Tremors & Cerebellar Disease Flashcards
myoclonus
a sudden, “lightening jerk”, involuntary movement of short duration caused by muscle contractions and pauses in muscle activity
occurs in a muscle, part of a muscle, or in groups of muscles
only in ONE area of the body
tremor
rhythmical oscillatory movement of a body part around an axis resulting from alternate or synchronous contraction of antagonistic muscle groups
focal or generalized
action tremors
occurs during voluntary contraction of skeletal muscle
can be postural or kinetic
postural action tremor
type of action tremor that occurs in a body part that is voluntarily maintained against gravity (ex. standing)
kinetic action tremor
a type of action tremor that occurs during directed voluntary movement
intention tremor
type of kinetic action tremor that increases in amplitude during the pursuit of a target
physiological tremors
normal oscillation that occurs in all body parts (imperceptible, fine action tremors)
enhanced physiological tremor
physiological tremor with greater than normal amplitude
typically stressed induced from stimulation of B receptors by adrenalin
what are differentials for tremors and myoclonus
- cerebellar disease
- diffuse CNS disease
- motor unit disease
dysmyelination of CNS axons
congenital defect causing dys- and hypomyelination of CNS axons
likely genetic/inherited (breed predilections - chow chows, weimeraners, springer spaniels)
present at birth but may not notice until starting to walk
clinical signs of dys/hypomyelination
generalized coarse action tremor with NO neurological deficits present
dys/hypomyelination treatment and diagnosis
no effective therapy
confirm with genetic testing
clinical signs of generalized tremor syndrome of dogs
acute onset
low amplitude
“fine” generalized action tremor
neurologically NORMAL on exam but may have seizures, vestibular, or cerebellar signs
generalized tremor syndrome of dogs
“little white shaker disease”
inflammatory cause of tremors that occurs in young (<2 yrs) small breed dogs
diagnosis of generalized tremor syndrome of dogs
minimum database
normal MRI
mild pleocytosis on CSF analysis
negative serology for infectious agents
treatment for generalized tremor syndrome of dogs
long term corticosteroids (immunosuppressive doses)
good prognosis
lysosomal storage diseases
accumulation of metabolic byproducts in neurons and other CNS tissues secondary to an enzyme deficiency
rare heritable condition
signalment for lysosomal storage diseases
young animals (<1 year)
clinical signs of lysosomal storage diseases
action tremor + systemic abnormalities
diagnostics for lysosomal storage diseases
WBC inclusions on CBC
genetic testing
MRI
treatment for lysosomal storage diseases
none - elect euthanasia due to poor QOL
how do metabolic diseases cause tremors
electrolyte abnormalities - alters resting membrane potential of muscles or nerves causing weakness and tremors due to spontaneous depolarization
diagnose with minimum database
function of the cerebellum
coordination of movement (rate, range, and force) that is initiated elsewhere
assists with maintenance of equilibrium
cerebellar anatomy
3 layers:
- molecular (axons)
- Purkinje cells
- granular
Purkinje layer and cerebellar nuclei form the external germinal layer –> germinal cells divide then migrate deep into the cerebellum to form the granule cell layer
deep cerebellar nuclei
3 pairs of nuclei buried deep within the white matter
should NOT be visible on MRI
signs of cerebellar dysfunction
IPSILATERAL signs
- ataxia
- dysmetria
- vestibular signs
- absent menace
- CP deficits
- increased muscle tone +/- hyperreflexia
ataxia
failure of motor coordination without muscle weakness
- broad based stance
- truncal ataxia (swaying torso)
dysmetria
abnormal rate, range, and force of movement
hypermetria - high stepping
head dysmetria - intention tremor
vestibular signs
occurs when there is a lesion in the flocconodular lobe or caudal cerebellar peduncle
signs may be PARADOXICAL to the actual lesion
- Ex. L lesion –> vestibular rights on the R, cerebellar signs on the L
what part of menace is causing it to be absent with cerebellar dysfunction
efferent pathway
vision is normal
acute decerebellation
dysfunction of the entire cerebellum, often seen with trauma
causes opisthotonus w/ pelvic limb extension or flexion
cerebellar abiotrophy
degenerative disease caused by spontaneous, premature neuronal death of purkinje cells
signalment for cerebellar abiotrophy
breeds: kerry blue terries, gordon setters, brittany spaniels
age: middle aged to older
clinical signs of cerebellar abiotrophy
progressive, diffuse, symmetrical cerebellar signs
diagnosis of cerebellar abiotrophy
MRI
biopsy (definitive)
cerebellar hypoplasia
idiopathic malformation of the cerebellum caused by in utero infections, toxins, or genetic disorders
perinatal infection/toxin –> destroys the external germinal layer –> germinal cells unable to divide and migrate –> hypoplasia of the granule cell layer –> loss of connections in the cerebellum
clinical signs of cerebellar hypoplasia
spectrum of cerebellar signs
present AT BIRTH
NOT progressive - will not improve or worsen throughout life
diagnosis and treatment of cerebellar hypoplasia
signalment, history, neuro exam
no effective treatment
ischemic infarction
vascular event in the rostral cerebellar artery causing acute onset of cerebellar disease
diagnosis and treatment of ischemic infarction
MRI - wedge shaped lesion
supportive care - symptoms improve with time
