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Seizure types are organized firstly according to whether the source of the seizure within the brain is localized (partial or focal onset seizures) or distributed (generalized seizures).
Partial SeizuresPartial seizures are further divided on the extent to which consciousness is affected. If it is unaffected, then it is a simple partial seizure; otherwise it is a complex partial (psychomotor) seizure. A partial seizure may spread within the brain - a process known as secondary generalization.
Generalised SeizuresGeneralized seizures are divided according to the effect on the body but all involve loss of consciousness. These include absence (petit mal), myoclonic, clonic, tonic, tonic-clonic (grand mal) and atonic seizures.
Seizure syndromesThere are many different epilepsy syndromes, each presenting with its own unique combination of seizure type, typical age of onset, EEG findings, treatment, and prognosis. Below are some common seizure syndromes:
• Infantile spasms (West syndrome) is associated with brain development abnormalities, tuberous sclerosis, and perinatal insults to the brain. It affects infants (as implied by its name), which by definition is between 30 days to 1 year of life.
It carries a poor prognosis such that only 5-10% of children with infantile spasms will develop normal to near-normal function, while more than two-thirds will have severe deficits.
The typical seizures are characterized by sudden flexor and extensor spasms of head, trunk, and extremities. The first line treatment for these patients is adrenocorticotropic hormone (ACTH or corticotropin) since traditional antiepileptic drugs generally cannot adequately control seizure activity. Vigabatrin is also used in many countries, and is particularly effective when tuberous sclerosis is the cause of seizures.
• Childhood absence epilepsy affects children between the ages of 4 and 12 years of age.
These patients have recurrent absence seizures that can occur hundreds of times a day. A subset of these patients will also develop generalized tonic-clonic seizures. This condition carries a fairly good prognosis in that these children do not usually show cognitive decline or neurological deficits. First line treatment for pure absence seizures is ethosuximide. If patients do not respond or have mixed seizures along with their absence seizures, then valproic acid can be used.
• Benign focal epilepsies of childhood. The most common syndromes comprising the benign focal epilepsies of childhood include Benign Childhood Epilepsy with Centro-Temporal Spikes (or benign rolandic epilepsy), and Benign Childhood Epilepsy with Occipital Paroxysms.
Benign rolandic epilepsy begins in children between the ages of 3 and 16 years. Apart from their seizure disorder, these patients are otherwise normal. Seizures typically occur at night, and are brief, focal motor events affecting facial and pharyngeal muscles, though may be generalized convulsions as well. Focal seizures may be less frequently reported than more obvious generalized seizures.
Prognosis is quite good overall with seizures disappearing by adolescence. There is no consensus on the first line treatment, however most cases respond well to most anticonvulsants.
• Juvenile myoclonic epilepsy (JME) begins in patients aged 8 to 20 years. These patients have normal IQ and are otherwise neurologically intact. JME is thought to be genetic, though that is not to say that JME will show in immediate family members.
The seizures are morning myoclonic jerks often with generalized tonic-clonic seizures that occur just after waking. 'Petit mal' or absence seizures are less common in cases of JME, but are known to occur more often in young girls. Interestingly, these patients are often first diagnosed when they have their first generalized tonic-clonic seizure later in life when they experience sleep deprivation (e.g., freshman year in college after staying up late to study for exams).
Alcohol is a major contributing factor and those with severe JME should monitor their intake of units.
Valproic acid is the first line treatment, whereas carbamazepine can actually worsen symptoms. This condition is lifelong, thus patients must be taught appropriate sleep hygiene to prevent generalized tonic-clonic seizures. The severity of JME varies from person to person - some will experience full blown tonic-clonic seizures regularly, others will suffer only under sufficient stress from lack of sleep and intoxication.
• Temporal lobe epilepsy is the most common epilepsy of adults. Seizures begin in late childhood and adolescence. There is an association with febrile seizures in childhood, and some studies have shown herpes simplex virus (HSV) DNA in these regions, suggesting that perhaps this epilepsy has an infectious etiology. Most of these patients have complex partial seizures sometimes preceded by an aura, and some TLE patients also suffer from secondary generalised tonic-clonic seizures. If the patient does not respond sufficiently to medical treatment, surgery may be considered.
• Fetal alcohol syndrome (FAS) is caused by prenatal alcohol exposure and results in central nervous system (CNS) damage. Seizure disorders due to prenatal alcohol exposure are one of several possible criteria for diagnosing FASD; however, any seizure disorder due to postnatal insult does not qualify as a diagnostic criterion for FASD.
• Frontal lobe epilepsy
• Lennox-Gastaut syndrome
• Occipital lobe epilepsy
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