Chapter 10: Epilepsy and Seizure Disorders

INTRODUCTION

In this chapter, we will review seizures, which are an abnormality of cerebral electrical activity.

A combination of tools and clinical signs are used to categorize this pathology including electroencephalograms (EEGs) which sample cerebral electrical activity with an array of electrodes placed onto the scalp. There are a multitude of antiseizure medications that can be tailored by onset time, efficacy, and side-effect profile. Patients with seizures refractory to multiple medications may be eligible for surgical interventions to help reduce the frequency and intensity of their seizures.

SEIZURE DISORDERS

Seizure: Abnormal electrical discharges among a group of neurons that persists long enough to interrupt normal functioning of that region of the brain.

Epilepsy: Disorder defined by a tendency toward multiple unprovoked seizures. Approximately 1% of the US population and 65 million people worldwide suffer from epilepsy. There is a bimodal presentation of the disease appearing most often in childhood (influenced by genetic abnormalities) and second most often in the elderly (often related to cerebral injuries including stroke).

Depending on the area of involvement, there may be associated contractions of groups of muscles, changes in sensation, or alterations in consciousness during an episode. These signs are typically stereotyped at each episode and can help approximate seizure focus in the brain and progression throughout the brain.

Focal Seizure

• Seizures originating in one hemisphere, even if from multiple onset zones, and spreading only to regions within this hemisphere.

  • Signs and symptoms (brain region dependent): Sensation change early in focal seizures is common and is called an aura.

    • - Typically, these include metallic taste, nausea, stomach upswelling sensation, déjà vu, vision changes, fear, panic, or euphoria. The stereotyped presentation favors a focal electrographic seizure.

  • May have perfectly intact awareness (simple) or impaired awareness at any point during the event (complex).

Secondarily Generalized Seizure

• Onset in one hemisphere, ideally as detected on EEG or with clear focal motor movement, with electrical spread to networks within both hemispheres.

• Typically causes loss of awareness and bilateral motor movements.

Generalized Seizure

• Activation of a network of abnormal epileptogenic that involves both hemispheres simultaneously. Starts with loss of awareness.

Myoclonic Seizure

• Contraction of either a single or group of muscles that coincides with abnormal electrographic discharge. Nonrhythmic and irregular jerks.

  • Subcortical myoclonic event: electrographic discharge(s) originating near or below the level of the deeper gray nuclei most commonly with uninhibited spinal circuits after diffuse cortical injury or direct trauma.

Tonic-Clonic Seizure (Grand Mal)

• Tonic Phase: Excessive ...