DAIM - Diseases of Abnormal Movement Flashcards
Define DAIM
abnormal, involuntary skeletal muscle contractions in the conscious animal
- can arise from skeletal muscle, peripheral nerve or CNS
Are majority of DAIM diseases HYPERkinetic or HYPOkinetic?
HYPERkinetic!
What are the 5 cardinal phenotypes of DAIM?
- Myotonia
- Myokymia/neuromyotonia
- Tetany
- Myoclonus
- Dyskinesia
What is myotonia?
HYPERkinetic – persistent, sustained muscle contraction with delayed muscle relaxation
- disease of Skeletal Muscle
What breeds predisposed to myotonia congenita?
Min. Schnauzer and Chow
What history and exam of myotonia congenita?
Clinical signs in first few months of life
- stiff saw-horse like gait that improves with exercise
- double muscled appearance
- dysphagia from tongue hypertrophy
- percussion dimpling of muscles
- signs get worse in cold weather
What pathophysiology of myotonia congenita?
autosomal recessive mutation in *Voltage-gated Chloride Channel mutation that causes issues with incomplete repolarization, prolonger depolarization and spontaneous depolarization
How do you DX myotonia congenita?
- Signalment (Min Schnauzer or Chow)
- History (CS in first few months of life)
- CS (stiff pelvic limbs with big proximal limb muscles, …)
EMG waxing and waning
- Also, genetic testing
How do you TX myotonia congenita?
Mexilitene, Procainamide, or Regular exercise program
PX and prevention of myotonia congenita
Fair to Good prognosis unless severe dysphagia present
Don’t breed these animals as it is autosomal recessive
What is acquired myotonia/pseudomyotonia?
most commonly a complication of Cushing’s (hyperadrenocorticism) but rare (<1%)
- can be seen with muscular dystrophy and 2,4-D tox
- may be French Poodle genetics
What are clinical signs of acquired myotonia/pseudomyotonia?
Comes with Cushing’s signs
Pathophys it unknown
How do you DX acquired myotonia/pseudomyotonia?
Cushing’s tests (ACTH stim, LDDS, etc.)
CS, HX, Signalment
EMG not waxing and waning but HIGH-frequency
How do you treat acquired myotonia/pseudomyotonia?
Also use, Procainamide
PX of acquired myotonia/pseudomyotonia?
:( does not resolve in most dogs with Cushing’s, even with treatment :(
what is myokymia?
vermicular (undulating, wavelike) muscle contraction that spreads across the surface of the muscle
- focal or generalized
what is neuromyotonia?
persistent muscle stiffness
- ranges from subclinical to intense contracture of distal extremities and face or episodic collapse
How are myokymia/neuromyotonia different from myotonia?
myokymia/neuromyotonia are a disease of motor axons or motor nerve terminals
myotonia is a disease of skeletal muscle
What is typical signalment of myokymia/neuromyotonia?
Jack Russell Terriers. It’s a.k.a. Continuous muscle fiber activity of the Terrier.
- young to adult dogs
- rarely in cats
What breed is predisposed to myokymia/neuromyokymia?
Jack Russell Terriers – Potassium gated channel defect
DX myokymia/neuromyotonia
Signalment (Jack Russell young to old); HX and CS
Characteristic EMG
can myokymia/neuromyotonia develop secondary to compressive, infiltrative, or degenerative disease?
YES but RARELY
Define Tetany and Tetanus
Tetany: intermittent sustained contraction of extensors mostly
Tetanus: persistent sustained contraction w/o relaxation
Causes of Tetany:
Anomalous: Familial Reflex Myoclonus (misnomer) of Labradors
Metabolic: Hypocalcemia (1˚ hypOpth), hypomagnesemia (grass tetany)
Toxic: C. tetani, strychnine
Traumatic: rostral cerebellum, midbrain, T-L spine
Pathophys of Familial Reflex Myoclonus of Labradors
glycine receptor deficiency in CNS
Dx, Tx, and Px of familial reflex myoclonus of labradors?
DX: signalment (lab puppies) and exam
TX: none
PX: Poor :(
Tx of C. tetani
- clean/debride wound
- antitoxin!
- systemic abx - Penicillins/metronidazole
- muscle relaxants - Diazepam, methocarbamol, barbiturates
- Monitor autonomic function
- minimize stimulation
Px of C. tetani
Good if no autonomic dysfunction; usually takes weeks or less but may take months
- so don’t want to see hyper/hypotension or brady/tachycardia
Strychnine presentation
causes seizures and tetany
HX of eating poison or relay toxicosis (eating dead wild life)
Strychnine pathophys
competetive and reversible glycine inhibitor
Strychnine DX
strychnine contents in the stomach, liver, kidney or urine if acute
Strychnine TX
stop the seizure; empty the stomach; diuresis; muscle relaxants; supportive care
What is myoclonus?
the sudden contraction of muscle groups followed immediately by relaxation
a.k.a. “tremor”
constant - persists in sleep
What is a major concern of myokymia/neuromyotonia?
- can last hours and lead to hyperthermia
What does EMG for myokymia/neuromyotonia sound like?
MOTORBOAT of UNDULATING frequencies
What is most frequent etiology of hypocalcemic tetany?
Primary Hypoparathyroidism
DX and TX of hypocalcemic tetany
Dx by Low Total and ionized Ca++, High Phosphorous, Low-NORMAL PTH
Tx: IV Calcium gluconate
Name species in order of susceptibility most to least to Tetanus
HORSES > Humans > dogs > cats > ruminant
What’s the name of the tetanus toxin?
Tetanospasmin - binds Renshaw cells and prevents release of neurotransmitter (Glycine and GABA)
Sporadic vs repetitive myoclonus
Sporadic usually looks like focal seizure
Repetitive can be different types:
- Resting: only seen at rest
- action related: during voluntary muscle contraction (cerebellar lesions)
- constant/continuous: persists even in sleep (Distemper)
What is usually the cause of constant/continuous, repetitive myclonus?
Distemper
What is idiopathic steroid-responsive tremor syndrome?
White Shakers Disease (West Highland Whites)
- diffuse, action related, repetitive myoclonus
- Acute onset
- Middle aged
- Small and toy breeds
Tx: prednisone
Px: excellent (possible relapses)
Head bobbers and shakers
Doberman, Bulldog, Boxer, Boston Terriers
- non-progressive and no other clinical signs
- VERY episodic, unpredictable
- Triggered by excitement*
- can interrupt the activity*
- totally conscious*
What does moldy cheese toxicity cause?
diffuse, action-related repetitive myoclonus
What is an orthostatic tremor?
Giant breeds of dogs (Great Dane)
- EMG Helicopter Rotor
- *Occur only when standing and relieved when sit down
- can INDUCE by simulating gravity on dogs paw
TX: Gabapentin, Pregabalin, Phenobarbital
PX: gets very bad eventually but may take a while (months to years)
What are dyskenisias?
heterogeneous group of CNS disorders that disrupt normal posture or locomotion
- Episodic
- *- Paroxysmal**
- triggered by excitement or stress
- age 3-48 months onset
- Episodes last seconds to minutes
What is athetosis?
writhing of the trunk
What is ballism?
flailing of the limbs
What is chorea?
brief rapid muscle contractions that look like dancing
What is dystonia?
sustained muscle contraction producing abnormal postures and inhibit normal movements
