Epilepsy (also called seizure disorder) is one of the most common neurological diseases in the world. It is not just a single condition; it is a group of conditions with different causes and treatments. Someone with epilepsy has the tendency to have epileptic seizures.
What are seizures?
Seizures are sudden bursts of electrical activity in the brain that temporarily disrupts how it works. So the brain’s messages become mixed up. Seizures are sometimes referred to as convulsions. Convulsions, however, are just a type of seizure. Not all seizures manifest as convulsions.
Seizures and epilepsy are not the same. A person may have seizures without having epilepsy. Every person who has epilepsy will have seizures but not everyone who has a seizure is epileptic. I hope you are not confused yet. Please read on for further clarifications.
Someone might have a seizure for example due to low blood sugar level ( hypoglycemia),very high blood sugar ( hyperglycaemia) or electrolyte imbalances like low sodium in the blood (hyponatraemia),low calcium in the blood (hypocalcaemia) and low chloride in the blood (hypochloraemia).
When these derangements are corrected, the person would stop having seizures. This individual is said to have had an ‘acute symptomatic seizure’ because the seizure was a symptom of an acute problem. Seizure is a symptom of epilepsy (and some other diseases), just as fever is a symptom of malaria, pneumonia and many other diseases.
There are factors that can provoke seizures in individuals who do not have epilepsy. These include drug overdose or sudden withdrawal from use of certain addictive substances. Factors that can provoke seizures are listed below. These are also seizure triggers in people with epilepsy. Note that this is by no means an exhaustive list.
Factors that provoke seizures in the general population.
- Drugs eg opioids
- Traumatic brain injury
- Electrolyte derangements (hyponatraemia, hypernatremia, hypochloraemia)
- Brain infections eg Meningitis/encephalitis
- Brain tumours
- Liver failure
- Kidney failure
How do seizures occur
The brain is made up a lot of nerve cells (neurones). These nerve cells communicate with each other through electrical signals. Seizures occur when there is a sudden burst of electrical activity in the brain that temporarily disrupts how it works. So, the brain’s messages become mixed up.
Symptoms of epilepsy
Seizure is one of the main symptoms of epilepsy.
Causes of epilepsy
Aetiologic classification of epilepsy is basically divided into six groups:
- Infectious causes -that is Brain infections
- Structural causes
- Immune-mediated causes
- Genetic causes
- Metabolic causes
Identification of aetiology is essential for appropriate counselling and treatment decision. The aetiology may be classified as unknown in resource poor settings even though a cause actually exists.
These are among the most common and include :
- Bacterial meningitis,
- Viral encephalitis, neurocysticercosis,
- Human immunodeficiency virus (HIV),
- Cytomegalovirus (CMV),
- Zika virus,
- Fungal infections – histoplasmosis, coccidioidomycosis
- Cerebral toxoplasmosis and
- Cerebral tuberculosis
These are from any event that changes the structure of the brain, be it in utero(eg maternal infections), during delivery, at birth or anytime between infancy and adulthood. These include
- Malformations of brain development such as focal cortical dysplasia;
- Trauma to the head that leaves a scar in the brain
- Brain tumour.
These may be due to the presence of a known mutation or an epilepsy syndrome. Some may be inherited in an autosomal dominant fashion, that is the type that “runs in families”.
Genetic cause includes:
- Genetic generalized epilepsy
- Autosomal dominant familial epilepsy, such as:
- Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE),
- Autosomal Dominant temporal lobe epilepsy (ADTLE),
- Familial focal epilepsy with variable foci (FFEVF).
- Epileptic encephalopathies eg Dravet syndrome, West syndrome, Lennox-Gastaut syndrome
- Progressive myoclonic epilepsy
These may overlap with genetic causes. These include
- Wilson disease
- Mitochondria disorders
- Niemann-Pick disease,
- Gaucher disease type III,
- Ceroid lipofuscinosis
These result from the body producing cells (called antibodies) that fight against the normal cells in the body. That is, the immune system fails to recognize self as such and begins to destroy normal body cells because it perceives them as foreign. Simply put, there is a loss of immune “tolerance”. Think of it as a war where the members of a particular group do not recognize some of their members hence they destroy both members and opponents.
- Anti-N-Methyl-D-aspartate (anti-NMDA) receptor encephalitis,
- Anti-leucine rich glioma inactivated 1 (anti-LG1) encephalitis,
- Anti-voltage gated potassium channel (anti VGKC) encephalitis
- Anti-glutamic acid decarboxylase 65 (anti-GAD65) encephalitis
Epilepsy aetiology is unknown in up to one-third of people with epilepsy. A cause may not be detected if there is limited access to appropriate brain imaging, immune antibody testing and genetic testing.