Triggers, Etiology and Pathophysiology of Seizures

When there is an excessive abnormal synchronous electric activity in the central nervous system leading to outward clinical manifestations with behaviour, consciousness, feelings, movement, and focal, then it is referred to as seizure. Seizures can be caused by several reasons/factors, which can be remembered with the mnemonic VITAMIN D,E..

Causes/Trigger of Seizure

Vascular Causes of seizures are common causes of focal types of seizures, and can also cause generalized types of seizures. It is no doubt responsible for chronic epilepsy caused by Acute ischemic Stroke, and Hemorrhages (intracerebral, and subarachnoid). When there is vasogenic edema in the posterior cerebral territory as a result of high blood pressure, causing Posterior Reversible Encephalopathy syndrome can lead to a seizure. Also, low oxygen being delivered to the brain can lead to seizures.,,,,.

Infectious Causes of seizures could vary from viral to bacteria, fungal, protozoan infection, and Helminthic Infestations. Meningitis which occurs close to the cortex can cause a seizure, encephalitis which is the irritation of the brain tissue can also lead to seizure, also, a brain abscess can lead to seizure among other infections that can trigger seizures.,.

Traumatic Causes of seizures usually occur as a result of an Epidural Hematoma (bleeding in the middle of the meningeal artery), or by Subdural hematoma. These traumas can trigger seizures in a person..

Autoimmune Causes of Seizures can occur as a result of antibody-mediated activity on the tissues of the brain, leading to autoimmune encephalitis. Systemic Lupus erythematosus, and paraneoplastic syndrome are the very common autoimmune cause of seizures. ,.

Metabolic Causes of seizures as the name implies can be caused by nutrients and metabolic activities, like in the instance of Thymine deficiency which occurs as a result of the decrease in Vitamin B1 could lead to a seizure. Deficiency in Thymine in cases such as Wernicke's encephalopathy and alcoholism could lead to a seizure. Hyperglycemia is a result of Glucose reduction and in some cases, high glucose levels can trigger seizures. A low amount of sodium, in the case of hyponatremia, can also trigger a seizure. Also, reduced phosphate levels cause hypophosphatemia can also be a trigger for seizures. In the body, an increase in Urea (metabolic waste)can trigger a seizure, the production of less ammonia by the liver which could be converted into Urea can cause ammonia to build causing a seizure. .

Idiopathic Causes of seizure are usually referred to as Epilepsy. Unlike seizures, epilepsy is referred to as two unprovoked seizures within a period of 24 hours, or about a 60% rate of reoccurrence. Patients with epilepsy syndromes such as West syndromes can trigger seizures. Idiopathic causes of seizures have to so with people who have epilepsy syndrome or are not complying with the Anti-Epileptic medication (AED). .

Neoplasia Cause of epilepsy has to do with having masts, or spasm, close to the cortex of the brain such as Glioblastoma Multiforme triggering a seizure. Other cases such as Meningioma in the cortex, or malignancy within the cortex could trigger seizures.,.

Drug causes of epilepsy shouldn't be something new. Taking drugs for seizure helps to lower the threshold and occurrence of the seizure. Some medications such as Opioids, tricyclic antidepressants, isoniazid (for tuberculosis treatment), salicylate toxicity, amphetamines, Lithium, Metronidazole, and Cefepime can trigger seizures.,,.

Eclampsia Causes of epilepsy cannot be overstated. It is common in pregnant women. People with high blood pressure can also have seizures as these can trigger it. In children with roseola, leading to fever, a seizure can be triggered.

Pathophysiology of Seizures

When there is a decrease in the GABA inhibitory pathway and an increase in the Glutamate stimulatory pathway, then seizures occur. The increase in glutamate in NMDA and the AMPA glutamate receptors. when glutamate binds to these receptors, cations such as Calcium, and sodium enter the neuron making the cell super positive, and depolarizing the axon, causing an action potential. , . When GABA acts on receptors, ions such as chloride, go into the cell, creating a negative charge, inhibiting the ability of action potentials down the axon, causing hyperpolarization, casing a decreased action potential. .

When there is a depolarization or hyperpolarization in the receptors in the brain, the electrical activities will spread to other parts of the brain while remaining in the hemisphere of origin, it is regarded as Focal seizure.. When there are irregular electrical activities occurring at all part of the cerebrum as well as the Bilateral cerebral hemisphere, it is known as a generalized seizure..

Clinical Features of Seizures

With Focal Seizures, it is important to know that there is a focal region where abnormal electrical activities are occurring, before spreading around the cerebral hemisphere. If the electric activity is excessive in the Frontal lobe, there can be abnormal movements on the contralateral side of the body.,,. When there is a seizure in the parietal lobe, there will be abnormal sensations on the arm and the leg on the contralateral side of the affected side.. Focal Seizure can lead to abnormal motor symptoms, sensory symptoms, and Autonomic symptoms. The ictal event allows knowing if a seizure is a focal seizure or a generalized seizure. Before the Ictal event, there are phases to seizure. These include the Prodrome stage which is the trigger phase, after which can lead to an Aura. Aura would consist of Deja Vu, nausea, Automatisms (lip smacking, abnormal chewing), then the Ictal event. After the ictal event is the post-ictal phase which occurs in seizures such as focal seizures with impairment, or in generalized seizures. This post-ictal phase includes symptoms such as confusion, drowsiness, amnesia, and Todd's paralysis (focal seizure) .

Focal Motor type Seizures are generated within the frontal lobe, and it can occur in different ways including Atonic seizures (Weak, relaxed or collapsed muscles), Tonic Seizure (Stiffening of the muscles), Clonic, Myoclonic (rapid jerking movement), and jacksonian march. Focal seizures could occur with or without impairment, they could also occur with or without generalized seizures. I will be explaining these, also Generalized seizures, the areas where the generalized seizures present, Diagnosis, treatment, and Epilepticus.

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