PBL - Schwannoma Of Vetsibulocochlear Nerve Flashcards by Izzie Setford

Define the term tinnitus.

Perception of sounds in the absense of external auditory stimulus

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What three things cause tinnitus.

Hearing loss
Sounds produced by adjacent structures
Other disease processes

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What sounds can be produced by tinnitus

Ringing of the ears
Hissing
Roaring 
Buzzing 
Humming sound

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Which two ways can tinnitus be defined?

Objective tinnitus

Subjective tinnitus

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What is objective tinnitus?

Sound is potentially detectable by another observer

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What are the causes of objective tinnitus?

Vascular abnormalities or neuromuscular disorders

sounds generated by turbulent blood flow conducted into auditory system
pulsatile

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What is subjective tinnitus

Noise perception when there is no noise stimulation in the cochlear

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What can cause transient tinnitus in normal people?

Aspirin
Nicotine
Coffee

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Name some conditions associated with more persistent subjective tinnitus.

Noise induced hearing loss
Prebycusis - sensorineural hearing loss
Hypertension 
Atherosclerosis 
Cochlear of labyrinthine infection
Inflammation

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What is the suggested pathophysiology of tinnitus?

Abnormal firing of auditory receptors
Dysfunction of cochlear neurotransmitters function or ionic balance
Alterations in central processing of the signal

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Define vertigo.

Illusion of motion associated with disorders of vestibular function

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Define objective and subjective vertigo?

Objective - person is in motion and environment is stationary
Subjective - person is stationary and environment is in motion

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What are some differential diagnoses of vertigo?

Light-headedness
Syncope
Faintness

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What can unstable gait be caused by?

Disorders of sensory input
Peripheral neuropathy
Gait problems

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Vertigo can be caused by peripheral and central vestibular problems, what is the difference between them?

Peripheral - severe in intensity, and episodic

Central - mild and consistent

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Describe motion sickness.

Normal physiological vertigo caused by repeated rhythmical stimulation of vestibular system

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Symptoms of motion sickness

Vertigo
Malaise 
Nausea
Vomiting 
Autonomic symptoms 
- lowered BP
- tachycardia 
- sweating 
Hyperventilation - can causes pooling of blood in lower extremities

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What is the pathology of Ménière’s disease?

Occurs due to distension of the endolymph compartment of the inner ear

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What is the ‘triad’ of Ménière’s disease?

Vertigo
Tinnitus
Hearing loss

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What are the suggested mechanisms that may cause Ménière’s disease.

Increased endolymph production
Decreased production of perilymph accompanied by compensatory increase in endolymph sac
Decreased endolymph absorption
- caused by malfunction of endolymph sac or blockage of endolymphatic pathways

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Name five things which are thought to cause Ménière’s disease.

Infection - syphilis 
Trauma 
Immunological 
Endocrine - adrenal-pituitary insufficiency and hypothyroidism 
Vascular disorders

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What is Ménière’s disease characterised by?

Fluctuating episodes of tinnitus, feeling of ear fullness, violent rotatory vertigo

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What happens to hearing loss as Ménière’s progresses?

Stops fluctuating and progressively worsens

Both ears become affected

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What happens to the vertigo as the Ménière’s progresses?

Episodes of vertigo diminish and disappear although the person may be unsteady

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List the differential diagnoses of Ménière's disease

``` ENT causes - acoustic neuroma - otitis media - earwax - too toxic drugs Intracranial pathology - vertebrobasilar insufficiency - tumours - migraine Systemic illness - Anaemia - hypothyroidism - DM - autoimmune disease - syphilis ```

What is a schwanomma of the vestibulocochlear nerve?

Benign Schwann cell tumour affecting CN VIII

How does a schwanomma cause unilateral sensorineural hearing loss?

Compresses the cochlear nerve of interferes with the blood supply to the nerve and cochlear

What genetic problem is through to cause tumour growth?

Tumour suppressor gene abnormality on chromosome p22 (schwanomma protein)

How do patients with a schwannoma present?

Decreased hearing | Episodes of vertigo

What does unilateral hearing loss do to your hearing?

Leaves you unable to localise sound

Which other nerves are likely to become affected if the tumour grows to big - and what problems will that cause?

``` Facial nerve - nystagmus - slowed blink - altered taste - altered tearing Trigeminal - facial numbness ```

What is the differential diagnosis for a schwannoma?

Meningioma Epidermoid Facial nerve schwannoma Trigeminal schwannoma

Where does the vestibulocochlear nerve arise?

From between the pons and the medulla

Where does the vestibulocochlear nerve leave the cranium?

Through the internal acoustic meatus

Where do the two parts of the vestibulocochlear merge when travelling back to the brain?

Inside the petrous part of the temporal bone

What does the vestibular nerve (vestibular ganglion) supply?

Three semi-circular ducts Utricle Saccule

How does the cochlear nerve innervate the cochlear?

Enters the base of the cochlear and passes up through the modiolus - branches pass through lamina of modiolus to innervate receptors on spiral organ

Describe what a neoplasm is

Abnormal mass of tissue with uncoordinated growth | - growth persists excessively after cessation of the initial stimuli

Describe the growth pattern of a benign tumour.

Expansive Capsule Localised Slow

Describe the growth pattern of a malignant tumour.

Infiltrative No capsule Metastasis Rapid

What effects can a slowly enlarging space occupying lesion have on the brain or spine

Atrophy of adjacent brain or spinal tissue

What effects can a rapidly enlarging space occupying lesion have on the brain or spine

Rise in pressure in affected compartment from the normal level of

What clinical signs can be seen when a space occupying lesion distorts the meninges and blood vessels?

Headache

What clinical signs can be seen when a space occupying lesion compresses the optic nerve

Papillodema

What clinical signs can be seen when a space occupying lesion distorts the medulla?

Vomiting

What clinical signs can be seen when a space occupying lesion compresses the oculomotor nerve

Pupillary constriction and then dilation

What clinical signs can be seen when a space occupying lesion causes traction of the abducens nerve?

Abducens palsy - false localising sign

What clinical signs can be seen when a space occupying lesion compresses the posterior cerebral artery?

Occipital infarction

What clinical signs can be seen when a space occupying lesion causes traction on brainstem arteries?

Fatal infarction of brainstem/heamorrhage

What are the two layers of the dura mater called?

Endocranial layer | Meningeal layer

Where is an intracranial venous sinus located?

In certain areas, the dura mater splits into its two layers to enclose venous channels

Where does venous drainage leave the skull?

Jugular foramen

What is the relation between the inferior sagittal sinus and the flax cerebri?

Located in the lower margin of the fall

Which two veins join to become the straight sinus - and where does this sinus run?

Inferior sagittal sinus and the great cerebral vein | Runs in the junction between the falx and the tentorium cerebelli

Which transverse sinus does the superior sagittal sinus drain to?

Right

Which transverse sinus does the inferior sagittal sinus drain to?

Left

Which sinus does the internal carotid artery, the three nerves that supply the eye muscles and V1 + V3 branches of the trigeminal nerve pass?

Cavernosa sinus

How can schwannoma removal surgery cause other nerve problems?

Vestibulocochlear and facial nerve share a common cause through the internal auditory canal. This proximity means the facial nerve is easily damaged during surgery = facial palsy

How does facial palsy present?

Weakness of muscles of facial expression and eye closure Face sags Face drawn to opposite side when smiling Corneal and conjunctiva damage because the eye is open all the time Mild dysarthria Difficulty eating

What can occur in very severe cases of facial palsy?

Loss of taste over anterior tongue | Intolerance to high-pitched or loud noises

How to distinguish between facial palsy and a lower motor neuron.

In lower motor neuron disease - Patient can't wrinkle forehead because the final common pathway to the muscles is destroyed Lesion must be in pons or outside the brainstem

How to distinguish between facial palsy and an upper motor neuron.

In upper motor neuron disease - upper facial muscle are partially spared (other pathways in brainstem) - appear to be different pathways for voluntary and emotional movement - face sagging is less obvious