Chapter 20 J. Stephen Huff Generalized convulsive seizures are frightening to observe and often result in EMS calls. Provoked seizures represent symptoms of an acute underlying medical or neurological condition. Seizures often occur without clear etiology or provocation. Epilepsy, sometimes referred to as a seizure disorder, is defined by recurrent unprovoked seizures. It is estimated that between 1% and 2% of emergency department (ED) visits are for seizure-related complaints, with many of these patients using EMS systems. Most receive advanced-level care [1]. In one study, seizures accounted for almost 12% of pediatric EMS transports [2]. One study showed that seizures were a common cause of repeated ambulance use [3]. Every community has a cadre of patients with poorly controlled seizures or alcohol-related seizures who use EMS frequently. This familiar group of frequent users may lead to a casual indifference to all patients with seizures. Physicians and providers must recall that seizures at some level are the symptom of some central nervous system (CNS) dysfunction and initiate appropriate management steps to terminate seizures to lessen morbidity. The concept of a seizure threshold suggests that everyone has the capacity to experience seizures at some level of individual physiological stress. The precipitating events may be electrolyte abnormalities, medications, medication withdrawal, toxins, hypoxia, CNS infections, systemic infections, trauma, or even sleep deprivation. A fundamental distinction in management is to determine whether a seizure results from some identifiable cause or if it is unprovoked. When seizures are secondary to some other condition, they are termed symptomatic seizures or provoked seizures. Unprovoked seizures occur without an identifiable cause. Again, epilepsy is defined by episodes of unprovoked seizures. At a cellular level, seizures are thought to originate in the cerebral cortex or thalamus. Lesions of the brainstem, deep white matter, and cerebellum are not epileptogenic. Seizures result from excitation of susceptible groups of cerebral neurons, with progressively larger groups of neurons developing synchronous discharges. Clinical signs and symptoms follow when a critical mass of neurons is reached [4]. At a biochemical level, there is a disturbance in the balance of cellular excitation and inhibition. Glutamate is the most common excitatory neurotransmitter and acts at the n-methyl-D-asparate (NMDA) receptor. Current theory is that failure of inhibition mediated by the neurotransmitter gamma-aminobutyric acid (GABA) system leads to prolongation of most seizure types. The neurotransmitter receptor sites are thought to be the sites of action of the antiepileptic drugs. With frequent or persistent seizure activity, physiological changes of hypoxia, acidosis, hyperthermia, hypotension, and reduced cerebral perfusion may occur. At one time these were thought to be the cause of neuronal injury. However, many different avenues of investigation have suggested that injury follows prolonged excessive neuronal discharges even if systemic pathophysiological factors are controlled [4]. Some experimental evidence suggests that neurotransmitter receptors may change in sensitivity or quantity with prolonged seizures; potentially effectiveness of medications might change as seizure duration persists [5,6]. There is a differential diagnosis for seizures since a number of clinical conditions may simulate generalized convulsions (Box 20.1). Syncope is a frequent consideration in the differential diagnosis. Loss of consciousness is abrupt in syncope and occasionally the brief myoclonic jerks that accompany the faint are a source of confusion. “Convulsive syncope” results from the cerebral hypoperfusion during the syncopal event. Investigations and treatments should be directed toward the cause of syncope [7]. A person suffering a blow to the head may have a brief episode of extremity stiffening at the time of impact that understandably may be confused with seizure activity. These events clinically resemble brief abnormal extensor posturing, though myoclonic and tonic-clonic movements are also described. Return to consciousness following these events is usually prompt. These “convulsive concussions” are not associated with injury or neurological sequelae and do not predict future seizures [8,9]. Posttraumatic epilepsy may occur after head trauma but is associated with more severe head injuries. These seizures are typical in appearance and associated with a postictal confusional state. In any series of stroke patients, seizures and postictal states are a significant source of diagnostic confusion [10,11]. Seizure patients may have postictal weakness or confusion that mimics some stroke symptoms. Subarachnoid hemorrhage may cause fragmentary or repetitive extensor posturing that at times is confused with seizures [12,13]. Non-epileptic seizures, also known as pseudoseizures, psychogenic, or hysterical seizures, often result in diagnostic uncertainty. Simply stated, the patient appears to be having a seizure but subsequent observations prove that the apparent convulsion does not follow from the excessive neuronal discharges that characterize epileptic seizures. The usual descriptions of non-epileptic seizures include side-to-side head movements, out-of-phase limb movements, and pelvic thrusting [14]. However, other reports indicate that simple unresponsiveness without motor movements is a frequent presentation [15]. In theory, almost any behavior or experience may result from the abnormal synchronous discharges of groups of neurons. Motor movements, sensory experiences, or abnormal behaviors may all represent seizures [16]. Patterns are seen that allow a categorization of seizures (Box 20.2) [17]. Modern classification schemes are based on video electroencephalogram (EEG) correlations, but at times seizure-type classification may be made from direct patient observation. A fundamental distinction is whether the seizure is of partial onset or generalized onset. This distinction may be important clinically because partial-onset seizures may imply focal or structural CNS abnormalities and because different medications are effective in different seizure types. In partial-onset seizures, clinical information indicates that seizure onset is limited to one part of the brain. Partial seizures may be further divided into simple partial seizures, complex partial seizures, and partial seizures that secondarily become generalized. In a simple partial seizure, the patient remains at normal consciousness. Partial seizures with sensory symptoms include some patients with episodic paresthesias. Special sensory symptoms delineate seizures with gustatory, olfactory, or auditory components. The term complex implies that consciousness is clouded. Symptoms of these patients are often altered mental status with confusion and simple repetitive motor movements such as lip smacking or picking at clothes. Sometimes prolonged confusional states occur with complex partial seizures, one of the types of non-convulsive status epilepticus [18]. Generalized-onset seizures imply that the cerebral cortex is bilaterally involved at seizure onset. This often requires EEG evaluation for definitive diagnosis. The types of generalized seizures are listed in Box 20.2. Some seizure types are typical enough in appearance that they can be classified by observation alone. Partial-onset seizures with secondary generalization are the most common type of generalized seizure in adults. An example of a partial-onset seizure with secondary generalization would be a patient with onset of finger twitching, progression of movements to the arm and face, and then a subsequent generalized convulsive seizure. However, often this secondary generalization occurs too rapidly to be appreciated by witnesses or in the field. A few words concerning terminology are in order. Convulsion refers to the motor movements associated with a seizure. Tonic refers to the stiffening of the extremities seen in convulsions. Clonic is the rhythmic, synchronized movements of the extremities. Some patients experience an aura, which is the initial subjective perception of a seizure. Grand mal is generally used in a manner to be synonymous with a generalized convulsion. Petit mal, however, is so frequently misused by patients and physicians that perhaps that term is best not used. Correctly used, it is synonymous with absence seizures, a generalized-onset seizure that has a characteristic EEG three-cycle-per-second pattern. In common usage, however, petit mal is corrupted by association with the word petite, meaning “small,” so that fragments of seizures or partial seizures are incorrectly labeled petit mal seizures. A basic point in assessment and management is whether a seizure is secondary to some medical condition, such as electrolyte abnormalities, toxins, hypoxia, CNS infections, systemic infections, or trauma. EMS plays a key role in gathering historical information to identify likely seizure causes and initiating therapy. A few causes of symptomatic seizures warrant particular comment. Alcohol withdrawal seizure is a type of symptomatic seizure that usually occurs within 48 hours of cessation of drinking [19]. Usually alcohol withdrawal seizures are single and brief, but up to 30% of patients have recurrent seizures in the ED [20,21]. Studies of patients with status epilepticus show that in a significant proportion, the seizures are alcohol related [22]. Many different toxins may cause seizures [23,24]. Sympathomimetics, including cocaine, are perhaps the most frequently encountered. Other toxins that may cause seizures include antidepressants, antihistamines, salicylates, and anticholinergics. Isoniazid, used to treat tuberculosis, deserves specific mention because the mechanism of action of the drug requires a specific antidote: pyridoxine (vitamin B6) [25]. Seizures in association with advanced pregnancy or in the postpartum patient may represent eclampsia. Hypertension is present. Treatment involves magnesium sulfate and possibly benzodiazepines. Febrile seizures are one of the most common seizure types encountered in emergency practice, in both the field and the ED. Definitions in the literature vary, but a seizure associated with fever in children aged 6 months to 5 years without evidence of intracranial infection or other definite cause of seizure is an accepted definition. The age-delineated definition acknowledges the sensitivity of the maturing brain to fever [26]. Excluded are febrile-associated seizures in patients who have experienced afebrile seizures. Peak incidence is at 18 months. Other events that may simulate seizures in this age group include rigors, breath-holding spells, apneic episodes, and anoxic seizures. History is key in sorting out these events. Many febrile seizures occur early in the course of the underlying illness and may be the presenting symptom of the illness. The magnitude and peak of the fever are likely to be more important than the rate of increase in provoking seizures. Antipyretics have not been shown to be effective in reducing the risk of febrile seizures [26]. Febrile seizures are often divided into simple and complex types. A simple febrile seizure is a generalized tonic-clonic convulsion without focal signs lasting less than 10 minutes, resolving spontaneously, and not recurring within 24 hours. Complex febrile seizures fall outside this definition due to focal signs during the seizures, seizure duration, or recurrence. By definition, a simple febrile seizure will likely have ceased by arrival of EMS, unless the response interval is very short. Recurrent or prolonged seizures exclude this diagnosis and point to a complex febrile seizure or another cause for the seizure. EMS and other sources of history are important in eliciting a history of irritability, decreased feeding, or abnormal consciousness that might suggest an underlying CNS infection. Most children experiencing febrile seizures recover within 30 minutes. Postictal alteration of consciousness persisting more than 60 minutes has been suggested as a risk factor for a complicating medical condition [27]. Ongoing seizures or status epilepticus may occur in any seizure type and terminology may be confusing (Box 20.3). Generalized convulsive status epilepticus represents a true emergency condition because the ongoing electrical seizure activity is itself injurious to the brain. In late or decompensated status epilepticus, there may be a dissociation between the ongoing electrical seizure activity and motor convulsions [28,29]. In other types of status epilepticus, such as the non-convulsive status seen in prolonged absence seizures, the link between prolonged electrical activity and neuronal injury is not established.
Seizures
Introduction
Pathophysiology
Differential diagnosis
Classification of seizure types
Symptomatic seizures
Febrile seizures
Status epilepticus
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
