Temporal lobe epilepsy, or TLE, is the most common type of focal epilepsy. Focal epilepsy, also called partial epilepsy, refers to seizure activity that only affects one side of the brain.
There are two types of TLE: mesial (or middle) TLE and neocortical (or lateral) TLE. These two types of seizures are named based on the area of the temporal lobe they begin in.
We currently refer to TLE as focal epilepsy with either intact or impaired awareness. Previously, these seizures were known by a lot of names, including psychomotor seizures, limbic seizures, complex partial seizures, and simple partial seizures. Regardless of the name, being familiar with the symptoms, causes, and treatments associated with TLE is an important step toward understanding your or your loved one’s diagnosis.
There isn’t a lot of information about how many people have TLE. One study from 1975 estimated that there are approximately 1 or 2 cases of TLE per 1,000 people. The same study estimated the overall number of epilepsy cases to be 6 to 7 people out of 1,000. According to the Epilepsy Foundation, roughly 6 out of 10 individuals with focal epilepsy have TLE.
All temporal lobe seizures start, as the name suggests, in the temporal lobe. The temporal lobe is one of the four major lobes of the brain. It sits just behind the ear (or temple). This part of the brain is responsible for processing auditory information, understanding speech and language, processing emotions, and encoding memories.
Mesial TLE seizures start in the internal structures of the temporal lobe, usually in the hippocampus or amygdala. Neocortical TLE seizures start in the outer part of the temporal lobe. These localized (focal) seizures are usually one of two types: focal onset aware seizures or focal onset impaired awareness seizures.
Besides seizures, other symptoms of TLE include impairments in attention, comprehension, and memory, as well as changes in mood and personality. Depression can also be a common symptom of TLE.
Focal onset aware seizures used to be called simple partial seizures. During these seizures, the person is conscious and typically knows that something is happening. Some people report feeling “frozen” during a focal onset aware seizure. These seizures can also act as auras — warning signs that another seizure is about to happen.
When a focal aware seizure starts in the temporal lobe, the symptoms may include a feeling in the stomach that has been described as a “rising” sensation, deja vu, unusual smells or tastes, or a sudden (and intense) emotion, such as fear or joy.
Focal onset impaired awareness seizures used to be referred to as complex partial seizures. During this type of seizure, a person’s consciousness is affected, and they don’t interact with people or things around them as they normally would. These types of seizures typically last from 30 seconds to two minutes.
If the seizure activity spreads to other parts of the brain, a focal seizure can turn into a generalized seizure with whole-body (tonic-clonic) jerking.
While the cause of many cases of TLE is unknown, there are some known risk factors. Brain injuries (such as head trauma), infections of the central nervous system, or abnormalities of temporal lobe structures can cause this type of epilepsy. This includes a type of scarring in the temporal lobe called mesial temporal sclerosis, or hippocampal sclerosis.
There may also be a genetic basis or predisposition to TLE in some people. There is only one gene that has been repeatedly shown to have an association with TLE — the LGI1 gene. This gene tells the brain how to make a protein called leucine-rich glioma inactivated 1, or epitempin. This protein plays a critical role in the regulation of the potassium channels that help control cell-to-cell communication in the brain. Future research may shed light on other underlying genetic factors.
Diagnosing TLE generally starts with a visit to a neurologist. The doctor will likely take a thorough medical history and perform a physical exam. They will want to hear a detailed account of what happened during any seizures the person has experienced. Blood tests may also be done to look for markers of infection.
Electroencephalogram (EEG) recordings of electrical activity within the brain are a critical component of an epilepsy diagnosis. A neurologist will also likely use CT scans, MRIs, or single-photon emission computerized tomography imaging to see if there is a structural problem in the brain that may be causing the seizures, such as scarring of temporal lobe structures (including hippocampal sclerosis).
Diagnosis is confirmed by capturing a typical episode of seizure activity in the temporal lobe region during an EEG.
TLE can be treated in several ways. These methods include anti-seizure (antiepileptic) medications, surgery, dietary therapy, and neuromodulatory devices. TLE can be difficult to treat and may often require more than one treatment approach.
Anti-seizure medications are effective in some people for the treatment of TLE. Some options include:
If one drug fails, often two medications that work differently can have more of a therapeutic effect. Unfortunately, these drugs are not without side effects. Common side effects include dizziness, nausea, headache, vomiting, fatigue, vertigo, ataxia (altered balance), blurred vision, and tremor.
Surgery may be an option for some individuals with TLE. In cases of focal epilepsy, surgery involves removing the part of the brain where the seizures are happening. When combined with antiepileptic drugs, this can be a very effective option. Surgery is also a good option for people with TLE who are resistant to drug therapy. Also, research shows that when the surgery is done earlier in life, clinical outcomes are better.
Vagus nerve stimulation is another treatment option for TLE. This technique involves the use of a device that electrically stimulates a part of the nervous system called the vagus nerve. The device is implanted under the skin in the chest, with a wire connecting it to the vagus nerve. The wire sends pulses of electricity to the vagus nerve, which then travel up to the brain. These constant pulses can dampen seizure activity. Research shows that this is an effective treatment option for many people with TLE who do not respond to medication alone.
Responsive neurostimulation, otherwise known as RNS therapy, works for epilepsy similar to how a pacemaker works for the heart. The RNS device is implanted into the skull, and electrodes are placed into the part of the brain where seizures start. The device monitors brain waves and sends electrical pulses to interrupt activity that looks like a seizure. This type of therapy causes no pain and can help people who have TLE, especially epilepsy that is resistant to drug treatment. One study showed that RNS therapy decreased seizures by 75 percent after nine years of treatment.
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