Seizure disorders are a set of neurologic conditions characterized by spontaneous firing of neurons in the cerebral cortex, which may lead to impaired consciousness, convulsions, and other neurologic deficits. Some patients have a genetic predisposition to developing seizures and have recurrent seizure activity – this condition is termed epilepsy. A subset of patients with seizure disorders develop seizures due to other conditions – such as stroke, meningitis, brain tumor, traumatic brain injury, electrolyte abnormalities, and low glucose.
Severe seizures or tonic-clonic seizures (previously referred to as grand-mal) are potentially life threatening – this is especially true in a condition called status epilepticus where seizure activity continues for a prolonged period of time. Long-lasting or repeated seizures in a short time period can lead to cumulative brain injury.
Epilepsy is generally caused by genetic and developmental factors in younger patients and by damage to the structure of the brain in older patients. There are also several metabolic changes that can result in more short lived seizure disorders that have the same symptoms as epilepsy. Some of the most common causes of seizures and seizure disorders such as epilepsy are:
- Meningitis or encephalitis – brain infection
- Traumatic brain injury
- High fever – temp >101
- Electrolyte abnormalities – elevated or low potassium, calcium, sodium, or magnesium
- Alcohol withdrawal
- Cocaine or amphetamine intoxication
- Certain medications can lower seizure threshold
These factors increase the number of signals produced by the neurons located in the cerebral cortex. If this exceeds a certain threshold it can lead to uncontrolled and continuous firing which triggers a seizure. This may occur on one side of the brain or both sides of the brain simultaneously. Seizure starting on one side of the brain and remaining there is called partial seizure. Seizures starting in both sides of the brain are called generalized seizures. Seizures accompanied by preserved consciousness are called simple, whereas those associated with loss of consciousness are called complex. Those that start in both hemispheres at onset tend to be associated with loss of consciousness (generalized complex seizure) – these are usually the most obvious seizures, the tonic-clonic seizures.
The terminology of seizure disorder continues to evolve and recently new changes were implemented; however, neurologists and neuroscientists still frequently use traditional terminology in practice.
It is difficult to determine the exact prevalence of epilepsy. There are many seizure disorders that mimic epilepsy, some that cannot be diagnosed without complex genetic and medical testing.
It is far easier to estimate the prevalence of seizure disorders as a whole. In the United States 8% – 10% of people experience a seizure disorder during their lifetime. Approximately 1.2% of people are thought to have seizures due to epilepsy in the U.S. based on CDC estimates.
While seizure disorders have a variety of presentations, the classic presentation of epilepsy is a tonic-clonic seizure. The most common findings in a tonic-clonic seizure are:
- Postictal confusion (recovery period following “black out”)
- Tongue biting
- Urinary or bowel incontinence
- Loss of consciousness
- Sensory loss
- Muscle weakness
- Myoclonus or muscle jerking
An epipeptic seizure generally begins with the sudden loss of consciousness and convulsions. Periods of muscle stiffness alternate with rhythmic shaking and occur for the duration of the seizure. These symptoms on average last for seconds to 2-3 minutes. In severe cases the seizure may continue longer than 5 minutes which is a medical emergency.
These prolonged seizures are known as status epilepticus. Prolonged seizures can result in brain injury as well as hypoxia (low oxygen levels). Patients may also aspirate vomitus or food in the mouth. Death is a rare complication of seizure and is far more common with status epilepticus.
The diagnosis of epilepsy is based on the history of seizures, the timing of when they occur, the age of the patient, and the presence or absence of any other medical conditions that can lead to seizure.
The diagnosis of epilepsy requires your physician to rule out other conditions that can lead to seizures. Your doctor will typically order neuroimaging with a head CT or brain MRI to evaluate for structural diseases such as tumor or stroke. If you have signs of meningitis – fever, still neck, headache – your doctor may perform a lumbar puncture (spinal tap). Your neurologist will usually obtain an electroencephalogram (EEG) to monitor your brain waves – occasionally they will capture a seizure as it is happening. The absence of epileptiform activity on an EEG does not mean a seizure disorder does not exist.
Other commonly ordered blood tests include a CMP (comprehensive metabolic panel), CBC (complete blood cell count), creatine phosphokinase (CPK), and thyroid function tests (TSH, free T4). Your doctor may also obtain a urinalysis and urine drug screen. Women who are of childbearing age may also be tested with a urine pregnancy screen.
Seizure disorders including epilepsy are treated with anticonvulsant medications – these are generally categorized as broad-spectrum or narrow-spectrum. Broad-spectrum anticonvulsants successfully treat most seizure types (e.g., focal or generalized at onset) and typically include:
- Lamictal (lamotrigine)
- Keppra (levetiracetam)
- Topamax (topiramate)
- Depakote (valproic acid)
In contrast, narrow-spectrum anticonvulsants are generally favored for focal-onset seizures. The most commonly prescribed narrow-spectrum agents include:
- Tegretol (carbamazepine)
- Neurontin (gabapentin)
- Luminal (phenobarbital)
- Dilantin (phenytoin)
These agents are used to treat specific forms of epilepsy. Absence-seizures are one of the most common. These are most common in school aged children and result in a loss of consciousness without shaking, collapse, or any other classic signs of seizure. The only symptoms are a lack of memory regarding the time of the seizure, a lack of responsiveness during a seizure, and occasionally repetitive movements of the jaw or face. This form of seizure is usually detected by teachers in school age children.
- Huff JS, Morris DL, Kothari RU, et al. Emergency department management of patients with seizures: a multicenter study. Acad Emerg Med 2001; 8:622. – https://www.ncbi.nlm.nih.gov/pubmed/11388937
- Brodie MJ, Perucca E, Ryvlin P, et al. Comparison of levetiracetam and controlled-release carbamazepine in newly diagnosed epilepsy. Neurology 2007; 68:402. – https://www.ncbi.nlm.nih.gov/pubmed/17283312
- Bonnett LJ, Tudur Smith C, Donegan S, Marson AG. Treatment outcome after failure of a first antiepileptic drug. Neurology 2014; 83:552. – https://www.ncbi.nlm.nih.gov/pubmed/24994842