consciousness is impaired, can lead to hypoxia, hypercarbia, and respiratory acidosis Patients with impaired consciousness may be unable to protect their airway and are at risk for aspiration Prolonged skeletal muscle activity can lead to lactic acidosis, rhabdomyolysis, hyperkalemia, hyperthermia, and hypoglycemia ETIOLOGY It is important to remember that a seizure does not constitute a diagnosis but is merely a symptom of an underlying pathologic process that requires a thorough investigation ( Table 72.1 ) Often, no underlying condition is identified, and the diagnosis of idiopathic epilepsy is made However, it is important not to exclude potentially treatable causes prematurely For instance, seizures that result from metabolic derangements (e.g., hyponatremia, hypoglycemia) are often refractory to anticonvulsant therapy until the abnormality is corrected Therefore, rapid point-of-care testing for glucose and sodium are recommended for pediatric status Furthermore, every effort should be made to rule out a potentially lifethreatening cause of seizures (e.g., intracranial injury or hemorrhage, meningitis, ingestions) before a less serious diagnosis is accepted TABLE 72.1 ETIOLOGY OF SEIZURES a Infectious Brain abscess Encephalitis Febrile (nonspecific) Meningitis Parasites (central nervous system) Syphilis Idiopathic Subtherapeutic anticonvulsant level Withdrawal Alcohol Hypnotics Toxicologic Anticonvulsant Camphor Carbon monoxide Cocaine Heavy metals (lead) Hypoglycemic agents Isoniazid Lithium Methylxanthines Pesticides (organophosphates) Phencyclidine Sympathomimetics Tricyclic antidepressants Topical anesthetics Degenerative cerebral disease Hypoxic ischemic injury Hepatic failure Metabolic Hyperosmolarity Hypocalcemia Hypoglycemia Hypomagnesemia Hyponatremia Hypoxia Inborn errors of metabolism Pyridoxine deficiency Uremia Vascular Cerebrovascular accident Hypertensive encephalopathy Oncologic Primary brain tumor Metastatic disease Endocrine Addison disease Hyper/hypothyroidism Obstetric Eclampsia Traumatic Cerebral contusion Diffuse axonal injury Intracranial hemorrhage Congenital anomalies a Bold type denotes most common causes Given their nature, virtually all these etiologies are potentially life-threatening, except perhaps febrile seizures Febrile seizures and breakthrough seizures of patients with known epilepsy (whether compliant with their medication or not) represent the majority of seizure episodes encountered in an emergency department setting DIFFERENTIAL DIAGNOSIS There are many different types of events that mimic seizure activity Syncope, or the transient loss of consciousness that results from inadequate cerebral perfusion or substrate delivery, is the most common alternative diagnosis given to patients who present for the evaluation of a seizure episode (see Chapter 76 Syncope ) Further complicating matters is the fact that a small percentage of patients with syncope exhibit some sort of convulsive movement Although vasovagal episodes or orthostatic hypotension is the most common cause for syncope, it is important to evaluate these patients for potential underlying cardiac disease ... compliant with their medication or not) represent the majority of seizure episodes encountered in an emergency department setting DIFFERENTIAL DIAGNOSIS There are many different types of events that