peripheral distribution of cn vii-xii Flashcards
what are the fibres of the facial nerve?
Branchiomotor Efferent (BE), General Visceral Efferent (GVE), Special Sensory Afferent (SA), General Somatic Afferent (GSA)
what do each of the fibres of the facial nerve innervate?
BE: muscles of facial expression, post digastric, stylohyoid & stapedius
GVE: parasympathetic- lacrimal, submandibular and sublingual glands, mucus membranes of nasopharynx
SSA: Taste from anterior 2/3 tongue and palates
GSA: skin of part of external ear and behind
how do the facial nerve fibres exit the skull?
through the internal acoustic meatus
what forms the nervus intermedius?
all the branches of the facial nerve apart from BE
where does the facial nerve start/originate?
the brainstem
describe the course of the facial nerve
brainstem –> internal acoustic meatus
branches into the facial canal and petrosal foramen
50% of parasympathetic supply comes off as greater petrosal nerve
other 50% goes down facial canal - joins special sensory to form chorda tymponi
motor component gives innervation to stapedius
leaves through stylomastoid foramen and innervates muscles of facial expression
passes through parotid gland
5 terminal branches
where is the geniculate ganglion found?
at the bend of the facial canal and petrosal foramen
what does the greater petrosal nerve innervate?
parasympathetic secretomotor to mucous glands and lacrimal glands
what forms the vidian nerve?
deep petrosal and greater petrosal
what does the vidian nerve innervate?
lacrimal glands and mucous glands
what forms the chorda tymponi nerve?
other 50% of parasympathetic fibres of facial nerve and the special sensory supply
what does the chorda tymponi innervate?
anterior 2/3 of the tongue
what other nerve runs along the chorda tymponi?
lingual nerve
what does the stapedius attach to and what is its function?
Attached onto the stapes, stopping it from shaking uncontrollably –> dampens sound
name the 5 terminal branches of the facial nerve (from top to bottom)
temporal zygomatic buccal marginal mandibular cervical
what is bell’s palsy?
facial muscle paralysis
LMN lesion
at what point along the LMN can a lesion occur in bell’s palsy?
any point
what causes bell’s palsy?
Unknown cause – can be due to swelling of nerve in facial canal, puts pressure on the nerve
what are indications/risks of bell’s palsy and why?
- Cornea at risk of drying out –> greater petrosal nerve innervates the lacrimal gland, which controls secretions onto cornea
- Hyperacusis –> stapedius muscle is affected, you become hypersensitive to sound
- Loss of taste (ant 2/3rd of tongue) –> chorda tymponi
what is bell’s palsy often confused with?
ischemic stroke