BB2 Revision6 Flashcards
Vestibular System Function
Name the 3 main functions of the vestibular system
- Detection and conscious perception of head perception and movement
- Compensatory eye movements during head movement in order to provide stabilisation of visual image and target fixation
- Compensatory postural adjustments of the trunk and limb muscles following head movement
Vestiublar system anatomy:
The vestibular system is connected with the spinal cord via which tracts? [2]
The vestibular system is connected with the cerebellum via the which lobe [1] and which nucleus [1]?
The vestibular system is connected to which CNs? [3]
The vestibular system is connected with the spinal cord via which medial and lateral vestibulospinal tracts
The vestibular system is connected with the cerebellum via the floccculonodular lobe and fastigial nucleus
The vestibular system is connected to CN III, IV & VI
Vestiublar system anatomy:
Name the parts of the vestibular apparatus (that lie within the inner ear)
- semi-circular canals
- utricle (which lies at the base of the semi-circular canals)
- saccule
Which of the following numbers depicted the vestibular tracts [1]
2c
Label A-F
A: (Macula of) utricle
B: (Macula of) saccule
C: cochlea
D: posterior semilunar canal
E: Stapes
F: Malleus and incus
Label
5 Cochlea
16 External acoustic meatus
17 Mastoid air cells
11 Posterior semicircular canal
(posterior canal)
Name and describe the function of the two types of solution found within the vesitubular apparatus.
Endolymph
* inside the semicircular canals and moves, and provides most of the signalling for the vestibular hair cells
Perilymph
* fills the scalae tympani and vestibuli.
What is the difference in ion concentration between endolymph and perilymph? [2]
Perilymph: has similar concentrations of ions to plasma; high sodium and low potassium
Endolymph: extremely low sodium and high potassium
Where in the vestibular system are vesitubular hair cells found? [3]
The ampulla, saccule and utricle is where vestibular hair cells are found.
Describe how the semicircular canals function to detect angular acceleration/deceleration of the head
There are three semicircular canals: anterior, posterior, and lateral. located in a different plane and each connect to an ampulla (widening of the canal) which conncects to the utricle
Within each ampulla there are hair cells and cristae with a gelatinous cupula above the hair cells * crista
Each canal is a continuous endolymph filled loop, when the head rotates endolymph displaces the gelitinous cupula and excites the hair cells causing depolarisation or hyperpolarisation
Movement towards the kinocilium causes the opening of channels and a subsequent depolarization of the cell. Movement away from the kinocilium causes the closure of channels leading to hyperpolarization of nerve fibers.
Describe the function of the utricle / saccle [1]
What is the macula of the utricle and saccle and what substance does it contain? [2]
Saccule and utricle is to keep the head vertically oriented with respect to gravity
Macula of utricle / saccle: cilia of hair cells embedded in a gelatinous mass.
Contains calcium carbonate crystals call otoliths
What is the difference in function betweenthe utricle and saccule? [2]
Describe how the saccule and utricle keep the head vertically oriented with respect to gravity [3]
Utricle: longitudinal acceleration,
Saccule: acceleration along the vertical axis
Mechanism:
* otoliths provide the inertia, so that when movement to one side occurs, the otolith-gel mass causes the hair cells to deviate
- The hair cells are excited, or inhibited, by bending of the stereocilia towards or away from the kinocilium, just as the hair cells in the semi-circular canals
- Linear acceleration of the head causes a shear force between the otolithic membrane and macula, causing displacement of the hair bundles.
Which direction are hair cells in the utrcile pushed during forward acceleration? [1]
Which direction are hair cells in the saccule pushed when a person descends?[1]
Utricle hairs pushed backwards during forward acceleration
Saccule hairs pushed upwards when person descends (gravitational force)
Describe the head-righting reflex.
If the head and body start to tilt, such as when a student falls asleep in a lecture, the vestibular nuclei will automatically compensate with the correct postural adjustments via activation of the VSTs
Describe the function of the vestibular-occular reflex
This reflex keeps the eyes fixed on a particular object when the rest of the body is in motion
Describe how the VOR works
Automatically sensing head rotations and elicits a compensatory adjustment in the opposite direction of the eyes
Causes innervation on the medial-lateral rectus muscles (adduction / abduction), the inferior rectus-superior oblique pair (depression and extorsion, elevation and intorsion) and the superior rectus-inferior oblique pair (elevation and intorsion, depression and extorsion via the ascending medial longitudinal fasciulus
The axonal connections between the vestibular and oculomotor nuclei that mediate the VOR travel in a tract called the []
The axonal connections between the vestibular and oculomotor nuclei that mediate the VOR travel in a tract called the medial longitudinal fasciculus (MLF)
Primary afferent fibres from the vestibular apparatus terminate mainly in the []
A small number of fibres project directly into the []
Primary afferent fibres from the vestibular apparatus terminate mainly in the vestibular nuclei (in the medulla and pons)
A small number of fibres project directly into the vestibulocerebellum (flocculo-nodual node & uvula)
Where do axons from the 4 vestibular subnuclei (LVN; MVN; SVN; DVN) project? [5]
- Vestibulocerebellum
- Thalamus and cortex
- Reticular formation
- Extraocular eye muscles
- Spinal cord motor neurones
Central pathways of the vestibular system
Where do the superior and medial vesibitular subnuclei recieve input from? [1]
Where do the lateral, inferior and medial vesibitular subnuclei receive inputs from? [1]
superior and medial: semi-circular canals
lateral, inferior and medial: saccule and utricle (together aka maculae)
Where does input from the: semi-circular canals to the superior and medial vestibular subnuclei project to? [4]
Where does input from the: saccule and utricle to the lateral, inferior and medial vesibitular subnucleii project to? [3]
Semi-circular goes to ocular nuclei and reticular formation, gaze centres and tectal nuclei
(double check which pathways these are sent via)
Saccule and utricle goes to spinal motor nuclei via the lateral and medial VSTs, which are involved in postural balance
The superior and lateral vestibular nuclei also interact with which structure in the brain [] ?
The superior and lateral vestibular nuclei also interact with the flocculo-nodular lobe of the cerebellum
Describe the neuronal connections that determine our conscious appreciation of equilibrium and head position.
Second order vestibular neurones project to the contralateral ventral posterior nucleus of the thalamus, and from there the somatosensory cortex and posterior parietal cortex.
What is the name given to the region of the cortex where there is convergence of the vestibular and proprioceptive signals?
What is important to rememver about this?
Parietal insular vestibular cortex
Remember that this is responsible for the contralateral side of the body/limb.
Describe the features of benign paroxysmal positional vertigo (BPPV) [1]
Describe the physiopathlogy behind BPPV? [1]
A brief, 60 second, intense sensation of vertigo that occurs because of a specific positional change of the head
Dislodged otolith from the utricle, which then gets stuck in the ampulla, making it sensitive to gravity.
In certain positions, the otolith can stimulate the cupula, causing abnormal sensations. These persist until the crystals relocate elsewhere or disperse
Describe the symptoms of Menieres disease [3]
Describe the pathophysiology of Menieres disease
Inner ear fluid balance disorder that causes episodes of vertigo, fluctuating hearing loss, tinnitus and the sensation of fullness in the ear
Caused by an imbalance between the production and reabsorption of endolymph, which eventually ruptures the membranes, causing changes in ion concentration of the solute, leading to depolarisation of the endolymph fluid, ultimately killing the hair cells.
An infection to which structure causes a labyrinthitis? [1]
Name two symptoms [2]
- Labyrinthitis is an infection or inflammation of the semi-circular canals causing dizziness and loss of balance
What is vestibular neuritis? [1]
What is a perilymph fistula? [1]
- Vestibular neuritis is a viral infection of the vestibular nerve
- Perilymph fistula is a leakage of inner ear fluid into the middle ear. It can occur after head injury or physical exertion, or is idiopathic
Describe 6 tests that can be conducted to test for balance disorders [6]
- Hallpike’s Manoeuvre: With the patient lying in supine position, the head is lowered quickly below the horizontal plane of the table and turned to one side. The patient then sits up and the test is repeated, turning the head to the other side. If there is vestibular dysfunction, the patient will develop nystagmus and complain of vertigo within 10 seconds of head movement
- Audiometry
- The caloric test: weak nystagmus or the absence of nystagmus may indicate an inner ear disorder. The way to remember the correct response is COWS: cold water in the ear should cause the nystagmus to be away from this ear, whereas warm water causes the nystagmus to be flickering towards this ear
- Imaging of the head and brain
- Posturography: this requires the individual to stand on a tilt table, capable of movement within a controlled visual environment. Body sway is recorded in response to movement of the platform and/or visual environment
- Videonystagmography
- Electronystagmography
Label A
Otoliths
The [] is more sensitive to horizontal acceleration in comparison to the [], which is more sensitive to vertical acceleration
The utricle is more sensitive to horizontal acceleration in comparison to the saccule, which is more sensitive to vertical acceleration
Which of the following is caused by ‘imbalance of production and absorbtion of endolymph, which ulitmately can result in tympanic membrane bursting’
benign paroxysmal positional vertigo (BPPV)
labyrinthitis
ménière’s disease
vestibular neuritis
perilymph fistula
Which of the following is caused by ‘imbalance of production and absorbtion of endolymph, which ulitmately can result in tympanic membrane bursting’
benign paroxysmal positional vertigo (BPPV)
labyrinthitis
ménière’s disease
vestibular neuritis
perilymph fistula
What does this image depict?
benign paroxysmal positional vertigo (BPPV)
labyrinthitis
ménière’s disease
vestibular neuritis
perilymph fistula
What does this image depict?
benign paroxysmal positional vertigo (BPPV)
labyrinthitis
ménière’s disease
vestibular neuritis
perilymph fistula
What does this image depict?
benign paroxysmal positional vertigo (BPPV)
labyrinthitis
ménière’s disease
vestibular neuritis
perilymph fistula
What does this image depict?
benign paroxysmal positional vertigo (BPPV)
labyrinthitis
ménière’s disease
vestibular neuritis
perilymph fistula
What is the name for this test of vestibular function / dysfunction? [1]
Hallpike’s Manoeuvre:
How do you perform Hallpikes manouevre? [1]
With the patient lying in supine position, the head is lowered quickly below the horizontal plane of the table and turned to one side.
The patient then sits up and the test is repeated, turning the head to the other side.
If there is vestibular dysfunction, the patient will develop nystagmus and complain of vertigo within 10 seconds of head movement
The caloric test assesses the function of which reflex? [1]
Vestibular-ocular reflex
A 17-year-old female presents with worsening hearing on her right side. The clinician identifies a significant amount of cerumen impaction in the right external auditory canal. The patient is positioned supine, and her head is elevated 30 degrees. The right auditory meatus is irrigated with warm water. After a large piece of cerumen dislodges, the clinician continues to irrigate; however, the patient states she “feels funny.” What will most likely be seen on an ocular exam?
A. Fast beating nystagmus towards the right
B. Fast beating nystagmus towards the left
C. Conjugate eye deviation towards the right
D. Conjugate eye deviation towards the left
A 17-year-old female presents with worsening hearing on her right side. The clinician identifies a significant amount of cerumen impaction in the right external auditory canal. The patient is positioned supine, and her head is elevated 30 degrees. The right auditory meatus is irrigated with warm water. After a large piece of cerumen dislodges, the clinician continues to irrigate; however, the patient states she “feels funny.” What will most likely be seen on an ocular exam?
A. Fast beating nystagmus towards the right
B. Fast beating nystagmus towards the left
C. Conjugate eye deviation towards the right
D. Conjugate eye deviation towards the left
A 14-year-old female is being evaluated after a high-speed motor vehicle collision. She was unresponsive at the scene and was immediately intubated by EMS for airway protection. Upon arrival at the hospital, she remains unresponsive though she has not required any sedation during transport. She has an intact gag reflex upon suctioning. Which of the following clinical findings is most likely to be present in this patient?
A. Stimulation of the left ear with cold water causes left nystagmus
B. Stimulation of the left ear with cold water causes right nystagmus
C. Stimulation of either ear with cold water causes rotary nystagmus
D. Stimulation of the right ear with warm water causes left nystagmus
B. Stimulation of the left ear with cold water causes right nystagmus
This patient has suffered a traumatic brain injury (TBI).
With an intact gag reflex, CN IX and X are intact, as is the vestibulo-ocular reflex (CV VIII and III/IV).
Therefore, one would expect a positive response to caloric testing, which can be remembered by recalling the pneumonic “COWS,” cold opposite, warm same.
Label A-C
A: ampullae
B: utricle
C: saccle
Label A-D
A: Ampulla
B: Cupulla
C: Crista
D: Vestibulocochlea nerve
Name 3 nociceptive channels and what they are activated by [6]
Acid-sensing ion channel (ASIC) channel:
* cation channel activated by pH changes and other stimuli - important in inflammatory response
(TRPM8)channel (cold and menthol receptor 1):
* ion channel activated by cold temperature and cooling agents (menthol).
Transient receptor potential cation channel subfamily V member 1 (TRPV1) channel (capsaicin receptor/vanilloid receptors 1):
* Non-selective cation channel that is activated by temperature, acid, capsaicin, and mustard/wasabi.
What are the three main subgroups of primary afferent sensory neurons and what are they stimulated by? [6]
ABeta fibre: non noxious; mechanical stimulus - cutaneous mechanoreceptors non-painful, mechanical stimuli (stroking, vibration)
Adelta fibres: noxious chemical stimulus - sharp, stinging, pricking (e.g. hit by hammer)
C fibres: activated by noxious chemicals & noxious heat / temp
Which type of Na channel is particularly important for nociceptive function [1]
State the gene that codes this channel [1]
Loss of NaV1.7 (sodium channel subunit).
SCN9A gene (encode sodium channel NaV1.7).
Loss of NaV1.7 can lead to which disease? [1]
Congenital insensitivity to pain (CIP): Rare condition in which individual cannot feel pain so often have wounds, broken bones, health issues not detected.
Name a disease if NaV1.7 is overexpressed / gain of function occurs [1]
Inherited erythromelalgia (IE): A painful neuropathy involving severe chronic burning pain sensations in hands and feet.
Neuropathy pain (loss of sensory fibres)
Name a disease that is caused by insensitivty to pain from a deficit in nerve growth factor [1]
Which gene mutates to create this disease? [1]
Congenital insensitivity to pain with anhidrosis (CIPA)
- TRKA gene codes for TrKA receptor to create nerve growth factor (NGF)
- NGF is crucial for development of Adelta and C-fibres
come back transmission !
Name an acquired neuropathy [1]
Diabetic neuropathy:
High blood glucose can damage nerve fibres, esp. legs and feet - loss of pain in peripheries
Different sensory neurons have distinct projections in the dorsal horn. State what they are
Lamina found within dorsal horn:
Lamina I to V
- Aβ: project deepest - lamina IV & V
- Aδ project middle: lamina I
- C fibres project into lamina I & II
Transmission
Describe the Aδ nociceptor pathway onto the dorsal horn [2]
Aδ nociceptor axon projects on to Lamina I via excitatory glutamate synapse on to either NMDA or AMPA receptors
Transmission
Describe the C-fibre nociceptor pathway [2]
C fibres activate lamina I cells via gluatmata onto excitatory interneurons in lamina II, which then excites lamina I dendrite with glutamate
Pathophysiology of ICH
What are potential complications of ICH? [3]
herniations (if bleed big enough)
* subfalcine hernia;
* transtentorial hernia (ascending or descending)
* tonsillar hernia
Raise ICP - reduces brain perfusion
Hydrocephalus: blood into ventricles can clog up CSF drainage pathways / cerebral aquaduct is block
Management of ICH
What would need to check what medicaton a patient is on and why? [2]
Confirm if on aspirin and warfarin & stop.
Warfarin worsens the severity of hemorrhage and dramatically increases the risk of mortality from ICH.
Management of ICH
What should you do if ICH patient has raised BP? [1]
Why is this a tricky problem to manage? [2]
Lower BP (if more than 150 mmHG systolic ) to about 140 mm HG
Higher chance of AKI
Patients might have **secondary raised ICH **- then reducing cerebral blood flow if lowering BP
(conflicting evidence on cost / benefit)
Ischaemic stroke pathophysiolgoy
Describe the ischaemic stroke cascade at microscopic level [4]
Cellular ischaemia:
- Na / K+ pump failure
- Causes depolarisation
- Causes Ca2+ food in
- Cascade of enzymes that respond to ischaemia (like caspases)
- Causes cell death
Ischaemic stroke
Which pathologies cause ischaemic stroke?
- Atherosclerosis of small vessels (25%)
- Atherosclerosis of large vessels (50%) carotid stenosis is 10% of all stroke
- Carotid dissections (<5%)
- Cardiac / AF (15%)
- Vasculitis (<1%)
Which cause of ischaemic stroke increases in younger patients? [1]
Carotid dissections
Risk factors for stroke?
What are the key medical conditions that increase risk of stroke? [4]
Hypertension
Hypercholesteroamia
Diabetes
Cardiac - AF
Stroke classification
What are the methods of classifying a stroke [3]
Clinical picture: Oxford Bamford Classification
By vascular anatomy
By aetiology: Toast classification
visual deficits with stroke
Describe the Oxford Bamford Classification of Stroke
Oxford Bamford Classification of Stroke:
Anterior circulation:
- strokes from MCA, ACA and carotid artery
Posterior Circulation
- PCA, basilar arteries and cerebellar arteries
Lacunar: absence of cortical signs
Describe the signs of anterior [3], posterior [4] and lacunar strokes [4]
Anterior:
* Unilateral motor deficit
* Homonymous hemianopia
* Neglect / dysphasia
Posterior:
* Pure hemianopia
* Cerebellar signs
* Dipolplia and CN palsy
* Bilateral / crossed sensory motor-signs
Lacanar:
* Pure motor
* Pure sensory
* Ataxic hemiparesis
* Senosorimotor
Stroke treatment
Antiplatelet therapy for stroke? [3]
Aspirin
Aspirin & Clopidogrel
Aspirin and Dipyridamole
TIA treatment?
