Brainstem Review Flashcards
Where does CN I exit the brainstem?
Telencephalon - Olfactory
Where does CN II exit the brainstem?
Diencephalon - Optic
Where does CN III exit the brainstem?
Midbrain - Occulomotor
Where does CN IV exit the brainstem?
Midbrain - Troclear
Where does CN V exit the brainstem?
Pons - Trigeminal
Where does CN VI exit the brainstem?
Pons - Abducens
Where does CN VII exit the brainstem?
Pons - Facial
Where does CN VIII exit the brainstem?
Pons/Medula - Vestibulocochlear
Where does CN IX exit the brainstem?
Medulla - Glossopharyngeal
Where does CN X exit the brainstem?
Medulla - Vagus
Where does CN XI exit the brainstem?
Medulla - Accessory
Where does CN XII exit the brainstem?
Medulla - Hypoglossus
How do you examine CN I?
History of head injury, smoking, URI, toxins/drugs. Ensure passages are open. Test nostrils separately with non-irritating stimuli.
How do you examine CN II?
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
How do you examine CN III?
Inspect gaze (eye movement), pupil, eyelid
How do you examine CN IV?
Superior oblique muscle depresses, intorts, and abducts the globe. Eye moves up when directed medially.
How do you examine CN V?
Corneal Blink reflex, Jaw jerk reflex, muscles of mastication, sensation on face
How do you examine CN VI?
Innervates the lateral rectus, which abducts the eye. Eye cannot move laterally past midpoint. Test with eye movements along CN III and CN IV.
How do you examine CN VII?
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.
How do you examine CN VIII?
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.
How do you examine CN IX?
Gag reflex. Also controls taste for posterior 1/3 of tongue.
How do you examine CN X?
Swallowing muscles
How do you examine CN XI?
Test strength of trapezius and SCM
How do you examine CN XII?
Check for tongue deviation. Deviation occurs in direction of the lesion.
What impairments may be detected in CN I?
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.
What impairments may be detected in CN II?
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.
What impairments may be detected in CN III?
Ptosis, Down and out gaze, abnormal pupil.
What impairments may be detected in CN IV?
Pts report vertical, torsional, or oblique diplopia, usually worse on downgaze. Pts adopt characteristic head tilt. Affected eye tracks upwards when it moves medially.
What impairments may be detected in CN V?
Jaw deviates towards injured side. Hyperreflexia of jaw jerk.
What impairments may be detected in CN VI?
Cannot abduct affected eye
What impairments may be detected in CN VII?
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.
What impairments may be detected in CN VIII?
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.
What impairments may be detected in CN IX?
No sensation intake of throat or abnormal/loss of gag reflex
What impairments may be detected in CN X?
Palate elevates asymmetrically, Uvula deviates to good side, gag disrupted, swallowing problematic
What impairments may be detected in CN XI?
Loss of form in the trapezius, winging of the trapezius
What impairments may be detected in CN XII?
Tongue deviates towards damaged side
