Introduction to Pediatric EEG

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Introduction to Pediatric EEG

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Pediatric EEG This is a basic introduction to Pediatric EEG and part of the Neurophysiology Fellows teaching lecture series. This covers from 1 month to age 20. There is another presentation for Neonatal and Newborn EEG. Pediatric EEG like Pediatric Neurology differs from Adult EEG and Adult Neurology because the electrical activity of the brain changes during growth and development. Therefore, children develop different pathological conditions from adults that are often age specific.

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The EEG recording itself is different in children than adults because the brain, meninges, skull, scalp, head size as well as the child's behavior and ability to cooperate all change over time. Therefore, Pediatric EEGs must be recorded and interpreted with special attention given to the child's age and developmental level. An EEGer must possess knowledge of normal as well as abnormal features for each age.

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What is an EEG? An electroencephalogram (EEG) records brainwave activity with the use of electrodes. This diagnostic tool translates the electrical brainwave activity into a series of wavy lines. This is a diagnostic test, not a treatment. The EEG does not measure intelligence, nor diagnose emotional or mental illness.

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How long does the EEG last? For a routine EEG recording, it takes approximately 20 minutes, but please allow one hour total for the application and removal of electrodes. For a sleep deprived EEG recording, it takes approximately 40-60 minutes. Allow two hours total for the application and removal of electrodes. 20-40 minutes

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How do I prepare for my EEG? Before the EEG, your physician may advise you to alter your medication(s) dosage(s). Continue with your normal meal intake. Do not use oils, hair spray, or conditioner on your hair the night before the EEG. Please arrive with clean, dry hair on the day of your EEG. If your physician recommends a sleep deprived EEG, be prepared to stay awake the night before the EEG and avoid caffeine intake the day of your EEG. For a pediatric routine EEG, it is recommended that the test be scheduled around naptime or limit your child’s sleep the night before the test.

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What should I expect during the EEG? First, the technologist will ask you a few questions about your medical history. Then, you will be asked to lie on a comfortable bed to begin the preparation for your EEG recording. Before the application of six small electrodes (discs), the technologist will apply a mild abrasive cleanser. This is followed with the use of a conductive cream to ensure a clearer recording for the physician to evaluate. An electrode cap is then placed on your scalp. Once each electrode cap site is also cleansed, you will continue to lie on the bed with your eyes closed and remain still while the technologist begins to record. At this point, it is important to stay as alert as possible. The recording includes photic stimulation, a flashing-strobe light given in eight, ten second intervals. In addition, you may be required to conduct a breathing exercise referred as hyperventilation, which lasts three to five minutes. After the exercise, you may feel a slight dizziness or numbness in your hands or feet. These symptoms will lessen once you begin normal breathing. During part of the EEG recoding, the technologist may ask you to sleep.

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What happens after the EEG? The technologist will remove the cap and electrodes from your scalp. After these are removed, you may have cream and gel in some areas of your hair. These are water-soluble and can easily be removed with shampoo. Please feel free to bring hair accessories such as a hairbrush or comb, a hat or cap, a hair clip or ponytail holder.

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When do I receive my EEG results? Once the EEG recording is completed, depending on various centers and institutes and country the report availability varies. In our centre the report is ready immediately with treatment plans.

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Interpretation of pediatric EEGs requires the understanding of what Blume calls: EEG Requirements Normalities Curiosities Abnormalities EEG

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Normalities Normal Pediatric EEG activity has more variation than adult EEG. Focalities are not always abnormal. EEG varies greatly by age, therefore interpretation needs to be age specific for the Conceptual Age. For a complete EEG, all states (Awake, Drowsy, and Sleep) should be recorded. Lack of state change is abnormal in infants. Dysmaturity is an non-specific abnormality; "baby encephalopathic slowing". General Features to remember about Pediatric EEGs:

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The ideal EEG Awake Drowsiness Transitions Sleep Arousal Activation The ideal EEG should contain: Hyperventilation: when able to cooperate and if not medically contraindicated (HgbSS, Congenital heart disease, CF or active asthma) Photic Stimulation: if greater than 6 months of age

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Curiosities Posterior Slow Activity (Waves) of Youth: Waking, sinusoidal 2.5 to 4.5 Hz slow wave that interrupts the background alpha with voltage similar to the alpha voltage. Mu Rhythm: Waking, central 9Hz (7-11 Hz) comb shaped that is blocked by movement (thought of movement) of the contra-lateral extremity. Lambda Waves: Waking, positive sharp waves over the occipital region from looking at a complex visual target. Usually 20 to 50 m V with a duration of 200 to 300 ms. Bilaterally synchronous with moderate voltage asymetries. Disappear with eye closure. Vertex: wider projection in children, usually fronto-central not just frontal as in adults. Often very high in voltage in early childhood, maximal ages 2-4. May appear on one side initially then be symmetrical once stage 2 sleep is well established. Repetitive or sequential at onset may look like fronto-central spikes. Pediatric EEG Curiosities

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POSTS (Positive Occipital Sharp Transients of Sleep): Surface positive, occipital waves during stage 1 and 2 sleep, typically bilaterally synchronous (may have voltage asymmetries), that occur in runs of 4 to 5 Hz. Onset as young as 4 years, maximal at 15-35 years. 14 and 6 Positive Spikes: Onset at 3 or 4 years, peaks at 13-14 years, minimal by 17-18 years. Rhythmic trains of spikes followed by a smooth rounded component lasting 0.5 to 1 s. Occur most often in the posterior temporal regions and may be asynchronous or appear independently on the two sides. (COMMENT: I haven't seen in age of digital EEG! I'm not sure if the digital, referrential amplifiers fail to pick up the activity or if the CRT displays of the EEG machine alter the presentation of &quot14 and 6" so it is not recognizable ) Psychomotor Variant is rhythmic theta (monomorphic and monorhythmic) burst often notched at 5 to 7 Hz. Psychomotor Variant occurs bilaterally and independently and may shift from side to side. Psychomotor Variant begins in late adolescence and continues into adulthood. Pediatric EEG Curiosities

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Photic Stimulation Photic stimulation (PS) is a very useful and important activation procedure in Pediatric EEG because of the activation of Generalized Spike-Wave activity. This is a common finding in children wiht Primary Generalized Epilepsy. The Photoparoxysmal Response (PPR) is bilaterally synchronous, generalized spike-and-slow-wave and can have multiple spike and slow wave complexes to repetitive flash stimulation, poly-spike waves are the most significant abnormality.

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Pediatric EEG Abnormalities Pediatric EEGs contain different abnormalities than adults because of the different pathological processes and different clinical epileptic syndromes that occur in childhood. Many of the pathological processes produce seizures. Therefore, most of the recognized pathological patterns in Pediatric EEG contain spike and spike-wave activity.

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Generalized 3-Hz spike-and wave complex is always abnormal. 3-Hz s-w activity may need to last 6 to 10 seconds before clinical absence seizure activity occurs. The generalized spikes may become poly-spikes in sleep and have a more variable frequency (especially in stage 3 and 4 sleep). During sustained burst of the &quot3-Hz" the frequency may begin closer to 3.5 to 4-Hz and slow to 2.5 to 3-Hz. Hyperventilation(HV) for 3 to 4 minutes usually will produce 3-Hz spike and wave activity if present. If 3-Hz activity is highly suspected based on history but does not occur than a second attempt at HV for 5 minutes should be performed. HV is as likely to record 3-Hz spike wave as 24 hours of continuous EEG. Onset of 3 Hz spike and wave with Absence seizures is commonly reported as most likely at 5-6 years of age. Often children have been having absence seizures for at least 6 months before diagnosis and occasionally have been having events consitently for year. Onset can occur before age 2. EEG in child of 23 months with 3-hz spike-wave and &quotpauses" in activity. Abnormal Pediatric EEG patterns and Clinical Correlations

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Hypsarrhythmia is a term to describe an EEG with 0.5 to 3 Hz chaotic, asynchronous slow waves with voltages greater than 300 mV. Voltages of 1000 to 2000 mV can occur. Multifocal spikes and sharp and slow waves are also present. Intervals of attenuation can occur with and without clinical myoclonic activity or flexor spasms. Hypsarrhythmia can begin at 3 to 4 months of age and may persist into the 2nd year of life. Hypsarrhythmia is present in about 2/3 of infants with infantile spasms. Hypsarrhythmia Infantile Spasms is a clinical syndrome of clusters of axial myoclonic seizures that occur in infants from 2 to 18 months of age.

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Modified Hypsarrhythmia Prolonged monitoring studies of patients with infantile spasms have shown that hypsarrhythmia is a highly variable and dynamic electroencephalographic pattern. Variations of the prototypic pattern (modified hypsarrhythmia) include hypsarrhythmia with increased interhemispheric synchronization, asymmetrical hypsarrhythmia, hypsarrhythmia with a consistent focus of abnormal discharge, hypsarrhythmia with episodes of attenuation, and hypsarrhythmia comprising primarily high-voltage slow activity with little sharp-wave or spike activity. Marked changes in the hypsarrhythmic pattern usually occur during sleep, chiefly during rapid eye movement sleep, when there is a marked reduction in, or total disappearance of, the hypsarrhythmic pattern. Relative normalization of the hypsarrhythmic pattern can also be seen immediately on arousal and during clusters of infantile spasms. Thus, the specific EEG features seen in a given patient depend on multiple factors, including the duration of the EEG recording, the clinical state of the patient, and the presence of various structural abnormalities of the brain.

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Infantile Spasms Infantile spasms constitute both a distinctive seizure type and an age-specific epilepsy syndrome that have been extensively described for over a century. Standardization of the classification of infantile spasms has evolved, culminating in recent recommendations for separately recognizing and distinguishing the seizure type (spasms or epileptic spasms) and the epilepsy syndrome of infantile spasms (West syndrome). More-detailed descriptions of the clinical and electrographic features of epileptic spasms and hypsarrhythmia have emerged. Advances in neuroimaging techniques have revealed clues about pathophysiology and increased the etiologic yield of the diagnostic evaluation of patients with infantile spasms. Adrenocorticotrophic hormone remains the treatment of choice for many neurologists. Recent controlled studies support vigabatrin as first-line therapy, and open-label studies suggest that topiramate, lamotrigine, and zonisamide may be useful in treating spasms. Recent reports of visual-field constriction with vigabatrin may limit its use. Surgical treatment has been used successfully in a select subgroup of patients with secondarily generalized spasms from a single epileptogenic zone. Although the prognosis for most patients with infantile spasms remains poor, further studies identifying predictors of favorable prognosis and recent advances in understanding the pathophysiology of infantile spasms offer hope of safer and more-effective therapies that improve long-term outcome.

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Slow Spike and Wave Slow Spike and Wave occurs at 1 o 2.5 Hz and may be widely distributed and synchronous over both hemispheres or may be asymmetric and present in only one hemisphere. Slow Spike and Wave is often seen for several seconds without any clinical change. There are usually other background abnormalities such as slowing and mutifocal spikes. Slow Spike and Wave usually appears between 2 and 6 years of age and activates with drowsiness and sleep. Slow spike and wave is not activated by HV and will block with eye opening.

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Slow Spike and Wave Slow spike and wave is one of 3 features of the Lennox-Gastaut Syndrome. The other 2 are refractory seizures and mental retardation.

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Multifocal Spike and Wave Multifocal Spike and Wave is defined as "spikes in 3 non-contiguous electrode positions with at least one focus in each hemisphere“. Multifocal Spike and Wave activity is frequently seen in children with multiple seizure types and retardation.

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Rolandic Spikes Rolandic Spikes occur exclusively in children with peak age of 6 to 10 years but may be present at age 2 or 3 years until age 12 to 15 years. Spikes are most commonly highest in voltage in the C3-C4 electrodes spreading into the T3-T4 electrodes. A horizontal dipole may be present with a surface positive field in the frontal-polar electrode.

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Rolandic Spikes During drowsiness and sleep the Rolandic spikes increase in numbers and often cluster in trains of 3 to 6 over 1-2 second intervals. Rolandic spikes may be unilateral, bilateral synchronous or bilateral independent. Rolandic spikes frequently seen as an incidental finding and have only a 50% correlation with underlying seizure disorder. Begin Rolandic Epilepsy (BRE) is a syndrome where simple partial seizures occur early in sleep or on awakening. Many children may have just one such event. Occasionally secondary generalization and rarely prolonged seizures occur. Rolandic spikes are also present in children with other generalized epileptiform activity.

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SSPE & Slowing SSPE Subacute sclerosing panencephalitis produces double and triple sine waves at about 1 Hz that may occur in long runs superimposed on normal background. Early in the illness, short burst of slow sharp waves may be produced by noise. SSPE is a delayed onset, progressive measles encephalitis. Slowing may be present post-ictally or with underlying structural abnormality which usually has to be large in size and involves the white matter.

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