Bb1 Cranial Nerves Part 2

Front 1

What are areas of the brain involved in olfaction called?

Back 1

Rhinencephalon or 'smell' brain

Front 2

CN I: describe the receptors.

Back 2

Modified neurons in nasal epithelium. Function as both receptors and conduction neurons. Undergo mitosis throughout life.

Front 3

CN I: general pathway until they enter the brain.

Back 3

Unmyelinated axons of sensory olfactory receptors form the olfactory nerves which pass through the cribiform plate of the ethmoid bone and enter the olfactory bulb in the CNS. Olfactory tract forms from second order neurons in the olfactory bulbs. Divides into lateral, medial, and intermediate stria and enter the brain.

Front 4

What 3 areas do the olfactory tract project to?

Back 4

Temporal lobe structures (lateral olfactory area)
Frontal lobe structures (medial olfactory area)
Intermediate olfactory area - small nuclei in area of anterior perforated substance

Front 5

Where in the temporal lobe do the olfactory tracts project to?

Back 5

Uncus
Entorhinal cortex
Amygdala

Front 6

What is the pyriform cortex? What is special about it?

Back 6

Uncus + adjacent area of parahippocampal gyrus

Unlike all other primary sensory cortical areas, input does not relay through thalamus

Front 7

What is the entorhinal cortex?

Back 7

Area 28 = neocortical limbic system area critically involved in learning and memory

Front 8

Amygdala: function?

Back 8

Learned and unlearned emotional responses and memory

Front 9

Where in the frontal lobe do the olfactory tracts project? What is their function?

Back 9

Septal nuclei

Not important for smeell, part of the limbic system - mediating emotional responses to odors

Front 10

What happens after the 3 olfactory areas? Why?

Back 10

Project to other structures in the limbic system, which all have complex connections with the reticular formation and the ANS

Underlie emotional and visceral responses to smells

Front 11

What are the presenting symptoms of uncinate seizures?

Back 11

Disagreeable odors
Stereotypic movements of lips and tongue
Altered emotional state

Front 12

What word means a loss of smell?

Back 12

Anosmia

Front 13

What kind of fractures can affect smell? Why? What are other symptoms?

Back 13

Skull fractures involving the cribiform plate and ethmoid sinus

Tear fibers of olfactory nerve

Leakage of CSF

Front 14

What general type of things do lesions from the optic tract to area 17 result in?

Back 14

Contralateral homonymous hemianopsias or scotomas that respect the vertical meridian

Front 15

Describe the nuclei of the oculomotor nerve.

Back 15

Number of paired nuclei which supply each of the extraocular muscles. There is one unpaired nucleus which supplies the LPS on each side.

Front 16

EW: function?

Back 16

Supplies parasympathetic input to the ciliary ganglion

Front 17

What nerve closes the eye?

Back 17

CN VII

Front 18

Location of oculomotor nuclear complex

Back 18

Medial in the midbrain at the level of the superior colliculus

Front 19

What will a unilateral lesion of the oculomotor nerve result in? What is this constellation of symptoms called?

Back 19

Lateral or external strabismus - unable to move ipsilateral eye medially (eye will be down and abducted)
Ptosis ipsilaterally
Dilation of pupil ipsilaterally - no response to light or accomodation

Called the oculomotor ophthalmoplegia

Front 20

When will diplopia occur with an oculomotor nerve lesion? What kind of diplopia would occur?

Back 20

Only if the eyelid is raised

In the horizontal plane

Front 21

What results from a unilateral lesion involving motor cortex or descending corticobulbar fibers in the internal capsule to the eye? Why?

Back 21

No appreciable weakness of eye movements or double vision since fibers are both crossed and uncrossed (slightly more crossed)

Front 22

Location of the trochlear nucleus

Back 22

Medially in the midbrain at the level of the inferior colliculus

Front 23

What results from unilateral lesions of the trochlear nucleus and initial segment of the nerve in the midbrain?

Back 23

Patient will have difficulty in depressing and intorting his/her contralateral eye. Eye will be elevated and extorted.

Front 24

What results from unilateral lesions of the trochlear nerve after the fibers have decussated?

Back 24

Ipsilateral deficits - Unable to depress and intort the eye. Affected eye will be extorted and slightly elevated.

Front 25

What kind of diplopia results from trochlear nucleus/nerve lesions and how do you try to compensate? What things will the patient have problems with?

Back 25

Vertical diplopia

Tilting the head so that the image from the normal eye aligns from the image with the affected eye

Walking down stairs

Front 26

What results from a unilateral lesion of the cortex or descending corticobulbar fibers in the internal capsule for the trochlear nerve?

Back 26

No appreciable problems - because fibers are crossed and uncrossed, slightly more crossed.

Front 27

CN V: where are the cell bodies of the primary sensory neurons?

Back 27

Trigeminal ganglion (mostly
Mesencephalic nucleus

Front 28

What nerves innervate the external ear (sensory)?

Back 28

V
VII
IX
X
2nd and 3rd cervical nerves

Front 29

CN V: What 3 nuclei can the central processes from the trigeminal ganglia and mesencephalic nucleus synapse in? What are their functions?

Back 29

Chief sensory nucleus - discriminative touch, conscious proprioception
Spinal trigeminal nucleus - pain, temp
Mesencephalic - unconscious proprioception

Front 30

Spinal trigeminal tract - general pathway?

Back 30

Smaller and/or unmyelinated fibers of sensory root enter the pons and form the spinal trigeminal tract. Synapse in the spinal nucleus of V and in the reticular formation.

Front 31

Describe the location of the spinal trigeminal nucleus/tract.

Back 31

Extends from pons at level of chief sensory nucleus to the medulla. Part of a column continuous with zone of Lissauer and the substantia gelatinosa.

Front 32

Mesencephalic nucleus: location?

Back 32

Extends from the area of the chief sensory nucleus in the pons up into the midbrain

Front 33

Where do central processes from the mesencephalic nucleus project? Why?

Back 33

Mainly to motor nucleus of V for reflex control of bite

Front 34

Where do peripheral processs from the mesencephalic nucleus for CN V go?

Back 34

Enter the motor root of V, distribute to the mandibular division of the nerve. End in deep proprioceptive receptors/neuromuscular spindles.

Front 35

Describe the pathway of the jaw jerk reflex.

Back 35

Stretch of masseter muscle evokes afferents in mancibular portion of V, which goes to mesencephalic nucleus, which goes to motor nucleus of V.

Front 36

Give the pathway for the corneal reflex.

Back 36

Afferent limb - ophthalmic division of V. Goes to chief sensory nucleus of V and/or spinal tract and nucleus of V. Efferent limb is the motor nucleus of VII to the orbicularis oculi muscle. Projects bilaterally to get to motor nucleus of VII.

Front 37

How do you test the corneal reflex and what is the normal response?

Back 37

When the cornea is slightly touched (end of a Q-tip), the eyelid of that eye will close (direct response) and the contralateral eyelid will also close (consensual response).

Front 38

What results from a lesion in the afferent limb of the corneal reflex?

Back 38

Ipsilateral loss of direct or consensual response. Contralateral side will be normal.

Front 39

What results from a lesion in the efferent limb of the corneal reflex?

Back 39

No ipsilateral direct response but there will be consensual response. Stimulation of contralateral cornea will elicit a direct response but no consensual response.

Front 40

Describe the conscious appreciation of touch/pain for the face and the head pathway.

Back 40

Projects from various nuclei to the thalamus. Fibers from chief sensory and spinal trigeminal nuclei cross or decussate at different levels and enter the VPM via the trigeminothalamic tract, which them projects primarily to SI.

Front 41

What results from a unilateral lesion f the spinal trigeminal nucleus/tract, regarding touch/pain?

Back 41

Loss of pain and temperature and some touch in the ipsilateral face

Front 42

What results from a lesion of the trigeminothalamic tract regarding pain/temp/touch?

Back 42

Loss of pain and temp in the contralateral face. If the lesion is above the level of the chief sensory nucelsu, there would be a loss of pain and temperature and a loss of discriminative touch in the contralateral face.

Front 43

What is trigeminal neuralgia also known as?

Back 43

Tic douloureux

Front 44

Tic douloureux: presentation?

Back 44

Excruciating paroxysms of sharp/stabbing pain in the area of distribution of one of the trigeminal divisions. Usually unilateral. May show periods of remissions and exacerbations.

Front 45

What nerve is most commonly involved in tic douloureux?

Back 45

Maxillary portion of V

Front 46

What type of treatment is available for tic douloureux?

Back 46

Vascular decompression or surgical interruption of pain pathways

Front 47

How can herpes zoster affect CN V?

Back 47

If it involves the opthalmic division, it can result in painful ulcerations on the cornea and in severe cases can cause blindness.