Chapter 13 Flashcards
(17 cards)
What are the two chief functions of the vestibular system?
- to keep head and body lined up on an even keel.
2. to keep eyes fixed on a target during brief movements.
What causes vertigo?
excessive vestibular stimulation or an imbalance exits between input from the right and left sides.
Where is the vertigo cortical area located and where is the input coming from?
the post central gyrus, base of intrparietal sulcus;
input is from the ventral posterior and posterior thalamic nuclei.
Equilibrium depends on input from what 3 sources?
visual, proprioceptive, and vestibular
What is Romberg sign?
when a person losses awareness of lower limb position when standing with feet together and eyes closed, swaying or falling occurs.
Describe the pathway that causes extension of the left limbs on falling towards the left?
impulses from the maculae of the utricles and saccules –> vestibular ganglion and nerve to the vestibular nuclei –> from L lateral vestibular nucleus, impulse depends via the left lateral vestibulospinal tract to the LMN that facilitate the extensor muscles of the L limbs
What structures in the internal ear are chiefly associate with equilibrium?
the otolithic membranes in the maculae or the utricle and saccule - the membranes shift on tilting the head or on linear acceleration - resulting in the initiation of the vestibulspinal reflexes associated with equilibrium.
What structures in the internal ear are chiefly associate with visual fixation?
the cupulae of the ampullary crest in the semicircular ducts - shift on rotation of the head - therefore initiating the vestibulo-ocular reflexes associated with visual fixation (keeping eyes on the target when the head is in motion)
Assuming an intact vestibulo-ocular reflex path, what response occurs on cold water irrigation of the right external auditory meatus in a patient who is conscious?
result in left nystagmus (COWS)
Assuming an intact vestibulo-ocular reflex path, what response occurs on cold water irrigation of the right external auditory meatus in a patient who is comatose?
with normal VOR - turing of the eyes to the same side as long as the irrigation continues (there is no fast phase in comatose patients)
What does cold and fast nystagmus referring to?
- slow drifting away from target (vestibular-ocular path)
- fast return to the target (cerebral cortex)
- *nystagmus is described according to the fast phase because it is more obvious than the slow.
What does COWS mean and does it represent the slow or fast phase of nystagmus?
- Cold Opposite Warm Away
- fast phase
In the exam room, a patient lying down with eyes closed complains of a sense that the head is rotating. If the lesion is in the inner ear the most likely source for the abnormal impulses would arise from the?
c: semicircular ducts
A 67-y/o man complains of recurring 2-4 hour attacks of vertigo accompanied by severe nausea and vomiting, tinnitus and sensation of fullness in the middle ear. These very debilitating bouts occur even when the head is not moving and with the eyes open or closed. A likely diagnosis would be?
c: Meniere disease
* *hallmark signs include: severe vertigo and vomiting, tinnitus and fluctuating aural fullness, and the occurrence with the eyes closed and not moving the head.
A 22 y/o woman, while replacing a light bulb, falls 6 feet from a ladder and bumps her head on the floor. 24 hours later she complains of spells of dizziness with a sudden onset and duration of about 30 seconds. The abnormal sensations are especially severe when sitting up, rolling over in bed, or putting her head between her legs. The most likely cause for the sudden onset of dizziness is?
e: displaced otoliths
* * this condition is also know as benign paroxysmal vertigo.
A 30 y/o man sustain multiple fractures in a automobile accident. At hospital he is treated with IV gentamicin for an open femur fracture. Several days later he complains of severe vertigo and oscilopsia. He has normal hearing in both ears. The most likely cause for the vertigo is?
d: gentamicin ototoxicity
* *gentamicin is cytotoxic to both vestibular and auditory receptors cells and can result in balance and hearing loss together or separately.
A patient with advanced DM and peripheral neuropathy becomes progressively more clumsy when getting out of bed during the night and walking in the dark. During the day or in a lighted room movements appear normal. A Romberg sign is present. What would account for the ataxia?
b: damage to the vestibular system
* *insert Dr. Z walk-off chuckle here**
