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Cranial Nerves
 
 

The Cranial Nerve Exam

 
 
 
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Overview

Wasting or weakness of the muscles of mastication may be due to a lesion affecting the mandibular branch of the trigeminal nerve (V3).
  • How to Elicit

  • Ask the patient to clench their teeth, and palpate the muscles of mastication. Ask the patient to open their mouth against resistance.
  • Causes of Weakness of the Muscles of Mastication

  • Upper motor neuron lesion - trauma, tumour, ischaemia, haemorrhage
  • Mandibular nerve (V3) lesion - trauma, ischaemia, tumour, ICA aneurysm, cavernous sinus thrombosis
  • Muscles Involved in Mastication

  • Masseter - laterallyElevation (mouth closing) and protraction (anterior movement) of the mandible
  • Temporalis - superiorly, over the temporal boneElevation (mouth closing) and retraction (posterior movement) of the mandible
  • Medial pterygoid - anterior to the ramus of the mandibleElevation (mouth closing) and lateral movement of the mandible
  • Lateral pterygoid - anterior to the TMJDepression (mouth opening) and lateral movement of the mandible
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