are its actions?
Superior Oblique - Abduction (alone) - Depression (when adducted) - Intorsion (medially rotates) (Reading position, looking down & in)
What is decussation?
The point where a nerve crosses from one side of the brain to another e.g. Trochlear nerve
Name the 4 types of trochlear nerve palsy
Acute e.g. trauma
Chronic e.g. congenital (nucleus, nerve formation)
Unilateral e.g. problem at nucleus or along course
Bilateral e.g. pathology where nerve decussates
How would a patient with a trochlear nerve palsy present?
Extorsion & Elevation of the eye (pupil)
Unopposed action of inferior oblique
Tilted head away from paralysed side (compensation for…)
…Diplopia (vertical, when looking down & in)
