Vestibular Dysfunction
What is the most common type of nystagmus (horizontal, vertical, rotary) and what is it most associated with?
1. horizontal
2. associated with peripheral disease
This structure in the eye is very sensitive to light stimulation. It is best-suited for low-light conditions (scotopic vision).
rods
An inherited/breed-predisposed condition with white, opaque spots due to mineral deposits (triglyceride, cholesterol, and calcium) within the connective tissue of the cornea.
corneal dystrophy
Clinical signs for brainstem dysfunction are: (ipsilateral/contralateral)
ipsilateral
Where do LMN deficits occur?
at the level of the lesion
A patient is circling to the left, falling to the left, fast phase nystagmus is to the right, and postural reactions are normal. What is the localization of this vestibular disease? (peripheral, central, or paradoxical)
peripheral vestibular disease
What structure in the midbrain do the nerve fibers used in the pupillary light reflex travel to?
pretectum of the midbrain
This is a sudden increase in eye pressure with severe pain, redness, and loss of vision.
BONUS: How do you diagnose?
1. closed-angle glaucoma
BONUS: tonometry & ophthalmoscopy (direct & indirect); gonioscopy; ocular ultrasonagraphy
With which type of lesion do we see headpressing and altered behavior?
cerebral syndrome
Sensory deficits occur:
at the level of AND caudal to the lesion
A patient has a head tilt and is falling to the left. There is a pathological nystagmus to the right. There are exaggerated postural reactions on the right side. What type of vestibular disease (peripheral, central, or paradoxical/cerebellum)?
cerebellar/paradoxical vestibular disease
What nerve(s) are tested using the pupillary light reflex?
CN II (optic) and CN III (oculomotor)
This is the most common form of this disease. It is due to an aqueous tear film deficiency. It is typically bilateral and idiopathic.
A patient presents to the clinic with tetraparesis, UMN reflexes, and proprioceptive ataxia. She also has a decrease in the menace response and dazzle reflex. There are some abnormalities in the heart rate and respiration. where is the lesion?
brainstem
A patient presents with normal mentation, behavior, and CN reflexes. Both thoracic and pelvic limbs show a decrease in strength (tetraparesis). Proprioceptive ataxia is present in all 4 limbs. All 4 limbs show hyperreflexia and hypertonia. Where is the lesion?
C1-C5 spinal cord lesion
What role does the cerebellum play?
inhibitory (with cerebellar vestibular disease, see loss of inhibition)
What nerve(s) are tested using the menace response test?
CN II (optic) & CN VII (facial)
This is a dysfunction in the sympathetic innervation of the eye. It results in miosis, ptosis, enophthalmos, and protrusion of the third eyelid.
Horner Syndrome
A patient comes in disoriented. Owner says he has had siezures and his behavior is abnormal. After a neuro exan, he has decreased postural reactions on the right side, and he seems unable to hear on the right side as well. When you walk him, he is circling to the left. Where is the lesion?
cerebrum
A patient presents with hyperreflexia and hypertonia in the pelvic limbs, and hyporeflexia and hypotonia in the thoracic limbs. He also shows signs of proprioceptive ataxia in all 4 limbs. Where is the lesion?
C6 - T2
*Two-Engine Gait
UMN signs in pelvic limbs and LMN signs in thoracic limbs
What type of antibiotic is ototoxic and may lead to peripheral vestibular disease?
aminoglycosides
retina, thalamus (LGN), midbrain/pretectum, optic striations, optic chiasm, visual cortex, CN III, optic tract
thalamus (LGN), optic striations, visual cortex
What is horner syndrom often associated with?
otitis media
A dog presents with altered behavior, contralateral postural reaction deficits, and contralateral deafness. The owner also lets you know that he has only been eating half of his bowl of food, and it perfectly resembles half the bowl being full, and half empty. What part of the brain is affected?
Diencephalic Syndrome (diencephalon is affected)
*clinically, they are grouped with cerebrum
A patient presents with normal mentation, behavior, and CNN function. There is no ataxia and postural reactions are WNL. All 4 limbs show hyporeflexia and hypotonia, and decreased strength. On x-ray, you note megaesophagus. Owner also reports he has been excessively drooling and sounds like he is struggling to breathe. What is this?
Myasthenia gravis
(junctionopathy)