Seizures in dogs
Seizures in dogs
A seizure or convulsion is the clinical manifestation of excessive hypersynchronous electrical activity in the cerebral cortex. This electrical event results is a loss or derangement of counsciousness, altered muscle tone, jaw chomping or trismus, salivation, and often involuntary urination and defecation. Most dogs have tonic-clonic, generalized (symmetric) motor seizures in which the animal experiences a period of extremely increased extensor muscle tone (tonus), falls into lateral recumbency, and then has periods of tonus alternating with periods of relaxation (clonus), resulting in rhythmic contractions of muscles manifested as paddling or jerking of the limbs and chewing movements.
The actual seizures in dogs may be preceded by minutes to hours of unusual behavior (preictal phase), including hiding, attention seeking, or agitation. In some dogs, seizures start during sleep or may be triggered by a specific stimulus or event (repetitive noise, flickering light). Estrus, certain drugs (especially phenothiazines), stress, and excitement can all precipitate seizures in dogs. In most animals, each seizure is followed by a short period of disorientation (postictal phase), during which ataxia, blindness, pacing and delirium are common.
Less common than generalized, symmetric tonic-clonic seizures in dogs are focal partial motor seizures. These seizures arise in part of one cerebral hemisphere, resulting in asymmetric signs that may include turning of the head away from the side of the lesion and focal twitching or tonic-clonic contractions of the contralateral facial or limb muscles. These seizures may ultimately become generalized. Although it is often stated that partial motor seizures in dogs are usually associated with structural brain disease, close observations of animals with idiopathic epilepsy reveals that many experience focal seizures with secondary generalization.
Psychomotor seizures in dogs are focal seizures manifested as stereotypic paroxysms of abnormal behavior such as rage, hysteria, hyperesthesia, self-mutilation, tail chasing, and fly biting. Withouth event-triggered electrodiagnostic testing, however, it is very difficult to distinguish these seizures from compulsive stereotypic behavior. In some cases, consciousness is impaired (complex focal seizures) or the seizure progresses to a generalized symmetric tonic-clonic seizure, aiding diagnosis of seizures in dogs.
A seizure or convulsion is the clinical manifestation of excessive hypersynchronous electrical activity in the cerebral cortex. This electrical event results is a loss or derangement of counsciousness, altered muscle tone, jaw chomping or trismus, salivation, and often involuntary urination and defecation. Most dogs have tonic-clonic, generalized (symmetric) motor seizures in which the animal experiences a period of extremely increased extensor muscle tone (tonus), falls into lateral recumbency, and then has periods of tonus alternating with periods of relaxation (clonus), resulting in rhythmic contractions of muscles manifested as paddling or jerking of the limbs and chewing movements.
The actual seizures in dogs may be preceded by minutes to hours of unusual behavior (preictal phase), including hiding, attention seeking, or agitation. In some dogs, seizures start during sleep or may be triggered by a specific stimulus or event (repetitive noise, flickering light). Estrus, certain drugs (especially phenothiazines), stress, and excitement can all precipitate seizures in dogs. In most animals, each seizure is followed by a short period of disorientation (postictal phase), during which ataxia, blindness, pacing and delirium are common.
Less common than generalized, symmetric tonic-clonic seizures in dogs are focal partial motor seizures. These seizures arise in part of one cerebral hemisphere, resulting in asymmetric signs that may include turning of the head away from the side of the lesion and focal twitching or tonic-clonic contractions of the contralateral facial or limb muscles. These seizures may ultimately become generalized. Although it is often stated that partial motor seizures in dogs are usually associated with structural brain disease, close observations of animals with idiopathic epilepsy reveals that many experience focal seizures with secondary generalization.
Psychomotor seizures in dogs are focal seizures manifested as stereotypic paroxysms of abnormal behavior such as rage, hysteria, hyperesthesia, self-mutilation, tail chasing, and fly biting. Withouth event-triggered electrodiagnostic testing, however, it is very difficult to distinguish these seizures from compulsive stereotypic behavior. In some cases, consciousness is impaired (complex focal seizures) or the seizure progresses to a generalized symmetric tonic-clonic seizure, aiding diagnosis of seizures in dogs.
