Common cranial nerve examination questions for medical finals, OSCEs and MRCP PACES: facial nerve (VII)
Click on the the questions below to see the answers, or click here for questions about other cranial nerves and click here to learn how to examine the cranial nerves.
What are the functions of the facial nerve?
- Mnemonic: “face, ear, taste, tear”
- Muscles of facial expression
- Motor control of the stapedius in the ear – needed to dampen down sounds
- Anterior two-thirds of the tongue
- Parasympathetic supply to the lacrimal glands
- The muscles of facial expression innervated by the 7th nerve are:
- Frontalis / orbicularis oculi / buccal muscles/ nasal muscles / orbicularis oris / platysma.
What is the difference between an upper motor neuron (UMN) and lower motor neurone (LMN) 7th nerve lesion?
- UMN: sparing of the forehead (frontalis) and at times orbicularis oculi
- Due to bilateral facial representation at the level of the 7th nerve nuclei
- LMN: all muscles of the face affected = Bell’s palsy
What are the causes of a Bell’s palsy?
- Viral infection (likely Herpes Simplex Virus)
- Treated with high dose steroids (60-80mg OD for 5 days) if diagnosed promptly
- Brainstem lesion: demyelination / stroke / tumour
- Cerebellopontine angle lesion: acoustic neuroma (vestibular schwannoma)
- Middle ear: infection
- Parotid gland: tumour / post-surgical resection of tumour
What is Bell’s phenomenon?
- In 7th LMN lesions the eye turns upwards on attempted closure. This is a normal reflex.
How to perform the cranial nerve exam for finals, OSCEs and PACES