Lecture 9 - Cranial Nerves Vll - Xll Flashcards
What kind of fibres does the trigeminal (CN V) carry?
What are the divisions of the trigeminal nerve and through which structures do they pass through?
- Motor & Sensory
1) Ophthalmic - through cavernous sinus & S.O.F
2) Maxillary - through cavernous sinus & foramen rotundum
3) Mandibular - through foramen ovale
Name 2 distal branches of the ophthalmic division of the trigeminal nerve and what areas of the face they supply
1) Frontal nerve - runs superiorly out of orbit onto forehead, supplies forehead/scalp via supraorbital and supratrochlea branches
2) Nasocilliary nerve - supplies tip of nose area, which is why this area is included in Va division. Crusting over of this region during shingles = Hutchinson’s sign
Name 2 distal branches of the trigeminal nerve in the maxillary division (Vb) and the areas of the face they supply
1) Infraorbital nerve - runs through floor of orbit to supply maxillary division. Can be damaged when there’s a fractured orbital floor
2) Superior alveolar nerves - supplies upper teeth and gums area, so orbital floor fractures may also affect sensory information in this area
Name 3 distal branches of the trigeminal nerve in the mandibular region and the areas of the face they supply
1) Auriculotemporal nerve - supplies side of head and ear
2) Lingual nerve - supplies tongue
3) Inferior alveolar nerve - supplies the lower teeth and gums. Passes thru mental foramen and becomes mental nerve, vulnerable in mandibular fractures
What kind of fibres does the facial nerve (CN Vll) carry?
What are its target tissues?
How would you test its function clinically?
- Motor, sensory (taste) & parasympathetic
- Muscles of mastication, anterior 2/3 of tongue, lacrimal glands, salivary glands (minus parotid) and mucosal glands
- Check for unilateral facial droop
Describe the course of the facial nerve, its 3 main branches and what they supply
- Facial nerve comes from pons passes through internal acoustic meatus to enter petrous bone. At geniculate ganglion, 3 branches form.
1) Greater petrosal nerve (parasympathetic) supplying the lacrimal, nasal and oral glands.
2) Nerve to stapedius (motor) which is in middle ear
3) Chorda tympani (sensory & parasympathetic) carries sensory info to ant 2/3 of tongue, and parasympathetic fibres to salivary glands
What will be the difference in facial droop between a pathology/injury affecting pathways from the PMC to the facial nerve motor nuclei vs pathology/injury affecting facial nerve anywhere from its exit from brainstem to target tissue?
1) Lesions affecting pathway from PMC to facial nerve nuclei in brainstem will only cause contralateral face droop on the lower half of the face. Upper half is spared due to dual cortical control (ipsilateral back up).
2) Lesion affecting pathway from brainstem to target tissue will cause whole ipsilateral face droop, as there’s no dual cortical control from here onwards.
What type of fibres does the vestibulocochlear nerve (CN Vlll) carry & what is its target tissues?
What are the clinical tests for CN Vlll function?
How are CN Vlll lesions typically caused?
- Special sensory (balance & hearing), masses through internal acoustic meatus to supply inner ear (vestibular system & cochlear)
- Hearing tests (whisper/tuning fork), patients present with hearing loss, dizziness, tinnitus
- Vestibular schwannoma (posterior cranial fossa tumour), base of skull fracture
What is the route of the glossopharyngeal (CN lX) and vagus (CN X) nerve and what are their target tissues?
- From medulla, run through posterior cranial fossa, exit jugular foramen and enter carotid sheath.
CN lX (sensory) - oropharynx/tonsils, post 1/3 tongue, parasympathetic to parotid gland
CN X (motor & sensory) - muscles of larynx/pharynx (soft palate), parasympathetic to a lot of tissues
What do patients with CN lX & CN X lesions present with?
How is function examined?
- Difficulty swallowing, weak cough, difficulties with speech
- “ahhh” soft palate elevation - each half of soft palate innervated by CN X, if lesion on one side, muscles will not elevate on one side and uvula swings off from midline towards unaffected side
Describe the course of the accessory (CN Xl) and hypoglossal (CN Xll) nerves
- Arise from medulla, runs through posterior cranial fossa, enters carotid sheath
- Hypoglossal exits and travels to tongue
- Accessory exits and heads towards posterior triangle
What is the target tissue of the hypoglossal nerve?
How are lesions caused?
How is this tested clinically?
- Tongue (tongue movements & protrusion)
- Surgery/pathology involving upper carotid sheath/posterior cranial fossa tumours
- Deviation of tongue (via genioglossus muscle) towards side that has lesion on it occurs
What are the target tissues of the accessory nerve (CN Xl)?
How is function tested clinically & how are lesions caused?
- SCM & trapezius, test action of SCM (turn head) and trapezius (shrug shoulders)
- Posterior cranial fossa tumours, base of skull fractures
- Lesions lead to shoulder drop on affected side and wasting of SCM muscle
