Epilepsy and Seizures: A Comprehensive Guide to Diagnosis and Management

Seizure Disorders 

1. INTRODUCTION 

A. Definitions 

1. Seizures are characterized by an excessive, hypersynchronous discharge of cortical neuron activity, which can be measured by the electroencephalogram(EEG). In addition, disturbances in consciousness, sensory-motor systems, subjective well-being, and objective behavior may occur. Seizures are usually brief, with a beginning and an end, and may produce post-seizure impairment.

2. Epilepsy is defined as a chronic seizure disorder or group of disorders characterized by seizures that usually recur unpredictably in the absence of a consistent provoking factor. The term epilepsy is derived from the Greek word meaning "to seize upon" or "take hold of." It was first described by Hughlings Jackson in the 19th century as an intermittent nervous system derangement due to a sudden, excessive, disorderly discharge of cerebral neurons.

3. Convulsions are violent, involuntary contractions of the voluntary muscles. A patient may have epilepsy or a seizure disorder without convulsions.

 

B. Classification.

An alternative seizure classification is being developed that is purely symptom-based. This consists of four categories: sensorial (auras), consciousness, autonomic, and motor. Also, the international league against epilepsy is establishing a four-level descriptive seizure classification based on symptoms, a pathophysiological seizure, an epileptic syndrome, and functional disability. At present, there are two systems of classification of seizure disorder: one is based on the seizure type and characteristics (Table 1), and the other is based on the characteristics of the epilepsy (including age at onset, etiological factors, and frequency) and characteristics of the seizure.

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1. Partial seizures

Partial seizures are the most common seizure type, occurring in approximately 80% of patients with epilepsy.

a. Clinical and EEG changes indicate initial activation of a system of neurons limited to part of one cerebral hemisphere that may spread to other or all brain areas. Manifestations of the seizures depend on the site of the epileptogenic focus in the brain.

b. Partial seizures are subclassified as simple (usually unilateral involvement) or complex (usually bilateral involvement). Impairment of consciousness is a feature of complex seizures. Consciousness is defined as the degree of awareness and responsiveness of the patient to externally applied stimuli.

 

I Simple partial seizures

Simple partial seizures generally do not cause loss of consciousness. Signs and symptoms of simple partial seizures may be primarily motor, sensory, somatosensory, autonomic, or behavioral. These signs and symptoms may help pinpoint the site of the abnormal brain discharge, for example, localized numbness or tingling reflects a dysfunction in the sensory cortex, located in the parietal lobe.

(a) Motor signs include convulsive jerking, chewing motions, and lip smacking.

(b) Sensory and somatosensory manifestations include paresthesias and auras.

(c) Autonomic signs include sweating, flushing, and pupil dilation

(d) Behavioral manifestations, which are sometimes accompanied by impaired consciousness, include déjà vu experiences, structured hallucinations, and dysphasia.

 

Table 1. INTERNATIONAL CLASSIFICATION OF EPILEPTIC SEIZURES

I.Partial seizures (seizures beginning locally) A. Simple partial seizures (consciousness not impaired) 1. With motor symptoms 2. With somatosensory or special sensory symptoms 3. With autonomic symptoms 4. With behavioral symptoms B. Complex partial seizures (with impairment of consciousness) 1. Beginning as simple partial seizures and progressing to impairment of consciousness a. Without automatisms b. With automatisms 2. With impairment of consciousness at onset. a. With no other features b. With features of simple partial seizures c. With automatism C. Partial seizures (simple or complex), secondarily generalized.   II. Generalized seizures (bilaterally symmetric, without localized onset) A. Absence seizures 1. True absence seizures (petit mal) 2. Atypical absence seizures B. Myoclonic seizures C. Clonic seizures D. Tonic seizures E. Tonic-clonic seizures (grand mal) F. Atonic seizures III. Unclassified seizures

 

(2) Complex partial seizures:

 Complex partial seizures are accompanied by impaired consciousness; however, in some cases, the impairment precedes or follows the seizure. These seizures have variable manifestations.

 

(a) Purposeless behavior is common.

(b) The affected person may have a glassy stare, may wander about aimlessly, and may speak unintelligibly.

(c) Psychomotor (temporal lobe) epilepsy may lead to aggressive behavior (e.g., outbursts of rage or violence).

(d) Postictal confusion usually persists for 1 to 2 mins after the seizure ends.

(e) Automatism (e.g. picking at clothes) is common and may follow visual, auditory, or olfactory hallucinations.

 

2. Generalised seizures:

Generalized seizures are diffuse, affecting both cerebral hemispheres.

a.  Clinical and EEG changes indicate initial involvement of both hemispheres.

(1) Consciousness may be impaired, and this impairment may be the initial manifestation.

(2) Motor manifestations are bilateral.

(3) The ictal EEG patterns initially are bilateral and presumably reflect neuronal discharge, which is widespread in both hemispheres.

b. There are three types of generalized seizures.

(1) Idiopathic epilepsies have an age-related onset, typical clinical and EEG characteristics, and a presumed genetic origin.

(2) Symptomatic epilepsies are considered the consequence of a known or suspected underlying disorder of the central nervous system (CNS).

(3) Cryptogenic epilepsy refers to a disorder for which the cause is hidden or occult; it is present to be symptomatic, but the casual factors are unknown. It is age related but to be often does not have well-defined clinical and EEG characteristics.

 

c.   Signs and symptoms of generalized seizures may be minor or major.

1) Absence (petit mal) seizures present as alterations of consciousness (absences) lasting 10 to 30 seconds.

(a). Staring (with occasional eye blinking) and loss or reduction in postural tone are typical. If the seizure takes place during conversation, the individual may break off in mid-sentence.

 (b). Enuresis and other autonomic components may occur during absence seizures.

(c). some patients experience 100 or more absences daily.

(d). Onset of this seizure type occurs from age 3 to 16 years; in most patients, absence seizures disappear by age 40.

 

(2) Myoclonic (bilateral massive epileptic myoclonus) seizures present as involuntary jerking of the facial, limb, or trunk muscles, possibly in a rhythmic manner.

(3) Clonic seizures are characterized by sustained muscle contractions alternating with relaxation.

(4) Tonic seizures involve sustained tonic muscle extension (stiffening).

(5) Generalized (grand mal) tonic-clonic seizures cause sudden loss of consciousness.

(a) The individual becomes rigid and falls to the ground. Respirations are interrupted, the legs extend, and the back arches; contraction of the diaphragm may induce grunting. This tonic phase lasts for about 1 min.

(b) A clonic phase follows, marked by rapid bilateral muscle jerking, muscle flaccidity, and hyperventilation. Incontinence, tongue biting, tachycardia, and heavy salivation sometimes occur.

(c) During the postictal phase, the individual may experience headache, confusion, disorientation, nausea, drowsiness, and muscle soreness. This phase may last for hours.

(d) Some patients with epilepsy have serial grand mal seizures, regaining consciousness briefly between attacks. In some cases, grand mal seizures occur repeatedly with no recovery of consciousness between attacks (status epileptics); this disorder is discussed in III.A.

 

(6) Atonic seizures (drop attacks) are characterized by a sudden loss of postural tone so that the individual falls to the ground. They occur primarily in children.

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C. Epidemiology 

1. Most common neurological disorder

2. Epilepsy has a prevalence of approximately 1% (Le., 500,000 cases per 50 million person. worldwide).

3. In the United States, the prevalence of epilepsy is 6.42 cases per 1000 people.

4. The onset of seizures is greatest during the first year of life, this probability decreases each decade after the first year until age 60. Approximately 1 of 50 children and 1 of 100 adults are affected.

5. Approximately 70% of people with epilepsy have only one seizure type, the remainder have two or more seizure types.

 

D. Causes of seizures:

Some seizures arise secondary to other conditions. However, in most cases, the cause of the seizure is unknown.

1.     Primary (idiopathic) seizures have no identifiable cause.

a. This type of seifare affects about 75% of people with epilepsy.

b. The onset of primary seizures typically occurs before age 20.

C. Birth trauma, hereditary factors, and unexplained metabolic disturbances have been proposed as possible causes.

2. Secondary seizures (symptomatic or acquired seizures) occurs secondary to an identifiable cause.

a. Disorders that may lead to secondary seizures include

(1) Intracranial neoplasms

(2) Infectious diseases, such as meningitis, influenza, toxoplasmosis, mumps, measles, and syphilis

(3) High fever (in children)

(4) Head trauma

(5) Congenital diseases

(6) Metabolic disorders, such as hypoglycemia and hypocalcemia. 

(7) Alcohol or drug withdrawal

(8) Lipid storage disorders

(9) Developmental abnormalities

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E. Pathophysiology of seizures.

Seizures reflect a sudden, abnormal, excessive neuronal discharge in the cerebral cortex. Any abnormal neuronal discharge could precipitate a seizure.

1. Normal firing of neurons, which usually originate from the gray matter of one or more cortical or subcortical areas, requires the following elements:

a. Voltage-dependent ion channels are involved in action-potential propagation or burst generation.

b. Neurotransmitters control neuronal firing, including excitatory neurotransmitters, acetylcholine, norepinephrine, histamine, corticotropin-releasing factors (CRFs), inhibitory neurotransmitters, y-aminobutyric acid (GABA), and dopamine; therefore, normal neuronal activity requires adequate ions (e.g., sodium, potassium, calcium); excitatory and inhibitory neurotransmitters; and glucose, oxygen, amino acids, and adequate systemic pH.

c. People with epilepsy may be genetically predisposed to a lower seizure threshold.

d. A diencephalic nerve group that normally suppresses excessive brain discharge may be differentiated, hypersensitive, and vulnerable to activation by various stimuli in individuals with epilepsy.

e. During seizures, there is an increased use of energy, oxygen, and, consequently, an increased Production of carbon dioxide. Because of the limited capacity to increase the blood flow to the brain, the blood supply may be oxygen-deficient. The ratio of supply to demand decreases when the seizure episode is prolonged, leading to increased ischemia and neuronal destruction. Thus, it is crucial to diagnose seizures and treat them as soon as possible.

 

2. Abnormal electrical brain activity occurring during a seizure usually produces characteristic changes on the EEG. Each part of the cortical area has its own function, and the clinical presentation of a seizure depends on the site, the degree of irritability of the area, and the intensity of the Impulse.

 

3. Seizure activity may include three major phases.

 a. Prodrome may precede the seizure by hours or days.

(1) Changes in behavior or mood typically occur during the prodrome.

(2) This phase may include an aura-a subjective sensation, such as an unusual smell or flashing light.

 

b. The ictal phase is the seizure itself. In some cases, its onset is heralded by a scream or cry.

c. The postictal phase takes place immediately after the seizure.

(1) Extensor plantar reflexes may appear.

(2) The patient typically exhibits lethargy, confusion, and behavioral changes.

 

F. Clinical evaluation

 

1. History includes an evaluation of the seizure, including interviews of the patient's family and eyewitness accounts to establish.

a. The frequency and duration of the episodes

b. Precipitating factors

c. The times at which episodes occur

d. The presence or absence of an aura

e. Ictal activity

f. Postictal state

2. Physical and neurological examinations are the tools with which to identify an underlying cause to rule out diseases that manifest as seizures.

3. Laboratory tests may also identify an underlying cause.

a. Liver and kidney function tests, complete blood count (CBC), urinalysis, and serum drug levels (e.g., antidepressants and amphetamines may precipitate seizures) are necessary.

b. Lumbar puncture may be required for evidence of cerebrospinal fluid (CSF) infection for patients with a fever who have seizures.

4. Neurological imaging studies, including MRI and/or CT, complement electrophysiological studies and can identify structural brain disorders (anatomical abnormalities).

a. An MRI can detect cerebral lesions related to epilepsy and should be used in all cases, especially in patients with partial seizure, to exclude brain abnormalities.

b. Positron-emission tomography (PET), single-photon emission CT (SPECT), and stable xenon-enhanced x-ray CT offer functional views of the brain to detect hypometabolism or relative hypoperfusion. PET and SPECT scans are not available in all institutions.

c. EEG studies measure the electrical activity of the brain. These studies help identify functional cerebral changes underlying structural abnormalities and are useful with MRI for patients considered for epilepsy surgery.

(1) An EEG is useful for classifying the seizure or as an additional diagnostic tool, but the EEG by itself cannot rule seizures in or out, because some patients with normal interictal EEGs have seizure disorders.

(2) The best time to obtain an EEG is during a seizure episode. EEG recordings done while the patient is asleep can often record the abnormal activity; therefore, EEGs performed during a sleep-induced state under normal conditions or in a sleep-deprived state can be more sensitive for making a diagnosis.

 

G. Treatment objectives

 

1. To prevent or suppress seizures or reduce their frequency through drug therapy.

2. To control or eliminate the factors that cause or precipitate seizures.

3. To prevent serious consequences of seizures, such as anoxia, airway occlusion, or injury by protecting the tongue and placing a pillow under the victim's head.

4. To encourage a normal lifestyle and prevent the patient from feeling like or being treated as an invalid.

5. Short- and long-term side effects

6. Drug interactions

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