Week 25 - ENT Flashcards
You are examining the eyes of a patient. When you instruct them to look straight ahead, their right eye is looking in a “down and out” position. You also notice partial ptosis and mydriasis. A lesion to which of the cranial nerves would cause this pathology?
= Oculomotor nerve (CN III)
CNIII controls 4 out of the 6 extraocular muscles (all except the Lateral Rectus and Superior Oblique)
Clinical features of injury:
- Ptosis (drooping upper eyelid) → due to paralysis of the levator palpabrae superiors
- ‘Down and out‘ position – due to paralysis of the superior, inferior and medial rectus, and the inferior oblique (& therefore the unopposed activity of the lateral rectus and inferiorly by the superior oblique) → The patient is unable to elevate, depress or adduct the eye
- Dilated pupil – due to the unopposed action of the dilator pupillae muscle
In the case of an orbital floor “blowout” fracture, which extraocular muscle may become entrapped resulting in restriction of upwards gaze?
- a) Superior rectus
- b) Inferior rectus
- c) Superior oblique
- d) Inferior oblique
- e) Medial rectus
In the case of an orbital floor “blowout” fracture, which extraocular muscle may become entrapped resulting in restriction of upwards gaze?
- a) Superior rectus
- b) Inferior rectus
- c) Superior oblique
- d) Inferior oblique
- e) Medial rectus
A pituitary macroadenoma compresses the optic chiasm. Which visual field defect would you typically observe with this pathology?
- a) Bitemporal hemianopia
- b) Binocular anopia
- c) Monocular anopia
- d) Binasal hemianopia
- e) Homonymous hemianopia
Optic Chiasma = a) Bitemporal hemianopia
What is the innervation of the a) lateral rectus and b) superior oblique?
a) lateral rectus = Abducens nerve (CN VI)
b) superior oblique = Trochlear nerve (CNIV)
What nerve is responsible for the a) afferent and b) efferent arms of the pupillary light reflex?
Afferent = a) Optic nerve (CN II)
Efferent = b) Oculomotor nerve (CN III)
What nerve is responsible for the a) afferent and b) efferent arms of the pupillary light reflex?
Afferent = a) Optic nerve (CN II)
Efferent = b) Oculomotor nerve (CN III)
