Disorders of the Peripheral Nervous System Flashcards
What are the 3 most common diagnostics used for PNS disorders?
- neurologic exam findings
- electrodiagnostics
- muscle/nerve biopsies
What are 3 signs of peripheral neuropathies?
- decreased to absent reflexes
- poor muscle tone
- neurogenic atrophy
How are most degenerative peripheral neuropathies diagnosed?
characteristic features and biopsies
What is thought to cause laryngeal paralysis/polyneuropathy complex? What is the most consistent sign?
axonopathy of unknown cause believed to be heritable —> seen in younger dogs!
laryngeal paralysis
What 4 breeds have reported laryngeal paralysis/polyneuropathy complex?
- Dalmatian
- Rottweiler
- Leonbergers
- Pyrenean Mountain dog
What are the 3 most common clinical signs associated with laryngeal paralysis/polyneuropathy complex? What is prognosis like?
- limb paresis with hyporeflexia
- megaesophagus
- laryngeal paralysis
poor —> no treatment
What is dancing Doberman disease? How does it initially present? What happens within months?
neuropathy with a wide age range of onset
flexing of one pelvic limb while standing
alternate flexing of pelvic limbs = dancing
How do dogs with dancing Doberman disease commonly act while not ambulating? What are 4 signs? What is prognosis like?
prefer to sit
- no lameness
- no apparent discomfort
- no dancing while ambulating
- gastrocnemius atrophy
good —> no tx, very slow progression
What is idiopathic facial paralysis? What breed is predisposed?
canine analog of human Bell’s Palsy
Cocker Spaniels
What is the most common sign of idiopathic facial paralysis? What must be ruled out to make a diagnosis? What treatment may be indicated?
unilateral lip droop with decreased to absent palpebral reflexes +/- VIII deficits
otitis, hypothyroidism
glucocorticoid therapy
What are the 2 forms of laryngeal paralysis? What are the most common signs? What is prognosis like?
- hereditary = young dogs
- acquired = older dogs
inspiratory stridor, respiratory distress, dysphonia
guarded —> surgical treatment required
What are 2 secondary effects of idiopathic megaesophagus? What treatment is recommended?
- regurgitation
- aspiration pneumonia
supportive - motility modifiers
What are the 2 most common metabolic causes of neuropathies?
- diabetes mellitus
- hypothyroidism
What are the 2 most common neoplastic causes of neuropathies?
- malignant nerve sheath tumors
- soft tissue tumor with nerve entrapment
What are the likely causes of paraneoplastic neuropathy?
- 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
What neoplasm is commonly associated with paraneoplastic neuropathy?
insulinomas - not thought to be related to hypoglycemia
(may resolve with successful treatment)
What cranial nerves are commonly affected by paraneoplastic neuropathies? What is it associated with?
trigeminal and facial
lymphoma
What is indicative of acute idiopathic polyradiculoneuritis? What is an additional sign?
coonhound paralysis —> rapidly progressive LMN paresis/plegia that starts at pelvic limbs and progresses to thoracic limbs
voice loss
What abilities are commonly left intact with acute idiopathic polyradiculoneuritis? What other signs are possibly seen?
- pain senation, often hyperesthetic
- urination ability
axonal loss and respiratory compromise
What is suspected to cause chronic inflammatory demyelinating polyneuropathy? What is the most common signalment and signs?
autoimmune disorder
mature dogs and cats
LMN signs in the pelvic limbs first
What treatment is recommended for chronic inflammatory demyelinating polyneuropathy?
Prednisone (autoimmune disorder!)
- relapse and refractoriness occasionally
What sign is most commoly associated with trigeminal neuritis?
acute onset of dysphagia
- self-limiting, apparently non-painful
What are the 4 most common signs associated with myopathies?
- weakness with preservation of sensory function
- muscle atrophy
- myalgia
- exercise intolerance
What is myotonia congenita? What is the cause? How is it diagnosed?
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)
What 2 breeds are overrepresented with autoimmune polymyositis?
- Newfoundland - early age
- Boxer - pre-neoplastic condition
What are the 5 most common signs associated with autoimmune polymyositis?
- generalized weakness
- stiff gait
- muscle atrophy
- myalgia
- dysphoria
What 3 diagnostics are used for autoimmune polymyositis? What do most patients respond to?
- elevated CK
- abnormal EMG
- muscle biopsy*
immunosuppression
What muscle fiber types are most commonly affected by masticatory myositis? What signalment is most commonly affected?
autoimmune disorder of Type IIM fibers of masticatory muscles
young adult large breeds
What are the most common signs of masticatory myositis? What is seen in the acute and chronic phases?
- painful swelling of masticatory muscles
- trismus - lockjaw, sustained tetanic spasms
- occasional fever
ACUTE = exophthalmos
CHRONIC = enophthalmos, muscle atrophy
What treatment is recommended for masticatory myositis? What side effect is commonly seen?
immunosuppression
accentuate muscle atrophy —> pred head
What are some causes of traumatic myopathies?
- infraspinatus contracture
- iliopsoas injury
- quadriceps contracture
- gastrocnemius avulsion
- coccygeal muscle injury
What is acquired myasthenia gravis?
autoimmune NMJ disorder caused by the production of antibodies directed against nicotinic ACh receptors, resulting in muscle weakness
What are the clinical forms of acquired myasthenia gravis?
- 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
What 4 dog breeds breeds are predisposed to acquired myasthenia gravis? 2 felines?
- Akitas
- Terriers
- Retrievers
- GSDs
Abyssinian and Somali cats
(bimodal age distribution)
What are the most common clinical signs associated with acquired myasthenia gravis?
- swallowing difficulty
- vomiting, regurgitation
- hypersalivation
- coughing
- labored breathing
- limb muscle weakness
- dysphoria
What are 3 diagnostics used for acquired myasthenia gravis?
- radioimmunoassay for serum AChR antibodies**
- positive Tensilon test (prevents the breakdown of the chemical acetylcholine)
- decremental repetitive nerve stimulation
What additional diagnostics are recommended for diagnosing myasthenia gravis?
- basic blood work
- thyroid levels
- thoracic radiographs
(megaesophagus!)
What medical treatments are recommended for acquired myasthenia gravis? What else may be indicated?
- anticholinesterase - Pyridostigmine
- immunosuppressive therapy
megaesophagus - feeding tube, pneumonia treatment
What causes the variable prognosis of acquired myasthenia gravis?
- persistence of megaesophagus and pneumonia
- higher spontaneous remission likely in dogs
What treatment is recommended if patients with acquired myasthenia gravis do not respond well to Pyridostigmine? What is avoided?
immunosuppression
glucocorticoids —> Prednisone can make pneumonia worse
