Vestibular & Visual System/Reflexes Flashcards
Function of Pretectum
Pupillary Light Reflex
In the Midbrain-Superior Colliculus, the Edinger-Wesphal nucleus is more (ventral/dorsal) in location in comparison to the Oculomotor Nucleus
Dorsal
The Edinger-Wesphal nucleus is responsible for (sympathetic/parasympathetic) control of the pupil and causes (constriction/dilation)
Parasympathetic; Constriction
Horner’s Syndrome is characterized by what 4 characteristics
Miosis (pupils constricted)
Ptosis (eyelid droop)
Anhidrosis (no sweat)
Facial Flushing (vasodilation)
Horner’s Syndome is usually (uni/bi)lateral and (contra/ipsi)lateral
unilateral; ipsilateral
Accomodation WITHOUT responsiveness; pupil is small and can constrict with PROXIMITY of objects but not with LIGHT; usually due to tertiary SYPHILIS
Argyll-Robertson Pupil
Argyll-Robertson Pupil is caused by what infectious disease
Syphilis
Argyll Robertson Pupil presentation
Pupil accommodates but doesn’t react to light
Relative Afferent Pupillary Defect or aka. Marcus Gunn Pupil is due to damage in what cranial nerve?
CN II (optic nerve)
What happens when light is shone to HEALTHY eye in RAPD patient?
Constriction of healthy eye and affected eye
- Direct and consensual constriction is intact
What happens when light is shone to affected eye in RAPD patient?
Both pupils dilate instead of constrict
- No CN II conduction of light information
The (utricle/saccule) detects static head position and linear head movements in the HORIZONTAL plane.
The (utricle/saccule) detects static head position and linear head movements in the VERTICAL plane.
Utricle
Saccule
Movement of the stereocilia bend TOWARD the Kinocilium, the hair cell is (de/hyper)polarized
Depolarized
*due to the opening of K+ channels allowing entry
Movement of the stereocilia bend AWAY from the Kinocilium, the hair cell is (de/hyper)polarized
Hyperpolarized
Filamentous bridges that connect hair bundles to kinocilium and pull open the ion channels
Tip links
The Utricle and Saccule have a (macula/crista) for the sensation of movement
Macula
The Semicircular Canals have a (macula/crista) within ampulla for the sensation of movement
Crista
The direction of the inertia of the endolymph displaces the cupula and hair cells (towards/away from) the direction of head motion, therefore causing depolarization of the hair cells
AWAY FROM
Describe the pathway for vestibular information to the CNS for balance
Vestibular Apparatus –> CN 8 –> Vestibular nuclei in ipsilateral medulla & Purkinje cells in ipsilateral cerebellum –> Vestibular nuclei in ipsilateral medulla –> Vestibulospinal (VST) UMN tracts –> control our posture/balance
The vestibular nuclei project to the spinal cord via ________ tract to control head and neck movements as well as posture to compensate for changes in position
Vestibulospinal UMN tracts
The vestibular nuclei project to the CN 3, 4, 6 nuclei via ____________ tract to control eye movements when we move our head
Medial Longitudinal Fasciculus (MLF)
Voluntary horizontal gaze (“look to the right”) is activated by the
cerebral cortex
Involuntary horizontal gaze (move head to the right) is activated by the
vestibular apparatus/nuclei
brainstem gaze center
PPRF (paramedian pontine reticular formation)
When asked to “look to the right”, voluntary control of horizontal gaze allows both eyes to look to the (left/right)
RIGHT
involuntary control of horizontal gaze is governed by
Vestibul-Ocular Reflex (VOR)
When asked to “move head to the right”, involuntary control of horizontal gaze allows both eyes to look to the (left/right).
LEFT
Under normal conditions, when the head is turned to the RIGHT, the firing rate of CN 8 ______ on the right side and _______ on the left side; that’s how the brain knows the head is turning to the right
increases; decreases
Under vestibular dysfunction on the LEFT side, the firing rate of CN 8 ______ on the left, therefore, the EYES are going to reflexively move to the ______ producing a nystagmus to the ______
decreases; LEFT; LEFT
- the brain thinks the head is moving to the right (when actually not), so eyes reflexively move the left.
In caloric testing to test for nystagmus, cold water stimulates eye movement to ____ side and warm water stimulates eye movement to ____ side if nystagmus is present.
opposite; same
- they are fast phase of nystagmus
What disorders can present with vertigo as one of their symptoms?
- MS
- Migraine
- Neoplasm (vestibular swannoma, meningioma)
- BPPV
- Meniere’s Disease
- Labyrinthitis
- Vestibular Neuritis
- Ototoxicity
- Perilymph Fistula
- Labyrinthine Fistula
caused by otoconia (canaliths) dislodging and migrating into one of the semicircular canals, most commonly the POSTERIOR semicircular canal, where it disrupts the endolymph dynamics
BPPV
Diagnosis of BPPV
- Dix-hallpike
- Vertigo > 1 minute with changes in head positions
- unaffected hearing
Tx for BPPV
Epley maneuver
a disorder of the inner ear caused by impaired endolymph resorption (increased endolymph pressure in scala media/cochlear duct); very strict diagnostic criteria
Meniere’s disease (aka. endolymph hydrops)
What are the diagnostic criteria of meniere’s disease?
- Episodic vertigo lasting at least 20 min
- Tinnitus
- Hearing loss (low frequency is affected first; interesting!)
- Aural fullness (feels like something is in the ear)
What could be a clue pointing to meniere’s disease when there is a HL?
low frequency (where as other sensorineural HL are high-frequency first)
Tx for Meniere’s disease
Medical (low salt, diuretics) or Surgical
Infection of the endolymph and perilymph caused by bacteria or virus
Labyrinthitis
the idiopathic inflammation of the vestibular nerve. It is thought to be viral in origin because it commonly occurs AFTER URI.
Vestibular neuritis
Only _____ is present in vestibular neuritis; no hearing loss and other symptoms
Vertigo
A congenital or acquired abnormal connection between the inner ear and middle ear. Can cause sensorineural hearing loss, dizziness, and vertigo.
Perilymph Fistula
An abnormal opening in the inner ear. This can result in leakage of the perilymph into the middle ear. Can cause sensorineural hearing loss and vertigo.
Labyrinthine Fistula
reactivation of VZV in the geniculate ganglion, affecting the seventh (facial) and eighth (vestibulocochlear) cranial nerves; clinical features include shingles in pinna/EAM, vertigo, SNHL, and facial paralysis
Herpes zoster oticus
- aka. Ramsay Hunt Syndrome
The most common site of lesion leading to Bell’s palsy
Meatal foramen of fallopian canal
Fallopian canal is aka.
facial nerve canal
Tx for Herpes zoster oticus and Bell’s Palsy
- Steroids
2. Antivirals (NOT for Bell’s Palsy though!)
