Clinical Presentation of Epilepsy and Seizure - Epilepsy is a disorder that is best viewed as a symptom of disturbed electrical activity in the brain, which may be caused by a wide variety of etiologies. It is a collection of many different types of seizures that vary widely in severity, appearance, cause, consequence, and management. Seizures that are prolonged or repetitive can be life-threatening.
Seizures occur because a group of cortical neurons discharge abnormally in synchrony. Anything that disrupts the normal homeostasis of neurons and their stability can trigger hyperexcitability and seizures. There are thousands of medical conditions that can cause epilepsy, from genetic mutations to traumatic brain injury. A genetic predisposition to seizures has been observed in many forms of primary generalized epilepsy. Patients with mental retardation, cerebral palsy, head injury, or strokes are at an increased risk for seizures and epilepsy. The more profound the degree of mental retardation as measured by the intelligence quotient (IQ), the greater is the incidence of epilepsy. In the elderly, seizures are primarily of partial onset associated with the focal neuronal injury induced by strokes, neuro- degenerative disorders (e.g., Alzheimer disease), and other conditions.
In some cases, if an etiology of seizures can be found and corrected, the patient may not require chronic antiepileptic drug (AED) treatment. Patients can also present with unprovoked seizures that do not have an identifiable cause, and thus by definition have idiopathic or cryptogenic epilepsy. Idiopathic etiology is the term used for suspected primary generalized seizures, whereas cryptogenic etiology is used if no obvious cause is found for partial-onset seizures. The incidence of idiopathic epilepsy is higher in children. Many factors have been shown to precipitate seizures in susceptible individuals. Hyperventilation can precipitate absence seizures.
Sleep, sleep deprivation, sensory stimuli, and emotional stress increase the frequency of seizures. Hormonal changes occurring around the time of menses, puberty, or pregnancy have also been associated with the onset of or an increased frequency of seizures. A careful history should be obtained from patients presenting with seizures because theophylline, alcohol, high-dose phenothiazines, antidepressants (especially maprotiline or bupropion), and street drug use have been associated with provoking seizures. Perinatal injuries and small gestational weight at birth are also risk factors for the development of partial-onset seizures. Immunizations have not been associated with an increased risk of epilepsy.
The International League Against Epilepsy (ILAE) has proposed two major schemes for the classification of seizures and epilepsies: the International Classification of Epileptic Seizures and the International Classification of the Epilepsies and Epilepsy Syndromes. The International Classification of Epileptic Seizures (Table bellow) combines the clinical description with certain electrophysiologic findings to classify epileptic seizures. Seizures are divided into two main pathophysiologic groups—partial seizures and generalized seizures— by EEG recordings and clinical symptomatology.
Partial (focal) seizures begin in one hemisphere of the brain and— unless they become secondarily generalized—result in an asymmetric motor manifestation. Partial seizures manifest as alterations in motor functions, sensory or somatosensory symptoms, or automatisms. Partial seizures with no loss of consciousness are classified as simple partial (SP). In some cases, patients will describe somatosensory symptoms as a “warning” prior to the development of a GTC seizure. These warnings are in fact simple partial seizures and frequently are termed auras. Partial seizures with an alteration of consciousness are described as complex partial (CP). With CP seizures, the patient can have automatisms, periods of memory loss, or aberrations of behavior. Some patients with CP epilepsy have been mistakenly diagnosed as having psychotic episodes. CP seizures also can progress to GTC seizures.
Patients with CP seizures typically are amnestic to these events. Generalized seizures have clinical manifestations that indicate involvement of both hemispheres. Motor manifestations are bilateral, and there is a loss of consciousness. Generalized seizures can be further subdivided by EEG and clinical manifestations. A partial seizure that becomes generalized is referred to as a secondarily generalized seizure. Generalized absence seizures are manifested by a sudden onset, interruption of ongoing activities, a blank stare, and possibly a brief upward rotation of the eyes. They generally occur in young children through adolescence. It is important to differentiate absence seizures from complex partial seizures.
International Classification of Epileptic Seizures
I. Partial seizures (seizures begin locally)
A. Simple (without impairment of consciousness)
1. With motor symptoms
2. With special sensory or somatosensory symptoms
3. With psychic symptoms
B. Complex (with impairment of consciousness)
1. Simple partial onset followed by impairment of consciousness with or without automatisms
2. Impaired consciousness at onset with or without automatisms
C. Secondarily generalized (partial onset evolving to generalized tonic-clonic seizures)
II. Generalized seizures (bilaterally symmetrical and without local onset)
G. Infantile spasms
III. Unclassified seizures
IV. Status epilepticus
GTC seizures are what many people think of as epilepsy. The seizure results in a sudden sharp tonic contraction of muscles followed by a period of rigidity and clonic movements. During the seizure, the patient may cry or moan, lose sphincter control, bite the tongue, or develop cyanosis. After the seizure, the patient may have altered consciousness, drowsiness, or confusion for a variable period of time (postictal period) and frequently goes into a deep sleep. Tonic and clonic seizures can occur separately. Brief shock-like muscular contractions of the face, trunk, and extremities are known as myoclonic jerks. They can be isolated events or rapidly repetitive. A sudden loss of muscle tone is known as an atonic seizure. This can be described as a head drop, the dropping of a limb, or a slumping to the ground. These patients often wear protective head ware to prevent trauma.
The International Classification of Epilepsies and Epilepsy Syndromes adds components such as age of onset, intellectual development, findings on neurologic examination, and results of neuroimaging studies to define epilepsy syndromes more fully. Syndromes can include one or many different seizure types (e.g., Lennox-Gastaut syndrome). The syndromic approach includes seizure type(s) and possible etiologic classifications (e.g., idiopathic, symptomatic, or unknown). Idiopathic describes syndromes that are presumably genetic but also those in which no underlying etiology is documented or suspected. A family history of seizures is commonly present, and neurologic function is essentially normal except for the occurrence of seizures. Symptomatic cases involve evidence of brain damage or a known underlying cause.
A cryptogenic syndrome is assumed to be symptomatic of an underlying condition that cannot be documented. Unknown or undetermined is used when no cause can be identified. This syndromic classification is more important for prognostic determinations than for a classification based simply on seizure type. The syndrome classification scheme requires more information and, in return, provides a more powerful tool for comprehensive clinical management. A patient’s epilepsy is classified based on seizure type (i.e., generalized versus partial) and syndromic type (i.e., idiopathic, symptomatic, or cryptogenic).
Clinical Presentation of Epilepsy
In most cases, the healthcare provider will not be in a position to witness a seizure. Many patients (particularly those with CP or GTC seizures) are amnestic to the actual seizure event. Obtaining an adequate history and description of the ictal event (including time course) from a third party (e.g., significant other, family member, or witness) is critically important. With treatment the typical clinical presentation of the seizure may change.
Symptoms of a specific seizure will depend on seizure type. Although seizures can vary between patients, they tend to be stereotyped within an individual.
- CP seizures can include somatosensory or focal motor features.
- CP seizures are associated with altered consciousness.
- Absence seizures can be almost nondetectable with only very brief (seconds) periods of altered consciousness.
- GTC seizures are major convulsive episodes and are always associated with a loss of consciousness.
Interictally (between seizure episodes), there are typically no objective or pathognomonic signs
There are currently no diagnostic laboratory tests for epilepsy. In some cases, particularly following GTC (or perhaps CP) seizures, serum prolactin levels can be transiently elevated. Laboratory tests can be done to rule out treatable causes of seizures (e.g., hypoglycemia, altered electrolyte concentrations, infections, etc.) that do not represent epilepsy.
Other Diagnostic Tests
- EEG is very useful in the diagnosis of various seizure disorders.
- An epileptiform EEG is found in only approximately 50% of the patients who have epilepsy.
- A prolactin serum level obtained within 10 to 20 minutes of a tonic-clonic seizure can be useful in differentiating seizure activity from pseudoseizure activity but not from syncope.
- Although magnetic resonance imaging (MRI) is very useful (especially imaging of the temporal lobes), a computed tomography (CT) scan typically is not helpful except in the initial evaluation for a brain tumor or cerebral bleeding.
Source: pharmacotherapy 7th