DAIM - Diseases of Abnormal Movement Flashcards by Blake Thordarson

Define DAIM

abnormal, involuntary skeletal muscle contractions in the conscious animal
- can arise from skeletal muscle, peripheral nerve or CNS

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Are majority of DAIM diseases HYPERkinetic or HYPOkinetic?

HYPERkinetic!

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What are the 5 cardinal phenotypes of DAIM?

Myotonia
Myokymia/neuromyotonia
Tetany
Myoclonus
Dyskinesia

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What is myotonia?

HYPERkinetic – persistent, sustained muscle contraction with delayed muscle relaxation
- disease of Skeletal Muscle

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What breeds predisposed to myotonia congenita?

Min. Schnauzer and Chow

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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

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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

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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

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How do you TX myotonia congenita?

Mexilitene, Procainamide, or Regular exercise program

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PX and prevention of myotonia congenita

Fair to Good prognosis unless severe dysphagia present

Don’t breed these animals as it is autosomal recessive

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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

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What are clinical signs of acquired myotonia/pseudomyotonia?

Comes with Cushing’s signs

Pathophys it unknown

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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

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How do you treat acquired myotonia/pseudomyotonia?

Also use, Procainamide

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PX of acquired myotonia/pseudomyotonia?

:( does not resolve in most dogs with Cushing’s, even with treatment :(

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what is myokymia?

vermicular (undulating, wavelike) muscle contraction that spreads across the surface of the muscle
- focal or generalized

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what is neuromyotonia?

persistent muscle stiffness

- ranges from subclinical to intense contracture of distal extremities and face or episodic collapse

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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

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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

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What breed is predisposed to myokymia/neuromyokymia?

Jack Russell Terriers – Potassium gated channel defect

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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

1. clean/debride wound 2. antitoxin! 3. systemic abx - Penicillins/metronidazole 4. muscle relaxants - Diazepam, methocarbamol, barbiturates 5. Monitor autonomic function 6. *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