Lectures 8, 10: Brainstem and Cranial Nerves

Question 1

The trochlear nerve emerges __________ and wraps around the brainstem at what junction?

Answer 1

Ventrally; at the junction b/t the midbrain and pons

Question 2

Motor nuclei are _______ and sensory nuclei are _______

Answer 2

Medial; lateral

Question 3

Cortical innervation of cranial nerves is bilateral in all cases except (2)

Answer 3

Portion of VII and XII

Question 4

What is the significance of bilateral cortical innervation of cranial nerves?

Answer 4

Unilateral cortical lesion would not impact nerve function

Question 5

What is the sole CN that crosses the midline?

Answer 5

IV

Question 6

Discuss the anatomy of the olfactory nerve

Answer 6

Short primary sensory nerves (cranial nerves) –> (cribiform plate) –> Olfactory bulb –> primary olfactory cortex

Question 7

What is one way to damage olfactory nerve fibers? What process of the cell is damaged?

Answer 7

Anterior cranial fossa fractures; primary axons

Question 8

How do you test for CSF rinorrhea?

Answer 8

Glucose or beta 2 transferrin

Question 9

Anosmia

Answer 9

Loss of sense of smell

Question 10

Parosmia

Answer 10

Perverted sense of smell

Question 11

Olfactory hallucinations are often caused by…

Answer 11

Temporal lobe (parahippocampal) seizures

Question 12

How do you test olfactory nerve function?

Answer 12

Coffee/vanilla, one side at a tie; note: don’t use an irritating smell

Question 13

Temporary anosmia caused by colds affects what level of the olfactory system?

Answer 13

The receptors

Question 14

What are four ways to damage the central processing structures of the olfactory system?

Answer 14

Contusion/laceration of olfactory bulb, aneurysm, olfactory groove meningioma, frontal lobe tumor

Question 15

What are the 3 trigeminal sensory nuclei and what do each control?

Answer 15

1. Spinal trigeminal: crude touch; 2. Pontine Trigeminal (chief): discriminative touch; 3. Mesencephalic: proprioception from muscles of mastication

Question 16

Where is the trigeminal motor nucleus?

Answer 16

The pons

Question 17

What are the 3 branches of the trigeminal nerve and where does each exit the skull?

Answer 17

V1: Opthalmic, superior orbital fissure; V2: Maxillary, foramen rotundum; V3: Mandibular, foramen ovale

Question 18

Where are the cell bodies of the sensory fibers of the trigeminal nerve?

Answer 18

Trigeminal ganglion

Question 19

What is unique about the cell bodies that control the jaw jerk reflex?

Answer 19

They are located in the mesencephalic nucleus, not the trigeminal ganglion

Question 20

What is one common condition associated with the trigeminal nerve? Describe this condition and a common cause

Answer 20

Trigeminal neuralgia; triggered by light touch/gustatory, rarely during sleep, pain-free intervals; common cause: vascular compression due to oligodendrocyte myelination

Question 21

The jaw deviates to the ________ side

Answer 21

Affected

Question 22

To test the 1st branch of the trigeminal ganglion, you can check which reflex?

Answer 22

Corneal

Question 23

What virus often effects the trigeminal nerve? What is one complication that must be evaluated for?

Answer 23

Herpes zoster; herpes opthalmicus (if it affets the opthalmic division)

Question 24

Why is the trigeminal nerve associated with an parasympathetic reflex?

Answer 24

Very close to superior salivatory nucleus –> sinus symptoms, watery eyes

Question 25

Where is the facial motor nucleus? The part of the nucleus supplying forehead muscles gets what type of innervation? What about lower facial muscles? What two muscles besides muscles of facial expression?

Answer 25

Pons; bilateral; contralateral; stapedius (dampens sound) and part of digastric

Question 26

Where are the cell bodies of the sensory fibers of the facial nerve? What nerve connects this ganglion to the brainstem nuclei?

Answer 26

Geniculate nucleus; nervous intermedius

Question 27

What does the GSA section of the facial nerve control? What nucleus?

Answer 27

Ear sensations (concha, behind ear, external auditory canal); spinal trigeminal

Question 28

What does the SVA section of the facial nerve control? What nucleus? What special nerve?

Answer 28

Taste from anterior 2/3 of tongue; solitary nucleus; chorda tympani

Question 29

What does the GVE section of the facial nerve control? What two nerves? What nucleus?

Answer 29

Lacrimal gland via V2 branches; Submandibular and sublingual via chorda tympani; superior salivatory nucleus

Question 30

Describe the basic anatomy of the facial nerve

Answer 30

Exits brainstem through cerebellopontine angle --> internal auditory meatus and facial canal --> stylomastoid foramen

Question 31

A lower motor neuron lesion causes facial palsy where? What are three common causes?

Answer 31

Palsy on same side as lesion on upper and lower face; Bell's palsy, meningeal process (Guillain-Barre), or a stroke involving the VII nucleus

Question 32

An upper motor neuron lesion causes facial palsy where? What is a common cause?

Answer 32

Palsy on contralateral side as lesion on lower face only; stroke

Question 33

Describe the fives types of information carried by the Glossopharyngeal nerve

Answer 33

SVE: stylopharyngeus (swallowing); GVE: parotid gland; GSA: middle ear; SVA: taste from posterior 1/3 of tongue; GVA: touch from pharynx and posterior 1/3 of tongue, afferent limb of gag reflex, carotid body/sinus

Question 34

Describe the basic anatomy of the glossopharyngeal nerve. What are the associated nuclei?

Answer 34

Exits the brainstem ventrally from upper medulla --> jugular foramen; spinal trigeminal, nucleus ambiguus, solitary nucleus, caudal solitary nucleus, inferior salivatory nucleus

Question 35

Lesions of the glossopharyngeal nerve can cause (5)

Answer 35

Difficulty swallowing, taste impairment, impaired gag refelx, reduced saliva, syncope

Question 36

One condition unique to glossopharyngeal nerve

Answer 36

Glossopharyngeal neuralgia

Question 37

Describe the basic anatomy of the vagus nerve

Answer 37

Exist the brainstem from the medulla --> jugular foramen --> carotid sheath (inbetween internal carotid and internal jugular)

Question 38

The vagus nerve synapses on what four nuclei? Fiber type and functions?

Answer 38

1. Dorsal nucleus of vagus nerve (GVE, parasympathetic output to viscera --> left colic flexure); 2. Nucleus ambiguus (SVE, brachial muscles of larynx/pharynx, upper esophagus, palate); 3. Solitary nucleus (SVA and GVA, epiglottal taste and sensation from mouth --> L colic flexure); 4. Trigeminal nucleus (GSA, dura, external ear and tympanic membrane)

Question 39

Six main functions of vagal nerve

Answer 39

Phonation, swallowing, palate elevation, taste, cutaneous sesnastion from ear, and visceral innervation (neck --> L colic flexure)

Question 40

What are some symptoms of vagal problems (4)

Answer 40

Loss of gag reflex, paralysis of soft palate (dyspnea, dysarthria, dysphagia), parasympathetic disturbances, lowering of palate and deviation of uvula

Question 41

What is unique about the uvula?

Answer 41

Deviates TOWARD normal side

Question 42

What are the two divisions of the spinal accessory nerve and how are they anatomically similar and different? What do they innervate?

Answer 42

Cranial division arises from the nucleus ambiguus --> jugular foramen --> intrinsic muscles of larynx but NOT cricothyroid; Spinal division arises from the ventral horn of C1 - C6 --> foramen magnum --> jugular foramen --> sternocleidomastoid and trapezius

Question 43

Three clinical correlations of the spinal accessory nerve

Answer 43

1. Difficulty turning head to contralateral side; 2. Shoulder droop; 3. Larynx paralysis

Question 44

Describe the anatomy and basic function of the hypoglossal nerve

Answer 44

Mediates tongue movement; hypoglossal nucleus --> hypoglossal canal --> intrinsic and extrinsic tongue muscles

Question 45

If LMNs are involved, the how does the tongue deviate? IF UMNs?

Answer 45

Toward lesion; away from lesion

Question 46

What is Pseduobulbar palsy?

Answer 46

Bilateral corticobulbar tracts involved; inability to control facial movements, swallowing, spastic speech, emotional outbursts