Cranial nerves III, IV & VI

Question 1

CN V modality…

Answer 1

Somatic sensory (skin, muscles, joints in head)

Question 2

CN X modality…

Answer 2

Viceral sensory (Cranial, thoracic, abdominal viscera)

Question 3

CN VII & IX modality…

Answer 3

Viceral Sensory (Taste buds)

Question 4

CN VIII modality…

Answer 4

Special (inner ear)

Question 5

CN III, IV &VI Modality….

Answer 5

Somatic motor (Extraocular muscles)

Question 6

CN XII modality…

Answer 6

Somatic motor (Tongue muscles)

Question 7

CN X modality…

Answer 7

Viceral motor (Parasympathetic ganglia for cranial, thoracic and abdominal.)

Question 8

CN V, VII, X, XI modality….

Answer 8

Brachial motor (Jaw muscles, facial muscles, laryngeal & pharyngeal muscles, middle ear muscles, SCM & trapezius muscles.)

Question 9

Function of Superior rectus muscle…

Answer 9

Elevation of eye

Question 10

Function of Inferior rectus muscle..

Answer 10

Depression of eye

Question 11

Function of lateral rectus..

Answer 11

Abduction of eye

Question 12

Function of Medial rectus…

Answer 12

Adduction of eye

Question 13

Function of superior oblique muscle..

Answer 13

Internal rotation of eye (intorsion)

Question 14

Function of Inferior oblique muscle

Answer 14

External rotation (Extorsion) of eye

Question 15

Results of CN III injury.. (8 things)

Answer 15

• Eye ipsilateral to lesion deviates laterally.
• Patient cannot move eye medially
• Vertical movement impaired
• Diplopia: double vision
• Ipsilateral levator palpebrae superioris is weak.
• Mydriasis = puplis on affected side is dilated.
• Pupil does not constrict in response to light.
• Lens cannot be focused for near vision

Question 16

CN IV innervates what?

Answer 16

Contralateral superior oblique muscle!

Question 17

Results of CN IV injury… (2 things)

Answer 17

• Much less noticeable than III
• Sup. Oblique moves eye downward and laterally.
• Patients report diplopia when going downstairs or reading.

Question 18

CN VI innervates what?

Answer 18

Ipsilateral Lateral rectus Muscle.

Question 19

Results of CN VI injury..

Answer 19

• Causes medial strabismus and lateral gaze paralysis
• Ipsilateral eye will not abduct past midpostion and contralateral eye will not adduct past midpostion.
• Nucleus contains motor neurons and internuclear neurons that ascend in the MLF (Medial longitudinal fasciculus)

Question 20

Describe the function of the Medial Longitudinal Fasciculus…

Answer 20

• MLF allows coordination of head and eye movements.

- Interconnects III, IV, & VI nuclei to allow this.

Question 21

MLF injury results in… (4 things)

Answer 21

• Internuclear ophthalmoplegia (Paralysis of the eye due to damage between the nuclei)
• Removes excitatory input to ipsilateral III nucleus.
• Eye Ipsilateral to lesion fails to move past midpostion during horizontal gaze.
• Both VI nuclei are intact so lateral movements of both eyes