Updated: 4/9/2020

Muscles Innervated by Cranial Nerves

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Overview

Snapshot
  • A 64-year-old man is brought to the emergency department by his son after noticing right eye deviation a few hours prior to presentation. The patient's trouble seeing progressively worsened over the course of a few hours which has never happened before. His medical history is significant for a myocardial infarction that was managed with a coronary artery bypass grafting, type 2 diabetes mellitus, and hypertension. He is currently on an appropriate medication regimen for his chronic illness. On physical examination, the right eye is deviated inferiolaterally with mydriasis of the affected eye. (Oculomotor nerve palsy likely secondary to a posterior communicating artery aneurysm compressing the nerve)
Introduction
 
Muscles Innervated by Cranial Nerves
Cranial Nerve
Muscle
Lesion
Oculomotor nerve (CN III) 
  • Extraocular muscles innervated by CN III are
    • superior rectus (SR)
    • infecrior rectus (IR)
    • medial rectus (MR)
    • inferior oblique (IO)
  • Levator palpebrae
    superioris
  • Ciliary muscle
  • Sphincter pupillae
  • Diplopia
  • Ptosis
  • Loss of accomodation
  • Dilated pupil and loss of light reflex
Trochlear nerve (CN IV)
  • Superior oblique
  • Difficulty looking down
  • Head tilt away from the side of the lesion
Mandibular branch of the trigeminal nerve (CN V3)
  • Muscles of mastication which include
    • Mandibular elevators
      • masseter muscle
      • temporalis muscle
      • medial pterygoid muscle 
    • Mandibular depressors
      • lateral pterygoid muscle  
      • anterior belly of the diagstric muscle
      • mylohyoid muscle
  • Tensor palati
  • Tesnor tympani
  • Jaw deviation towards the side of the lesion 
Abducens nerve (CN VI)
  • Lateral rectus
  • Horizontal diplopia
Facial nerve (CN VII)
  • Muscles of facial expression
  • Posterior belly of digastric muscle
  • Stylohyoid muscle
  • Stapedius muscle

 

  • Bell's palsy
  • Loss of blink reflex
  • Hyperacusis (when the stapedius is involved)

 

 

Glossopharyngeal nerve (CN IX)
  • Stylopharyngeus muscle
-
Vagus nerve (CN X)
  • Muscles of the palate and pharynx except
    • tensor palati muscle (CN V3)
    • Stylopharyngeus muscle (CN IX)
  • All muscles of the larynx
  • Palate droop
  • Dysphagia
  • Deviation of the uvula away from the side of the lesion
  • Loss of gag reflex (the sensory component of this reflex is mostly via CN IX)
Accessory nerve (CN XI)
  • Sternocleidomastoid muscle
  • Trapezius muscle
  • Weakness with turning of the head
  • Shoulder droop
Hypoglossal nerve (CN XII)
  • Muscles of the tongue except for the
    • palatoglossus muscles
  • Tongue deviation towards the side of the lesion
 

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