Disorders of the Peripheral Nervous System

Question 1

What are the 3 most common diagnostics used for PNS disorders?

Answer 1

1. neurologic exam findings
2. electrodiagnostics
3. muscle/nerve biopsies

Question 2

What are 3 signs of peripheral neuropathies?

Answer 2

1. decreased to absent reflexes
2. poor muscle tone
3. neurogenic atrophy

Question 3

How are most degenerative peripheral neuropathies diagnosed?

Answer 3

characteristic features and biopsies

Question 4

What is thought to cause laryngeal paralysis/polyneuropathy complex? What is the most consistent sign?

Answer 4

axonopathy of unknown cause believed to be heritable —> seen in younger dogs!

laryngeal paralysis

Question 5

What 4 breeds have reported laryngeal paralysis/polyneuropathy complex?

Answer 5

1. Dalmatian
2. Rottweiler
3. Leonbergers
4. Pyrenean Mountain dog

Question 6

What are the 3 most common clinical signs associated with laryngeal paralysis/polyneuropathy complex? What is prognosis like?

Answer 6

1. limb paresis with hyporeflexia
2. megaesophagus
3. laryngeal paralysis

poor —> no treatment

Question 7

What is dancing Doberman disease? How does it initially present? What happens within months?

Answer 7

neuropathy with a wide age range of onset

flexing of one pelvic limb while standing

alternate flexing of pelvic limbs = dancing

Question 8

How do dogs with dancing Doberman disease commonly act while not ambulating? What are 4 signs? What is prognosis like?

Answer 8

prefer to sit

1. no lameness
2. no apparent discomfort
3. no dancing while ambulating
4. gastrocnemius atrophy

good —> no tx, very slow progression

Question 9

What is idiopathic facial paralysis? What breed is predisposed?

Answer 9

canine analog of human Bell’s Palsy

Cocker Spaniels

Question 10

What is the most common sign of idiopathic facial paralysis? What must be ruled out to make a diagnosis? What treatment may be indicated?

Answer 10

unilateral lip droop with decreased to absent palpebral reflexes +/- VIII deficits

otitis, hypothyroidism

glucocorticoid therapy

Question 11

What are the 2 forms of laryngeal paralysis? What are the most common signs? What is prognosis like?

Answer 11

1. hereditary = young dogs
2. acquired = older dogs

inspiratory stridor, respiratory distress, dysphonia

guarded —> surgical treatment required

Question 12

What are 2 secondary effects of idiopathic megaesophagus? What treatment is recommended?

Answer 12

1. regurgitation
2. aspiration pneumonia

supportive - motility modifiers

Question 13

What are the 2 most common metabolic causes of neuropathies?

Answer 13

1. diabetes mellitus
2. hypothyroidism

Question 14

What are the 2 most common neoplastic causes of neuropathies?

Answer 14

1. malignant nerve sheath tumors
2. soft tissue tumor with nerve entrapment

Question 15

What are the likely causes of paraneoplastic neuropathy?

Answer 15

• neoplastic release of neurotoxic factors
• innocent bystander effect - cells or tissues are injured by immunologic reactions in response to neoplastic cells
• axonal or Schwann cell dysfunction

Question 16

What neoplasm is commonly associated with paraneoplastic neuropathy?

Answer 16

insulinomas - not thought to be related to hypoglycemia

(may resolve with successful treatment)

Question 17

What cranial nerves are commonly affected by paraneoplastic neuropathies? What is it associated with?

Answer 17

trigeminal and facial

lymphoma

Question 18

What is indicative of acute idiopathic polyradiculoneuritis? What is an additional sign?

Answer 18

coonhound paralysis —> rapidly progressive LMN paresis/plegia that starts at pelvic limbs and progresses to thoracic limbs

voice loss

Question 19

What abilities are commonly left intact with acute idiopathic polyradiculoneuritis? What other signs are possibly seen?

Answer 19

• pain senation, often hyperesthetic
• urination ability

axonal loss and respiratory compromise

Question 20

What is suspected to cause chronic inflammatory demyelinating polyneuropathy? What is the most common signalment and signs?

Answer 20

autoimmune disorder

mature dogs and cats

LMN signs in the pelvic limbs first

Question 21

What treatment is recommended for chronic inflammatory demyelinating polyneuropathy?

Answer 21

Prednisone (autoimmune disorder!)

• relapse and refractoriness occasionally

Question 22

What sign is most commoly associated with trigeminal neuritis?

Answer 22

acute onset of dysphagia

• self-limiting, apparently non-painful

Question 23

What are the 4 most common signs associated with myopathies?

Answer 23

1. weakness with preservation of sensory function
2. muscle atrophy
3. myalgia
4. exercise intolerance

Question 24

What is myotonia congenita? What is the cause? How is it diagnosed?

Answer 24

heritable trait in dogs and DSH with failure of muscular relaxation

abnormal sarcolemmal ion conductance

dive bomber waxing and waning EMG - differentiates from muscular disease

(supportive treatment only)

Question 25

What 2 breeds are overrepresented with autoimmune polymyositis?

Answer 25

1. Newfoundland - early age 2. Boxer - pre-neoplastic condition

Question 26

What are the 5 most common signs associated with autoimmune polymyositis?

Answer 26

1. generalized weakness 2. stiff gait 3. muscle atrophy 4. myalgia 5. dysphoria

Question 27

What 3 diagnostics are used for autoimmune polymyositis? What do most patients respond to?

Answer 27

1. elevated CK 2. abnormal EMG 3. muscle biopsy* immunosuppression

Question 28

What muscle fiber types are most commonly affected by masticatory myositis? What signalment is most commonly affected?

Answer 28

autoimmune disorder of Type IIM fibers of masticatory muscles young adult large breeds

Question 29

What are the most common signs of masticatory myositis? What is seen in the acute and chronic phases?

Answer 29

- painful swelling of masticatory muscles - trismus - lockjaw, sustained tetanic spasms - occasional fever ACUTE = exophthalmos CHRONIC = enophthalmos, muscle atrophy

Question 30

What treatment is recommended for masticatory myositis? What side effect is commonly seen?

Answer 30

immunosuppression accentuate muscle atrophy ---> pred head

Question 31

What are some causes of traumatic myopathies?

Answer 31

- infraspinatus contracture - iliopsoas injury - quadriceps contracture - gastrocnemius avulsion - coccygeal muscle injury

Question 32

What is acquired myasthenia gravis?

Answer 32

autoimmune NMJ disorder caused by the production of antibodies directed against nicotinic ACh receptors, resulting in muscle weakness

Question 33

What are the clinical forms of acquired myasthenia gravis?

Answer 33

- focal: megaesophagus - generalized: obvious appendicular weakness (+/-megaesophagus), facial, pharyngeal, or laryngeal weakness - acute fulminating: rapidly progressive, severe form in which generalized weakness occurs over hours to a few days

Question 34

What 4 dog breeds breeds are predisposed to acquired myasthenia gravis? 2 felines?

Answer 34

1. Akitas 2. Terriers 3. Retrievers 4. GSDs Abyssinian and Somali cats (bimodal age distribution)

Question 35

What are the most common clinical signs associated with acquired myasthenia gravis?

Answer 35

- swallowing difficulty - vomiting, regurgitation - hypersalivation - coughing - labored breathing - limb muscle weakness - dysphoria

Question 36

What are 3 diagnostics used for acquired myasthenia gravis?

Answer 36

1. radioimmunoassay for serum AChR antibodies** 2. positive Tensilon test (prevents the breakdown of the chemical acetylcholine) 3. decremental repetitive nerve stimulation

Question 37

What additional diagnostics are recommended for diagnosing myasthenia gravis?

Answer 37

- basic blood work - thyroid levels - thoracic radiographs (megaesophagus!)

Question 38

What medical treatments are recommended for acquired myasthenia gravis? What else may be indicated?

Answer 38

- anticholinesterase - Pyridostigmine - immunosuppressive therapy megaesophagus - feeding tube, pneumonia treatment

Question 39

What causes the variable prognosis of acquired myasthenia gravis?

Answer 39

- persistence of megaesophagus and pneumonia - higher spontaneous remission likely in dogs

Question 40

What treatment is recommended if patients with acquired myasthenia gravis do not respond well to Pyridostigmine? What is avoided?

Answer 40

immunosuppression glucocorticoids ---> Prednisone can make pneumonia worse