Ear and Vestibulocochlear nerve Flashcards
Describe the pathway of the vestibulocochlear nerve
Vestibular and Cochlear branches run between pons and medulla and emerge through internal acoustic meatus.
They join to produce CN8 at petrous part of temporal bone to run to ear
What is the function of CN8?
Hearing and balance
How can a surgical procedure to CN8 cause facial palsy?
Runs in close proximity to facial nerve and therefore can damage CN7
Why might tarsorrhaphy be required after facial palsy?
innervation to voluntarily close eyes lost so therefore the cornea and conjunctiva are at risk of damage - this will sew ear together slightly in order to prevent this
What is an acoustic neuroma?
Schwannoma of CN8 - tumour involving the schwann cells which causes hearing loss due to compression of cochlear nerve or obstruction of blood vessels.
What is Menieres disease and how might it be caused?
Auditory disease characterised b sudden onset of tinnitus, vertigo and low frequency hearing loss. Caused by:
- ENT causes - e.g. acoustic neuroma, otitis media, trauma - Intracranial pathology - e.g. vertebrobasilar insufficiency, tumours, migraine - Systemic illness - DM, autoimmune, allergies, lyme disease
What is tinnitus?
Perception of sound in the absence of stimulus:
- Objective tinnitus - possible that someone else can also here (e.g. vascuar abnormalities or neuromuscular disorders) - Subjective tinnitus - noise perception is caused with no stimulus whatsoever (e.g. earwax, abnormal firing of auditory receptors, neurotransmitter dysfunction etc)
What is vertigo?
Illusion of motion associated with disorders of vestibular function. Characterised by spinning sensation and unstable gait:
- Subjective - stationary person, moving environment - Moving person, stationary environment
What is motion sickness?
Repeated rhythmical stimulation of vestibular system, resulting in nausea, malaise and vertigo
If hyperventilation occurs, can result with blood pooling and therefore postural hypotension
