The Cerebrum and Epilepsy

June 20, 2023

Video explaining the cerebrum and epilepsy using a real patient case study!


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Written by: Robert Tallitsch, PhD

Seeing someone have — or experiencing an epileptic seizure yourself — can be a terrifying experience. In this Brain Builder, we will discuss the anatomy of the brain in general, and the anatomy of the cerebral hemispheres in more detail. We will also talk about what a seizure is, the different types of epileptic seizures, and some of the most common forms of treatment for epileptic seizures.

An Introduction to the Nervous System

The nervous system comprises two subdivisions: the peripheral nervous system (PNS) and the central nervous system (CNS).

The PNS contains all of the nervous tissue outside of the CNS. The CNS is composed of the spinal cord and the brain. The brain is composed of three basic subdivisions:

1. Cerebral hemispheres

2. Brain stem, which is subdivided into the

  • Diencephalon
  • Mesencephalon (midbrain)
  • Metencephalon (pons)
  • Myelencephalon (medulla)

3. Cerebellum

Cerebral Hemispheres

The paired right and left cerebral hemispheres are partially separated from each other by the longitudinal fissure and are joined by the corpus callosum. Each hemisphere is composed of a highly convoluted cortex, consisting of the neuronal gray matter, an underlying layer of white matter consisting of glial cells and neuronal processes, and a collection of deeply located nuclear masses termed the basal ganglia. The cerebral cortex is responsible for the thought processes of the brain. Glial cells help maintain the intercellular environment of the nervous system and provide a supporting network. There are more glial cells than neurons.

The surface of each hemisphere is convoluted and composed of grooves (sulci) and elevations (gyri). These increase the surface area of the cerebrum. Each hemisphere is subdivided into lobes — each of which is named for the bone of the skull superficial to it.

The frontal lobe, which is the largest lobe of the brain, is found deep in the frontal bone. The primary motor area, premotor area, and prefrontal areas are located within the frontal lobe. The pre-motor area plans motor movement while the primary motor area controls voluntary motor movement. The prefrontal areas are found rostral to the primary motor area. These areas are involved in judgment and the setting and achievement of goals.

The parietal lobe houses the primary somesthetic (primary sensory) area and the cortical association areas of the brain. The primary somesthetic area perceives somesthetic sensory information. The cortical association areas understand and interpret somesthetic sensory information.

The temporal lobe houses the primary auditory cortex, which receives auditory sensory information, and the primary olfactory cortex, which receives olfactory sensory information.

The occipital lobe is the location of the visual cortex. It receives and interprets visual information.

The limbic lobe of the cerebral hemisphere consists of large cortical convolutions on the medial aspect of the cerebral hemisphere. Simply put, the limbic lobe is responsible for behaviors that are essential to the preservation of the species.

White Matter of the Hemispheres

The white matter forms the medullary core of the hemispheres and consists of three types of neuronal fibers:

  • Projection fibers convey neuronal information from the cerebral cortex to different locations within the CNS.
  • Association fibers interconnect various cortical regions of the same cerebral hemisphere.
  • Commissural fibers interconnect cortical regions of the two hemispheres.

Epilepsy — Causes and Symptoms

Epilepsy is defined as a medical condition in which a person has experienced two or more recurring seizures. While an individual may experience a single seizure due to a variety of medical reasons (high fever, lack of oxygen, severe head injury, oxygen toxicity, or a variety of other factors) an individual with epilepsy experiences recurring seizures.

Usually, the brain generates electrical activity in an orderly manner, and this electrical activity spreads from one region of the brain to another along the neurons and neuronal processes within the brain. In an individual with epilepsy, the brain’s normal electrical activity becomes unpredictable and imbalanced, resulting in abnormal bursts of electrical activity. This is termed a seizure. A person having a seizure will exhibit some, or all of the following symptoms: muscle spasms, loss of consciousness, confusion, and uncontrolled body movements. A seizure typically lasts from seconds to minutes.

An individual that has a seizure without a clearly definable cause (such as a head injury, brain infection, or brain tumor) will typically experience a second seizure within six months. And, if an individual has two seizures, the chances of having more throughout their lifetime increase significantly.

Seizures are typically characterized into two types. A generalized seizure is a seizure that starts with abnormal electrical activity on both sides of the brain at the same time. The most common forms of generalized seizures are termed “absence seizures” (also termed petit mall or staring seizures) and tonic-clonic convulsions (also termed grand mal seizures).

The second type of seizure is termed a focal (or partial) seizure. This type typically starts as an abnormal electrical activity within only one limited region of the brain. Although the abnormal activity starts within one area of the brain it can, and sometimes does, spread to other parts of the brain.

The following factors increase the chances of more frequent seizures: alcohol or drug use, failure to take prescribed medications, stress, and lack of sleep.

Diagnosis of Epilepsy

A physician will utilize the patient’s signs and symptoms and a variety of tests, including an EEG (electroencephalogram), CT or CAT scan, or an MRI to diagnose whether or not a patient has epilepsy and, if so, what type.

Treatment of Epilepsy

The three most common forms of epilepsy treatment are antiepileptic medications (AEDs), changes in diet, and surgery.

The number of AEDs available has increased significantly, and choosing the correct drug and dosage is a rather complicated process. It is important for epilepsy patients to follow their physician’s instructions completely and consistently.

Changes in diet (also termed food therapy) are utilized in patients with particular types of epilepsy. The two most common forms of food therapy are the modified Atkins diet and the ketogenic diet.

Approximately seventy percent of epilepsy patients are able to control their seizures with AEDs or food therapy. The remaining thirty percent are termed medically resistant, and surgery is the best option for complete control of their seizures.

Most people with epilepsy rarely think about it other than when they are taking their medications or during a physician’s visit. Being well-informed about the disease, advances in treatment, taking any medications as prescribed, and working closely with a physician are important steps toward living and maintaining a normal lifestyle.


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