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Diagnosing and Localizing Seizures at the Bedside and in Clinic
Despite the availability of sophisticated neurodiagnostic tests, identification of seizures and epilepsy is predicated on clinical evaluation. There is no substitute for a comprehensive history and physical for diagnosis and localization of seizures at the bedside. Oftentimes when a patient presents with a seizure, the first step is computed tomography (CT) of the head or routine electroencephalography (EEG), with little time spent obtaining detailed descriptions of how the spell occurred and the circumstances surrounding its presentation. Diagnosing and localizing seizures is based upon a thorough and comprehensive clinical history, with the physical examination and supporting laboratory, imaging, and neurophysiologic studies used only to confirm that a seizure occurred and investigate the etiology.
In this chapter, we focus on diagnosis and localization of seizures without using any supporting laboratory evaluation, dealing with the essential issues to be addressed when a patient presents with an episode. Fundamental questions need to be asked to arrive at an appropriate diagnosis which, in turn, leads to the correct therapeutic choices and, ultimately, improved quality of life. One cannot stress too greatly the importance of a comprehensive history and physical, because once a patient is diagnosed with seizures and treatment is initiated, very few physicians will ever refute or question the label of epilepsy. This is why getting the diagnosis right from the onset is such an important issue. This chapter is organized around three important diagnostic questions addressed at the bedside that provide a logical, stepwise approach to making the appropriate diagnosis and guiding management of any patient presenting with a spell.
TIPS AND TRICKS- Is it a seizure?
- What are the surrounding circumstances?
- What kind of seizure is it?
Is it a seizure?
The most important question is whether the episode is actually a seizure or one of its mimics. Inquiry about the duration of the event, the description of what the patient felt or did, the postictal characteristics, and the frequency of the events is essential. Getting the diagnosis right from the onset is important because treatment to prevent future spells depends upon their etiology.
Table 5.1. Distinguishing between seizures and their common mimics at bedside.
A number of differential diagnoses should be considered when a patient presents with an event. The three most common possibilities are an epileptic seizure, syncope, and a psychogenic nonepileptic event. In addition, several other conditions can also present in a paroxysmal manner, including panic attacks, hyperventilation episodes, transient ischemic attacks, migraines and migraine equivalents, narcolepsy, cataplexy, parasomnias, paroxysmal dyskinesias or dystonias, hyperekplexia, paroxysmal vertigo, and hypoglycemic events. For further information on the differential diagnosis of spells, see Chapters 1, 2, and 6. The present chapter will focus on the aspects of the clinical history suggesting seizures and epilepsy.
An epileptic seizure is a hypersynchronous, self-limited activity of neurons in the brain, occurring either as a symptom of an underlying condition or without clear provocation. Seizures last from seconds to a few minutes. There can be a prodrome or warning prior to an event, followed by a distinct warning known as an aura, followed by the actual seizure itself, followed ultimately by the postictal period – the time after a seizure. In the attempt to confirm that a seizure has occurred, initial questions must center on what occurred throughout these phases. Oftentimes, patients are amnestic for the event, so one has to rely on witnesses. It is critically important to record a detailed description of the attack in the patient’s own words so that this account can be compared with descriptions of any subsequent episodes.
Epileptic seizures are stereotyped in their clinical presentation and duration, whereas psychogenic, nonepileptic events are often variable. Individuals with epilepsy often are amnestic for their events, so obtaining as much additional information from other family members, caregivers, and coworkers is important. In many ways, the diagnosis of seizures is like a classic detective novel in which the neurologist must interview all involved parties to get an accurate portrayal of what occurred. Table 5.1 provides an overview of the semiology of various paroxysmal event types, useful for distinguishing between epileptic seizures and psychogenic nonepileptic events. No diagnosis should ever depend on any single feature. When considering the onset of an episode, it is important to establish its clinical characteristics (semiology) and its progression, making certain that they are consistent with the overall findings of the physical examination and the rest of the history.
The onset of a seizure provides important diagnostic information. Myoclonic jerks may precede generalized tonic–clonic seizures in juvenile myoclonic epilepsy. There may be déjà vu or an aura of gastrointestinal distress that occurs prior to a temporal lobe seizure. The features of the onset of an attack are useful for distinguishing among various seizure types. A sensation of feeling hot, sweating, pallor, tunnel vision, vision closing in, and tinnitus are more common at the onset of syncope. Episodes in which the patient simply drops without warning or experiences drop attacks and returns rapidly to full conscious on the ground suggest circulatory disturbances such as syncope or arrhythmia as opposed to a seizure. Obtaining a history with those characteristics will be particularly helpful to diagnosing syncope if the episodes are also associated with orthostatic posture changes.
Psychogenic nonepileptic events can start suddenly or be preceded by a prodrome such as vague anxiety complaints. An important distinguishing feature is that seizures can occur out of sleep, but psychogenic events do not. However, many patients describe events that occur at night, yet on confirmatory video–EEG monitoring they are shown to be awake. Investigating this detail is important because events that awaken the patient out of sleep suggest a pathophysiological etiology rather than a psychiatric one.
TIPS AND TRICKS:The manifestations of a seizure depend on the location of its onset and the regions to which the epileptic discharge spreads. Motor activity during a generalized tonic-clonic seizure, the most common seizure type, consists of vigorous, forceful, and repetitive movements persisting for more than 30 s. The frequency of muscle contractions in the clonic phase declines gradually in epileptic seizures, whereas it does not tend to change during a psychogenic nonepileptic event. Syncopal events are usually brief unless the patient is maintained in an upright posture. Myoclonic jerks during syncope are common, as is vocalization, brief limb posturing, upward and lateral deviation of the eyes, and eyelid flickering.
The duration of an event helps to differentiate spells. Syncopal attacks tend to last for a few seconds to a minute as opposed to epileptic seizures, which often last about a minute or more. Psychogenic nonepileptic events can last for more than 2 min to several hours. The eyes are typically closed in psychogenic nonepileptic events and open during epileptic seizures. Motor activity in psychogenic episodes commonly shows a reprise phenomenon in which activity either starts or stops without apparent pattern, with limb movements often more asynchronous or purposeful than in an epileptic seizure (for example, pushing away the examiner). Prolonged episodes of immobility with eyes closed, of looking around without responding, or of fixed dystonic posturing are unlikely to be epileptic events. Psychogenic nonepileptic events can also manifest as limpness with rapid recovery, which can easily be confused with syncope. Patients with psychogenic nonepileptic event may “foam at the mouth” during attacks. Reports of a bitten tongue without characterization of the severity of the injury do not reliably distinguish between patients with epilepsy and psychogenic nonepileptic events, nor does urinary incontinence. Both can occur in syncope. However, severe injuries to the tongue resulting in lateral bruising, taking days to heal, are more consistent with epilepsy than psychogenic events.
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