Epilepsy is a brain disorder where clusters of cells in the brain called neurons
send abnormal signals. It's these abnormal brain signals that make people with epilepsy
prone to seizures.1 There are many types of seizures and they can vary
from brief disruptions of the senses, to short periods of unconsciousness, to convulsions.
It is important to note that all people with epilepsy will have seizures, but all
people with seizures will not necessarily be diagnosed with epilepsy.
Epileptic seizures are typically classified into categories:
Partial seizures originate in a specific
part of the brain, and include:
Generalized seizures involve the entire
brain, and include:
Unclassified epileptic seizures
Infantile spasms are a specific type of
seizure seen in an epilepsy syndrome of infancy and childhood also known as West Syndrome
Partial seizures
Partial seizures start in a specific area of the brain and are categorized by whether
or not the person loses consciousness.2
- Simple partial seizures do not involve a loss
of consciousness. Symptoms vary depending on the area of the brain involved in the
seizure, but may include muscle contractions or twitching, numbness and tingling
in body parts, hallucinations, a feeling of déjà vu, jerky motions, or weakness
of a body part. Simple partial seizures usually last less than 2 minutes.2,3
- Complex partial seizures impair consciousness,
where the person is unable to respond to commands, interact with their surroundings,
or recall events that occurred during the seizure. This seizure type originates
in one particular area of the brain and can produce motor and behavioral disturbances.
As a complex partial seizure begins, the person may present with a blank or wide-eyed
stare followed by such activities as chewing, lip smacking, picking at their shirt,
or other repetitive, purposeless movements. Typically, complex partial seizures
last between 30 and 90 seconds, and are often followed by a period of disorientation,
confusion and/or fatigue.3,4,5
- Secondarily generalized seizures are
partial seizures that have spread to other regions of the brain. Complex partial
seizures that evolve to secondarily generalized seizures last no more than a few
minutes, are difficult to distinguish from primary generalized seizures, and are
more likely to manifest as a tonic-clonic seizure.3
Generalized seizures
In contrast to partial seizures, generalized seizures involve both sides of the
brain at once.
- Absence (Petit mal) seizures are brief seizures
usually lasting 5 to 15 seconds. Petit mal seizures involve sudden, brief impairment
of consciousness, including a blank stare with motor or behavioral disturbances.
These seizures frequently begin in childhood and may persist into adulthood. If
untreated, these seizures may occur multiple times per day.3
- Myoclonic seizures are rapid, brief episodes
of alternating contractions and relaxations (jerking or twitching) of a muscle or
a group of muscles. Myoclonic seizures usually cause abnormal movements on both
sides of the body at the same time.4
- Clonic seizures appear as repetitive jerking
movements or contractions of a group of muscles. The arms, neck and facial muscles
are involved. The movements cannot be stopped by restraining or repositioning the
arms or legs. Clonic seizures vary in length between 1 to 2 minutes.3,4,5
- Tonic seizures involve sudden stiffening of
the muscles. Tonic seizures most often occur during sleep and usually involve all
or most of the brain, affecting both sides of the body. During a tonic seizure,
the person will usually remain conscious, and the seizure will usually last less
than 20 seconds.4
- Tonic-clonic (grand mal) seizures combine
the characteristics of both tonic and clonic seizures. They may begin with loss
of consciousness and stiffening of the body or extremities (tonic phase) followed
by jerky movements (clonic phase). The seizure may last 1 or 2 minutes and is often
associated with loss of control of the bladder or bowels. Patients look cyanotic
(blue), salivate profusely, and bite their tongues. In the period following the
seizure, the person may experience stupor, sleepiness, confusion, headache, and
muscle soreness.3
- Atonic seizures occur when the muscles suddenly
lose strength. The eyelids may droop, the head may nod, and the person may drop
things and often falls to the ground. These seizures are also called "drop attacks"
or "drop seizures." The person usually remains conscious and the seizures generally
last less than 15 seconds.4
Unclassified seizures
Some seizures do not easily fit into the abovementioned categories. These seizures
are referred to as unclassified. This group also includes those seizures with an
unclear nature.3
Infantile spasms
Infantile spasms are clusters of brief seizures appearing in the first year of life.
During these spasms, the child may suddenly bend forward, stiffen his or her body,
arms and legs, or arch his or her torso. A child may experience dozens of these
clusters of spasms each day. An individual spasm typically lasts for less than one
second, but may last up to 5 seconds. Infants may have dozens of clusters and several
hundred spasms per day.6
References:
- National Institute of Neurological Disorders and Stroke. NINDS Epilepsy Information
page. Available at: http://www.ninds.nih.gov/disorders/epilepsy/epilepsy.htm. Updated
July 2, 2008. Accessed July 14, 2008.
- Foldvary-Schaefer N, Wyllie E. Epilepsy. In: Goetz CG. Textbook
of Clinical Neurology. 3rd ed. Philadelphia, PA: WB Saunders; 2007.
- Sadler RM. Epilepsy and Seizures. In: Noble J, et al, eds.
Textbook of Primary Care Medicine. 3rd ed. St.Louis, MO: Mosby; 2001.
- Epilepsy.com. Available at: http://www.epilepsy.com. Accessed February 25, 2008.
- Aminoff MJ. Electrophysiology. In: Goetz CG. Textbook of Clinical
Neurology. 3rd ed. Philadelphia, PA: WB Saunders; 2007.
- National Institute of Neurological Disorders and Stroke. NINDS Infantile Spasms
Information Page. http://www.ninds.nih.gov/disorders/infantilespasms/infantilespasms.htm.
Last accessed 08/6/2009.