Schwannoma, ear and cranial nerves Flashcards
(132 cards)
1
Q
Define the term tinnitus.
A
Perception of sounds in the absense of external auditory stimulus
2
Q
What three things cause tinnitus.
A
- Hearing loss
- Sounds produced by adjacent structures
- Other disease processes
3
Q
What sounds can be produced by tinnitus
A
- Ringing of the ears
- Hissing
- Roaring
- Buzzing
- Humming sound
4
Q
Which two ways can tinnitus be defined?
A
- Objective tinnitus
- Subjective tinnitus
5
Q
What is objective tinnitus?
A
Sound is potentially detectable by another observer
6
Q
What are the causes of objective tinnitus?
A
Vascular abnormalities or neuromuscular disorders- sounds generated by turbulent blood flow conducted into auditory system - pulsatile
7
Q
What is subjective tinnitus
A
Noise perception when there is no noise stimulation in the cochlear
8
Q
What can cause transient tinnitus in normal people?
A
- Aspirin
- Nicotine
- Coffee
9
Q
What is the suggested pathophysiology of tinnitus?
A
- Abnormal firing of auditory receptors
- Dysfunction of cochlear neurotransmitters function or ionic balance
- Alterations in central processing of the signal
10
Q
Define vertigo.
A
Illusion of motion associated with disorders of vestibular function
11
Q
Define objective and subjective vertigo?
A
Objective - person is in motion and environment is stationary Subjective - person is stationary and environment is in motion
12
Q
What are some differential diagnoses of vertigo?
A
- Light-headedness
- Syncope
- Faintness
13
Q
Vertigo can be caused by peripheral and central vestibular problems, what is the difference between them?
A
- Peripheral - severe in intensity, and episodic
- Central - mild and consistent
14
Q
Describe motion sickness.
A
Normal physiological vertigo caused by repeated rhythmical stimulation of vestibular system
15
Q
Symptoms of motion sickness
A
Vertigo
Malaise
Nausea
Vomiting
Autonomic symptoms: lowered BP, tachycardia, sweating
Hyperventilation - can causes pooling of blood in lower extremities
16
Q
What is the pathology of Ménière’s disease?
A
Excessive accumulation of endolymph in the membranous labyrinth - increases with the distention of the scala media until the membrane ruptures Cochlear organs degenerate
17
Q
What is the ‘triad’ of Ménière’s disease?
A
- Vertigo
- Tinnitus
- Hearing loss
18
Q
What are the suggested mechanisms that may cause Ménière’s disease?
A
- Increased endolymph production
- Decreased production of perilymph accompanied by a compensatory increase in endolymph sac
- Decreased endolymph absorption- caused by malfunction of endolymph sac or blockage of endolymphatic pathways
19
Q
Name five things which are thought to cause Ménière’s disease.
A
- Viral and bacterial agents - syphilis
- Trauma
- Immunological - Allergies
- Metabolic derangements
- Vascular disorders
20
Q
What is Ménière’s disease characterized by?
A
Fluctuating episodes of tinnitus, feeling of ear fullness, violent rotatory vertigo
21
Q
What happens to hearing loss as Ménière’s progresses?
A
Stops fluctuating and progressively worsens
Both ears become affected
22
Q
What happens to the vertigo as the Ménière’s progresses?
A
Episodes of vertigo diminish and disappear although the person may be unsteady
23
Q
List the differential diagnoses of Ménière’s disease
A
ENT causes
- acoustic neuroma
- otitis media
- earwax
- too toxic drugs
Intracranial pathology
- vertebrobasilar insufficiency
- tumours
- migraine
Systemic illness
- Anaemia
- hypothyroidism
- DM
- autoimmune disease
- syphilis
24
Q
What is a schwanomma of the vestibulocochlear nerve?
A
Benign Schwann cell tumour affecting CN VIII
25
How does a schwanomma cause unilateral sensorineural hearing loss?
Compresses the cochlear nerve, interferes with the blood supply to the nerve and cochlear
26
What genetic problem is thought to cause tumour growth in schwannoma?
Tumour suppressor gene abnormality on chromosome p22 (schwanomma protein)
27
How do patients with a schwannoma present?
Decreased hearing Episodes of vertigo
28
What does unilateral hearing loss do to your hearing?
Leaves you unable to localise sound
29
Which other nerves are likely to become affected if the tumour grows too big - and what problems will that cause?
Facial nerve
* nystagmus
* slowed blink
* altered taste
* altered tearing
Trigeminal - facial numbness
30
What is the differential diagnosis for a schwannoma?
* Meningioma
* Epidermoid
* Facial nerve schwannoma
* Trigeminal schwannoma
31
Where does the vestibulocochlear nerve arise?
Vestibular nuclei
1. superior and lateral
2. medial and inferior
Cochlear nuclei (auditory component) - dorsal-lateral medulla
1. posterior
2. anterior
32
Where does the vestibulocochlear nerve leave the cranium?
Through the internal acoustic meatus
33
Where do the two parts of the vestibulocochlear merge when travelling back to the brain?
Inside the petrous part of the temporal bone
34
What does the vestibular nerve (vestibular ganglion) supply?
* Three semi-circular ducts
* Utricle
* Saccule
35
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
36
Describe what a neoplasm is
Abnormal mass of tissue with uncoordinated growth - growth persists excessively after cessation of the initial stimuli
37
Describe the growth pattern of a benign tumour.
* Expansive
* Capsule
* Localised
* Slow
38
Describe the growth pattern of a malignant tumour.
* Infiltrative
* No capsule
* Metastasis
* Rapid
39
What effects can a slowly enlarging space occupying lesion have on the brain or spine
Atrophy of adjacent brain or spinal tissue
40
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
41
What clinical signs can be seen when a space occupying lesion distorts the meninges and blood vessels?
Headache
42
What clinical signs can be seen when a space occupying lesion compresses the optic nerve
Papillodema
43
What clinical signs can be seen when a space occupying lesion distorts the medulla?
Vomiting
44
What clinical signs can be seen when a space occupying lesion compresses the occulomotor nerve
Pupillary constriction and then dilation
45
What clinical signs can be seen when a space occupying lesion causes traction of the abducens nerve?
Abducens palsy - false localising sign
46
What clinical signs can be seen when a space occupying lesion compresses the posterior cerebral artery?
Occipital infarction
47
What clinical signs can be seen when a space occupying lesion causes traction on brainstem arteries?
Fatal infarction of brainstem/heamorrhage
48
What are the two layers of the dura mater called?
* Endocranial layer
* Meningeal layer
49
Where is an intracranial venous sinus located?
In certain areas, the dura mater splits into its two layers to enclose venous channels
50
Where does venous drainage leave the skull?
Jugular foramen
51
What is the relation between the inferior sagittal sinus and the flax cerebri?
Located in the lower margin of the fall
52
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
53
Which transverse sinus does the superior sagital sinus drain to?
Right
54
Which transverse sinus does the inferior sagittal sinus drain to?
Left
55
Which sinus does the internal carotid artery, the three nerves that supply the eye muscles and V1 + V3 branches of the trigeminal nerve pass?
Cavernous sinus
56
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
57
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
58
What can occur in very severe cases of facial palsy?
Loss of taste over anterior tongue Intolerance to high-pitched or loud noises
59
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
60
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
61
What is the treatment for Meniere's disease?
Symptomatic relief - antiemetics, diuretics and anticholinergics Lifestyle changes: stop smoking, low-sodium diet, stress management, caffeine elimination Surgical: shunts to drain excess endolymph, removal of portion of vestibulocochlear nerve and destruction of the membraneous labyrinth
62
What are the 2 branches of the Vestibulocochlear nerve and where do they form?
Vestibular branch Cochlear branch - within the acoustic meatus
63
Where does the Vestibulocochlear nerve attaches to the brainstem?
At the cerebellopontine angle - most laterally of all the nerves
64
Where do the secondary neurons of the vestibulocochlear nerve pass to?
Bilaterally to the midbrain, medial geniculate bodies and to the auditory cortex in the upper part of the temporal lobe
65
What are the clinical features of Schwannoma?
Unilateral sensorineural hearing loss, intermittent dizziness and facial numbness Headaches, coordination difficulties, obstructive hydrocephalus May be life threathening
66
Describe hydrocephalus
Accumulation of cerebrospinal fluid (CSF) within the brain. This typically causes increased pressure inside the skull.
67
How can you test vestibulocochlear nerve?
Tuning fork tests and audiometry to distinguish between external and middle ear deafness and inner ear nerve deafness Others - electrical neurophysiological testing - Caloric test
68
Describe the basis of the caloric test
Irrigating the external acoustic meatus with warm and cold water, convection currents affect the lateral semi-circular duct which provokes nystagmus (jerky eye movements), duration measured and compared to normal subject
69
What is Bell's palsy?
Unilateral lower motor lesion affecting face - forehead not wrinkled - eyeballs rolls up, eyelid does not close - flat nasolabial fold, paealysis of lower face
70
What is the treatment of acoustic schwannoma and its symptoms??
Cerebreal oedema - managed with steroids, intravenous or oral dexamethasone Epilepsy - anticonvulsants Oral alkylating agents (chemo) - Vincristine, procarbazine and temozolomide Surgery - can be removed, but 10% mortality rate
71
What is tarsorrpathy and when is it used?
Surgical procedure in which the eyelids are partially sewn together to narrow the eyelid opening - done to protect the eyes eyes, associated pain with them drying up
72
Name the 4 stages of Schwannoma
Intracanalicular Cisternal Compressive Hydrocephalus
73
What does the olfactory nerve do?
Sensory - sense of smell
74
What does the optic nerve do?
Sensory - sight
75
What does the occulomotor nerve do?
Motor - eyelid movement - eyeball movement (medial, superior and interior rectus and inferior oblique) - pupillary constriction - accommodation of lens for near vision
76
What does the trochlear nerve do?
Motor- eyeball movement (superior oblique)
77
What does the trigeminal nerve do?
Both sensory and motor - sensory to the face (opthalamic, maxillary and mandibular) - motor to the muscles of mastication (masseter, temporalis, pterygoids)
78
What does the abducens nerve do?
Motor- movement of eyeball (lateral rectus)
79
What does the facial nerve do?
Both - sensory to skin of external ear and anterior tongue - motor to muscles of facial expression and helps secrete saliva and tears
80
What does the vestibulocochlear nerve do?
Sensory- hearing and equilibrium
81
What does the glossopharyngeal nerve do?
Both sensory and motor - motor is for swallowing and speech and secretion of saliva - sensory: carotid body and sinus; tonsils, pharynx and taste for posterior tongue
82
What does the vagus nerve do?
Both sensory and motor innervation - swallowing and speech - parasympathetic innervation
83
What does the accessory nerve do?
Motor - sternocleidomastoid and trapezius -movement of head and shoulders
84
What does the hypoglossal nerve do?
Motor- movements of the tongue
85
What are the layers from skin to brain?
Skin Aponeurosis Periosteum Bone Meninges - dura, arachnoid an pia
86
What are the layers of the bone of the skull?
Outer table - cortical compact bone, thick and tough Diploe - the spongy cancellous bone separating the inner and outer layers of the cortical bone Inner table - cortical bone, thin, dense and brittle
87
What is a vault?
Something resembling arched dome
88
What is Crista galli?
Upper part of the perpendicular plate of the ethmoid bone, which rises above the cribriform plate The falx cerebri attaches to the crista galli The olfactory bulbs of the olfactory nerve lie on either side of the crista galli on top of the cribriform plate
89
What is the exit of the olfactory nerve?
Cribriform plate
90
What is the exit of the optic nerve?
Optic canal
91
What is the exit of the oculomot nerve?
Superior orbital fissue
92
What is the exit of the trochlear nerve?
Superior orbital fissure
93
What is the exit of the trigeminal nerve?
V1 Opthalmic - Superior orbital fissure V2 Maxillary - foramen rotundum V3 Mandibular - Foramen ovale
94
What is the exit of the Abducens nerve?
Superior orbital fissure
95
What is the exit of the facial nerve?
Internal Acoustic meatus
96
What is the exit of the Vestibulocochlear nerve?
Internal acoustic meatus
97
What is the exit of the glossopharyngeal nerve?
Jugular foramen
98
What is the exit of the Vagus nerve?
Jugular foramen
99
What is the exit of the Spinal Accessory nerve?
Jugular Foramen
100
What is the exit of the Hypoglossal nerve?
Hypoglossal canal
101
Which cranial nerves originate in forebrain?
Olfactory and optic
102
Which cranial nerves originate in midbrain?
Oculomotor and trochlear
103
Which cranial nerves originate in Pons?
Trigeminal, Abducens, Facial, Vestibulocochlear
104
Which cranial nerves originate in Medulla?
Glossopharyngeal Vagus Spinal Accessory Hypoglossal
105
Where does the olfactory nerve terminate?
In the olfactory sensory neurons embedded in the olfactory epithelium - upper part of the nasal cavity
106
How do you test olfactory nerve?
Give odor samples to smell, test one nostril at a time Control test: ammonia - it is an irritant causing pain and can be still detected by the nasal mucosa
107
Which nerve provides somatosensory innervation to the nasal cavity?
Trigeminal V1 and V2
108
What are the signs that oculomotor is not functioning?
Ptosis Outward and slightly downward deviation of the eye Dilated and fixed pupil
109
What are the signs that trochlear is not functioning?
Torsitional diplopia (double vision) Compensatory tilted head
110
What are the signs that abducens is not functioning?
Reduced abduction Positioned medially
111
How do you test eye movements?
Subject sits upright Hold head still with one hand Observe normal position and lack of spontaneous movements Eye movement: - moving object to be followed by eyes - H shape
112
Whar are the 3 main divisions of the trigeminal nerve?
V1 - ophtalmic V2 - Maxillary V3 - Mandibular
113
What are the branches of the trigeminal nerve that pass through the foramina of the fronta normalis?
Supra-orbital nerve Infra-orbital nerve Mental nerve
114
How do you test trigeminal nerve?
Sensory innervation of skin: The skin areas in the 3 divisions with a piece of cotton Motor function: - clench teeth - open the mouth - jaw jerk reflex
115
How do you test the facial nerve?
Motor function: - Raise eyebrows - frown -smile - puff out their cheeks Cornea reflex - wisp the cornea with sterile cotton
116
Which large glands are innervated by the facial nerve?
Sublingual and Submandibular
117
How do you test the vestibulocochlear nerve esp. hearing?
Whisper voice test - whisper postero laterally to the person starting at arms length - needs to repeast at least 3/6 numbers Audiometry
118
What are the classic physiological tests of vestibulocochlear nerve?
Rinne test - test of air vs bone conducting sound - vibrating fork behind the mastoid bone - when the subject cant hear it move it to the outer ear canal Weber test - test of symmetrical inner ear function - vibrating fork to the midline of forehead
119
What are the tests for glossopharyngeal and vagus nerves?
Speech Swallowing Observe - the position of the palate and the uvula Symmetrical position and movements of uvula Gag reflex - back of the throat is touched with a tongue blade
120
What is the test for accessory spinal nerve?
Place your arms firmly on the shoulders of your subject and ask them to raise shoulders
121
What is the test for Hypoglossal nerve?
Stick tongue out - tip will deviate to the weak side - check movements in all directions
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