A seizure is an episode of chaotic, disorderly electrical activity involving part or all of the brain. It is most often seen in epilepsy, but seizure can also occur acutely due to hypoglycemia, eclampsia, stroke, head trauma, alcohol withdrawal, and other causes.
Seizures are typically divided into two major types, partial seizures which involve only a portion of the brain, and generalized seizures which involve the entire brain.
Partial seizures are further divided into simple partial and complex partial seizures. In a simple partial seizure, consciousness is maintained, but unusual sensory, motor, or emotional sensations are observed — muscular tics, visual disturbances, strange feelings, and more are all possible depending on the area of the brain affected. Most often, this will then proceed into a larger seizure, in which case these early effects are called an aura, and used as a warning sign. Complex partial seizures are similar, but involve both hemispheres of the brain, and are distinguished by a loss of awareness or memory — the individual’s consciousness is impaired during the episode. This is the most common form of seizure.
The best known generalized seizures are tonic-clonic seizures, known historically (and still called by many laymen) “grand mal” seizures. They are characterized by two phases: a tonic phase, where the body becomes rigid and immobile, followed by a clonic phase, where full-body involuntary muscular jerking occurs. This is usually followed by a post-ictal period, where the patient may be unresponsive, or behave unusually, appearing combative, stuporous, or otherwise impaired. Either the tonic or clonic phase may be minimal or absent.
Absence seizures, historically “petit mal,” are characterized by a loss of awareness with a lack of outward activity. The individual may simply stare without moving or speaking, and after cessation of the seizure resume where he left off with no memory of the episode. Absence seizures may also present with some outward seizure activity, in which case the distinction between types becomes blurred.
Febrile seizures are seizures caused by elevated temperature (usually >100 degrees), most often seen in infants and young children. They are typically tonic-clonic in nature and almost always have benign outcomes; they rarely go on to develop into adult epilepsy.
Status epilepticus describes a prolonged seizure state, customarily defined as a seizure lasting over 30 minutes or multiple seizures without a full recovery in between. Some authorities draw the line at any seizure over 10 minutes, and there is evidence that even seizures longer than 5 minutes are unlikely to end without medical intervention. Status epilepticus is a true life-threatening emergency with high mortality; the continued chaotic activity of the brain can lead to permanent brain damage or death. Definitive treatment is the use of anti-convulsants, which attenuate the neuronal activity; in the field these are typically benzodiazepines like lorazepam (Ativan), diazepam (Valium), or midazolam (Versed). Since the duration from 911 call to EMS arrival on scene is often greater than 5-10 minutes, a seizure that is still ongoing upon your arrival should raise immediate suspicion of status epilepticus; a careful history should be obtained from bystanders when possible, including time since onset and any intervening recovery.
In some cases, seizures will be followed by a persistent, unilateral focal weakness in muscles that were active during the seizure. This is called Todd’s paresis, and since it can closely mimic the signs of stroke (even impairing eyesight or speech), it is wise to ask about recent seizure activity in patients with a history of a seizure disorder who present with signs of stroke.
Field care for seizure generally involves preventing secondary injury, such as blunt trauma caused by hitting or landing on nearby objects. During the tonic phase, respirations may be minimal, resulting in cyanosis; this is usually brief enough not to cause harm. The greatest concern is to maintain an open airway and prevent aspiration; when possible the patient should be placed in the lateral recovery position to help prevent soft tissue obstruction and allow fluids to drain away. Suction may be valuable, and an NPA may be considered in prolonged episodes. Supplemental oxygen is always appropriate, although a non-rebreather mask may not be tolerated in the post-ictal period. If respiration appears inadequate in prolonged seizures, positive pressure ventilation (by BVM or invasive airway) may be attempted.
This video from Dr. Robert S. Fisher is an excellent summary of the basic types of seizure. (Here is another on partial seizures; these are unusually good educational videos for a free resource.)
Here is an example of a simple partial seizure in a child, in this case manifesting as a repetitive facial tic. Note that the child retains consciousness throughout.
Here is an example of a complex partial seizure, also in a child. Note the repetitive, aimless movements of the arm and head, which are known as automatisms and are wholly involuntary; if spoken to, she would not respond.
Another complex partial seizure, in a young adult. Note the automatisms of the mouth and the wandering posturing of the arm.
An absence seizure in a child. Note the lack of any outward signs, except a total lack of responsiveness.
An excellent video of a tonic-clonic seizure in an adult. Note the labored breathing and obvious altered level of consciousness post-ictally.
Another good tonic-clonic in an adult. You see his awareness of its onset due to an aura, followed by gradual tonicity and then clonic jerks. Also note the snoring respirations; better positioning (and the suction catheter that the nurse couldn’t find) would have helped here.
Tonic-clonic in an infant, this one of febrile etiology.
Tonic-clonic in a sleeping adult; skip to 1:00 if you see better with lights.