Neurophysiology: Vestibular System- Pt 2

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Questions and Answers

What is the outcome when an animal has vestibular disease?

They have no impact on their movement.

They have enhanced extensor tone on both sides.

They have improved balance and equilibrium.

They have difficulty moving. (correct)

What happens when there is a lesion on one side of the vestibular system?

There is no effect on the extensor muscles.

There is an increase in facilitation of the extensor muscles on the same side.

There is a lack of facilitation of the extensor muscles on the opposite side.

There is a lack of facilitation of the extensor muscles on that side. (correct)

In which direction will the normal side of the body push the head and body in a vestibular lesion?

In a circular motion.

Towards the abnormal side. (correct)

In a random direction.

Towards the normal side.

What is the direction of the head tilt in a patient with a vestibular lesion on the left side of the brain?

To the left. Signup and view all the answers

What type of nystagmus is a sign of vestibular disease?

Jerk nystagmus. Signup and view all the answers

What is the characteristic of jerk nystagmus?

It involves a fast and slow phase of eye movement. Signup and view all the answers

In jerk nystagmus, which direction does the fast phase of eye movement occur?

Away from the side of the lesion. Signup and view all the answers

Which breed is more predisposed to pendular nystagmus due to a congenital defect?

Siamese cat. Signup and view all the answers

What percentage of decussation is seen in the optic nerve of mice?

97% Signup and view all the answers

What is the primary function of the vestibular system in controlling posture?

Maintaining balance and orientation Signup and view all the answers

What is a common clinical sign of vestibular dysfunction in animals?

Motion sickness Signup and view all the answers

What is the significance of vomiting in motion sickness?

It helps remove potential toxins from the body Signup and view all the answers

What is the primary difference between a patient with vestibular dysfunction and a patient with a vision or cerebral cortex issue?

The presence of vestibular ataxia Signup and view all the answers

What is the function of the vestibulospinal nerves in the vestibular system?

Controlling the orientation of the eyes, head, and trunk Signup and view all the answers

What is the significance of a severe presentation of vestibular signs in an animal?

It does not indicate the severity of the disease or prognosis Signup and view all the answers

What is the primary role of the vestibular system in controlling posture?

Sensing gravity and head acceleration Signup and view all the answers

What is the direction of the fast phase of jerk nystagmus if the lesion is on the right side of the brain?

Towards the left Signup and view all the answers

What type of jerk nystagmus is characterized by both eyes moving in the same direction?

Conjugate jerk nystagmus Signup and view all the answers

What is the cause of spontaneous nystagmus?

Abnormal, asymmetric action potential inputs to the brainstem from the vestibular apparatus Signup and view all the answers

What is the function of the vestibulocochlear reflex?

To maintain the eyes' position relative to the position of the head in space Signup and view all the answers

What is the normal response when a doctor turns a patient's head to the left during a physical exam?

The patient's eyes also turn to the left Signup and view all the answers

What type of nystagmus is generated when the head turns and the eyes remain fixed on the original field of vision?

Physiological nystagmus Signup and view all the answers

What is the primary difference between central vestibular dysfunction and peripheral vestibular dysfunction?

The location of the affected structures Signup and view all the answers

What is required for the reflex eye movement pattern in physiological nystagmus?

Normal sensory input from semicircular ducts Signup and view all the answers

Which of the following symptoms is more likely to indicate central vestibular dysfunction?

Altered mentation Signup and view all the answers

What is the direction of the slow phase of physiological nystagmus?

Opposite to the head's rotation Signup and view all the answers

Which type of nystagmus is more benign than jerk nystagmus?

Pendular nystagmus Signup and view all the answers

What is the primary indication for treatment of peripheral vestibular dysfunction?

otitis media Signup and view all the answers

What is the likely diagnosis for a cat presenting with vestibular ataxia and horizontal nystagmus?

Peripheral vestibular dysfunction Signup and view all the answers

Which of the following clinical signs can indicate either central or peripheral vestibular dysfunction?

Head tilt Signup and view all the answers

What is the significance of vertical nystagmus in a patient with vestibular dysfunction?

It always indicates central vestibular dysfunction Signup and view all the answers

What is the primary complaint of animals with vestibular dysfunction?

Head tilt, nystagmus, or ataxia Signup and view all the answers

What is the primary focus when investigating vestibular disease?

Identifying the underlying primary disease Signup and view all the answers

What is the most common cause of vestibular dysfunction in dogs and cats?

Idiopathic vestibular disease Signup and view all the answers

In which age group is idiopathic vestibular disease most common in cats?

Cats around 4 years old Signup and view all the answers

What is the typical prognosis for idiopathic vestibular disease?

Good, with signs resolving rapidly without definitive treatment Signup and view all the answers

How is idiopathic vestibular disease typically diagnosed?

By ruling out all other causes of peripheral vestibular dysfunction Signup and view all the answers

What is a characteristic of idiopathic vestibular disease in dogs?

It is more common in senior/geriatric dogs Signup and view all the answers

Study Notes

Optic Nerve (CN2) Decussation in Different Species

Birds and Lizards: 100% no consensual pupillary light reflex (PLR)
Mice: 97% not detectable consensual PLR
Large animals: 80-90% very weak consensual PLR
Dogs: 75% direct PLR is better than consensual PLR
Cats: 65% direct PLR is better than consensual PLR
Primates: 50% direct PLR is equal to consensual PLR

Vestibular Dysfunction: Clinical Signs

Motion sickness (vomiting) is a common clinical sign
Vomiting is beneficial for removing potential toxins
Head tilt
Wide stance (unbalanced)
Vestibular ataxia (leaning/falling)
Circling
"Alligator" rolling
Nystagmus
A severe presentation of vestibular signs does not indicate poor prognosis or severity of disease

Non-Vestibular Signs

Circling can be mistaken for vestibular dysfunction, but lacks vestibular ataxia and head tilt
Circling can be caused by vision or cerebral cortex issues

Vestibular System: Posture

Vestibular system acts as a sensor of gravity and head acceleration
Controls balance and posture
Contributes to motor control
Receives information from vestibular and other pathways to control eye, head, and trunk orientation
With a lesion, there is a lack of facilitation of extensor muscles on the affected side
The normal side will "push" the body and head towards the affected side
The side of the brain with the lesion is the same side of the body that the patient tilts their head

Nystagmus

Rhythmic, involuntary oscillation of the eyes
Can be pendular (short, equal eye movements) or jerk (fast and slow phases)
Pendular nystagmus is not a sign of vestibular disease and is often benign
Jerk nystagmus can be horizontal, vertical, rotatory, or conjugate
Conjugate jerk nystagmus means both eyes move in the same direction
Unconjugated jerk nystagmus is very rare
Jerk nystagmus can be spontaneous or positional
Jerk nystagmus tends to be more problematic than pendular nystagmus

Vestibular System: Eye Position

Vestibular system maintains eye position relative to head position
Controls extraocular muscles of the eye (vestibulocochlear reflex)
Coordinates eye and head movements to maintain a fixed field of vision
Physiological nystagmus is a normal reflexive movement
Abnormal reflexive movement patterns can indicate vestibular dysfunction

Vestibular Dysfunction

Central vestibular dysfunction involves the brainstem and cerebellum
Peripheral vestibular dysfunction involves the inner ear or cranial nerve 8
Central vestibular dysfunction can have symptoms lacking in peripheral dysfunction, such as altered mentation, proprioceptive deficits, and cerebellar signs
Peripheral vestibular dysfunction can be due to otitis or idiopathic vestibular disease
If a cat presents with vestibular ataxia and horizontal nystagmus, it likely has a peripheral vestibular dysfunction
Vertical nystagmus always indicates central vestibular dysfunction

Idiopathic Vestibular Disease

Most common cause of vestibular dysfunction in dogs and cats
Often has severe clinical signs with rolling and rapid nystagmus
Always from peripheral dysfunction, never from central dysfunction
No sex or breed predilection
In cats, most common in 4-year-olds, but any age can be affected
In dogs, usually senior/geriatric dogs are affected
Has a good prognosis, with signs resolving rapidly without definitive treatment in 1-3 weeks

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Description

This quiz covers the optic nerve decussation patterns and vestibular dysfunction clinical signs in various species, including birds, mammals, and primates.