Lecture 6: Cranial Nerves Flashcards
What is the general organisation of CN nuclei in the brainstem?
Sensory nuclei lie lateral and motor nuclei lie more medial.
The most medial is somatic motor with parasympathetic motor beside them and head and neck motor below. Laterally to this is the visceral sensory, somatic sensory and special sensory nuclei. There are about 17 types of nuclei. They are located in the Tegmentum of the brainstem.
Which cranial nerves are purely efferent, afferent or mixed?
Efferent (motor) (5):
- Trochlear Nerve
- Abducens Nerve
- Spinal Accessory
- Hypoglossal
- Occulomotor Nerve
Afferent (sensory) (3):
- Optic Nerve
- Olfactory Nerve
- Vestibulocochlear
Mixed ():
- Facial Nerve
- Trigeminal
- Glossopharyngeal
- Vagus
For cranial Nerve I and II:
(a) Location
(b) Exit foramina
(c) Function
(d) Test
CN I - Olfactory Nerve
(a) Nasal Epithelium
(b) Cribriform Plate
(c) Special sensory - olfaction
(d) Change in sense of smell
CN II - Optic Nerve
(a) Emerging from the retina
(b) Optic canals
(c) Special Sensory - Vision
(d) Various vision Test such as Snellen’s Test, Fundoscopy, Colour vision etc.
Which sensory modality does not go through the thalamus?
Olfaction
For cranial Nerve III, IV and VI:
(a) Location
(b) Exit foramina
(c) Function
(d) Test
CN III Occulomtor Nerve
(a) Pontomesencephilic junction
(b) Superior orbital fissure
(c) Somatic motor - 4 extra ocular muscles and visceral motor (parasympathetic) - cillary and papillae muscles
(d) H Test
CN IV Trochlear
(a) Dorsal midbrain
(b) Superior orbital fissure
(c) Somatic motor - Superior oblique muscle
(d) H Test
CN VI Abducens
(a) Pontomedullary junction
(b) Superior orbital fissure
(c) Somatic motor - Lateral rectus
(d) H Test
Along which axes can the eye move?
The eyeball can move in 3 different axis - vertical axis through the eyeball, horizontal axis through the eyeball and an anterior-posterior axis. Adduction and abduction of the eyeballs refers to movement along the horizontal plane. Elevation and depression is along the vertical axis. Medial and lateral rotation is movement along the anterior-posterior axis. The top of the eyeball either intort or extorts. Muscles also do not act in isolation.
What muscles are used to:
- Close the eye lid?
- Open the eyelid?
Close the eyelid: Orbicularis oculi (CN VII)
Open the eyelid:
- Levator palpebrae superioris (CN III)
- Superior tarsal muscle - keeps the eyelid open (sympathetic)
What muscles are used to dilate and constrict the pupil and lens? What are these muscles innervated by?
Dilate the pupil - Dilators of the iris (sympathetic)
Constrict the pupil - Sphincter pupillae (CN III parasympathetic)
Change the lens shape: Cillary muscles (CN III parasympathetic)
For cranial Nerve V:
(a) Location
(b) Exit foramina
(c) Function
(d) Test
CN V - Trigeminal Nerve V1 - Olfactory Branch (a) Pons (b) Superior orbital fissure (c) Somatic sensory to the upper face around the eyes (d) Test sensation around the area
V2 - Maxillary Branch
(a) Pons
(b) Foreman Rotandum
(c) Somatic sensory to the middle of the face between the eyes and mouth
(d) Test sensation around the area
V3 - Mandibular Branch
(a) Pons
(b) Foramen Ovale
(c) Somatic sensory to the lower face around the mandible. Also branchial motor supply to the muscles of mastication, anterior belly of the digastric, tensor tympani etc.
(d) Test sensation around the area. To test motor component as the patient to protrude their jaw and move it side to side against resistance (ptypergoids).
Which 4 autonomic ganglia are associated with CN V?
- Cillary ganglia
- Pterygopalatine
- Submandibular
- Otic
For cranial Nerve VII and VIII:
(a) Location
(b) Exit foramina
(c) Function
(d) Test
CN VII - Facial Nerve
(a) Cerebellopoutine angle
(b) Internal acoustic meatus (entry) Stylomastoid foramen (exist)
(c) Somatic sensory - skin of the ear
Visceral motor - glands except the parotid
Special sensory - taste to the anterior 2/3rds of the tongue
Branchial motor - muscles of facial expression, stapedius and posterior belly of the digastric
(d) facial movements, taste and salivation
CN VIII -Vestibulococcular
(a) Cerebellopoutine angle
(b) Internal acoustic meatus
(c) Special sensory - hearing
(d) beside hearing tests
Give examples of branches CN VII gives off before existing the skull.
On its path before it exists the skull, it gives rise to many branches such as the greater petrosal branch of VII which innervates some of the glands causing secretion. It also gives rise to the branch to the chorda tympani. The terminal branches continue and exist through the stylomastoid foreman.
For cranial Nerve IX and X:
(a) Location
(b) Exit foramina
(c) Function
(d) Test
CN IX - Glossopharyngeal
(a) Posterolateral sulcus of the medulla (lateral to the olives)
(b) Jugular Foreamen
(c) Branchial motor - supplies muscles of the pharynx for swallowing
Visceral motor - parotid gland
Special sensory - taste to the posterior 1/3rd of the tongue
Somatic sensation - middle ear, pharynx and posterior tongue
Visceral sensory - carotid body and carotid sinus
(d) gag reflex
CN X - Vagus Nerve
(a) Posterolateral sulcus of the medulla
(b) Jugular foramen
(c) Branchial motor - larynx, uvula and pharynx
Visceral motor and Visceral sensory - GI and thorax
Special sensory - taste to the epiglottis and palette
Somatic sensation - epiglottis, skin of the external ear and larynx
(d) Test with speech and looking for any deviation of the uvula.
For cranial Nerve XI and XII:
(a) Location
(b) Exit foramina
(c) Function
(d) Test
CN XI - Spinal Accessory Nerve
(a) Posterolateral sulcus of the medulla, caudal medulla and rostral spinal cord
(b) Jugular foreamen
(c) Somatic motor to the sternocleidomastoid muscle and trapezius
(d) Shrugging the shoulders and rotating the head against resistance.
CN XII - Hypoglossal Nerve
(a) Anterolateral sulcus of the medulla
(b) Hypoglossal canal
(c) Somatic motor to the tongue
(d) Ask the patient to protrude their tongue and see if it is deviated
If the right CN XII is damaged which side will the tongue deviate to?
The right:
If the CN XII is functioning on both sides the two muscles should contract simultaneously and the tongue should protrude straight. If there is an injury to the hypoglossal nerve, it will deviate to the side of the lesion as the muscle on the correct side will take over.
