Evaluation in the ED Setting
The classification of a seizure does not often change the ED management of seizures, but it is important to be able to recognize that seizures may present with different clinical appearances. It is also important to remember that not all seizure-like activity is due to epilepsy or abnormal neuronal discharges. There are several other conditions that can present with physical symptoms and characteristics similar to seizure, and are often misdiagnosed as seizures. The next section describes several of these seizure mimics and how to recognize or differentiate them from seizures through a careful history, physical examination, and laboratory evaluation; as one diagnostic tool, the EEG, is not routinely available to the emergency physician (EP).
Seizure Mimics
Syncope
Syncope is secondary to decreased cerebral perfusion, which results in brief loss of consciousness and postural tone, and often with brief convulsions. Myoclonic jerking lasting a few seconds can be seen in many syncopal episodes, and if present is termed convulsive syncope. Following any syncopal episode, patients generally return to their baseline mental status without a postictal period. A prodrome of pallor and sweating can be helpful clues to identify a syncopal episode. In addition, a patient’s eyes may remain open during the event.
There are several types of syncope: cardiac, orthostatic, or neurocardiogenic (vasovagal). History and physical examination can help distinguish syncope from seizure.
Cardiac Syncope. Cardiogenic causes of syncope may be seen in elderly patients who lack a prodrome prior to the event, chest pain may have been present, the event may occur with exercise, or there is evidence of underlying heart disease. An electrocardiogram (ECG) should be done to detect cardiac dysrhythmias. Orthostatic Syncope. Vital signs may be useful in assessing for an orthostatic cause of syncope (drop in systolic blood pressure [BP] by 20 mm Hg or more and drop in diastolic BP by 10 mm Hg or more within 3 minutes of standing), though orthostatic hypotension is common in the elderly.7-8 Dysautonomia as a cause of orthostatic hypotension may show a delayed drop in BP after standing 5 to 10 minutes, in contrast to hypovolemia which tends to be present with immediate standing.Neurocardiogenic Syncope. Neurocardiogenic syncope, a somewhat confusing term, is perhaps better described as a reflex syncope, or simple faint. Often this is referred to as “vasovagal” syncope. Typically, there are physical or psychological noxious stimuli prior to the brief loss of consciousness and postural tone. Pain or strong emotions are common triggers.
Convulsive Concussion
Another seizure mimic is convulsive concussion in which the patient exhibits nonepileptic movement following a closed head injury. It is hypothesized that these post-traumatic convulsions are due to transient functional abnormalities, rather than structural brain injury. In one study, 22 cases of concussive convulsions were identified in which tonic-clonic convulsions began within 2 seconds of impact, and lasted for up to 150 seconds. These patients generally have good outcomes and do not require antiepileptic treatment; they also do not need to abstain from sports or other physical activities.9-11
Movement Disorders
Certain movement disorders can appear similar to seizures with sustained muscle contractions, repetitive movements, dystonias, or even abnormal posturing. However, these abnormal movements are generally painful and there is often impairment of consciousness. They may be genetic in nature or secondary to a neurologic disease or medications such as neuroleptics or antipsychotics.
Psychogenic Nonepileptic Seizures
Psychogenic nonepileptic seizures (PNES) are defined as episodes of altered movements or sensations that appear similar to epileptic seizures, but have an underlying psychological etiology rather than abnormal neuronal discharges. Seventy percent of these patients have a psychiatric illness, such as depression, post-traumatic stress disorder, or personality disorders. Features that can help distinguish PNES from epileptic seizures include long duration, fluctuating symptoms, asynchronous or non-rhythmic movements, pelvic thrusting, side-to-side head or body movements, closed eyes, lack of tongue biting, memory recall, crying, or suppression by distraction. Laboratory testing provides little benefit, aside from a lactate level, which if elevated can suggest a possible epileptic etiology.12 These cases may require consultation with neurology and psychiatry or video-EEG monitoring to correctly diagnose.13-14
Other non-epileptic and possible seizure mimic diagnoses to be considered include stroke, transient ischemic attack, migraine headache, and sleep disorders.
Evaluation
When assessing a patient presenting with seizure-like activity or altered mental status, the clinician must keep a broad differential diagnosis. The first step is to evaluate the ABCs. Once that is completed, a blood glucose should be obtained, as it is a quick test and can determine whether hypoglycemia is the likely cause. Intravenous (IV) access should be obtained and routine labs ordered, including a complete blood count (CBC), a comprehensive metabolic profile (CMP), magnesium, urinalysis, ECG, and lactate. Other labs that may be of clinical utility in certain cases include anticonvulsant levels (in patients that are on these medications), toxicology screens, and cerebrospinal fluid studies, if indicated. It is important to note that anticonvulsant reference ranges are trough values, so levels that are drawn within a few hours of the last dose taken reflect a peak and falsely elevated level. Useful imaging may include computed tomography (CT) scan of the head and magnetic resonance imaging (MRI) of the brain.15 The American Academy of Neurology recommends cross-sectional imaging via CT of the head if there is a focal seizure onset, persistent neurologic deficit, if the patient is immunocompromised, or if the patient does not return to their baseline mental status.16If a patient does not show progressive signs of increasing arousal or awareness within 30 minutes, an immediate EEG is indicated to assess for non-convulsive status epilepticus.