Medical Conditions Related to Brain Injury: Seizures
Understanding Seizures
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Sometimes referred to as electrical storms, seizures result from abnormal electrical activity in the brain. Instead of discharging a controlled electrical energy, the brain cells fire excessively. Certain stimuli, or triggers, provoke this malfunction in individuals with low seizure thresholds. Common triggers include exposure to flashing lights, missed medication, poor nutrition, sleep deprivation, hyperventilation, emotional stress, fever, drug or alcohol toxicity, or a blow to the head.
Approximately 10 percent of Americans will experience a single seizure episode during their lifetime, and about 3 percent of these people will experience recurring seizures. When seizures recur over an extended period, a person is thought to have a seizure disorder, or low seizure threshold, and is diagnosed with epilepsy.
For seven out of ten people with epilepsy, a cause will not be found. In children, the disorder may be attributed to developmental defects, birth injuries, lead poisoning, or metabolic disease. Among the elderly, brain tumors or cerebrovascular disease are underlying conditions usually responsible for seizure activity. Survivors of traumatic brain injury may experience seizures as a complication of their injury. Similar to other causes of epilepsy, the head injury is thought to disrupt the pathways of the brain, resulting in what could be viewed as a short circuit of the brain's electrical functioning. As the brain heals, seizure activity may dissipate, but in some cases it persists, and the TBI survivor is diagnosed with epilepsy.
Types of Seizures
There are a number of types of seizures, all of which fall into one of two categories, generalized or partial. Generalized seizures, also called local seizures, cause an immediate loss of consciousness and motor function reflecting the diffuse discharge that radiates throughout the brain. In partial seizures, the surplus discharge is contained in one specific area of the brain. Partial seizures are sometimes referred to as focal seizures, and the area of the brain generating the seizure is called the focus. Determining the type of seizure is important for purposes of treatment and prognosis.
Generalized Tonic-Clonic Seizures
Commonly known as grand mal seizures, primary generalized tonic-clonic seizures are characterized by convulsions that are preceded by a loss of consciousness. The initial tonic phase consists of a 15 to 20 second period of muscle rigidity and is followed by a clonic period of violent, rhythmic convulsions lasting approximately two minute. During the seizure, a person may lose bladder and bowel control, and appear bluish due to impaired breathing. After the seizure, he or she will experience a headache accompanied by drowsiness and confusion.
Petite Mal Seizures
Petite mal seizures, also known as absence attacks or primary generalized seizures, occur almost exclusively in children and people under the age of twenty. They are experienced as an abrupt interruption of consciousness during which time the child appears to "zone-out". Episodes are of short duration where the child continues in the activity he or she was doing, although his or her actions have lost intention. Engaging the child is not possible during the seizure, and once it has passed, the child is unaware of a lapse having occurred. In their subtlety, petite mal seizures can be overlooked or mistaken in the classroom as learning or behavioral difficulties.
Atonic Seizures
A brief but complete loss of muscle tone and consciousness reflect the primary generalized seizure known as an atonic seizure. Like petite mal seizures, atonic episodes are a phenomenon of childhood with most children outgrowing them by late adolescence.
Myoclonic Seizures
The age of onset for generalized myocolonic seizures is between 12 and 18 years old, and half the individuals affected by them will experience episodes throughout their life. The seizures are marked by lightening-fast jerks of a limb or limbs, as well as absence episodes that can mimic petit mal seizures. Sleep deprivation provokes their occurrence, with repetitively episodes leading to tonic-clonic seizures without loss of consciousness.
Complex Partial Seizures
Complex partial seizures are classified as "partial" because the electrical misfiring is contained within the temporal lobe of the brain, and yet they are considered "complex" because consciousness is impaired by the episode. A warning, or aura, precedes these events. It may take the form of a hallucinatory sound, smell, taste, or visual disturbance. Awareness then diminishes, and as though a switch were flipped, the affected person appears to operate on "automatic pilot". The seizure may include repetitive, non purposeful acts like lip smacking, swallowing, picking at things, or garbled, random speech. Amnesia withholds the period of the seizure and possibly the events preceding and following it from one’s memory.
In some people, complex partial seizures can lead to convulsions as the electrical activity spreads from the temporal lobe and travels through the brain. When tonic-clonic seizures follow complex partial seizures, they are classified as secondary generalized seizures, a distinction that denotes a different mechanism as the source of the disturbance.
Simple Partial Seizures
Simple partial seizures arise as a complication of stroke, hemorrhage, or brain tumor. The resulting electrical discharge is contained in one part of the brain and does not alter consciousness. Brief rhythmic cycles of face twitching, accompanied by jerking movements of a hand, arm or leg suggest a simple partial seizure. Episodes last for a few minutes, but have been known to persist for hours and even days. In some individuals, a simple partial seizure signals the onset of a generalized or convulsive event.
Diagnosing Seizure Activity
Determining the type of seizure affecting a person is integral to determining a course of treatment. A medical history exploring trends within the family, possible infections, head trauma, or toxic exposures will be asked of the patient; and his or her family may be recruited to keep a journal, recording the seizures’ traits, durations, and intervals between episodes, as well as the circumstances in which seizures have occurred. Was the person awake, standing, or lying down? Was he or she hungry, tired, or stressed? Providing a physician with details such as these are the first steps to making a diagnosis, and from the information gathered, any or all of the following tests might be performed.
- Electroencephalography (EEG). This procedure measures the electrical activity in the brain. Small electrodes are attached to the scalp with paste. These pick up the brain’s electrical impulses and send them to the EEG machine, which records the brain waves on a computer where they can be assessed by a doctor. The patient will be asked to lie still. At times, a light may flash and the patient may be asked to breathe deeply and steadily for several minutes or to stare at a patterned board. These actions are meant to stimulate brain activity to provide a comprehensive examination.
- Blood chemistry. Blood tests are used to diagnose and manage a vast number of conditions. While they may rule out some causes of seizures, they can also reveal a chemical imbalance, the presence of toxic substances, or infection.
- Magnetic resonance imaging (MRI) or computerized tomography (CT) scan. In some cases, images taken of the brain help to determine the source and location of the seizure-producing disorder.
Treatment for Seizures
If the underlying cause of seizures is identified, treating the condition usually stops their occurrence. Treatment may include antibiotics to eradicate infection or surgery to remove a brain lesion. For some people, however, epilepsy is a lifelong condition. Anti-seizure medications help to control or limit the number of seizures in most people. The type of medicine prescribed will depend on the type of seizure diagnosed. More than twenty medications are available to treat seizures. In the event that seizures are unresponsive to medication, surgery to remove the seizure focus, those brain cells responsible for misfiring, may be recommended. Another popular therapy found to benefit refractory epilepsy is vagus nerve stimulation (VNS).
Adopting proactive behaviors that ensure a healthy diet, proper water intake, regular rest and adequate sleep, along with the avoidance of alcohol, caffeine, and stimulants have been shown to reduce one's tendency for seizures and are always advisable.
Content for this article has been provided by the Brain Injury Resource Foundation Board of Physicians.