A 45 years old male patient complaints of double vision when walking upstairs. His past history is significant for Type-ll diabetes, well controlled with glyburide. The nerve most probably involved is
Answer: (a) Abducent nerve.* Patient is having an injury to the abducent nerve (CN VI).* It innervates the lateral rectus muscle. Lateral rectus muscle moves the eyeball laterally (outwards). Therefore, a lesion of the abducent nerve results in internal strabismus (medial deviation) and diplopia (double vision).* The innervation of extraocular muscles can be remembered by a simple mnemonic, S04, LR6, 03. Superior oblique is innervated by 4th cranial nerve (trochlear), Lateral rectus by 6th cranial nerve (abducent), and others by 3rd cranial nerve (oculomotor).* The other muscles are superior, inferior and medial recti, and inferior oblique muscles.* The oculomotor nerve also supplies to levator palpabrae and carries parasympathetic fibers.* In abducent nerve lesion, the eye cannot look outwards due to paralysis of the lateral rectus.* The eye is turned inwards when trying to look straight ahead, due to the unopposed action of the medial, superior and inferior recti muscles supplied by the oculomotor nerve.
Abducent nerve
Oculomotor nerve
Trochlear nerve
Trigeminal nerve
Head & Neck