Page 793 - Clinical Small Animal Internal Medicine

70 Seizures and Movement Disorders 761

Axis 2: Seizure Type cluster seizures. A genetic basis has been reported in
VetBooks.ir types. Focal seizures are the manifestation of a discrete, numerous dog breeds, including Belgian shepherd dogs,
Epileptic seizures are divided into focal and generalized
border collies, poodles, beagles, springer spaniels,
epileptogenic event in the cerebral cortex. The focal
Romagnolos, and retrievers. True genetic epilepsy is
nature of this seizure type is associated with a higher Shetland sheepdogs, vizslas, Irish wolfhounds, lagotto
incidence of focal intracranial pathology. Focal seizures much less common in cats due to their more diverse
can be associated with or without impaired conscious- genetic background. As such, all cats should be evaluated
ness or awareness and are typically characterized by for underlying structural or metabolic seizures before a
motor or sensory disturbances. diagnosis of genetic epilepsy is made.
Focal motor seizures are commonly seen as facial mus-
cle twitching whereas sensory focal seizures are mani- Structural or Symptomatic Epilepsy
fested by more abnormal behavioral disorders. These types of epileptic seizures are the direct result of
More complex behavior patterns with focal seizures either structural brain pathology or metabolic disease.
include impaired consciousness, often with bizarre Younger animals are more prone to developmental and
behavioral activity. Previously termed complex partial or encephalitic diseases, while older dogs (>7 years of age)
psychomotor seizures, these events are now classified as are more likely to develop intracranial neoplasia. As
automatisms or automotor seizures. Animals may show expected with underlying cerebral pathology, these ani-
“fly‐biting” behavior patterns, become aggressive with- mals are more likely to exhibit focal or multifocal neuro-
out provocation, howl incessantly, become restless or logic deficits. However, focal lesions in “silent” cortical
exhibit a variety of motor disturbances. Cats may show a areas of the brain (e.g., olfactory, pyriform and occipital
variety of abnormal behaviors or motor signs, including lobes) may have seizures as the only neurologic problem.
drooling, hippus, excessive vocalization or random, This presentation has been seen in cats due to feline
rapid running behaviors indoors. Whenever a focal sei- infectious peritonitis (FIP) and meningioma. Metabolic
zure is suspected, the clinician should be suspicious of a (formerly reactive) epileptic seizures are a reaction of the
focal cerebral disturbance and plan the diagnostic work‐ normal brain to transient systemic insult, toxic reaction
up accordingly. or physiologic stresses. Animals of any age may be
Generalized seizures are subdivided into tonic‐clonic, affected. Small‐breed dogs are more predisposed to
tonic, clonic, myoclonic, atonic or absence types. The develop seizures secondary to portosystemic shunts at a
terms convulsive (grand mal) and nonconvulsive (petit younger age. Typically, a higher seizure frequency occurs
mal) seizures are no longer in use. Generalized seizures initially until the underlying metabolic or toxic insult is
originate from both cerebral hemispheres from the start, corrected, but evidence of systemic illness is often
or more commonly progress secondarily from focal sei- present concurrently.
zures. Unlike focal seizures, generalized seizures are not
necessarily associated with focal cerebrocortical disease. Unknown Cause of Epileptic Seizures
Epileptic spasms are currently classified as a discrete A variety of epileptic seizures arise without an apparent
seizure type, as it has yet to be determined whether these cause but are thought to have a more specific etiology.
events have a focal or generalized onset based on elec- Previously termed or cryptogenic epileptic seizures,
troclinical data from humans. these events are believed to be due to an underlying uni-
dentified brain disease. Many of these dogs are over the
Axis 3: Syndrome age of 7 without identifiable brain lesions but with a high
By definition, a syndrome is a group of signs or charac- prevalence of drug‐resistant epilepsy, with close to 90%
teristics that defines a particular combination of clinical of the cases requiring more than one antiepileptic drug
abnormalities, often due to a specific genetic disorder. (AED) for treatment.
Epilepsy syndromes are not well defined in veterinary
medicine, although familial epilepsies are now being Axis 5: Impairment from Epilepsy
identified with segregation analysis. The majority of postictal signs in cats and dogs are tran-
sient, such as disorientation, visual impairment, saliva-
Axis 4: Etiology tion, incontinence, and altered behavior. More prolonged
Genetic (Idiopathic) Epilepsy or recurrent seizure activity can lead to permanent sen-
A diagnosis of genetic epilepsy is most common in pure‐ sory deficits (vision deficits), cognitive changes (altered
bred dogs with the first onset of seizures between 1 and obedience), and loss of normal personality. Chronic sei-
5 years old, a normal interictal neurologic examination, zures have been shown to induce microglial activation
and if there is a lengthy initial interictal period (>4 and cerebral angiogenesis in Shetland sheepdogs with
weeks). A high percentage of these patients also exhibit familial epilepsy.