SDL 1: Cranial nerves Flashcards
Which cranial nerves emerge from the cerebellopontine angle?
Facial (VII)7
Vestibulocochlear (VIII)8
?Trigeminal (V)5 (comes off pons)
Which cranial nerves emerge from the interpeduncular fossa?
Optic (II)2
Oculomotor (III)3
Which cranial nerves emerge immediately lateral to the medullary pyramid?
Hypoglossal (XII)12
Where are the true, peripheral olfactory nerves? How do they enter the cranial cavity?
The sensory cells of the nasal mucosa project their axons into the CNS. These tiny fibres that are the true peripheral olfactory nerves, pierce the cribriform plate of the ethamoid bone and synapse in the olfactory bulb, which is part of the CNS.
Suggest the mechanism by which the olfactory nerve might be damaged during head injury.
Disruption of the olfactory fibres prior to their decussation.
How might a patient’s visual fields be tested?
The visual fields of both eyes overlap; therefore each eye is tested independently. The patient should cover their right eye with their right hand (vice versa when testing the opposite eye). With the examiner seated directly across from the patient, the patient should direct their gaze to the corresponding eye of the examiner. A moving target should start outside the usual 180 º visual field, then move slowly to a more central position until the patient confirms visualization of the target. All 4 quadrants (upper and lower, temporal and nasal) should be tested.
What is the brainstem attachment and skull exit location of the oculomotor nerve (III)3?
Brainstem attachment: midbrain via interpeduncular fossa
Skull exit: superior orbital fissure
What is the brainstem attachment and skull exit location of the trochlear nerve (IV)4?
Brainstem attachment: midbrain on dorsal surface of brainstem
Skull exit: superior orbital fissure
What is the brainstem attachment and skull exit location of the abducens nerve (VI)6?
Brainstem attachment: pons
Skull exit: superior orbital fissure
What are the three divisions of the trigeminal nerve?
Opthalmic (V1)
Maxillary (V2)
Mandibular (V3)
What do the sensory components of the trigeminal nerve supply?
Skin, teeth, mucous membranes of the face, anterior scalp and the dura.
What do the motor fibres of the trigeminal nerve supply?
Four main muscles of mastication, number of others involved in swallowing, tensor tympani (dampens amplitude of vibration of tympanic membrane).
Where are the cell bodies of (most of) the trigeminal sensory fibres located?
Trigeminal sensory nucleus
Through which foramina do the three divisions of the trigeminal nerve exit the cranial cavity?
V1 - superior orbital fissure
V2 - foramen rotundum
V3 - foramen ovale
Name the four autonomic ganglia of the face?
Submandibular
Pterygopalatine
Ciliary
Otic
Hanging from the pterygopalatine ganglion are two nerves: greater and lesser palatine. What do they supply?
Motor and sensory to the roof of the mouth, soft palate, tonsil, and lining membrane of the nasal cavity.
How would you test the functioning of the sensory component of the trigeminal nerve?
Light touch is tested in each of the three divisions of the trigeminal nerve and on each side of the face using a cotton wisp or tissue paper. The ophthalmic division is tested by touching the forehead, the maxillary division is tested by touching the cheeks, and the mandibular division is tested by touching the chin. A common mistake is to use a stroking motion, which will trigger pain and temperature nerves. Instead, a point stimulus should be applied.
Which two reflexes are tested when examining the trigeminal nerve?
Corneal reflex
Jaw jerk reflex
What is trigeminal neuralgia?
A neuropathic disorder characterized by episodes of intense pain in the face.
List the four main muscles of mastication.
Masseter
Temporalis
Lateral pterygoid
Medial pterygoid
What division of the trigeminal nerve supplies the muscles of mastication?
Mandibular branch (V3)
How would you test the functioning of the motor division of the trigeminal nerve?
Muscles of mastication (temporalis, masseter) should be inspected for atrophy. Palpate the temporalis and masseter as the patient clenches the jaw. The pterygoids can be tested by asking the patient to keep the mouth open against resistance, and move from side to side against resistance. A jaw jerk reflex can be tested by placing a finger over the patient’s chin and then tapping the finger with a reflex hammer. Normally the jaw moves minimally.
In a patients with unilateral damage to the motor root of the trigeminal, the jaw deviates to one side when opened against resistance. Does it deviate to towards the lesioned side or towards the intact side?
The mandible upon opening deviates toward the paralyzed side when there is unilateral paralysis of the masticatory muscles. This direction of the mandible is due to the action of normal pterygoids on the opposite side.
What are the sensory functions of the facial nerve?
Sensory input from part of the external acoustic meatus and deeper parts of the auricle.
Taste from the anterior two-thirds of the tongue.
Where are the cell bodies of the sensory fibres running in the facial nerve located?
Nucleus solitarus
What are the parasympathetic functions of the facial nerve?
Secretomotor activity in the lacrimal gland, submandibular and sublingual salivary glands, and glands in the mucous membranes of the nasal cavity, and hard and soft palates.
What are the branches of the facial nerve?
Temporal Zygomatic Buccal Marginal mandibular Cervical.
(To zanzibar by motor car - superior to inferior)
What is the function of the nerve fibres making up the chorda tympani?
The chorda tympani carries two types of nerve fibers:
- Special sensory fibers providing taste sensation from the anterior two-thirds of the tongue (Facial nerve).
- Presynaptic parasympathetic fibers to the submandibular ganglion, providing secretomotor innervation to two salivary glands: the submandibular gland and sublingual gland (facial nerve) and to the vessels of the tongue, which when stimulated, cause a dilation of blood vessels of the tongue.
Chorda tympani carries fibres between the facial nerve and which other nerve? Why?
Involved in a very complex negative feedback loop with the lingual nerve.
What is the function of the facial nerve fibres running in in the greater petrosal nerve?
Carries parasympathetic preganglionic fibers from the facial nerve, continues as the nerve of the pterygoid canal and ultimately synapses with the pterygopalatine ganglion whose parasympathetic postganglionic fibers synapse with the lacrimal gland and the mucosal glands of the nose, palate, and pharynx.
What is Bell’s palsy?
Bell’s palsy is a form of facial paralysis resulting from a dysfunction of the cranial nerve VII (the facial nerve) causing an inability to control facial muscles on the affected side. Often the eye in the affected side cannot be closed.
What is hyperacusis?
a health condition characterized by an increased sensitivity to certain frequency and volume ranges of sound (a collapsed tolerance to usual environmental sound). A facial nerve lesion may cause abnormal responses in the tensor tympani and stapedius muscles.
Why does an ischaemic stroke result in contralateral lower facial paralysis only, whereas a facial nerve lesion will result in complete ipsilateral facial paralysis?
The eyes and forehead receive innervation from both hemispheres, while the lower face only receives innervation from the contralateral hemisphere
The strictly contralateral innervation of the lower half of the face and dual innervation of the upper half of the face is critical when assessing facial weakness. Lesions that damage the motor cortex, such as acute ischemic strokes, will result in contralateral facial weakness of the lower face only, with preservation of the muscles of the upper face on both sides, due to the dual innervation of the upper face. Patients will have a weak smile, but will be able to close their eye tightly and wrinkle their forehead symmetrically. This pattern is often referred to as “central facial weakness,” because it’s caused by injury to the cerebral cortex, which is a part of the central nervous system.
Lesions that damage the facial nerve in the brainstem, or after it exits the brainstem, result in ipsilateral facial weakness involving both the upper and lower face. It doesn’t matter where the innervation is coming from; if the nerve is damaged, all the muscles on that side of the face are weak. These lesions are referred to as “peripheral lesions” because they affect the facial nerve as it exits the brainstem. Patients will be unable to wrinkle their forehead, tightly close their eye, or smile on the affected side. This distinction can aid in localizing the lesion to the appropriate place in the nervous system, thereby narrowing the differential diagnosis.
How can hearing be tested at the bedside?
Whispering into each of the ears individually.
Which nerves are affected by acoustic neuromas?
Facial (VII)7 and vestibulocochlear (VIII)8 - due to compression by the tumour.
What are dysphagia, dysphonia and dysathria?
Dysphagia - difficulty swallowing
Dysphonia - an impairment in the ability to produce voice sounds
Dysarthria - a motor speech disorder resulting from neurological injury of the motor component of the motor-speech system and is characterized by poor articulation of phonemes
Which cranial nerve(s) may be involved in dysarthria?
Trigeminal nerve’s motor branch (V)5
Facial nerve (VII)7
Glossopharyngeal nerve (IX)9
Vagus nerve (X)10
Hypoglossal nerve (XII)12.
Which cranial nerve(s) may be involved in dysphagia?
Glossopharyngeal (IX)9
Vagus (X)10
Accessory (XI)11
Hypoglossal (XII)12.
Which cranial nerve(s) are involved in dysphonia?
Vagus (X)10, ?anything else
What kind of sensory fibres are carried by the glossopharyngeal nerve?
General sensory fibres from posterior 1/3 of tongue.
Visceral sensory fibres from baroreceptors of the carotid sinus and chemoreceptors of the carotid body.
The glossopharyngeal nerve also has a parasympathetic component. What does this supply?
Ipsilateral parotid gland.
To where does the vagus nerve supply parasympathetic and motor innervation?
Thoracic and abdominal viscera.
What is the root of the spinal accessory nerve?
Cervical rootlets (more specific?)
Where does the spinal accessory nerve enter the cranial cavity?
Via the foramen magnum, briefly joining the cranial root of the accessory nerve before exiting through the jugular foramen.
How would you test the functioning of the spinal root of the accessory nerve.
The trapezius muscle is tested by asking the patient to shrug their shoulders with and without resistance. A one-sided weakness is indicative of an injury to the spinal accessory nerve on the same side (termed ipsilateral) of the body being assessed. The sternocleidomastoid muscle is tested by asking the patient to turn their head to the left or right against resistance. Weakness in head-turning suggests injury to the contralateral spinal accessory nerve: a weak leftward turn is indicative of a weak right sternocleidomastoid muscle (and thus right spinal accessory nerve injury), while a weak rightward turn is indicative of a weak left sternocleidomastoid muscle (and thus left spinal accessory nerve).
Where is the spinal nerve particularly at risk of damage?
?Posterior cervical neck
How would you assess the functioning of the Hypoglossal nerve (XII)12?
Ask the patient to stick out the tongue and move from side to side. Inspect for tongue atrophy, fasciculations or asymmetry in movement or appearance.
Tongue curves towards lesioned side
What would you deduce if a patient’s tongue deviated to one side when protruded?
There is a lesion in the hypoglossal nerve on the side the tongue points to.
What kind of fibres does the pterygopalatine ganglion receive?
Parasympathetic fibres from the facial nerve and supplies the lacrimal glands, palatine glands, and mucosa of the nasal cavity.
What kind of fibres does the otic ganglion receive?
Parasympathetic fibres from the glossopharyngeal nerve and supplies the parotid gland.
What kind of fibres does the submandibular gland recieve?
Parasympathetic fibres from the facial nerve; supplies the submandibular and sublingual glands.
Do sympathetic fibres pass through the facial ganglia?
Yes, but they do not synapse within them.
Which cranial nerve exits through the cribriform plate of the ethmoid bone?
Olfactory (I)1
Which cranial nerve exits through the optic canal?
Optic (II)2
Which cranial nerves exit through the superior orbital fissure?
Oculomotor (III)3
Trochlear (IV)4
Opthalmic division of the trigeminal (V1)
Abducens nerve (VI)6
Which cranial nerve exits via the foramen rotundum?
Maxillary division of the trigeminal (V2)
Which cranial nerve exits via the foramen ovale?
Mandibular division of the trigeminal (V3)
Which cranial nerve exits via the stylomastoid foramen?
Facial (VII)7
Which cranial nerve exits via the internal acoustic meatus?
Vestibulocochlear (VIII)8
Which cranial nerves exit through the jugular foramen?
Glossopharyngeal (IX)9
Vagus (X)10
Accessory nerve (XI)11
Which cranial nerve exits through the hypoglossal canal?
Hypoglossal (XII)12
What are the functions of the olfactory nerve (I)1?
Smell
What are the functions of the optic nerve (II)2?
Vision
What are the functions of the oculomotor nerve (III)3?
General somatic efferent — innervates levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, and inferior oblique muscles
General visceral efferent — innervates sphincter pupillae for pupillary constriction; ciliary muscles for accommodation of the lens for near vision
What are the functions of the trochlear nerve (IV)4?
Innervates superior oblique muscle
What are the functions of the trigeminal nerve (V)5?
General somatic afferent — sensory from: ophthalmic division [V1]—eyes, conjunctiva, orbital contents, nasal cavity, frontal sinus, ethmoidal cells, upper eyelid, dorsum of nose, anterior part of scalp, dura in anterior cranial fossa, superior part of tentorium cerebelli; maxillary nerve [V2]—dura in middle cranial fossa, nasopharynx, palate, nasal cavity, upper teeth, maxillary sinus, skin covering the side of the nose, lower eyelid, cheek, upper lip; mandibular division [V3]—skin of lower face, cheek, lower lip, anterior part of external ear, part of external acoustic meatus, temporal fossa, anterior two-thirds of tongue, lower teeth, mastoid air cells, mucous membranes of cheek, mandible, dura in middle cranial fossa
Brachial efferent — innervates temporalis, masseter, medial and lateral pterygoids, tensor tympani, tensor veli palatini, anterior belly of digastric, and mylohyoid muscles
What is the function of the abducens nerve (VI)6?
Innervates lateral rectus muscle
What are the functions of the facial nerve (VII)7?
General somatic afferent — sensory from part of external acoustic meatus and deeper parts of auricle
Special afferent — taste from anterior two-thirds of tongue
General visceral afferent — innervates lacrimal gland, submandibular and sublingual salivary glands, and mucous membranes of nasal cavity, hard and soft palates
Brachial efferent — innervates muscles of face (muscles of facial expression) and scalp derived from the second pharyngeal arch, and stapedius, posterior belly of digastric, stylohyoid muscles
What are the functions of the vestibulocochlear nerve (VIII)8?
Vestibular division—balance
Cochlear division—hearing
What are the functions of the glossopharyngeal nerve?
General visceral afferent — sensory from carotid body and sinus
General somatic afferent —posterior one-third of tongue, palatine tonsils, oropharynx, and mucosa of middle ear, pharyngotympanic tube, and mastoid air cells
Special afferent — taste from posterior one-third of tongue
General visceral efferent — innervates parotid salivary gland
Brachial efferent —innervates stylopharyngeus muscle
What are the functions of the vagus nerve (X)10?
General somatic afferent —sensory from larynx, laryngopharynx, deeper parts of auricle, part of external acoustic meatus, and dura in posterior cranial fossa
General visceral afferent — sensory from aortic body chemoreceptors and aortic arch baroreceptors, esophagus, bronchi, lungs, heart, and abdominal viscera of the foregut and midgut
Special afferent — taste from the epiglottis and pharynx
General visceral efferent — innervates smooth muscle and glands in the pharynx, larynx, thoracic viscera, and abdominal viscera of the foregut and midgut
Brachial efferent—innervates one tongue muscle (palatoglossus), muscles of soft palate (except tensor veli palatini), pharynx (except stylopharyngeus), and larynx
What are the functions of the accessory nerve (XI)11?
Innervates sternocleidomastoid and trapezius muscles.
What are the functions of the hypoglossal nerve (XII)12?
Innervates hyoglossus, genioglossus, and styloglossus muscles and all intrinsic muscles of the tongue.
What is the general function of general somatic afferent fibres?
Perception of touch, pain, temperature.
What is the general function of general visceral afferent fibres?
Sensory input from viscera.
What is the general function of special afferent fibres?
Smell, taste, vision, hearing, and balance.
What is the general function of general somatic efferent fibres?
Motor innervation to skeletal (voluntary) muscles
What is the general function of general visceral efferent fibres?
Motor innervation to smooth muscle, heart muscle, and glands.
What is the general function of brachial efferent fibres?
Motor innervation to skeletal muscles derived from pharyngeal arch mesoderm.
