Chapter 12 part 1 Flashcards by Morgan Evans

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

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

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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?

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.

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

1) Bony labyrinth
2) Membranous labyrinth.

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The bony labyrinth is filled with ________ called ______

fluid; perilymph

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What does perilymph do?

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

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

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

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

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

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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?

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

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

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

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

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

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What do the otoliths do?

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

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Vestibular nuclei are important for what 3 things?

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

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The vestibular nuclei have intimate connections with what 3 things?

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

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What pathway provides an awareness of head position?

An ascending pathway through the thalamus to the cortex

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

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

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

1) Semicircular canals
2) Otolith organs

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

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.

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?

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.

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

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

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

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

Name two parts of the medial descending motor system

1) Lateral vestibulospinal tract
2) Medial vestibulospinal tract

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

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.

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

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

What does the MLF pathway do?

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

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

1) Cerebellum 2) Vestibulocerebellum.

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

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.

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?

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

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

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

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

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

Dix-Hallpike testing can help differentiate between what?

Central or peripheral causes of vertigo

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

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

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?

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

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?

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

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?

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.

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

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)

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

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

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

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.

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

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.

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?

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

Name two common causes of central vertigo

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

What are some common causes of dizziness?

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