Chapter 16 Park 2 Flashcards
Oscillopsia
Lack of visual stabilization; e.g., the world appears to bounce up and down as a result of a failure of the vestibulo-ocular reflex
Nystagmus
Involuntary back-and-forth movements of the eyes composed of slow component in one direction and interrupted by fast saccadic-like movements in the opposite direction.
Pathologic nystagmus
Abnormal oscillating eye movements that occur with or without external stimulation.
Physiologic nystagmus
Normal involuntary back-and-forth eye movements that can be elicited in an intact nervous system by rotational or temperature stimulation of the semicircular canals or by moving the eyes to the extreme horizontal position.
Fistula
an abnormal passage that leads from one hollow organ or part to another
Paroxysm
a sudden attack or increase of symptoms of a disease (such as pain, coughing, shaking, etc.) that often occurs again and again
Vertigo
Illusion of motion; is common in vestibular disorders
What is the most common symptom of vestibular disorder?
vertigo
What disorders does vertigo occur with?
peripheral and central
What does vertigo arise from?
arises from a disturbance of spatial orientation in the vestibular cortex.
What always accompanies peripheral vertigo?
nystagmus
What does peripheral vestibular disorders typically cause?
recurring periods of vertigo and more severe nausea than central disorders
Common peripheral vestibular disorders:
benign paroxysmal positional vertigo (BPPV), vestibular neuritis, Ménière’s disease, traumatic injury, and perilymph fistula
Inner ear disorders that cause the acute onset of vertigo and nystagmus are
benign
paroxysmal
positional
Benign:
Is not malignant
Paroxysmal
Has a sudden onset of a symptom or disease
Positional
Denotes head position as the provoking stimulus
What are activities that provoke BPPV?
Getting into or out of bed
Bending over to look under a bed
Reaching up to retrieve something from a high shelf
Turning over in bed
What causes BPPV?
the displacement of otoconia from the macula into a semicircular canal
Vestibular Neuritis
an inflammation of the vestibular nerve and is usually caused by a virus
Symptoms of vestibular neuritis:
dysequilibrium,
spontaneous nystagmus, nausea, and
severe vertigo
hearing is unaffected
Ménière Disease
Causes a sensation of fullness in the ear, tinnitus, severe acute vertigo, nausea, vomiting, and hearing loss.
Is associated with abnormal fluid pressure in the inner ear
What is perilymph?
fluid in the space between the bone and the membranous labyrinth in the inner ear
When does a fistula occur?
an opening occurs between the middle and inner ear
What happens with a fistula?
perilymph to leak from the inner ear into the middle ear
What does a perilymph fistula cause?
the abrupt onset of hearing loss, tinnitus, and vertigo
Bilateral Lesions of the Vestibular Nerve
Interfere with reflexive eye movements in response to head movement
What is oscillopsia?
the subjective sensation of visual objects bouncing when the head is moving or the persons is walking
Why does oscillopsia occur?
because normal reflexive adjustments for head movement are decreased
Central Vestibular Disorders
Are the result of damage to the vestibular nuclei or to the connections within the brain
Symptoms Central Vestibular Disorders:
Typically produce milder symptoms than peripheral disorders
What are central vestibular disorders commonly the result of?
ischemia or tumors in the brainstem/cerebellar region cerebellar degeneration, multiple sclerosis, or Arnold-Chiari malformation
Unilateral Vestibular Loss
Causes problems with posture, eye movement control, and nausea because signals from the intact side are not balanced by those from the lesion side
Cortically blind:
have no awareness of any visual information
Blind sight
is the ability of an individual who is cortically blind to orient or point to visual objects
What is blind sight contingent upon?
intact function of retina and pathways from retina to superior colliculus
Anopsia
Loss of sight in one or both eyes
Hemianopsia
Loss of sight in one half of the visual field
Homonymous hemianopsia
Loss of vision in the left or right visual field of both eyes
