CN/NO

Question 1

Which EOM extort and intort the eye?

Answer 1

Extortion: Inferior muscles (inferior rectus and inferior oblique)

Intortion: Superior muscles (superior rectus and superior oblique)

Question 2

How do hydroxyamphetamine drops help localize Horner’s syndrome?

Answer 2

Will dilate in 1st and 2nd order neuron lesions but not in 3rd order lesions.

(Hydroxyamphetamine causes release of NE, so if 3rd order intact will cause dilation).

(Contrast with cocaine, which inhibits NE reuptake and so will only dilate the pupil if the entire sympathetic pathway is intact).

Question 3

Which oculomotor (CN III) subnucleus supplies its respective EOM on the contralateral side?

Answer 3

Superior rectus (all others - inferior rectus, medial rectus, inferior oblique - are ipsilateral).

(Recall the superior oblique also supplied by contralateral nucleus, although trochlear - so both superior EOM supplied by contralateral nucleus).

Question 4

Where do parasympathetic fibers to the pupil originate?

Answer 4

Edinger-Westphal subnuclei (rostral midbrain at the level of the superior colliculus).

(Each E`dinger-Westphal nucleus receives input from bilateral pretectal nuclei, which is why bilateral pupillary response occurs).

Question 5

What single lesion can lead to bilateral ptosis?

Answer 5

Central caudal nucleus - A single unpaired oculomotor subnucleus which innervates both levator palpebrae superioris (although getting an isolated lesion to this subnucleus would be exceedingly rare).

Question 6

Which muscle does a given trochlear nucleus innervate?

Trochlear nerve?

Answer 6

Nucleus: contralateral superior oblique

Nerve: ipsilateral superior oblique

(Fibers decussate prior to exiting the brainstem).

(Note superior rectus analogously supplied by contralateral oculomotor subnucleus, while other oculomotor-supplied muscles are aupplied by ipsilateral nucleus).

Question 7

Aneurysms in what vessels can cause compressive CN III palsy?

Answer 7

Pcomm (most common), PCA, SCA, tip of the basilar.

(PICA aneurysm would not cause it).

(Basically, the posterior circulation in and near the COW).

Question 8

What does an MLF lesion produce?

Answer 8

INO where ipsilateral eye does not adduct on contralateral gaze.

(So with R MLF lesion, R eye does not adduct in L gaze).

(Because MLF crosses midline in pons and then ascends up on the side of the CN III nucleus it connects to).

Question 9

Idiopathic tonic pupil (Adie’s pupil):

Acute findings?

Chronic?

Answer 9

Acute: enlarged and nonreactive to light and accomodation (loss of parasympathetics)

Chronic: small and nonreactive to light but with intact (but slow) reactivity to accomodation

(Idiopathic tonic pupil thought to be postgangionic parasympathetic lesion, possibly viral).

Question 10

Which sensory modality does not have a thalamic synapse?

Answer 10

Olfaction (direct connection from olfactory bulb to olfactory cortex)

Question 11

Do the following features pertain to peripheral or central causes of vertigo?

1. Fatiguability
2. Latency
3. Suppression by visual fixation
4. Lasting >1 minute
5. Occurring in multiple directions of gaze?

Answer 11

1. Fatiguability: peripheral
2. Latency: peripheral (typically 2-20 s)
3. Suppression by visual fixation: Peripheral
4. Lasting >1 minute: central
5. Occurring in multiple directions of gaze: central

Question 12

What are the primary muscles of mastication? What is their innervation?

Answer 12

Masseter, temporalis, medial and lateral pterygoids.

All innervated by V3.

Question 13

What are the intratympanic muscles and what is their innervation?

Answer 13

1. Tensor tympani - V3/mandibular
2. Stapedius - VII/facial

Question 14

What is the only muscle innervated by the glossopharyngeal nerve?

Answer 14

Stylopharyngeus (swallowing)

Question 15

Innervation of salivary glands

Answer 15

Sublingual and submandibular: facial

Parotids: glossopharyngeal

Question 16

Non-motor structures supplied by facial nerve?

Answer 16

1. Parasympathetic to lacrimal, submandibular, and sublingual glands (NOT parotid, which is glossopharyngeal)
2. Taste for anterior 2/3 tongue
3. Sensory from external auditory canal and pinna

Question 17

Branches of facial nerve, what do they supply, and where do they branch?

Answer 17

1. Greater petrosal nerve - parasympathetic to lacrimal gland - branches at geniculate ganglion.
   (Note that this synapes at the pterygopalatine ganglion, and postsynaptic fibers travel with V).
2. Nerve to stapedius - stapedius muscle - no specific landmark but prior to exit from stylomastoid foramen
3. Chorda tympani nerve - taste from anterior 2/3 tongue and parasympathetic to sublingual and submandibular glands - just before exit from stylomastoid foramen
4. Then rest of facial nerve - facial muscle - branche after exit stylomastoid foramen

(So segments go to eye, ear, mouth-ish, and face).

Question 18

Role of nucleus tractus solitarius

Answer 18

1. Taste (rostral nucleus (from facial, glossopharyngeal, and vagus)
2. Baroreceptor input (caudal nucleus, from vagus)

(So 2 special senses).

Question 19

Role of nucleus ambiguus

Answer 19

Motor to larynx and pharynx (via IX and X)

Question 20

Role of superior and inferior salivary nuclei

Answer 20

Superior: parasympathetic to head and neck (including submandibular and sublimgual glands as well as lacrimal gland, via VII and then V3)

Inferior: parotid gland (via IX)

Question 21

Innervation of muscles of mastication

Answer 21

V3

Question 22

Exit points in skull for V1, V2, and V3

Answer 22

V1: Superior orbital fissure
V2: Foramen rotundum
V3: Foramen ovale

Question 23

What reside’s in Meckel’s cave? Where is it?

Answer 23

Trigeminal ganglion (sensory ganglion of V).

It is on the floor of the middle cranial fossa. Lateral to cavernous sinus and ICA.

Question 24

Muscles innervated by CN XI

Answer 24

SCM and trap (contralateral turners). Also causes ipsilateral head tilt.

Question 25

What travels through the jugular foramen?

Answer 25

CN IX, X, XI

Question 26

What passes through the internal acoustic meatus?

Answer 26

CN VII/7 and VIII/8

Question 27

Afferent and efferent limbs of gag reflex

Answer 27

Afferent: IX
Efferent: X

Question 28

What is direction of compensatory head tilt in CN IV palsy?

Answer 28

Contralateral

(Superior oblique intorts eye, so lesion leads to extorsion, so tilt head contralaterally to intort opposite eye to match extorted eye on side of lesion)