(often referred to as a '''seizure disorder''') is a
Chronic Neurological condition characterized by recurrent unprovoked
Seizure s. The condition is named from the Greek ''epilepsis'' ("to take a firm grip on"). It is commonly controlled with medication, although
Surgical methods are used as well.
The diagnosis of epilepsy requires the presence of recurrent, unprovoked seizures; accordingly, it is usually made based on the
Medical History .
EEG , brain
MRI ,
SPECT ,
PET , and
Magnetoencephalography may be useful to discover an
Etiology for the epilepsy, discover the affected brain region, or classify the epileptic syndrome, but these studies are not useful in making the initial diagnosis.
Long-term Video-EEG Monitoring for epilepsy is the gold standard for diagnosis, but it is not routinely employed owing to its high cost and inconvenience.
Convulsive or other seizure-like activity, non-epileptic in origin, can be observed in many other medical conditions. These
Non-epileptic Seizures can be hard to differentiate and may lead to misdiagnosis.
Epilepsies are classified five ways:
# By their first cause (or
Etiology ).
# By the observable manifestations of the seizures, known as "semiology."
# By the location in the brain where the seizures originate.
# As a part of discrete, identifiable medical
Syndrome s.
# By the event that triggers the seizures, as in
Primary Reading Epilepsy .
All the causes (or
Etiologies ) of epilepsy are not known, but many predisposing factors have been identified, including brain damage resulting from malformations during brain development,
Head Trauma , neurosurgical operations, other penetrating wounds of the brain,
Brain Tumor , high
Fever , bacterial or viral
Encephalitis ,
Stroke ,
Intoxication , or acute or inborn disturbances of
Metabolism .
Hereditary or
Genetic factors also play a role.
Seizures may occur in any person under certain circumstances, including acute illness and
Drug Overdose s, but these provoked seizures are not part of the definition of epilepsy. Epilepsy connotes that an individual has unprovoked seizures which recur over time. Approximately 50% of cases are cryptogenic – there is no cause for epilepsy that is detectable even with currently state-of-the-art investigations. In many, but not all cases, abnormal electrical activity can be detected in the brain with an
Electroencephalogram (EEG), either during (
Ictal ) or between seizures (inter-ictal).
The most common ages of
Incidence are under the age of 18 and over the age of 65. It has been estimated that about 1% of the population meets the diagnostic criteria for epilepsy at any given time, but some theorize that the
Prevalence may be much higher in fact.
A significant and measurable decline in
Cognitive function is known to be associated with epilepsy, although it has not been entirely clear to what extent this is due to the epilepsy itself or to the drugs used to treat it.
Phenobarbital , in particular, has been shown to decrease
IQ and classroom performance when used to treat epilepsy in children; the effects persist even after the phenobarbital is stopped. Some newer anti-epileptic drugs are considered by some to have less severe cognitive effects than older drugs. On an individual level, a person's reaction to epileptic seizures and/or anti-epileptic drugs may be
Idiosyncratic , so it is difficult to predict how a particular person might be affected.
Mutation s in several
Gene s have been linked to some types of epilepsy. Several genes that code for
Protein subunits of
Voltage-gated and
Ligand-gated Ion Channel s have been associated with forms of generalized epilepsy and infantile seizure syndromes
1 Full text online: . Several ligand-gated ion channels have been linked to some types of frontal and generalized epilepsies. Epilepsy-related mutations in some non-ion channel genes have also been identified.
One interesting finding in animals is that repeated low-level electrical stimulation to some brain sites can lead to permanent increases in seizure susceptibility: in other words, a permanent decrease in seizure "threshold." This phenomenon, known as
Kindling (by analogy with the use of burning twigs to start a larger fire) was discovered by Dr.
Graham Goddard in 1967. Chemical stimulation can also induce seizures; repeated exposures to some pesticides have been shown to induce seizures in both humans and animals. One mechanism proposed for this is called
Excitotoxicity . The roles of kindling and excitotoxicity, if any, in human epilepsy are currently hotly debated.
Some people with epilepsy have certain triggers or provocants that will reliably produce a seizure. If the provocant can reasonably be considered to be part of normal daily life, and yet it causes a seizure, the seizures are considered 'unprovoked' for the purpose of diagnosing the person with epilepsy. Examples of these 'normal provocants' include reading, hot water on the head,
Hyperventilation and flashing or flickering lights. This last provocant is a special type of
Reflex Epilepsy called
Photosensitive Epilepsy .
Epileptic seizures are classified both by their patterns of activity in the
Brain and their effects on behaviour.
In terms of their pattern of activity, seizures may be described as either ''partial'' (focal) or ''generalised''. Partial seizures only involve a localised part of the brain, whereas generalised seizures involve the entire
Cortex . The term 'secondary generalisation' may be used to describe a partial seizure that later spreads to the whole of the cortex and becomes generalised.
Partial seizures may be further subdivided into both ''simple'' and ''complex'' seizures. This refers to the effect of such a seizure on
Consciousness ; simple seizures cause no interruption to consciousness (although they may cause sensory distortions or other sensations), whereas complex seizures interrupt consciousness to varying degrees. This does not necessarily mean that the person experiencing this sort of seizure will fall unconscious (like fainting). For example, a
Complex Partial Seizure may involve the unconscious repetition of simple actions, gestures or verbal utterances, or simply a blank stare and apparent unawareness of the occurrence of the seizure, followed by no memory of the seizure. Other patients may report a feeling of tunnel vision or dissociation, which represents a diminishment of awareness without full loss of consciousness. Still other patients can perform complicated actions, such as travel or shopping, while in the midst of a complex partial seizure.
The effects of partial seizures can be quite dependent on the area of the brain in which they are active. For example, a partial seizure in areas involved in perception may cause a particular sensory experience (for example, the perception of a scent, music or flashes of light) whereas, when centred in the
Motor Cortex , a partial seizure might cause movement in particular groups of
Muscle s. This type of seizure may also produce particular thoughts or internal visual images or even experiences which may be distinct but not easily described. Seizures centred on the
Temporal Lobe s are known to produce
Mystical or
Ecstatic experiences in some people. These may result in a misdiagnosis of
Psychosis or even
Schizophrenia , if other symptoms of seizure are disregarded and other tests are not performed. Unfortunately for those with epilepsy,
Anti-psychotic medications prescribed without
Anti-convulsant s in this case can actually lower the seizure threshold further and worsen the symptoms.
When the effects of a partial seizure appear as a 'warning sign' before a more serious seizure, they are known as an
Aura : it is frequently the case that a partial seizure will spread to other parts of the brain and eventually become generalized, resulting in a tonic-clonic convulsion. The subjective experience of an aura, like other partial seizures, will tend to reflect the function of the affected part of the brain.
Generalised seizures can be sub-classified into a number of categories, depending on their behavioural effects:
- '' Absence Seizure s'' (sometimes referred to as ''petit mal'' seizures) involve an interruption to consciousness where the person experiencing the seizure seems to become vacant and unresponsive for a short period of time (usually up to 30 seconds). Slight muscle twitching may occur.
- '' Tonic-clonic Seizure s'' (sometimes referred to as ''grand mal'' seizures), involve an initial contraction of the Muscle s (''tonic phase'') which may involve Tongue biting, Urinary Incontinence and the absence of Breathing . This is followed by rhythmic muscle contractions (''clonic phase''). This type of seizure is usually what is referred to when the term 'epileptic fit' is used colloquially.
- '' Myoclonic Seizure s'' involve sporadic muscle contraction and can result in jerky movements of muscles or muscle groups.
- '' Atonic Seizure s'' involve the loss of muscle tone, causing the person to fall to the ground. These are sometimes called 'drop attacks' but should be distinguished from similar looking attacks that may occur in Narcolepsy or Cataplexy .
- '' Status Epilepticus '' refers to continuous seizure activity with no recovery between successive tonic-clonic seizures. This is a life-threatening condition and emergency medical assistance should be called immediately if this is suspected. A tonic-clonic seizure lasting longer than 5 minutes (or two minutes longer than a given person's usual seizures) is usually considered grounds for calling the emergency services.
- '' Epilepsia Partialis Continua '' is a rare type of focal motor seizure ( Hand s and Face ) which recurs every few seconds or minutes for extended periods (days or years). It is usually due to strokes in adults and focal cortical inflammatory processes in children ( Rasmussen's Encephalitis ), possibly caused by chronic Viral Infection s or Autoimmune processes.
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 Hypsarrhythmia , 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.
- '' 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. On EEG, one finds the stereotyped generalized 3 Hz spike and wave discharges. 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 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, 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). 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 .
- '' Frontal Lobe Epilepsy ''
- '' Lennox-Gastaut Syndrome ''
Epilepsy is usually treated with
Medication prescribed by a
Physician ;
Primary Care givers,
Neurologist s, and
Neurosurgeon s all frequently care for people with epilepsy. In some cases the implantation of a stimulator of the
Vagus Nerve , or a special diet can be helpful. Neurosurgical operations for epilepsy can be
Palliative , reducing the frequency or severity of seizures; or, in some patients, an operation can be curative.
In most cases, the proper emergency response to a generalized tonic-clonic epileptic seizure is simply to prevent the patient from self-injury by moving him or her away from sharp edges, placing something soft beneath the
Head , and carefully rolling the person onto his or her side to avoid
Asphyxiation . Should the person regurgitate, the material should be allowed to drip out the side of the patient's mouth by itself. If the seizure lasts longer than 5 minutes,
Emergency Medical Services should be contacted. Prolonged seizures may develop into ''
Status Epilepticus '', a dangerous condition requiring hospitalization and emergency treatment.
Objects should be placed in a person's
Mouth during a seizure as this could result in injury to the person's mouth or obstruction of the airway. Despite common
Folklore , it is not possible for a person to swallow their own
Tongue during a seizure.
After a seizure, it is typical for a person to be confused, disoriented, and possibly agitated or sleepy. It is important to stay with the person until this passes; people should not eat or drink until they have returned to their normal level of awareness, and they should not be allowed to wander about unsupervised. Many patients will sleep deeply for a few hours after a seizure; this is not dangerous. In about 50% of people with epilepsy, headaches may occur after a seizure. These headaches share many features with
Migraine s, and respond to the same medications.
Some medications can be taken daily in order to prevent seizures altogether or reduce the frequency of their occurrence. These are termed "anticonvulsant" or "antiepileptic" drugs (sometimes AEDs). All such drugs have side effects which are idiosyncratic and others which are dose-dependent; it is not possible to predict who will suffer from side effects or at what dose the side effects will appear.
Some people with epilepsy will experience a complete remission when treated with an anticonvulsant medication. If this does not occur, the dose of medication may be increased, or another medication may be added to the first. The general strategy is to increase the medication dose until either the seizures are controlled, or until dose-limiting side effects appear; at which point the medication dose is reduced to the highest amount that did not produce undesirable side effects.
Serum levels of AEDs can be checked to determine medication
Compliance and to assess the effects of drug-drug interactions; serum levels are generally not useful to predict anticonvulsant efficacy in an individual patient, though in some cases (such as a seizure flurry) it can be useful to know if the level is very high or very low.
If a person's epilepsy cannot be brought under control after adequate trials of two different drugs, that person's epilepsy is generally said to be 'medically refractory.'
Various drugs may prevent seizures or reduce seizure frequency: these include
Carbamazepine (common brand name Tegretol),
Clobazam (Frisium),
Clonazepam (Klonopin),
Ethosuximide (Zarontin),
Felbamate (Felbatol),
Fosphenytoin (Cerebyx),
Flurazepam (Dalmane),
Gabapentin (Neurontin),
Lamotrigine (Lamictal),
Levetiracetam (Keppra),
Oxcarbazepine (Trileptal),
Mephenytoin (Mesantoin),
Phenobarbital (Luminal),
Phenytoin (Dilantin),
Pregabalin (Lyrica),
Primidone (Mysoline),
Sodium Valproate (Epilim),
Tiagabine (Gabitril),
Topiramate (Topamax),
Valproate Semisodium (Depakote),
Valproic Acid (Depakene, Convulex), and
Vigabatrin (Sabril).
Other drugs are commonly used to abort an active seizure or interrupt a seizure flurry; these include
Diazepam (Valium) and
Lorazepam (Ativan). Drugs used only in the treatment of refractory
Status Epilepticus include
Paraldehyde (Paral) and
Pentobarbital (Nembutal).
Surgical treatment can be an option for epilepsy when an underlying brain abnormality, such as a benign
Tumor or an area of scar tissue (e.g.
Hippocampal Sclerosis ) can be identified. The abnormality must be removable by a neurosurgeon.
Surgery is usually only offered to patients when their epilepsy has not been controlled by adequate attempts with multiple medications. Before surgery is offered, the medical team conducts many tests to assess whether removal of brain tissue will result in unacceptable problems with
Memory ,
Vision ,
Language or
Movement , which are controlled by different parts of the
Brain . These tests usually include a
Neuropsychological Evaluation , which sometimes includes an
Intracarotid Sodium Amobarbital Test (
Wada Test ). Resective surgery, as opposed to palliative, successfully eliminates or significantly reduces seizures in about 50-90% of the patients who undergo it (the exact percentage depends on the particulars of the case in question.) Many patients decide not to undergo surgery owing to fear or the uncertainty of having a brain operation.
The most common form of resective surgical treatment for epilepsy is to remove the front part of either the right or left
Temporal Lobe . A study of 48 patients who underwent this operation,
Anterior Temporal Lobectomy , between
1965 and
1974 determined the long-term success of the procedure. Of the 48 patients, 21 had had no seizures that caused loss of consciousness since the operation. Three others had been free of seizures for at least 19 years. The rest had either never been completely free of seizures or had died between the time of the surgery and commencement of the study.
3
Palliative surgery for epilepsy is intended to reduce the frequency or severity of seizures. Examples are
Callosotomy or
Commissurotomy to prevent seizures from generalizing (spreading to involve the entire brain), which results in a loss of consciousness. This procedure can therefore prevent injury due to the person falling to the ground after losing consciousness. It is performed only when the seizures cannot be controlled by other means. Resective surgery can be considered palliative if it is undertaken with the expectation that it will reduce but not eliminate seizures.
Hemispherectomy is a drastic operation in which most or all of one half of the cerebral cortex is removed. It is reserved for people suffering from the most catastrophic epilepsies, such as those due to
Rasmussen Syndrome . If the surgery is performed on very young patients (2-5 years old), the remaining hemisphere may acquire some rudimentary motor control of the ipsilateral body; in older patients, paralysis results on the side of the body opposite to the part of the brain that was removed. Because of these and other side effects it is usually reserved for patients who have exhausted other treatment options.
Ketogenic Diet s may occasionally be effective in controlling some types of epilepsy; although the mechanism behind the effect is not fully understood, shifting of
PH towards a
Metabolic Acidosis and alteration of brain
Metabolism may be involved. Ketogenic diets are high in
Fat and extremely low in
Carbohydrate s, with intake of fluids often limited. This treatment, originated as early as the
1920s at
Johns Hopkins Medical Center, was largely abandoned with the discovery of modern anti-epileptic drugs, but recently has returned to the anti-epileptic treatment arsenal. Ketogenic diets are sometimes prescribed in severe cases where drugs have proven ineffective.
There are several downsides to what initially seems a benign
Therapy , however. The ketogenic diet is not good for the
Heart or
Kidney s and medical problems resulting from the diet have been reported. In addition, the diet is extremely unpalatable and few patients are able to tolerate it for any length of time. Since a single potato chip is adequate to break the
Ketosis , staying on the diet requires either great willpower or perfect control of a person's dietary intake. People fed via
Gastrostomy or young children who receive all their food in the presence of a caregiver are better candidates.
Vagus Nerve Stimulation is a recently developed form of seizure control which uses an implanted electrical device, similar in size, shape and implant location to a
Heart Pacemaker , which connects to the
Vagus Nerve in the
Neck . Once in place the device can be set to emit electronic pulses, stimulating the vagus nerve at pre-set intervals and milliamp levels. Treatment studies have shown that approximately 50% of those treated in this fashion will show significant seizure reduction.
Some people with epilepsy receive a special
Dog which has the rare talent of sensing the onset of a seizure and is trained to alert the human so they can reach a safe location before their seizure puts them in danger. Other
epilepsy care dogs do not sense seizures, but serve as companions and guardians during the loss of consciousness accompanying a seizure.
The Institutes For The Achievement Of Human Potential promulgate a home program consisting of a healthy diet, clean air, and respiratory training. This alternative approach is regarded as unscientific by most medical practicioners.
