Introduction
Epilepsy is a neurological disorder that occurs due to abnormal electrical activity in parts of the brain characterized by seizures, unusual behavior, and sometimes even loss of awareness. Two or more seizure episodes without any known trigger and separated by a time interval of at least 24 hours constitute a diagnosis of epilepsy. Epilepsy is classified under two broad categories based on the areas of the brain involved. If seizures arise from one part of the brain, then it is called focal, whereas all the areas of the brain being involved make it generalized. Focal seizures may occur without an alteration in the state of consciousness (simple partial seizures) or involve loss of awareness (earlier known as complex partial seizures). Generalized seizures are further designated into six subtypes - absence; tonic; clonic; myoclonic; atonic and tonic-clonic seizures.
What Is Nocturnal Frontal Lobe Epilepsy (NFLE)?
It is a form of focal epilepsy resulting from a period of aberrant electrical activity in the frontal lobe of the brain. The frontal lobe is the largest of the four lobes of the brain and is responsible for various important functions such as an individual’s behavior and personality, thinking, learning and remembering (cognitive) abilities, speech, and movement. Hence in addition to seizures, frontal lobe epilepsy has the potential to cause changes in personality and sleep disturbances. It can also occur when one is awake, but more commonly happens when one is sleeping.
How Common Is NFLE?
It comprises about 20 % to 30% of all focal epilepsy cases. It may begin anytime between infancy and adulthood. Individuals with abnormal brain development or other developmental disorders are more susceptible.
What Causes NFLE?
Many cases of NFLE are due to a developmental disturbance in the brain. Sometimes the outermost layer of the brain, called the cortex, does not develop completely. It may also be caused due to brain infections, injury or trauma to brain tissue, and tumors or other lesions of the brain. Experiencing seizures in early childhood increases the chance of NFLE. It can also occur in conjunction with other developmental disabilities.
Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is an inherited form of NFLE that runs in families. A mutation in genes like CHRNA2, CHRNA4, or CHRNB2 can cause ADNFLE. These genetic abnormalities impede the normal uptake and release of neurotransmitters in the brain. It is a very rare condition.
What Are the Symptoms?
An episode of NFLE typically lasts from a few seconds to minutes (5 seconds to 5 minutes). It is preceded by an aura. The aura is characterized by a dizzy feeling like one is falling, tingling or numbness, and loss of balance. Some people also experience breathlessness or a choking sensation. It serves as a warning sign for an upcoming episode but may not be present in all cases. While some cases are triggered by fatigue or stress, there are no recognizable triggers in most individuals. Symptoms of NFLE include:
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Periodic arousal from sleep
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Turning the head or eyes to one side
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Alarming screams or laughter. Swearing is also common
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Kicking or pedaling with one’s legs
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Thrusting the pelvis.
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Urinary incontinence (urine is leaked/passed without one’s control)
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Sleep-walking could be a component of NFLE
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Thrusting or twitching movements
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Abnormal postures such as extension or flexion of arms; repetitive flinging or throwing actions
It is common to feel confused or groggy after an episode. When consciousness is retained during an episode, the individual may feel scared to fall asleep, fearing more seizures. Episodes decrease in frequency and intensity with increasing age. Episodes are more likely to occur during Stage 2 (light sleep) of the sleep cycle.
How Is It Diagnosed?
Diagnosis is based on personal history. It is important to evaluate family history since ADNFLE is inherited. The doctor may do neurological testing. Tests to assess an individual’s brain activity include:
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An MRI (magnetic resonance imaging) scan helps visualize the soft tissues of the brain. This can be used to check for the presence of abnormal lesions or tumors or any other damage in the brain.
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EEG (Electroencephalography) - It is a test that determines the site of origin of a seizure. It can be used to measure the electrical activity in the brain during a seizure (ictal) or in the time between two seizures (interictal).
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SEEG (Stereoelectroencephalography) - This is an advanced technique in which electrodes are surgically implanted into one’s brain. It is capable of detecting seizure activity deep in your brain, even in areas that are missed on an EEG.
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Video EEG - In this test, an individual’s behavior and movements are monitored alongside the electrical activity in the brain. Since NFLE mostly occurs at night, this test may require an overnight hospital stay when video EEG monitoring is done throughout one’s sleep.
When family history is positive, gene testing may be advised in cases of ADNFLE.
What Are the Possible Complications?
Complications can include:
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Physical injuries during the episode. One’s cheek or tongue may be injured due to the jerking movements. Bruises or cuts and even fractures may result from episodes depending upon one’s surroundings and objects around.
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Status epilepticus is a serious life-threatening emergency that may occur sometimes. It is characterized by seizures that last longer than five minutes or prolonged loss of consciousness between seizures. Immediate medical attention is necessary.
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Sudden unexplained death in epilepsy can occur. The cause of death is not understood. It is rare and occurs in about one in a thousand individuals with seizures.
What Is the Treatment for NFLE?
Treatment approaches for NFLE include:
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Medications - Pharmacological management is the first choice in treating NFLE. The drug carbamazepine is commonly prescribed; a combination of antiepileptic drugs may also be used. Drugs modulate the brain’s electrical activity and help decrease the frequency of episodes. However, carbamazepine is ineffective in about 30 % of NFLE cases. Alternate treatment strategies need to be adopted in such cases.
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Surgical Management - Cases unresponsive to medication are treated surgically. Preparation for surgery includes analyzing the brain to identify problematic areas and areas of important function.
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A technique called brain mapping uses electrodes implanted in the brain; with electrical stimulation in a particular area, it is determined if the area has an important function. Surgery is avoided in areas having important functions.
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Functional MRI is done to map the language area of the brain.
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Advanced imaging like SPECT (Single Photon Emission Computed Tomography) may also be used to pinpoint areas in which seizures originate.
Depending on the area of seizure activity, the following may be achieved through surgery:
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Removal of the Focal Point - When seizures consistently begin from the same spot, removing a small amount of brain tissue can stop the seizure activity.
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Isolation of the Focal Spot - If the point of origin is important functionally and has to be conserved, it is separated from the rest of the brain through small cuts to prevent the spreading of seizures into other brain areas
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Vagus Nerve Stimulation - An implanted device analogous to a cardiac pacemaker stimulates the vagus nerve and decreases episodes.
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Responsive Neurotransmitters may be implanted in the brain. This device is activated when a seizure begins and stops it.
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Deep Brain Stimulation is another method involving electrical stimulation of the brain by means of implanted electrodes.
Post-surgery anti-seizure drugs are prescribed. In addition, a ketogenic diet (high fat and low carbohydrate) is advised in epileptic individuals; it is associated with fewer seizures and is more effective in children.
Conclusion
Nocturnal Frontal Lobe Epilepsy is a form of seizure disorder mostly occurring at night during sleep. The seizures originate from the frontal lobes located behind the forehead. It can be successfully managed with medication. Surgery is advised when medication is not effective.
