Chapter 12 part 1

Question 1

1) What is the vestibular system? What does it do?
2) What allows it to work?

Answer 1

1) Sensory system that senses balance and spatial orientation coordinating movement with balance
2) The inner ear and cochlea

Question 2

1) Describe how sound waves go from the tympanic membrane to inner ear structures
2) What is the inner ear also called? What structures does it contain?

Answer 2

1) Sound waves are transmitted by the tympanic membrane and amplified by the middle ear ossicles (malleus, incus and stapes) to the oval window.
From there the vibrations reach the inner ear structures.
2) Labyrinth; the cochlea, vestibule and semicircular canals.

Question 3

What are the two parts of the labyrinth of the inner ear?

Answer 3

1) Bony labyrinth
2) Membranous labyrinth.

Question 4

The bony labyrinth is filled with ________ called ______

Answer 4

fluid; perilymph

Question 5

What does perilymph do?

Answer 5

Communicates with the subarachnoid space via a small perilymph duct. (helps to equalize pressure changes.)

Question 6

1) What makes up the membranous labyrinth?
2) Where is it?
3) What is the membranous labyrinth filled with?

Answer 6

1) The cochlear duct, utricle, saccule and semicircular canals
2) Suspended in the perilymph.
3) Filled with endolymph.

Question 7

1) The semicircular canals detect what?
2) What does this cause?

Answer 7

1) Angular acceleration around 3 angular axes
2) Rotation of the head around any of these axes causes movement of endolymph through the ampullae.

Question 8

1) What does the movement of endolymph through the ampullae form? (don’t rlly need to know)
2) What do the hair cells do? What does this do?

Answer 8

1) The gelatinous cupula within which the hair cells are embedded.
2) Activate terminals of primary sensory neurons; send axons to the vestibular nerves.

Question 9

1) What are maculae?
2) Where are they found?
3) What do they do?

Answer 9

1) Receptors containing hair cells
2) Within the utricle and saccule
3) Detect linear acceleration and head tilt.

Question 10

What do the maculae consist of and what are they called? Where are they?

Answer 10

Calcified crystals called otoliths sitting in a gelatinous layer where mechanoreceptor hair cells are embedded

Question 11

What do the otoliths do?

Answer 11

Gravity or other linear acceleration pull on these crystals and activate the hair cells

Question 12

Vestibular nuclei are important for what 3 things?

Answer 12

1) Adjustment of posture
2) Muscle tone
3) Eye position in response to movements of the head in space

Question 13

The vestibular nuclei have intimate connections with what 3 things?

Answer 13

1) Cerebellum
2) The brainstem motor system
3) Extraocular systems.

Question 14

What pathway provides an awareness of head position?

Answer 14

An ascending pathway through the thalamus to the cortex

Question 15

1) Primary vestibular neurons in the vestibular ganglia convey information about what?
2) Where does this information come from?
3) Where is it conveyed?

Answer 15

1) Angular and linear acceleration
2) Semicircular canals hair cells + otolith organs
3) Vestibular division of CN VIII to the vestibular nuclei.

Question 16

1) What provides info about angular acceleration?
2) What provides info about linear acceleration?

Answer 16

1) Semicircular canals
2) Otolith organs

Question 17

1) How many vestibular nuclei are there?
2) Where? Be specific

Answer 17

1) 4 vestibular nuclei
2) On each side of the brainstem, lying on the lateral floor of the fourth ventricle in the pons and rostral medulla.

Question 18

1) The lateral vestibular nucleus gives rise to what?
2) What is this a part of?
3) Where is it?
4) What two things is it important in?

Answer 18

1) The lateral vestibulospinal tract (LVT)
2) Part of the medial descending motor system.
3) LVT extends the entire length of the spinal cord
4) In maintaining balance and extensor tone.

Question 19

1) The medial vestibular nucleus gives rise to what?
2) What else contributes to this?
3) What is this?

Answer 19

1) The medial vestibulospinal tract
2) Inferior vestibular nucleus.
3) MVT is a medial descending motor system

Question 20

1) Where is the MVT found?
2) What is it important in?

Answer 20

1) Extends only to the cervical spine
2) Important in controlling head and neck position

Question 21

Name two parts of the medial descending motor system

Answer 21

1) Lateral vestibulospinal tract
2) Medial vestibulospinal tract

Question 22

1) What is the medial longitudinal fasciculus (MLF)?
2) What does it do? (2 things)

Answer 22

1) Bundle of nerve fibers
2) Conjugates the gaze (allows eyes to move together) and connects the nuclei involved in eye movements to each other and to the vestibular nuclei.

Question 23

1) What things ascend in the MLF?
2) Where do they go?

Answer 23

1) Fibers arising from the medial and some superior vestibular nuclei
2) To CN 3, 4, and 6 nuclei

Question 24

What does the MLF pathway do?

Answer 24

Mediates the vestibulo -ocular reflex (eye movements adjust for changes in head position.)

Question 25

1) The vestibular nuclei have many important reciprocal connections with what?
2) What are those parts of the cerebellum called because of these connections?

Answer 25

1) Cerebellum
2) Vestibulocerebellum.

Question 26

1) Define dizziness
2) Define vertigo
3) What does vertigo suggest? What can cause this?

Answer 26

1) Very subjective and has a variety of definitions; lightheadedness, faint, nausea, woozy, or unsteady on one’s feet.
2) Spinning sensation
3) Suggests vestibular disease; can be caused by a lesion anywhere in the vestibular pathway from the inner ear to vestibular nerve to the cerebellum.

Question 27

1) Most vertigo cases are caused by what? Is it benign or urgent?
2) What is a less common cause of vertigo? Is it benign or urgent?

Answer 27

1) Peripheral disorders/ lesions involving the inner ear (usually benign.)
2) Central disorders/ lesions of the brainstem or cerebellum are less common (usually urgent.)

Question 28

1) Why is it important to take a thorough and detailed history of associated symptoms when a patient complains of vertigo?
2) Give examples of associated symptoms

Answer 28

1) A brainstem stroke could cause vertigo (and that may be presenting complaint)
2) Diplopia, dysarthria, weakness, incoordination, other visual changes, or somatosensory changes

Question 29

What should always be checked when a patient complains of vertigo? Why?

Answer 29

1) Orthostatic BP.
2) A positive finding could point to something outside of the vestibular system

Question 30

Dix-Hallpike testing can help differentiate between what?

Answer 30

Central or peripheral causes of vertigo

Question 31

1) What does Dix-Hallpike maneuver do?
2) What is the patient’s position and what are you looking for?

Answer 31

1) Stimulates the posterior semicircular canal
2) The patient is placed supine and the examiner looks for nystagmus.

Question 32

1) What does the Dix-Hallpike test look like if the patient has peripheral lesions of the inner ear?
2) What does the nystagmus look like?
3) Is there adaptation if it’s repeated?

Answer 32

1) There is usually a 2-5 second delay in vertigo and nystagmus
2) The nystagmus is horizontal or rotary and does not change directions
3) Yes; often adaptation/habituation/fatiguing so it’s less intense each time

Question 33

1) What does the Dix-Hallpike test look like if the patient has central lesions?
2) What does the nystagmus look like?
3) Is there adaptation if it’s repeated?

Answer 33

1) Nystagmus and vertigo may begin immediately in supine position
2) Vertical nystagmus, nystagmus that changes directions while the patient is in the same position or prominent nystagmus in the absence of vertigo are only seen with central lesions.
3) No adaptation

Question 34

1) What is the most common cause of vertigo?
2) Describe when it happens and the duration
3) What is it like when symptoms first occur? What about later?
4) How intense can it be?

Answer 34

1) Benign paroxysmal positional vertigo (BPPV)
2) Brief episodes of vertigo lasting for a few seconds
occur with change of position
3) When the symptoms first occur, pt may be dizzy for several hours; after the first episode, symptoms are usually brief and only occur with change of position.
4) Can be so intense, patients cannot walk.

Question 35

1) What is the typical cause of Benign paroxysmal positional vertigo (BPPV)?
2) What makes symptoms worse?
3) How is it treated?

Answer 35

1) The cause is thought to be otolithic debris in the semicircular canals (esp posterior)that push against the cupula.
2) Symptoms are brought on if patient lays down (to sleep) on affected side or if the patient turns to the affected side.
3) Canalith repositioning maneuvers to dislodge debris can be beneficial in most patients (Epley maneuver)

Question 36

1) What are the symptoms of Meniere’s disease?
2) What is the etiology?
3) What is the common treatment?

Answer 36

1) Recurrent episodes of vertigo with progressive hearing loss and tinnitus (sometimes patients will complain of a full feeling in the ear.)
2) Excess fluid and pressure in the endolymphatic system.
3) Salt restriction and diuretics

Question 37

1) What can acoustic neuroma cause?
2) How is it different from Meniere’s disease?
3) Is it true vertigo? What does it cause?
4) Does it have episodes

Answer 37

Acoustic neuroma can also cause hearing loss and tinnitus with associated dizziness.
Though unlike Meniere’s Disease, acoustic neuroma causes unsteadiness and not true vertigo and does not have discrete episodes.

Question 38

1) What is the second most common cause of vertigo?
2) What is it origin?
3) Who does it affect the most?

Answer 38

1) Vestibular neuritis
thought to be of viral origin
Most commonly affects persons 30 to 50 years of age.
Men and women are affected equally.

Question 39

1) Describe hearing with vestibular neuritis
2) What is the prognosis of vestibular neuritis?
3) What can happen after a vestibular neuritis attack? How often?

Answer 39

1) Hearing is not impaired in this condition
2) The prognosis is excellent
3) Development of BPPV after an attack of vestibular neuritis may occur in 15% of patients

Question 40

Name two common causes of central vertigo

Answer 40

1) Vertebrobasilar ischemia or infarct
2) Small hemorrhage in cerebellum or brainstem

Question 41

What are some common causes of dizziness?

Answer 41

Toxins, drugs (including gentamicin, which can cause bilateral dysfunction), viral causes, syphilis