Seizures (Case 54)
Case: A 22-year-old woman was brought in by ambulance. She was at home sitting on the couch when her mother said that she became confused, her eyes rolled back, and then she fell to the floor and started shaking. She had been up late the night before studying for an exam. Upon arrival at the ED she was initially sleepy but then returned to her baseline mental status. During the episode she bit her tongue and had urinary incontinence. Her mother says she had a seizure once as a baby, associated with a fever. She had a normal birth history, normal development, and no prior medical problems. There is no family history of seizures.
Generalized tonic-clonic seizure
Simple partial seizure
Complex partial seizure
Psychogenic non-epileptic seizure (PNES)
Status epilepticus (SE)
When encountering a patient with a suspected seizure, be sure the patient is stabilized. Then obtain a detailed history and perform a physical and neurologic examination. Consider the differential diagnosis of seizure versus other acute-onset neurologic events, such as syncope, stroke/transient ischemic attack (TIA), and migraine. It is important to find out if the patient has a prior history of seizures and is already being treated with antiepileptic drugs. If the episode is determined to be a seizure, then search for an acute cause, including metabolic abnormalities (hypoglycemia), fever or infection, intoxications (alcohol or drugs), organic lesions (tumor, stroke), and noncompliance with antiepileptic medications. A blood glucose level, blood counts, and electrolyte panels may be helpful in determining the cause of the seizure. In the ED setting, a non-contrast CT scan of the head is the initial imaging modality of choice. If meningitis is suspected, an LP should be performed, usually preceded by a CT scan of the head. Subsequently, you can pursue an MRI of the brain and EEG to complete the workup. The decision whether to treat with antiepileptic medications may vary depending on the characteristics of each individual case.
• Generalized seizures are separated into those that are truly generalized in onset (primary generalized seizures) from those that begin locally and then spread to become generalized (secondarily generalized seizures).
• An epilepsy syndrome is a disorder characterized by similar seizure types, clinical features, neurologic abnormalities, and EEG pattern, with a somewhat predictable clinical course and response to antiepileptic drugs.
• Depending on the seizure classification or epilepsy syndrome, one can gain clues as to the underlying etiology of the seizure. Primary generalized epilepsies are most likely genetic or idiopathic, and are not associated with underlying structural abnormalities. On the other hand, partial seizures or secondarily generalized seizures are typically the result of an underlying brain lesion, such as congenital malformations, tumors, prior strokes, traumatic brain injury, or mesial temporal sclerosis.
• The history should include detailed questions regarding the characteristics of the seizure, including the prodrome(s), initial manifestations, pattern of evolution, postictal symptoms, level of consciousness, and associated bowel/bladder incontinence or tongue biting. If the patient loses consciousness during the seizure, a witness may be able to provide these details.
• The initial manifestations and pattern of evolution of the seizure can provide clues as to the localization of seizure onset. A history of a preceding aura is also important, as it provides a clue that the seizure is probably focal in origin, with the type of aura providing clues as to the location of the seizure focus. For example, a preceding epigastric aura suggests onset in the mesial temporal lobe.
• Additional information that should be obtained includes birth history; prior episodes of seizure; febrile seizure; history of head trauma, meningitis, or encephalitis; social history including alcohol and/or drug use; and a family history of epilepsy.
|Clinical Entities||Medical Knowledge|
Generalized Tonic-Clonic Seizure
Seizures result from a paroxysmal high-voltage electrical discharge of hyperexcitable neurons within an epileptogenic focus. Different mechanisms have been hypothesized to explain generalized seizures, including (1) an abnormal response of hyperexcitable cortical neurons to a normal thalamic input, (2) a primary subcortical abnormal trigger, and (3) an abnormal cortical innervation from subcortical structures.
A generalized seizure may be preceded by a prodrome, which consists of nonspecific premonitory symptoms for minutes to hours before the seizure, or an aura, which consists of the focal onset and helps localize the causative lesion within the cortex. A generalized seizure is characterized by a sudden loss of consciousness, with a tonic phase (bilateral stiffening, eyes open and rolled upward, loud vocalization, and incontinence) followed by a clonic phase (synchronous muscle jerking, tongue biting). The seizure is typically followed by a postictal state, at which time the patient is drowsy and confused.
The EEG reveals generalized epileptiform discharges. The frequency and type (polyspike or spike-and-wave) of epileptiform discharges vary depending on the epilepsy type. Focal onset of discharges with spread to the bilateral hemispheres can be seen in secondarily generalized seizures. During the postictal phase, the EEG is generally slow and disorganized.
Pharmacotherapy depends on the etiology and type of seizure, but in general valproic acid, lamotrigine, levetiracetam, topiramate, and zonisamide are considered broad-spectrum antiepileptic medications and are effective for primary and secondarily generalized seizures. Carbamazepine, oxcarbazepine, phenobarbital, phenytoin, tiagabine, gabapentin, and pregabalin are indicated for secondarily generalized seizures and may worsen some primary generalized seizures. See Cecil Essentials 126.
Simple Partial Seizure
Focal abnormal neuronal discharges without alteration of consciousness constitute this diagnosis.
Symptoms depend on the brain area where the abnormal neuronal discharge originates. Focal motor seizures originate from the frontal lobe. Typically head and eyes turn to the side opposite the seizure focus, which shows tonic contractions, possibly followed by clonic movements. A typical, albeit less common, presentation is the classic “Jacksonian march,” characterized by the progressive involvement of muscle groups that follows the distribution of the homunculus along the motor cortex. When the epileptic focus is in the occipital lobe there may be unformed visual phenomena. Autonomic symptoms such as rising epigastric sensation, pallor, flushing, or pupillary changes may occur when the focus is in the temporal lobe, as well as automatisms, formed visual phenomena, and unpleasant odors or taste. Finally, abnormal sensory events can arise from a parietal lobe focus.
Focal EEG abnormalities confirm the involvement of only one cerebral region or hemisphere.
Medications indicated for simple partial seizures include carbamazepine, valproic acid, gabapentin, lamotrigine, topiramate, oxcarbazepine, zonisamide, levetiracetam, phenytoin, pregabalin, tiagabine, and phenobarbital. See Cecil Essentials 126.
Complex Partial Seizures
Focal onset of neuronal discharges with alteration of consciousness is diagnostic. Complex partial seizures typically originate from the temporal lobe and less frequently from the frontal lobe. They are usually associated with an acquired structural lesion such as a tumor or mesial temporal (hippocampal) sclerosis.
Complex partial seizures are typically preceded by an aura (e.g., a rising gastric sensation, emotional content, déjà vu, or visual disturbances). The aura is followed by automatisms, characterized by stereotyped, repetitive actions such as lip smacking, swallowing, or chewing. Patients can be confused and disoriented during the postictal phase for several minutes.
EEG reveals focal epileptiform discharges.
Medications indicated for complex partial seizures are the same as those listed for simple partial seizures and include carbamazepine, valproic acid, gabapentin, lamotrigine, topiramate, oxcarbazepine, zonisamide, levetiracetam, phenytoin, pregabalin, tiagabine, and phenobarbital. See Cecil Essentials 126.
SE can be either convulsive or nonconvulsive. Convulsive SE is life-threatening and can originate as a focal seizure with secondary generalization or be primary generalized. The most frequent cause of SE is noncompliance with seizure medications in a patient with known epilepsy. Other common causes include metabolic derangements, consumption of alcohol or other drugs, anoxia, infection, underlying cerebral lesion (such as stroke or tumor), and trauma.
Convulsive SE is a medical emergency that requires prompt recognition and treatment. Traditionally, SE is defined as either continuous seizure activity that lasts at least 30 minutes or two or more seizures occurring without recovery of consciousness between the seizures. However, a more practical definition suggests that any seizure activity lasting >5 minutes should be considered SE. Nonconvulsive SE can present as a confusional state or a failure to return to baseline mental status after convulsive seizures are treated.
It is important to promptly formulate a diagnosis of convulsive SE, since early treatment increases the likelihood of effective seizure control and prevention of irreversible neuronal injury or death. Diagnosis of nonconvulsive SE can be challenging on purely clinical grounds. It usually requires the demonstration of ictal EEG patterns in a confused or comatose patient in the absence of active convulsions.
Treatment of SE should begin as soon as possible after diagnosis so as to limit cerebral damage. Initial management is the ABCs, with thiamine 100 mg IV and then 50 mL D50 (unless an adequate glucose level is known). Lorazepam (up to 0.1 mg/kg) is the first treatment of choice, followed by fosphenytoin 20 mg/kg phenytoin equivalents at 150 mg/min (or phenytoin 20 mg/kg at 50 mg/min) with blood pressure and telemetry monitoring. An additional dose of fosphenytoin or phenytoin 5 mg/kg IV × 2 can be given. The patient will probably have to be intubated to implement more aggressive treatment with phenobarbital, pentobarbital, midazolam, or propofol, with the target of eliminating convulsive activity and/or EEG spikes. See Cecil Essentials 126.
Psychogenic Non-Epileptic Seizure
In PNES, an underlying psychological problem is translated into a physical symptom, which clinically mimics a convulsion. PNESs have a wide range of associated psychiatric morbidities, including depression, anxiety, psychosis, or post-traumatic stress disorder (PTSD). PNESs and epileptic seizures can frequently coexist in the same patient.
Patients have atypical or variable attacks with triggers that may include an emotional or psychological etiology. Certain seizure phenomena point toward PNES, including flailing or thrashing of arms and/or legs, side-to-side head movements, pelvic thrusting, starting and stopping of symptoms, and eyes closed. Incontinence and physical injuries during the seizure are unlikely with non-epileptic seizures.
Long-term video and/or EEG monitoring is often necessary to make a diagnosis. PNES clinical spells are not associated with typical EEG epileptic activity. Diagnosis may also be suggested by a history of physical or sexual abuse, or psychiatric disease.
Treatment options are based on the idea that the seizures are psychogenic in nature and therefore will require psychiatric treatment. See Cecil Essentials 126.
a. Syncope: Transient loss of consciousness and loss of muscular tone that result from an acute global reduction in cerebral blood flow. Syncope has many diverse causes; a neurologic cause for syncope is found in fewer than 10% of cases. (See also Chapter 65, Dizziness and Vertigo, for a discussion of light-headedness and presyncope.)
b. Sensory TIA: Sensory symptoms with seizures are usually positive phenomena with tingling and paresthesias, whereas sensory TIAs typically present with a negative phenomenon such as numbness or loss of sensation. (See also Chapter 66, Weakness, for a discussion of TIA and stroke.)
c. Migraine: Basilar artery migraine is associated with episodes of confusion and even loss of consciousness, which may mimic a seizure. In children, migraine may present as cyclic vomiting. Positive visual phenomena occur in both migraine and occipital seizures. Typically the visual phenomena in a seizure are shorter lasting (<2 minutes) and patients see colors, whereas with migraine the symptoms last longer (>5 minutes) and patients typically see straight or jagged lines, scintillations, or black-and-white phenomena. (See also Chapter 64, Headache, for a discussion of migraine.)
d. Hypoglycemia: Most commonly presents with nonspecific complaints such as sweating, nausea, light-headedness, pallor, vomiting, abdominal pain, and hunger. Since the CNS functioning depends on glucose, cerebral symptoms also occur such as paresthesias, blurred vision, focal neurologic abnormalities, and/or seizures.
e. Panic attacks: Patients report palpitations, chest pain, shortness of breath, sweating, trembling, gastrointestinal discomfort, loss of control, feeling of choking, nausea, dizziness, paresthesias, chills, hot flashes, and intense fear, especially of dying. An attack usually lasts 5 to 30 minutes.
f. Sleep disorders: Narcolepsy–cataplexy syndrome consists of (1) narcolepsy, short sleep attacks; (2) cataplexy, sudden loss of muscle tone induced by changes in emotion; (3) sleep paralysis, episodes that occur during the transition between sleep and wakefulness, when a patient is awake but unable to move because of generalized hypotonia; and (4) hypnagogic hallucinations, vivid hallucinations that occur at the transition between sleep and wakefulness.
g. Acute dystonic reaction: Sustained involuntary muscle contractions in the face, neck, trunk, or extremities that occur shortly after the initiation of neuroleptic drug therapy. Treatment is effective, including discontinuing the offending agent and administration of benztropine.