Principles of vestibular disease and cerebellar disease Flashcards
What is ataxia?
A neurological sign consisting of gross incoordination of muscle movements, and is an aspecific clinical manifestation.
Can see less ataxia when walking quicker - run animal at different paces
What are the three types of ataxia?
- Sensory ataxia
- Vestibular ataxia
- Cerebellar ataxia
What are the questions to ask regarding looking at animal with potential ataxia?
- How are the limbs moving?
- What about the head?
- How is the trunk moving during locomotion?
What is hypometria?
Shorter protraction phase of gait (stride)
What is hypermetria?
Longer protraction phase of gait (stride)
high stepping gait
What is dysmetria?
Combo of hypometria and hypermetria
Inability to control the distance, power, speed of action
What are the general proprioceptive pathways?
- Peripheral nerve
- Dorsal root
- Spinal cord
- Brainstem
- Forebrain
What are the clinical signs of sensory ataxia?
- Abnormal postural reactions
- Limb paresis (inability to create movement)
What are three areas where a lesion can cause vestibular ataxia?
In the vestibular apparatus -
- vestibular nuclei (central)
- vestibular portion of VIII
- vestibular receptors (peripheral)
What are the clinical signs of vestibular ataxia?
- Head tilt (to side of lesion)
- Leaning, falling or rolling to one side
- Abnormal nystagmus
- Positional strabismus
- Normal (peripheral) or abnormal (central) postural reactions
What is the function of the Cerebellum?
- fine tunes movement
- stops over-reach - no counter regulation = tremors
What are the clinical signs of cerebellar ataxia?
Wide based stance ** - over reaching
- Intention tremors of the head
- Loss of balance and truncal sway
- Delayed onset and dysmetric hopping
- Ipsilateral menace deficits with normal vision
- No limb paresis or conscious proprioception deficits
- Pendular nystagmus
Not as much lateralisation
What part of the nervous system has a direct inhibitory effect on the vestibular nuclei?
Cerebellum
In the neuro-exam
a) what can you observe?
b) what would you exam by testing hands-on?
a) Mental status/behaviour Postures Gait Abnormal involuntary behaviour
b) Posture reaction Cranial nerves spinal reflexes, muscle tone and size sensory examination
What head positions indicate vestibular disease?
- Head tilt: rotation of the median plane of the head (one ear lower than the other)
- if on the left - muscle tone increases on that side
-Head turn: nose turned to one side, median plane of head is perpendicular to the ground
In which breeds is a pendular nystagmus a congenital abnormality?
Siamese
Birman
Himalayan
In what diseases is pendular nystagmus present?
Cerebellar disorders and visual deficits
What are the types of nystagmus can be seen in vestibular disease?
- Pendular nystagmus
2. Jerk nystagmus - horizontal, vertical, rotatory
What is positional strabismus?
One eye drops down when head lifts up
What is Horner’s syndrome?
Loss of sympathetic innervation to the eye
- Enopthalmos
- Third eyelid protrusion
- Ptosis (drooping eyelid)
- Miosis (small pupil - smooth muscle)
- (congested vessels) - increase temp of eye on side of lesion
What is the additional sign seen in horses with Horner’s syndrome?
They sweat on the ipsilateral side of the lesion
Nasal and conjunctival hyperaemia
How does sweating give an indication of location of the lesion?
Regional sweating patterns helps indicate which nerves are affected and where the lesion is
What clinical signs are seen in central vestibular disease?
- Paresis possible
- Conscious proprioceptive deficits possible
- May be normal, obtunded, stuporous, comatose
- Cranial nerves V-XII may be affected
- Horner’s syndrome rare
- Horizontal, rotary, and vertical nystagmus present
- Nystagmus will change with head position
What clinical signs are seen in peripheral vestibular disease?
- NO paresis*
- NO conscious proprioceptive deficits*
- Can be alert or disorientated
- ONLY Cranial VII nerve deficit
- Horner’s syndrome possible
- Horizontal and rotary nystagmus present (NOT vertical nystagmus)
- NO nystagmus changes with head position
