5.1.3 Cranial Nerves VIII,IX and X

Question 1

What fibres does CNVIII (vestibulochochlear) carry?

Answer 1

Speical sensory- hearing and balance

Question 2

What parts of CNVIII are responsible for each special sense?

Answer 2

Cochlea- hearing
Semiricular canals- balance

Question 3

How do you test CNVIII?

Answer 3

Gross bedside hearing tests, whisper/ finger rub

Tuning fork testing (Webers * Rinnes - separate deck on these two alone later on)

Question 4

What do patients with CNVIII lesions present with?

Answer 4

Hearing loss
+/- dizziness (vertigo) +/- tinnitus (constant ringing sound in the ears)

Question 5

What are some causes of CNVIII lesions?

Answer 5

• Vestibular schwannoma (accoustic neuroma)
• Occlusion of labyrinthine artery (supplies the nerve)
• Base of skull fracture (involving petrous bone)
• Brainstem lesions in the pons, very rare

Question 6

What is a vestibular schwannoma (acoustic neuroma)?

Answer 6

Benign tumour involving schwann cells associated with vestibulochochlear

Slow growing

Usually unilateral

Question 7

What are the symptoms of an acoustic neuroma?

Answer 7

• Unilateral hearing loss
• Tinnitus
• Vertigo
• Numbness, pain or weakness down one half of face (remember both CNVII and CNVIII enter petrous bone, so closely related)

Question 8

What nerve fibres does the glossopharyngeal nerve (CNIX) carry?

Answer 8

Special sensory, sensory, motor and parasympathetics

Question 9

Outline the path of the glossopharyngeal nerve

Answer 9

1. Medulla
2. Run through posterior cranial fossa
3. Exit through jugular foramen
4. Enter into carotid sheath (therefore close relationship with ICA and ECA)
5. Glossopharyngeal leaves sheath superiorly

Question 10

Outline the function of each of the fibres carried by CNIX

Answer 10

Sensory
Oropharynx, tonsils, middle ear cavity
Posterior 1/3 tongue (SS and GS)

Motor
Stylopharyngeus in the pharynx

Parasympathetic
Parotid gland, afferents from carotid sinus and body

Question 11

How do glossopharyngeal and vagus nerve lesions present?

Answer 11

• Difficulty with swallowing
• Weak cough (CNX)
• Difficulties with speech or changes in voice (CNX)

Question 12

How do you test CNIX and CNX

Answer 12

Speech,swallow,cough
Soft palate movement & uvula position (CNX)
Gag reflex (IX-afferent X-efferent)

Question 13

How can CNIX and X be damaged?

Answer 13

RLN branch of CN X- (thyroid pathology or surgery; superior thorax/mediastinal pathology)

Pathology or surgery involving carotid sheath structures
(e.g. common or internal carotid artery dissection, carotid endartectomy)

Posterior cranial fossa tumours, base of skull fractures (jugular foramen)

Brainstem (medullary) lesions e.g. infarct, MND

Question 14

Outline the path of CNX (vagus)

Answer 14

1. Medulla
2. Run through posterior cranial fossa
3. Exit through jugular foramen
4. Carotid sheath
5. Vagus contiues down entire length giving off superior laryngeal branches and recurrent larygneal branches

Question 15

What fibres does CNX carry and what are their functions?

Answer 15

Motor
Muscles of larynx/pharynx, including soft palate

Sensory
Larynx/laryngopharynx

Parasympathetic
MANY TISSUES, heart, thorax, bowel etc…

Question 16

Explain uvula deviation in vagus nerve lesions

Answer 16

Uvula pulled to side with no lesion, so if there is a left sided lesion, the uvula doesnt get pulled to the left so its only pulled to the right