Epilepsy Physiology Notes

Epilepsy Introduction

• Epilepsy is a brain disorder characterized by convulsive seizures or loss of consciousness, or both. Convulsion refers to uncontrolled involuntary muscular contractions Convulsive seizure means a sudden attack of uncontrolled involuntary muscular contractions.
• It occurs due to paroxysmal (sudden and usually recurring periodically) uncontrolled discharge of impulses from neurons of the brain, particularly the cerebral cortex.
• The person with epilepsy remains normal in between seizures. The epileptic attack develops only when the excitability of the neuron is increased, causing excessive neuronal discharge. The persons affected by epilepsy are known as epileptics.

Read And Learn More: Medical Physiology Notes

Types Of Epilepsy

Epilepsy is divided into two categories:

1. Generalized epilepsy
2. Localized epilepsy.

Generalized Epilepsy

Generalized epilepsy is the type of epilepsy that occurs due to the excessive discharge of impulses from all parts of the brain. It is also called general onset seizure or general onset epilepsy.

Generalized epilepsy is subdivided into three types:

1. Grand mal
2. Petit mal
3. Psychomotor epilepsy

1. Grand mal: Grand mal is characterized by the sudden loss of consciousness mess followed by convulsion. Just before the onset of convulsions, the person feels the warming sensation in the form of some hallucination. It is called an epileptic aura.

1. The convulsions occur in two stages:
2. Tonic stage
3. Clonic stage.

1. Tonic Stage: Initially, the seizure is characterized by tonic contractions of muscle leading to spasms. The spasm causes twisting facial features, flexion of the arm, and extension of lower limbs.

2. Clonic Stage: Clonic convulsions develop after the tonic stage. This stage is characterized by violent jerky movements of limbs and face due to alternate severe contraction and relaxation of muscles.

• At the end of the attack, alternative tonic and clonic convulsions are seen. During the entire period of seizure, the tongue may be bitten.
• In EEG recording, fast waves with a frequency of 15 -30 per second are seen during the tonic stage. During the clonic phase, slow and large waves appear. After the attack, slow waves are recorded for some time. In between seizures, the EEG shows delta waves in all types of epileptics.

Causes of Grand Mai: The cause of grand mal epilepsy is the excess neural activity in all parts of the brain. And the reason for the stoppage of attack is neuronal fatigue. The factors which accelerate the neural activity resulting in grand mal epilepsy are:

• • • Strong emotional stimuli
    • Hyperventilation and alkalosis
    • Effects of some drugs
    • Uncontrolled high fever
    • Loud noises or bright light
    • Traumatic lesions in any part of the brain.

2. Petit Mal:

• In this type of epilepsy, the person becomes unconscious suddenly without any warning. The unconsciousness lasts for a very short period of 3–30 seconds. Convulsions do not occur. However, the muscles of the face show twitch-like contractions and there is blinking of eyes. Afterward, the person recovers automatically and becomes normal.
• The frequency of attack maybe once in many months, or many attacks may appear in rapid series. It usually occurs in late childhood and disappears completely at the age of 30 or above.
• The EEG recording shows slow and large waves during the attack. Each wave is followed by a sharp spike. This type of wave appears from recording over any part of the cerebral cortex, indicating the involvement of the whole brain. Delta waves appear in between the seizures.

Causes of Petit Mal: The cause of petit mal is not known. It occurs in the conditions like head injury, stroke, brain tumor, and brain infection.

3. Psychomotor Epilepsy:

• It is characterized by emotional outbursts such as abnormal rage, sudden anxiety, fear or discomfort. There is amnesia or a confused mental state for some period. Some persons have the tendency to attack others bodily or rub their own faces vigorously.
• In most cases, the persons are not aware of their activities. Some persons are very well aware of their actions, but still, abnormal actions cannot be controlled.
• The EEG recordings show low-frequency rectangular waves, ranging between 2 and 4 per second.

Causes of Psychomotor Epilepsy: The causes of psychomotor epilepsy are abnormalities in the temporal lobe and tumors in the hypothalamus and other regions of a limbic system like the amygdala and hippocampus.

Localized Epilepsy

• Epilepsy that occurs because of excessive discharge of impulses from one part of the brain is called localized epilepsy It is otherwise known as local or focal epilepsy or local seizure, it involves only a localized area of the cerebral cortex or the deeper parts of the cerebellum, which are affected by the tumor, abscess or vascular defects.
• The abnormality starts from a particular area and spreads to adjacent areas, developing slow-spreading muscular contractions. The contractions usually start in the mouth region and spread down toward the legs. This type of seizure is also known as Jacksonian epilepsy.

Causes of Localized Epilepsy: Localized epilepsy is caused by brain tumors.