Vestibular Disease, Geriatric - Dogs

DEFINITION
Acute nonprogressive disturbance of the peripheral vestibular system in old dogs

PATHOPHYSIOLOGY
Unknown
Suspected abnormal flow of the endolymphatic fluid in the semicircular canals of the inner ear secondary to disturbance in production, circulation, or absorption of the fluid
Possible intoxication of the vestibular receptors or inflammation of the vestibular portion of the vestibulocochlear nerve (cranial nerve VIII)
Often incorrectly referred to as a stroke (disease is neither central in location nor suspected to be vascular or ischemic in origin)

Ventricular Tachycardia

DEFINITION
ECG Features
Three or more ventricular premature contractions in a row
May be intermittent (paroxysmal) or sustained; heart rate > 150 bpm with a regular rhythm
QRS complexes—typically wide and bizarre.
If P waves—dissociated from the QRS complexes

PATHOPHYSIOLOGY
Potentially life-threatening arrhythmia, usually signifying myocardial disease or metabolic derangement; mechanisms include increased automaticity, reentry, and delayed afterdepolarizations

Vasculitis, Cutaneous

OVERVIEW
An inflammation of blood vessels with a neutrophilic (leukocytoclastic/nonleukocytoclastic), lymphocytic, rarely eosinophilic, granulomatous, or mixed cell types
Pathomechanisms—type III (immune complex) and type I (immediate) reactions

Vaccine-Associated Sarcoma

OVERVIEW
Cats—vaccination may induce development of sarcoma (primarily fibrosarcoma) at the injection site, primarily in the muscle, skin, and subcutaneous tissues; malignant fibrous histiocytoma, osteosarcoma, rhabdomyosarcoma, and chondrosarcoma also associated
FeLV and rabies vaccines—most common
Interval from vaccination to tumor development—may be as short as several months
Metastasis common
Fibrosarcoma—prevalence in cats unknown; estimated at 20/100,000 cats

Uveal Melanoma - Cats

OVERVIEW
The most common primary intraocular tumor in cats
Usually arise from the anterior iridal surface with extension to the ciliary body and choroid
Tend to be flat and diffuse, not nodular (unlike intraocular melanomas in dogs)
Initially has a benign clinical and histologic appearance
Unique feature—may develop metastatic disease up to several years later
Metastasize to regional lymph nodes, numerous visceral organs (especially those in the abdominal cavity), lungs, and less commonly, the skeleton