The Cranial Nerve Exam
February 15th, 2021
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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