Seizures (Proceedings)

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Seizures (Proceedings)

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Nov 01, 2010

Definitions

          o Seizure: Clinical manifestation of abnormal electrical activity in the cerebral cortex
          o Paroxysm: Sudden event with abrupt onset and end, used when exact nature of event is in doubt; seizures are paroxysms, but not all paroxysms are seizures
          o Prodrome: Period before the seizure, potential for abnormal behavior, can last hours to days
          o Aura: Initial sensation of the seizure in humans associated with start of abnormal electrical activity (may be manifested as stereotypic movements, salivation, attention seeking in animals)
          o Ictus: Actual seizure event, usually seconds to minutes
          o Postictal period: Transient clinical abnormalities in brain function following completion of the seizure, usually minutes to hours
          o Interictal period: Time between resolution of postictal signs and onset of next seizure
          o Epilepsy: Chronic condition characterized by recurrent seizures, i.e. not a single seizure; a broad category of disorders
          o Provoked (Reactive) seizures: Occur at the time of systemic disorder or insult to the brain and stop when underlying condition is resolved, i.e. not epilepsy
          o Idiopathic epilepsy: No identifiable brain abnormality other than seizures, implies no interictal neurologic deficits
          o Symptomatic epilepsy: Seizures result from a specific cause
          o Cryptogenic epilepsy: Recurrent seizures presumed to be symptomatic but currently of unknown cause
          o Generalized: 1st clinical signs reflect bilateral involvement of cerebrum, consciousness generally impaired and motor signs bilateral, include tonic-clonic, tonic, clonic, atonic, myoclonic and absence
          o Focal (Partial): 1st clinical signs reflect abnormal activity in one location of cerebral hemisphere, "simple" when consciousness is maintained, "complex" when consciousness is impaired, manifestations may be motor, sensory or autonomic, secondary generalization possible
          o Cluster seizures: ≥ 2 seizures over brief period (minutes to within 24 hours) with normal consciousness obtained between seizures
          o Status epilepticus: Seizure lasting >20-30 minutes in humans; generally used in VM for seizure lasting > 5 minutes or ≥ 2 seizures without full recovery of consciousness between seizures

Confirm seizures have occurred -history, video example, physical and neurologic exams, lectroencephalography (EEG)

Differential diagnoses

          o Extracranial – seizures more likely to be generalized
               • Endogenous toxins, secondary to hepatic or renal disease
               • Metabolic abnormalities, e.g. hypoglycemia, electrolyte disturbances
               • Endocrine disease, e.g. hypothyroidism, hyperosmolar non ketotic DM
               • Toxicoses, e.g. metaldehyde, organophosphate, theobromine, caffeine, lead
          o Intracranial – often characterized as progressive vs. non progressive
               • Degenerative – storage diseases
               • Anomalous/congenital – hydrocephalus, lissencephaly
               • Metabolic – see above
               • Neoplastic – primary and metastatic
               • Nutritional – thiamine deficiency
               • Infectious – bacterial, viral, fungal, protozoal, rickettsial, parasitic
               • Inflammatory – granulomatous meningoencephalitis, necrotizing encephalitis
               • Idiopathic – inherited, aquired epilepsy
               • Iatrogenic – metronidazole toxicosis, overzealous correction of hyponatremia
               • Traumatic – cranial trauma, cerebral hypoxia
               • Toxic – see above
               • Vascular – ischemic, hemorrhagic