Paroxysmal Events: Differentiating Epileptic Seizures From Nonepileptic Spells
Paroxysmal Events: Differentiating Epileptic Seizures From Nonepileptic Spells
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It can be difficult to determine whether unusual, paroxysmal behavior represents a seizure or a nonepileptic event. Patients with sudden flailing movements or unresponsive staring may, in fact, be experiencing psychogenic events. Other types of pathological spells, such as syncope and migraine, can also be mistaken for epileptic seizures. When epilepsy is incorrectly diagnosed in these patients, unnecessary seizure medication is likely to be prescribed, and correct diagnosis and treatment is delayed. It is also the case that epileptic seizures can be subtle and difficult to recognize. Inattentive staring may be attributed to attention deficit disorder but may, in fact, be due to either absence or complex partial seizures. An orderly approach to the differential diagnosis of paroxysmal events is the best way to avoid misdiagnosis. A careful, detailed history and physical examination supplemented by an electroencephalogram (EEG) will, in most cases, result in a correct diagnosis.
Epileptic seizures are paroxysmal, abnormal behaviors caused by excessive, hypersynchronous firing of neurons in the brain. Most seizures arise in the cerebral cortex, although subcortical structures can also generate seizures.1,2 The incidence of epilepsy is highest in early childhood and peaks again late in life.3 When epilepsy is attributed to a brain abnormality (eg, mental retardation, cerebral palsy, malformation), it is classified as “symptomatic.” Epilepsy is considered “idiopathic” when there is no recognized brain abnormality.4
The risk of recurrence within 2 years after a first-time, unprovoked seizure is approximately 35% to 40%.5 Increased risk of recurrence is associated with factors such as a remote, symptomatic cause (eg, brain injury); abnormal EEG; and seizure during sleep. Treatment with antiepileptic medication reduces the risk of a recurrence after a first seizure, but there is little evidence that treatment prevents the later development of epilepsy.6
Prolonged seizures can cause brain injury, but epidemiological studies have not provided evidence that prolonged first seizures in otherwise healthy persons increase the risk of subsequent seizures.7 Furthermore, the number of seizures that occur before treatment is initiated is not necessarily associated with a greater likelihood of medical intractability. 8 Seizure frequency and whether the seizures are generalized or partial have stronger predictive power. Therefore, little advantage is gained by treating first-time seizures, whether they are provoked by an identified acute insult or they occur out of the blue. The rationale for treating persons with recurrent seizures is that treatment will ameliorate seizure recurrence.
Most often, seizure history related by the patient or family members and the physical findings will lead the physician to suspect epilepsy. For example, a history of febrile seizures (particularly if prolonged) is a well-recognized risk factor for the development of temporal lobe epilepsy caused by mesial temporal sclerosis. 9,10 An additional helpful clue from the history is a past brain injury from trauma or infection. It is generally understood that relatively remote trauma of a minor degree confers very little risk, but prolonged loss of consciousness or a penetrating head injury are significant risk factors for seizure episodes.11,12 A family history is important, because epilepsy in firstdegree relatives is another risk factor.
Physical examination findings that indicate an abnormality of brain function provide further evidence of an increased likelihood of seizures. They also help classify epilepsy as either symptomatic or idiopathic. For example, mental retardation, cerebral palsy, or the presence of neurocutaneous lesions is noteworthy. Cerebral imaging studies may demonstrate a structural brain abnormality.
erroneously heighten suspicion of seizures by the patient, caregiver, and physician. Benign or at least nonepileptic behaviors may be mistakenly identified as seizures or described in rather dramatic terms. Table 1 provides a brief overview of nonepileptic events that mimic specific seizure types that occur particularly in children.
Parents of children who have health challenges that may include previous seizures may be very sensitive to any perceived abnormality in the child’s health. Benign events, such as hypnic jerks, may prove very frightening to the parents of a child who recently suffered a febrile seizure. A child with autism may have stereotyped movements that convince a concerned parent that the child is having seizures. Munchausen syndrome and Munchausen syndrome by proxy also may present as seizures.13,14 When the history suggests seizure, a careful differential diagnosis is important.
Nonepileptic seizures are behavioral events that resemble epileptic seizures but are not caused by abnormal, hypersynchronous neuronal discharges in the brain. The term “pseudoseizure” is discouraged, since the events themselves are real and disabling. Nonepileptic events can be caused by psychological disorders, or they can be manifestations of other pathological or physiological neurological conditions.
Alternating hemiplegia. This is characterized by repeated bouts of dystonic posturing accompanied by nystagmus. Hemiplegia can occur on either side or bilaterally. It occurs in the presence of developmental regression and persistent developmental delay. Onset is usually during infancy. The condition has been variously attributed to a migrainous mechanism, epilepsy, and movement disorder. The underlying cause has been linked to mitochondrial dysfunction, channelopathies, and small vessel disease. The calcium channel blocker flunarizine has been used in treatment, as has topiramate.15,16
Benign sleep movements. Benign myoclonus or hypnic jerks often occur shortly after falling asleep. Movements during rapid eye movement sleep also may be mistaken for seizures. Correct identification of these events often will allay the anxiety of patients and caregivers. However, if a child has experienced a seizure (eg, a febrile convulsion) previously, parents may be hypervigilant. Asking the parents to record a video of such movements may be helpful.17
Breath-holding spells (BHS). These spells commonly begin between the ages of 6 and 18 months. They are characterized by hard crying in response to injury or anger and breath-holding, stiffening, and cyanosis (or sometimes pallor) followed by brief loss of muscle tone and consciousness.
Pallid BHS are a type of syncope. They are more likely to occur in reaction to an event causing injury, pain, or emotional distress.18,19 Some children hold their breath on inspiration before getting the first cry out. Others hold their breath in expiration. They usually stop the behavior by age 5 or 6 years. A family history of BHS is common.
BHS are generally benign but can occasionally provoke acute reactive seizures, presumably caused by transient cerebral hypoxia in much the same way syncope can provoke acute seizures. Recognition depends on taking a careful history that looks for consistent initial crying and cyanosis or pallor early in the attack. Treatment for routine BHS consists of reassurance. Some evidence suggests that iron supplementation helps some children.20
Gastroesophageal reflux. Symptoms associated with gastroesophageal reflux may be mistaken for seizures. Infants may have stiffening and crying episodes suggestive of infantile spasms. Older children and adults, particularly if they are cognitively impaired and not able to communicate well, may have reflux-related pain leading to stiffening episodes that are reminiscent of tonic seizures, or they may have sudden behavior changes suggesting partial seizures. Abnormal posturing in patients with gastroesophageal reflux is often referred to as Sandifer syndrome.21,22
Syncope. The distinction between epileptic seizures and syncope can be particularly challenging. Transient loss of consciousness—particularly if accompanied by body stiffening— can suggest seizures, but positive motor signs are common in syncope. At the same time, transient cerebral hypoperfusion occurring during syncope can cause an acute reactive seizure (convulsive syncope).
Features suggesting syncope include preceding light-headedness, sweating, pallor, prolonged standing, sudden changes in posture—from lying down to sitting or standing— and precipitation by vagal stimuli, such as micturition. Conversely, typical aura (eg, epigastric rising sensation, dj vu), postictal delirium, and focal physical features, such as head turning, are suggestive of seizure.23 An EEG showing epileptiform discharges or postictal slowing can help confirm the diagnosis. An ECG revealing an arrhythmia or a positive tilt table test suggests syncope.24
There are also rare cases in which a seizure provokes asystole. When such cases are recognized, the insertion of a pacemaker is often recommended.25