Cranial nerve origins, functions, and lesion presentations tested on USMLE Step 1.
31 cards · basic cards · AI-written, checked twice. Edit anything.
- What is the primary function of the olfactory nerve (CN I)?
- Smell (olfaction)
- Through which skull opening does CN I pass?
- Cribriform plate of the ethmoid bone
- What is the primary function of the optic nerve (CN II)?
- Vision
- Through which skull opening does CN II pass?
- Optic canal
- A lesion of CN II causes what visual deficit?
- Monocular blindness in the affected eye
- Which extraocular muscles does CN III innervate?
- All extraocular muscles except the lateral rectus and superior oblique
- Through which skull opening does CN III pass?
- Superior orbital fissure
- Describe the classic resting eye position in a complete CN III palsy.
- The eye is deviated down and out
- A CN III palsy with a dilated, nonreactive pupil suggests what type of cause?
- Compressive lesion, such as a posterior communicating artery aneurysm
- A CN III palsy that spares the pupil suggests what type of cause?
- Ischemic or microvascular cause, such as diabetes
- Which muscle does CN IV innervate?
- Superior oblique
- A CN IV lesion causes difficulty with what eye movement?
- Looking down and inward, causing vertical diplopia
- What is the general sensory function of CN V?
- Sensation of the face and anterior scalp
- Besides sensation, what motor function does CN V provide?
- Muscles of mastication (chewing)
- Through which opening does the ophthalmic division (V1) of CN V pass?
- Superior orbital fissure