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994 Tremors and Myoclonus

Advanced or Confirmatory Testing Chronic Treatment PEARLS & CONSIDERATIONS
Definitive diagnosis is made by polymerase Electrochemotherapy with bleomycin has been Comments
VetBooks.ir a biopsy specimen (after formalin fixation and Behavior/Exercise With any kind of vaginal or preputial bleeding
tried for vincristine-resistant TVT.
chain reaction assay or histologic classification of
• Cytologic exam for TVT cells
staining with hematoxylin and eosin) and by
immunochemistry testing to determine degree
present (contagion risk).
of malignancy. • Breeding should be avoided when TVT is • Visual exam of clitoral fossa and preputial
fornix for gross TVT lesions
• Erection from excitement with preputial
TREATMENT extrusion of the penis with a TVT tumor Prevention
may result in paraphimosis. Pet dogs should avoid contact with stray dogs.
Treatment Overview
The goal of treatment is elimination of the Drug Interactions Technician Tips
tumor. Spontaneous regression occurs in Severe bronchospasm has been reported in There has been an increased incidence of TVT
experimental and clinical cases. humans when vinca alkaloids are used in lesions in pet (nonbreeding) dogs coincident
combination with mitomycin C. with the increased movement of dogs within
Acute General Treatment and between countries, especially the movement
• Surgical excision: physically removes the mass Possible Complications of dogs into U.S. shelters for adoption from
and induces an immune response. Effective • Extravasation injuries associated with perivas- Mexico, the Caribbean, and South America.
for small masses; excision of large tumors cular injection of vincristine can range from TVT should be considered as a rule-out for any
(>2 cm in diameter) is often followed by irritation to necrosis and tissue sloughing. dog presenting with a friable, hemorrhagic mass.
tumor regrowth. • Combined chemotherapy with vincristine
• Intratumoral injection (1-4 treatments) causes more side effects (vomiting, diarrhea, Client Education
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with vincristine 0.5-0.7 mg/m and and neutropenia) than vincristine alone. In areas where TVT is endemic, pet dogs should
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interleukin-2 (IL-2) 2 × 10 units has be confined and spayed or neutered to reduce
impressive therapeutic effects. However, IL-2 Recommended Monitoring the risk of disease transmission.
alone did not cause tumor regression in all • Monitor for efficacy (tumor reduction).
cases. • Monitor for toxicosis, using peripheral SUGGESTED READING
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• Chemotherapy with vincristine 0.7 mg/m neuropathic clinical signs, CBCs with Ganguly B, et al: Canine transmissible venereal
IV (highly corrosive if extravascular [pp. 152 platelets, and liver tests before, during, and tumour: a review. Vet Comp Oncol 14(1):1-12,
and 609] for precautions) once weekly for after treatment. 2016.
6 weeks until complete tumor regression is AUTHOR: Rosa María Páramo-Ramírez, MVZ, PhD
the treatment of choice for metastatic or PROGNOSIS & OUTCOME EDITOR: Michelle A. Kutzler, DVM, PhD, DACT
multifocal TVT.
• Orthovoltage radiotherapy is effective (100% Despite the location or pattern of metastasis,
cure with a single radiation dose of 10 Gy); the prognosis for TVT is excellent with recom-
it requires an appropriate facility. mended therapy.

Tremors and Myoclonus

BASIC INFORMATION GENETICS, BREED PREDISPOSITION CONTAGION AND ZOONOSIS
Dogs: Canine distemper virus (myoclonus); in utero
Definition • Idiopathic/glucocorticoid-responsive tremor panleukopenia virus in cats (intention tremor)
• Tremor: involuntary rhythmic oscillatory syndrome: Maltese, West Highland white Clinical Presentation
contraction of a muscle group terriers, other small-breed white or nonwhite
• Myoclonus: sudden, brief, sporadic, or dogs (p. 530) DISEASE FORMS/SUBTYPES
repetitive contraction of a group of muscle • Idiopathic head tremors: English bulldog, • Action-related generalized tremor: diffuse,
cells followed by immediate relaxation Doberman pinscher, Shetland sheepdog, high-frequency skeletal muscle tremor that
(p. 661) others worsens with activity and resolves with sleep
• Idiopathic head tremor, familial myoclonus: ○ Congenital: hypomyelination or dysmy-
Synonyms Labrador retriever elination; present at birth
• Tremor: trembling, twitching • Orthostatic tremor: Great Dane, Scottish ○ Acquired: idiopathic glucocorticoid-
• Myoclonus: jerk, spasm deerhound responsive tremor syndrome, toxicosis
• Hypomyelination/dysmyelination: springer • Postural tremor
Epidemiology spaniel, Samoyed, chow chow, Weimaraner, ○ Episodic (several-minute duration) head
SPECIES, AGE, SEX lurcher, Bernese mountain dog, Dalmatian, tremor that is a high-frequency “yes or
Any dog or cat; age may vary with underlying Siamese cats no” movement of the head and is often
cause • Central axonopathy: Scottish terriers confused with focal seizures
• Dogs: puppies (hypomyelination/dysmy- ○ Pelvic limb tremor in older dogs (benign)
elination, familial myoclonus); older adults RISK FACTORS or young Great Danes (orthostatic), which
(senile tremors) Exposure to tremorgenic drugs or toxins, lack occurs while standing but resolves when
• Cats: kittens (hypomyelination) of vaccination moving or recumbent

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