EEG findings in patients with Neurological Disorders

Instructor: Dr. Gharibzadeh

By: Fahime Sheikhzadeh

Electrodes for recording EEG

A = Ear lobe, C = Central, Pg = Nasopharyngeal, P = Parietal,

F = Frontal, Fp = Frontal Polar, O = Occipital.

American Electroencephalographic Society

Normal EEG

This EEG displays the activity of an awake state showing normal amplitudes, frequencies, waveforms; similar features between hemispheres; and no epileptiform activity.

Disorders

Here we discuss in EEG finding in these neurological disorders;

Epilepsy Tumors Coma

Epilepsy

Epilepsy is a common chronic neurological disorder that is characterized by recurrent unprovoked seizures. These seizures are transient signs and/or symptoms due to abnormal, excessive or synchronous neuronal activity in the brain.

Epilepsy should not be understood as a single disorder, but rather as a group of syndromes with vastly divergent symptoms but all involving episodic abnormal electrical activity in the brain.

Ictal, Post-Ictal, Inter-Ictal

Ictal refers to a physiologic state or event such as a seizure, stroke or headache. In electroencephalography, or EEG, the recording during an actual seizure is said to be "ictal". Post-ictal refers to the state after the event. Inter-ictal refers to the state between events. Inter-ictal EEG discharges are those abnormal waveforms not associated with seizure symptoms.

Generalized

Partial Simple-partial Complex-partial

The types of epilepsy

The types of epilepsy Generalized: Generalized seizures affect the entire brain at

once; Partial: Partial seizures affect only a small part of the

brain. As the partial seizure develops, it may remain localized to a small part of the brain or

it may spread and affect the entire brain. In either case it is still called a partial seizure because it began in only part of the brain.

Grand mal epilepsy Petit mal epilepsy Focal epilepsy (Partial epilepsy)

Epilepsy Classifications

EEG in different kinds of epilepsies

Grand mal epilepsy

Tonic-clonic seizures (also known as Grand Mal Seizures, though this term is now discouraged and rarely used in

a clinical setting) are a type of generalized seizure affecting the whole brain. Tonic-clonic seizures are the

seizure type most commonly associated with epilepsy and seizures in general, though it is a misconception

that they are the only type.

EEG finding in Grand mal epilepsy

In patients with Grand mal (tonic-clonic) seizures, generalized, bilaterally synchronous spike discharges, or bursts of spike wave or poly spike wave activity, or

both may be seen inter-ictally.

The earliest change during a tonic-clonic convulsion is often the appearance of generalized low voltage fast

activity. This activity then becomes slower, more conspicuous, and more extensive in distribution and

depending on recording technique, may take the form of multiple spike or repetitive sharp wave discharges

that have a frequency of about 10 Hz and are seen during the tonic phase of the attack.

EEG Traces of Generalized Epilepsy

Grand mal epilepsy

Paroxysmal, generalized, bilaterally synchronous spike-wave and poly spike wave discharges seen interictally in the EEG of 62-year olds woman with tonic-clonic seizures.

Petit mal epilepsy

Absence seizures are one of several kinds of seizures. These seizures are sometimes referred to as petit mal

seizures, which is an older term.

In absence seizures, the person may appear to be staring into space with or without jerking or twitching

movements of the eye muscles. These periods last for seconds, or even tense of seconds. Those experiencing absence seizures sometimes move from one location to

another without any purpose.

EEG finding in Petit mal epilepsy

In patients with Petit mal (Absence) seizures, this epileptiform activity consist of well-organized 2.5 to 3

Hz spike-wave discharges, which may be seen both inter-ictally and ictally.

The frequency of the complexes is often a little faster than 3 Hz at onset and tends to slow to about 2 Hz before

terminating.

Petit mal epilepsy

Paroxysmal, generalized, bilaterally synchronous and symmetric 2.5 to 3 Hz spike-wave activity recorded inter-ictally in the EEG of a patient with absence (petit mal) seizures.

Progression of Absence Seizure

Focal (Partial) epilepsy

Focal seizures (also called partial seizures) are seizures which affect only a small part of the brain, and are split

into two main categories; simple partial seizures and complex partial seizures

A simple partial seizure will often be a precursor to a larger seizure such as a complex partial seizure, or a tonic-clonic seizure. When this is the case, the simple

partial seizure is usually called an aura.

Focal seizures are common in temporal lobe epilepsy.

EEG findings in Focal (Partial) epilepsy

The interictal EEG findings may vary considerably at different times in patients with focal epilepsy,

especially in those with complex symptomatology.

In some patients with partial seizures, and especially those with elementary symptomatology, the scalp

recorded EEG shows no change during the ictal event. More commonly, however, the EEG shows localized discharges or more diffuse changes during the ictal

period.

Focal (Partial) epilepsy

Focal (Partial) epilepsy

EEG of a 13 years old boy with frequent attacks of dimming out. A burst of repetitive spikes is seen to occur in the right temporal region; during this time he experienced an attack.

Tumors

Tumors may affect the EEG by causing compression, displacement, or destruction of nervous tissue.

Tumors

This abnormalities depend at;

Part Size Rate of growth of the tumor Age

EEG findings in Cerebral lesion

Depression of electrical activity over a discrete region of the brain

The presence of a focal polymorphic slow wave disturbance.

Tumors

Polymorphic slow wave activity in the left frontal region in the EEG of a 62 years ld man with a glioma

Coma

Altered state of consciousness may result from many causes, it is therefore not surprising that the EEG findings in comatose patients are variable.

A change in electro cerebral activity can be expected to occur following stimulation of a patients with a mildly depressed level of consciousness; this reactivity becomes inconstant, delayed, or lost as the depth of coma increases.

With further progression, repeated stimulation may be needed to produce any EEG change, and finally the EEG becomes unresponsive.

EEG findings in Comatose patients

Coma

EEG of a comatose child showing attenuation of the diffuse background slow activity in response to a sudden loud noise.

Brain death

Brains are Cool!!Brains are Cool!!

Any Questions?