The idiopathic epilepsy or primary is a predominantly genetic type of epilepsy in which seizures occur, but no neurological alterations or structural lesions are observed in the brain.
Epilepsy is a neurological disease characterized by episodes of strong increases in neuronal arousal. These produce the seizures, also known as epileptic seizures. During these attacks, patients may experience seizures, confusion, and altered consciousness..
Epilepsy is the most common neurological disease. In developed countries its prevalence is approximately 0.2%, while in developing countries its frequency is even higher..
According to the World Health Organization, idiopathic epilepsy is the most common type of epilepsy, affecting 60% of epileptic patients. The characteristic of this condition is that it does not have an identifiable cause, unlike secondary or symptomatic epilepsy.
However, in the child population it seems that it constitutes 30% of all childhood epilepsies, although the percentage varies according to the researchers.
The epileptic syndromes that are part of idiopathic epilepsy are genetically inherited epilepsies involving several different genes, and which are currently not defined in detail. Also included are rare epilepsies involving a single gene and epilepsy is the sole or predominant feature..
Since the exact cause is not yet known, idiopathic epilepsy cannot be prevented. However, it appears that many cases resolve themselves. Thus, epileptic seizures manifest in childhood, but then disappear as they develop.
For its treatment, antiepileptic drugs are usually chosen.
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There are two main types of idiopathic epilepsy, generalized and focused or partial. The main difference between them is the type of seizure.
In the generalized one, the alterations in the cerebral electrical activity occupy all the brain; while in focal the altered activity is concentrated in a certain area (at least most of the time).
However, it should be noted that this distinction is physiologically relative. This is because some of the idiopathic epilepsies considered focal may have generalized physiological changes, but it is difficult to determine.
Generalized idiopathic epilepsy is the one that appears most frequently in the literature, since it seems to be the most common form of this type of epilepsy. This type represents about 40% of all forms of epilepsy up to the age of 40..
There is often a family history of associated epilepsy and it tends to appear during childhood or adolescence.
On an EEG (a test that measures electrical impulses in the brain), these patients may have epileptic discharges that affect multiple areas of the brain..
Patients with this condition can develop different subtypes of generalized seizures. For example, generalized tonic-clonic seizures (this can be subdivided into "random grand mal" or "waking grand mal"), infantile absences, juvenile absences, or juvenile myoclonic epilepsy.
It is also called benign focal epilepsy. The most common focused idiopathic epilepsy is benign partial epilepsy with centro-temporal spikes. It is also known as rolandic epilepsy, since, when examining these patients through the electroencephalogram, paroxysms associated with an area of the brain called the Rolando fissure are observed..
On the other hand, there are a number of rare partial idiopathic epilepsies and syndromes that have genetic causes..
The exact mechanism by which this type of epilepsy develops is not exactly known, but everything seems to indicate that its causes are genetic.
This does not mean that idiopathic epilepsy is inherited per se, but that perhaps what is inherited is a predisposition or susceptibility to developing it. This predisposition can be inherited from one or both parents, and occurs due to some genetic modification before the affected person is born..
This genetic tendency to suffer from epilepsy may be associated with the existence of a low seizure threshold. This threshold is part of our genetic makeup and can be transmitted from parents to children, and it is our individual level of resistance to epileptic seizures or electrical imbalances of the brain..
Anyone has the potential for seizures, although some individuals are more prone than others. People with low seizure thresholds are more likely to start having seizures than others with higher thresholds.
However, it is important to note here that having seizures does not necessarily mean the existence of epilepsy..
A possible genetic locus for juvenile myoclonic epilepsy (a subtype of idiopathic epilepsy) would be 6p21.2 in the EJM1 gene, 8q24 for idiopathic generalized epilepsy; and in benign neonatal seizures, 20q13.2 in the EBN1 gene.
In a study at the University of Cologne in Germany, they describe a relationship between idiopathic epilepsy and a deletion in a region of chromosome 15. This region seems to be related to a wide variety of neurological conditions such as autism, schizophrenia and mental retardation, being idiopathic epilepsy generalized the most common. One of the genes involved is CHRNA7, which appears to be involved in the regulation of neuronal synapses..
Idiopathic epilepsy, like many types of epilepsy, is associated with somewhat unusual EEG activity and the sudden onset of epileptic seizures. There are no motor sequelae, neither of cognitive abilities or intelligence. In fact, many cases of idiopathic epilepsy remit spontaneously.
During seizures, different types of seizures can occur in patients with idiopathic epilepsy:
- Myoclonic crisis: are sudden, of very short duration and are characterized by jerking of the extremities.
- Absence crisis: they are distinguished by loss of consciousness, fixed gaze and lack of response to stimuli.
- Tonic-clonic crisis (or great evil): it is characterized by a sudden loss of consciousness, body rigidity (tonic phase) and then rhythmic jerks (clonic phase). The lips turn bluish, there may be biting of the inside of the mouth and tongue, and urinary incontinence.
However, the symptoms vary slightly depending on the exact syndrome we are talking about. The following section describes in more detail.
There is a wide variety of epileptic conditions that fall into the category of idiopathic epilepsy. To better describe each one, the syndromes have been classified according to whether they are generalized or partial..
All tend to have in common the absence of neuro-psychic disorders, frequent family history of febrile seizures and / or epilepsy. In addition to electroencephalography (EEG) with normal baseline activity, but with bilateral spike-wave complexes (POCs).
It is a condition that appears between the age of 3 and puberty. It is noted for daily crises that begin and end abruptly, in which there is a brief alteration of consciousness. Electroencephalogram reflects rapid generalized spike-wave discharges.
Absence epilepsy usually disappears spontaneously and in 80% of cases it is treated effectively with antiepileptic drugs.
It can also appear between the ages of 10 and 17, and is called juvenile absences epilepsy. Nieto Barrera, Fernández Mensaque and Nieto Jiménez (2008) indicate that 11.5% of the cases have a family history of epilepsy. Seizures arise more easily with if the patient sleeps less than they should or with hyperventilation.
Also called Janz disease (JME), it constitutes between 5 and 10% of all epilepsies. Its course is usually benign, without affecting mental abilities.
It is characterized by sudden jerks that can affect the upper limbs predominantly, but also the lower ones. They do not usually affect the face. They often occur upon awakening, although sleep deprivation and alcohol use also facilitate it..
It affects both sexes and appears between the ages of 8 and 26. As it is repeated in families in 25% of cases, this condition seems to be associated with genetic factors. Specifically, it has been linked to a marker located on chromosome 6p.
Also called “epilepsy with generalized tonic-clonic seizures”, it is predominantly male and begins between the ages of 9 and 18. 15% of these patients have a clear family history of epilepsy.
Their seizures last approximately 30 to 60 seconds. They begin with stiffness, then clonic jerks of all limbs, accompanied by irregular breathing, and guttural noises. The affected person can bite the tongue or the inside of the mouth during this period, and even lose control of the sphincters.
Fortunately, attacks are not very common, with sleep deprivation, stress and alcohol being the risk factors.
These syndromes have in common that they are genetically determined, the absence of neurological and psychological alterations; and a good evolution. Symptoms, seizure frequencies, and EEG abnormalities are highly variable.
It is characterized by appearing exclusively in second childhood (between 3 and 12 years old), in the absence of brain lesions of any kind. Seizures partially affect the brain in 75% of cases, and often occur during sleep (when falling asleep, in the middle of the night, and upon waking). These attacks mainly affect the orofacial motor region. However, these crises do not recur after the age of 12.
Its main cause is a certain hereditary predisposition. Most of the parents and / or siblings of these children have had epileptic seizures in childhood.
It appears between the ages of 8 and 17 in children with a family history of febrile seizures. Seizures usually present with rotation of the head and eyes to one side.
It is also usually accompanied by a sudden turn of the whole body of at least 180 degrees, and there may or may not be a loss of consciousness. These patients usually respond well to antiepileptic drugs.
Seizures usually appear during the day, and begin around 12 years of age. They are usually partial (affecting specific areas of the brain) and symptoms vary according to the active areas of the brain.
The age of onset ranges between 4 and 50 years, but usually appears in adolescence or early adulthood. It is associated with a molecular marker on chromosome 10q22-24.
Its name is due to the fact that its main manifestations are auditory symptoms. That is, the patient hears poorly defined noises, buzzing, or ringing. In some people there are distortions such as volume changes, complex sounds (they hear specific voices or songs).
Sometimes it is accompanied by ictal receptive aphasia, that is, a sudden inability to understand language. Interestingly, some attacks appear after hearing a sound, such as a telephone ringing. Its course is benign and responds well to medication (Ottman, 2007).
This type is more frequent in women, and appears for the first time at 12 years of age. It is linked to a mutation in 20q13.2 and the seizures are distinguished by sensations of suffocation, epigastric discomfort, fear, and repetitive and disorganized movements of the extremities at night.
It begins between the ages of 10 and 30 and has an autosomal dominant inheritance. Associate with certain locations on chromosomes 4q, 18q, 1q, and 12q.
The seizures are accompanied by a sensation of "deja vu", fear, visual, auditory, and / or olfactory hallucinations..
As mentioned, many of the idiopathic epileptic syndromes are benign. That is, they resolve on their own at a certain age. However, in other conditions the patient may need to take antiepileptic medication for life..
Adequate rest, limiting alcohol consumption, and dealing with stress are important; since these factors easily trigger epileptic seizures. The most common in these cases is to use antiepileptic drugs, which are usually very effective in controlling the attacks..
For epilepsy that is generalized throughout the electrical activity of the brain, valproate is used. According to Nieto, Fernández and Nieto (2008); in women it tends to be switched to lamotrigine.
On the other hand, if the epilepsy is focal idiopathic, it is recommended to wait for the second or third seizure. To adapt the treatment to its frequency, schedule, characteristics, or repercussions. The most commonly used drugs are carbamazepine, oxcarbazepine, lamotrigine, as well as valproate..
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