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It is important to note that seizures are symptoms of specific illnesses, one
example being epilepsy. Other diseases that can cause seizures include brain
tumors, infection (e.g., encephalitis), traumatic injury to the brain, and
metabolic or electrolyte abnormalities. Seizures arising from these conditions
are not considered epilepsy because, once the inciting event is removed or
alleviated, the seizures stop. There 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 key EEG finding in these patients is a hypsarrythmia, or a
high-voltage slow wave with multifocal spikes. 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.
* Benign focal epilepsy of childhood (Benign Rolandic epilepsy) begins in
children between the ages of 4 and 13 years. Apart from their seizure disorder,
these patients are otherwise normal. Seizures occur at night and sleep promotes
secondary generalization. As such, parents only report generalized seizures
because focal manifestations are often subtle and go unnoticed. Between
seizures, patients have a stereotyped EEG pattern that includes di- or triphasic
sharp waves over the central-midtemporal (Rolandic) regions. Prognosis is
uniformly good with seizures disappearing by adolescence. Carbamazepine is the
first line treatment, though phenytoin and phenobarbital have also been used
with some efficacy.
* Juvenile myoclonic epilepsy (JME) begins in patients aged 8 to 20 years.
These patients have normal IQ and are otherwise neurologically intact. There is
usually a family history of similar seizures. The seizures are morning myoclonic
jerks often with generalized tonic-clonic seizures that occur just after waking.
EEG readings reveal generalized spikes with 4-6 Hz spike wave discharges and
multiple spike discharges. Interestingly, thse 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). Valproic acid is the first line
treatment. This condition is lifelong, thus patients must be taught appropriate
sleep hygiene to prevent generalized tonic-clonic seizures.
* Temporal lobe epilepsy is the most common epilepsy of adults. In most cases, the epileptogenic region is found in the mesial temporal structures (e.g., the hippocampus, amygdala, and parahippocampal gyrus). 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 often preceded by an aura.