Brainstem Review

Question 1

Where does CN I exit the brainstem?

Answer 1

Telencephalon - Olfactory

Question 2

Where does CN II exit the brainstem?

Answer 2

Diencephalon - Optic

Question 3

Where does CN III exit the brainstem?

Answer 3

Midbrain - Occulomotor

Question 4

Where does CN IV exit the brainstem?

Answer 4

Midbrain - Troclear

Question 5

Where does CN V exit the brainstem?

Answer 5

Pons - Trigeminal

Question 6

Where does CN VI exit the brainstem?

Answer 6

Pons - Abducens

Question 7

Where does CN VII exit the brainstem?

Answer 7

Pons - Facial

Question 8

Where does CN VIII exit the brainstem?

Answer 8

Pons/Medula - Vestibulocochlear

Question 9

Where does CN IX exit the brainstem?

Answer 9

Medulla - Glossopharyngeal

Question 10

Where does CN X exit the brainstem?

Answer 10

Medulla - Vagus

Question 11

Where does CN XI exit the brainstem?

Answer 11

Medulla - Accessory

Question 12

Where does CN XII exit the brainstem?

Answer 12

Medulla - Hypoglossus

Question 13

How do you examine CN I?

Answer 13

History of head injury, smoking, URI, toxins/drugs. Ensure passages are open. Test nostrils separately with non-irritating stimuli.

Question 14

How do you examine CN II?

Answer 14

VISUAL ACUITY - Snellen eye chart. VISUAL FIELDS - peripheral eye vision. DIRECT OPHTHALMOSCOPY - Red reflex, opacities, fundus (cup:disk ratio ~ 0.3). PUPILLARY EXAM - Size, reactivity, accommodation, swinging flashlight

Question 15

How do you examine CN III?

Answer 15

Inspect gaze (eye movement), pupil, eyelid

Question 16

How do you examine CN IV?

Answer 16

Superior oblique muscle depresses, intorts, and abducts the globe. Eye moves up when directed medially.

Question 17

How do you examine CN V?

Answer 17

Corneal Blink reflex, Jaw jerk reflex, muscles of mastication, sensation on face

Question 18

How do you examine CN VI?

Answer 18

Innervates the lateral rectus, which abducts the eye. Eye cannot move laterally past midpoint. Test with eye movements along CN III and CN IV.

Question 19

How do you examine CN VII?

Answer 19

Corneal blink reflex (with V1). Test facial expressions and eye closing. Upper half of face is dually innervated (Left + right motor cortex). Lower half of face is innervated by contralateral motor cortex.

Question 20

How do you examine CN VIII?

Answer 20

Weber test: tuning fork on top of skull. Is sound lateralized? Rinne test: tuning fork on mastoid process and then air. Normally air conduction > bone conduction. Vestibulocular reflex. Examine hearing and balance.

Question 21

How do you examine CN IX?

Answer 21

Gag reflex. Also controls taste for posterior 1/3 of tongue.

Question 22

How do you examine CN X?

Answer 22

Swallowing muscles

Question 23

How do you examine CN XI?

Answer 23

Test strength of trapezius and SCM

Question 24

How do you examine CN XII?

Answer 24

Check for tongue deviation. Deviation occurs in direction of the lesion.

Question 25

What impairments may be detected in CN I?

Answer 25

Impairments may result from failure of odorants to reach olfactory mucosa or sensorineural deficits. Unilateral impairments are more often sensorineural, bilateral impairments are more often conductive.

Question 26

What impairments may be detected in CN II?

Answer 26

PAPILLEDEMA - hyperemia that is caused by the dilation of the disk capillaries, swelling of axons in the peripapillary nerve fiber layer, which causes blurred disk margin, elevation of the disk, “red cell” shape, retinal nerve fiber layer hemorrhage. SYMPATHETIC DYSFUNCTION - aniscoria worse in dark (can’t dilate). PARASYMPATHETIC DYSFUNCTION - aniscoria worse in light (can’t contract) AFFERENT PUPILLARY DEFECT - swinging flashlight elicits constriction reflex from good eye, dilation from bad eye.

Question 27

What impairments may be detected in CN III?

Answer 27

Ptosis, Down and out gaze, abnormal pupil.

Question 28

What impairments may be detected in CN IV?

Answer 28

Pts report vertical, torsional, or oblique diplopia, usually worse on downgaze. Pts adopt characteristic head tilt. Affected eye tracks upwards when it moves medially.

Question 29

What impairments may be detected in CN V?

Answer 29

Jaw deviates towards injured side. Hyperreflexia of jaw jerk.

Question 30

What impairments may be detected in CN VI?

Answer 30

Cannot abduct affected eye

Question 31

What impairments may be detected in CN VII?

Answer 31

Defects of the lower half of one side of the face indicate central lesion on the contralateral cortex (upper face is dually innervated and compensates). Defects of both upper and lower face indicate ipsilateral lesion of the facial nerve itself.

Question 32

What impairments may be detected in CN VIII?

Answer 32

If Weber test is louder on affected side, or bone conductance > air conductance, indicates conduction hearing loss. If Weber is louder on unaffected side, or air conductance > bone conductance, indicates sensorineural hearing loss.

Question 33

What impairments may be detected in CN IX?

Answer 33

No sensation intake of throat or abnormal/loss of gag reflex

Question 34

What impairments may be detected in CN X?

Answer 34

Palate elevates asymmetrically, Uvula deviates to good side, gag disrupted, swallowing problematic

Question 35

What impairments may be detected in CN XI?

Answer 35

Loss of form in the trapezius, winging of the trapezius

Question 36

What impairments may be detected in CN XII?

Answer 36

Tongue deviates towards damaged side