Pathogenesis and Neurotransmitter Imbalance
Clinical manifestations of the disease directly depend on the precise localization of the activity focus. Patients may experience motor disturbances (classical convulsions), autonomic disorders, or psychiatric changes. Pharmacological antieptic treatments serve two main goals: the prevention (prophylaxis) of seizures or their equivalents, and the rapid termination of an ongoing attack.
Pathogenetic mechanisms of epilepsy are closely linked to the disruption of delicate neurotransmitter balance. The formation of persistent epileptogenic activity is based on a breakdown in equilibrium between the inhibitory and excitatory systems of the central nervous system.
- Inhibitory systems: normally, activity is suppressed by gamma-aminobutyric acid (GABA) and glycine.
- Excitatory systems: stimulatory actions are exerted by the amino acids glutamate and aspartate.
Biochemical studies show that within the established epileptogenic focus, an abnormally elevated concentration of glutamate is consistently recorded. Meanwhile, GABA content is globally decreased in the brain tissue of epilepsy patients. Excitatory amino acids released in excess actively bind to specific neuronal receptors — NMDA and AMPA. Because these receptors are structurally and functionally coupled with fast sodium channels, their activation leads to powerful pathological neuronal excitation.
A genetic factor is also recognized: hereditary forms of epilepsy exist that are directly caused by polymorphism (structural alteration) of voltage-gated sodium channels.
Generalized Seizures
The primary classification of epilepsy forms is based on the dissemination of pathological electrical activity recorded via electroencephalography (EEG). If seizure waves are recorded completely synchronously in both cerebral hemispheres, these seizures are classified as generalized.
This group includes the following main types:
- Grand mal seizures (grand mal). Manifest as generalized tonic-clonic convulsions. The seizure is always accompanied by a complete loss of consciousness and concludes with a phase of general muscular relaxation. There is a strict danger criterion: if a major seizure lasts longer than 5 minutes or seizures occur successively without recovery of consciousness, the condition is regarded as a life-threatening status epilepticus.
- Absence seizures (petit mal). The main symptom is a brief loss of consciousness lasting only 5–10 seconds. Characteristic specific changes are recorded on the EEG during an absence seizure.
- Myoclonic epilepsy. This type is characterized by isolated or serial involuntary twitching of specific muscle groups. Such attacks are usually brief. The primary distinguishing feature of myoclonic epilepsy is that it occurs without a loss of consciousness.
Focal Seizures and Status Epilepticus
Unlike generalized forms, focal (partial) seizures have a strict localization. According to EEG characteristics, pathological changes during these attacks are restricted to a specific area of the brain. Due to the multitude of possible focus locations, the clinical picture of focal seizures encompasses diverse forms. They are variable regarding the preservation of consciousness: they may occur either with or without impaired consciousness.
Status epilepticus occupies a special place in the classification. By definition, it is a critical condition in which convulsive seizures follow one another. Its key feature is that the patient does not regain consciousness in the intervals between seizure episodes.