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