Exam 3 Week 14 ppt 13 & 14 Vestibular Reflexes & Vestibular Pathology

Question 1

What are the functions of the Vestibulo-ocular Reflex? (3)

Answer 1

1. –Elicits compensatory eye movements through a network of neural connections
2. –Stabilizing eye position with movements that are equal in magnitude and opposite in direction to the head movement
3. –Suppressed at will to focus on a moving target while turning the head in the same direction

The Vestibulo-ocular Reflex Elicits compensatory eye movements through a network of neural connections for Stabilizing eye position with movements that are equal in magnitude and opposite in direction to the head movement. However this can be Suppressed at will to focus on a moving target while turning the head in the same direction

Question 2

Describe the pathways of the Vestibulo-ocular Reflex and how the eyes are activated: (4)

Answer 2

1. –Afferent fibers from the semi-circular canals end in medial vestibular nucleus
2. –Medial vestibular nucleus projects bilaterally via MLF to abducens nucleus (CN VI)
3. –Axons from abducens nucleus (CN VI) actives lateral rectus & contralateral oculomotor nucleus (CN III)
4. –Oculomotor nucleus (CN III) activates medial rectus

Lets first look at the anatomy of the connections for the vestibulo-ocular reflex. Afferent fibers from the semi-circular canals end in medial vestibular nucleus. The Medial vestibular nucleus projects bilaterally via MLF to abducens nucleus (CN VI). Axons from abducens nucleus (CN VI) actives lateral rectus & contralateral oculomotor nucleus (CN III). The contralateral Oculomotor nucleus (CN III) activates the contralateral medial rectus

Question 3

Vestibulo-ocular Reflex: what direction do the eyes move relative to the head when it rotates, and which muscles are activated by the reflex?

Answer 3

–Rotate head in a direction (left in illustration)

• §Opposite lateral rectus & same side medial rectus contract
• §Both eyes move in opposite direction (right here)

So as the Rotation of the head occurs in a direction (left in illustration) there is an activation of the right (contralateral) lateral rectus and the left (ipsilateral) medial rectus to move the eyes to the opposite direction – in this case to the right.

Question 4

How many pairs of semicircular canals does the vestibulo-ocular reflex operate therough?

Answer 4

–Operates through all 3 pairs of canals - horizontal canal pair easiest to visualize
–Head rotates to left - eyes must move to right at identical angle to fix the gaze

The Vestibulo-ocular Reflex Operates through all 3 pairs of canals - horizontal canal pair easiest to visualize. As you can see here when the Head rotates to left - eyes must move to right at identical angle to fix the gaze

Question 5

What is nystagmus? (3)

Answer 5

•Nystagmus

• –Jerky bidirectional eye movements
• –Slow & quick movements in opposite directions
• –The quick movement is termed a saccade

Nystagmus is Jerky bidirectional eye movements. There are two phases to this movement, a Slow & a quick movements in opposite directions. The quick movement is termed a saccade

Question 6

What is a saccade?

Answer 6

The quick movement during nystagmus

Nystagmus is Jerky bidirectional eye movements. There are two phases to this movement, a Slow & a quick movements in opposite directions. The quick movement is termed a saccade

Question 7

Is nystagmus physiological or pathological?

Answer 7

iIt can be either

Question 8

what are two types of physiological nystagmus?

Answer 8

1. –Physiological – post-rotatory
2. –Physiological - Opticokinetic nystagmus

Question 9

Epxlain how Nystagmus is a Physiological post-rotatory event: (3)

Answer 9

–Physiological – post-rotatory

1. §Very quick full circle rotation –
2. §Occurs when rotation exceeds (vestibulo-occular reflex) VOR ability to provide compensation
3. §Compensatory eye movement with a quick saccade in direction of rotation & slow movement in opposite direction

Nystagmus is a Physiological post-rotatory event. With a very quick full circle rotation nystagmus can occur when when rotation exceeds VOR ability to provide compensation – as can be seen in this video from YouTube: http://www.youtube.com/watch?v=RYTYTy_5Xn0

Nystagmus Occurs as a Compensatory eye movement with a quick saccade in direction of rotation & slow movement in opposite direction

Question 10

VOS

Answer 10

Vestibulo-ocular Reflex

Question 11

Physiological Nystagmus: Explain Opticokinetic nystagmus: (3)

Answer 11

–Physiological - Opticokinetic nystagmus

1. §Induced by looking at moving visual stimuli, such as moving vertical lines or objects
2. §Slow movement in direction of moving objects then fast saccade back
3. §Produced by parieto-occipital cortex and frontal eye fields respectively

Opticokinetic nystagmus is a physiological response Induced by looking at moving visual stimuli, such as moving vertical lines or objects. There is a Slow movement in direction of moving objects then fast saccade back. Opticokinetic nystagmus is produced by two areas of the cortex parieto-occipital cortex and frontal eye fields with the slow movement produced by the parieto-occipital cortex and the quick movement back produced by the frontal eye fields. You can see an example of Opticokinetic nystagmus in this video clip from YouTube: http://www.youtube.com/watch?v=XFTWgCMnXrs

Question 12

Explain Pathological Nystagmus (2)

Answer 12

–Pathological

1. §Nystagmus occurs without fulfilling its normal function
2. §Result of damage to one or more components of the vestibular system, including semicircular canals, otolith organs, and/or floculonodular lobe (vestibulocerebellum)

Of course there is also Pathological forms of Nystagmus occurs without fulfilling its normal function.

Nystagmus can be the Result of damage to one or more components of the vestibular system, including semicircular canals, otolith organs, and/or floculonodular lobe (vestibulocerebellum)

Question 13

What are two ways to test VOR?

Answer 13

–Rotatory or optokinetic testing
–Caloric testing

Question 14

Explain Caloric VOR testing:

Answer 14

–Caloric testing

1. §Put cold or warm water into external acoustic meatus
2. §Evokes endolymph convection currents
3. §COWS – cold opposite & warm same

Testing Vestibulo-ocular Reflex can also be done with Caloric testing. If you put cold or warm water into external acoustic meatus it will evoke endolymph convection currents. The pattern of these movements are cold opposite direction saccadic eye movements to the side of fluid infusion & warm same direction saccadic eye movements – cold opposite warm same (COWS). This by the way is why if fluid is used to clear out ear wax it should be a neutral temperature

Question 15

What is the Vestibulocollic Reflex?

Answer 15

•Neck movements to compensate to maintain head in upright position when movement of the body

Question 16

Does the vestibulocollic reflex interact with visual reflexes?

If so, explain what happens with vision intact or blind

Answer 16

there is an interaction with visual reflexes so with either blindfolded (b in this illustration) or vision intact with & vestibular damage (c in this illustration) head-righting will occur

•Damage to both visual and vestibulocollic reflexes will result in no head-righting (a)

Question 17

Describe the interaction of Vestibular and neck reflexes

Answer 17

• •Neck and vestibular reflexes are integrated to allow controlled movement
• •In young infants or in brain damaged adults these can be seen in isolation as:
  
  • –Tonic labyrinthine reflexes
  • –Symmetric neck reflexes
  • –Asymmetric neck reflexes

Question 18

what are the three types of reflexes that show the interaction of vestibular and neck reflexes in isolation in young infants or in brain damaged adults?

Answer 18

1. –Tonic labyrinthine reflexes
2. –Symmetric neck reflexes
3. –Asymmetric neck reflexes

Question 19

Describe Tonic labyrinthine reflex

Answer 19

Tonic labyrinthine reflexes are produced when

• Head tilted backward – arms & legs extended (superman posture)
• Head tilted forward – arms & legs flexed (rolling head over heels)

Question 20

•Symmetric Tonic Neck Reflex

Answer 20

Symmetric Tonic Neck Reflex

1. Tilt head forward – arms flexed & legs extended as you can see the infant in the picture above (lower of the two infant pictures) or preparing to jump off the diving board
2. Tilt head back – arms extended & legs flexed as you can see in the upper picture of the infant or in the look up – jump up pose

Question 21

•Asymmetric Tonic Neck Reflex

Answer 21

Asymmetric Tonic Neck Reflex occurs when the head is turned – extension of the limbs in direction of head turned & contralateral flexion of the limbs as can be seen in the infant

Question 22

Three main things to assass in evaluation of the Vestibular System:

Answer 22

1. •Observation of stance and gait
2. •Observation for spontaneous or positional nystagmus
3. •Nystagmus testing

Evaluation of the Vestibular System begins with Observation of stance and gait. A person with vestibular problems will likely have a Wide base of support and are likely to be seen drifting from side to side in gait. Also you should Observe for spontaneous or positional nystagmus. Often then Nystagmus testing is done either using Caloric test for vestibular function or Tests of optokinetic nystagmus. You can do this testing visually or using a recording of eye muscle activation called Electronystagmography

Question 23

What will you notice when evaluating the vestibular system in a sympotomatic person’s gait?

Answer 23

•Observation of stance and gait

• –Wide base of support
• –Drifting side to side in gait

Question 24

What are three ways you can do Nystagmus testing?

Answer 24

1. –Caloric test for vestibular function
2. –Tests of optokinetic nystagmus
3. –Electronystagmography

Question 25

What is the cardinal sign of vestibular dysfunction?

Answer 25

Vertigo

Question 26

define vertigo

Answer 26

any subjective or objective illusions of motion or position

Question 27

What are three main symptoms of Vestibular disorders? (3)

Answer 27

1. •Wide base of support & unusual gait 2. •Vertigo is the cardinal sign of vestibular dysfunction * –Any subjective or objective illusions of motion or position 3. •Autonomic signs * –Nausea, vomiting, pallor, perspiration, blood pressure drop, tachycardia In addition to a Wide base of support & unusual gait, Vertigo is the cardinal sign of vestibular dysfunction. Vertigo is dizziness in which a patient inappropriately experiences the perception of motion, usually a spinning motion. As mentioned previously this symptom is often accompanied by the sign of pathologic nystagmus. There may also be Autonomic signs including: Nausea, vomiting, pallor, perspiration, blood pressure drop, tachycardia

Question 28

What are some autononic signs of vestibular disorders? (6)

Answer 28

1. –Nausea, 2. vomiting, 3. pallor, 4. perspiration, 5. blood pressure drop, 6. tachycardia

Question 29

What are the two main categories of vestibular disease

Answer 29

1. •Central vestibular disease * –Pathology of the vestibular nuclei, their projections or central sites of termination * –Infarct, tumors, and viral infections 2. •Peripheral vestibular disease * –Pathology of the labyrinth or vestibular nerve * –Trauma, benign positional vertigo, neuritis, toxicity, Meneire's disease, herpes zoster, tumors Patient can suffer from either Central or peripheral vestibular diseases. Central vestibular conditions include Pathology of the vestibular nuclei, their projections or central sites of termination which can be the result of vascular Infarct, tumors, and viral infections Peripheral vestibular disease involve Pathology of the labyrinth or vestibular nerve which can result from Trauma, benign positional vertigo, neuritis, toxicity, Meneire's disease, herpes zoster, tumors

Question 30

What is Central vestibular disease? examples? (3)

Answer 30

•Central vestibular disease * –Pathology of the vestibular nuclei, their projections or central sites of termination Examples * Infarct, * tumors, and * viral infections

Question 31

What is peripheral vestibular disease? examples? (6)

Answer 31

•Peripheral vestibular disease * –Pathology of the labyrinth or vestibular nerve Examples: 1. –Trauma, 2. benign positional vertigo, 3. neuritis, toxicity, 4. Meneire's disease, 5. herpes zoster, 6. tumors

Question 32

BPV

Answer 32

Benign Positional Vertigo

Question 33

Describe Benign Positional Vertigo (VPV)? (4) What is it? How is it diagnosed? How is it treated?

Answer 33

1. –Common cause of vertigo due to macular debris being displaced into a semicircular canal (posterior canal most often affected) 2. –With rapid changes in head position, symptoms occur 3. –Diagnosed by the Dix-Hallpike maneuver 4. –Treated with a series of specific head movements Lets talk about Benign Positional Vertigo (BPV) which is one of the more common peripheral vestibular conditions. It is a Common cause of vertigo and is due to macular debris being displaced into a semicircular canal with the posterior canal most often affected. Symptoms occur with rapid changes in head position, such as getting up from bed quickly the person gets extreme vertigo and has to lie right back down again. This can be quite disabling. Diagnosed by the Dix-Hallpike maneuver and is Treated with a series of specific head movements to move the debris back into the macula.

Question 34

what is the name of the manuver that is used to diagnose BPV?

Answer 34

Dix-Hallpike maneuver

Question 35

Describe how to perform the Dix-Hallpike manuver?

Answer 35

•Dix-Hallpike maneuver * –Person begins in a long sit position with head held by examiner * –Examiner rotates head 30-45° (a) & assists the person to lie down, carrying head into 25-30° of extension (b) Dix-Hallpike maneuver first begins with the patient in a long sit position with head held by examiner. The Examiner rotates head 30-45° (as shown in picture A) & assists the person to lie down, carrying head into 25-30° of extension (B in this picture)

Question 36

Explain what happens during the Dix-Hallpike manuver (why it is diagnostic)?

Answer 36

* –Movement causes otoliths to move within endolymph, thereby * –This creates waves of endolymph movement and bending of hair cells stereocilia in involved canal * –This induces vertigo and nystagmus In the Dix-Hallpike maneuver, Movement causes otoliths to move within endolymph, thereby creating waves of endolymph movement and bending of hair cells stereocilia in involved canal. This induces vertigo and nystagmus

Question 37

Describe Vestibular Neuroitis (include symptoms)

Answer 37

•Vestibular Neuritis * –Unilateral vestibular disorder due to inflammation of vestibular nerve * –Diminished or absent response to caloric testing of horizontal canal on affected side * –Symptoms include nausea and vomiting, which resolve within a few days Vestibular Neuritis is a Unilateral vestibular disorder due to inflammation of vestibular nerve. There is a Diminished or absent response to caloric testing of horizontal canal on affected side. Symptoms again include nausea and vomiting, which resolve within a few days

Question 38

What is Meniere's Disease? (3) | (include symptoms)

Answer 38

•Meniere’s Disease * –Episodic syndrome dues to excess fluid in inner ear that affects hearing & equilibrium * –Abrupt attacks vary in frequency & severity * –Characterized by sensorineural hearing loss, tinnitus, aural fullness, nausea & vomiting Meniere’s Disease is an Episodic syndrome dues to excess fluid in inner ear that affects hearing & equilibrium. Most commonly seen as a “ringng” in the ears – tinnitus, it can also disrupt balance. It is generally seen as Abrupt attacks which vary in frequency & severity Characterized by sensorineural hearing loss, tinnitus, aural fullness, nausea & vomiting

Question 39

What are three other causes of vertigo?

Answer 39

•Other causes of vertigo 1. –Cerebellar lesions may directly or indirectly apply pressure on the brainstem and the vestibular nuclei 2. –Irritation of upper cervical dorsal roots 3. –Drug and alcohol intoxication