Introduction to Pediatric EEG

Electroencephalogram (EEG) is a crucial diagnostic tool in pediatric neurology. It records the electrical activity of the brain through electrodes placed on the scalp. In pediatrics, EEG plays a vital role in diagnosing and managing various neurological conditions, including epilepsy, developmental disorders, and encephalopathies.

Key points:

• Non-invasive technique for measuring brain activity
• Particularly useful in pediatrics due to the developing nature of the child's brain
• Helps in diagnosing and monitoring neurological conditions
• Requires specialized interpretation due to age-dependent EEG patterns

Indications for Pediatric EEG

EEG is indicated in various pediatric neurological conditions:

1. Suspected seizures or epilepsy
2. Evaluation of altered mental status or encephalopathy
3. Assessment of developmental delays or regression
4. Diagnosis of sleep disorders
5. Monitoring of antiepileptic drug efficacy
6. Evaluation of unexplained behavioral changes
7. Assessment of brain death

The choice between routine EEG, prolonged EEG monitoring, or video EEG depends on the clinical scenario and the information needed for diagnosis or management.

EEG Procedure in Pediatrics

Performing an EEG in children requires special considerations:

1. Preparation:
   • Child-friendly environment to reduce anxiety
   • Age-appropriate explanation of the procedure
   • Involvement of parents or caregivers
2. Electrode Placement:
   • Use of the International 10-20 system, adapted for smaller head sizes
   • Careful application to ensure good contact and comfort
3. Recording:
   • Standard duration of 20-40 minutes for routine EEG
   • Incorporation of activation procedures (e.g., hyperventilation, photic stimulation)
   • Recording during both wakefulness and sleep when possible
4. Special Considerations:
   • Use of melatonin or other sleep-inducing methods for sleep-deprived EEGs
   • Prolonged monitoring (24 hours or more) for certain indications
   • Video EEG for correlation of clinical events with EEG findings

Normal EEG Patterns in Pediatrics

Understanding normal EEG patterns is crucial for accurate interpretation. These patterns evolve with age:

1. Neonatal Period (0-30 days):
   • Discontinuous background activity
   • Trace alternant pattern in quiet sleep
   • Absence of well-defined sleep stages
2. Infancy (1-12 months):
   • Gradual transition to continuous background activity
   • Emergence of sleep spindles and K-complexes
   • Development of posterior dominant rhythm
3. Early Childhood (1-5 years):
   • Establishment of posterior dominant rhythm (usually 7-8 Hz)
   • Presence of vertex waves and sleep spindles
   • Occurrence of benign focal epileptiform discharges of childhood
4. Late Childhood and Adolescence (6-18 years):
   • Maturation of posterior dominant rhythm to adult frequency (8-12 Hz)
   • Well-defined sleep architecture
   • Persistence of some childhood patterns (e.g., posterior slow waves of youth)

Abnormal EEG Findings in Pediatrics

Common abnormal EEG findings in children include:

1. Epileptiform Discharges:
   • Focal or generalized spikes, sharp waves, or spike-wave complexes
   • Hypsarrhythmia in infantile spasms
   • 3 Hz spike-wave discharges in absence epilepsy
2. Background Abnormalities:
   • Slowing (focal or generalized)
   • Voltage attenuation
   • Asymmetry
   • Lack of age-appropriate features
3. Specific Patterns:
   • Burst-suppression in severe encephalopathies
   • Rhythmic delta activity in subcortical lesions
   • Periodic lateralized epileptiform discharges (PLEDs) in acute focal pathologies
4. Ictal Patterns:
   • Evolving rhythmic activity
   • Electrodecremental events
   • Epileptic spasms

Interpretation of these findings must always be in the context of the child's age, clinical presentation, and overall health status.

Age-Specific Considerations in Pediatric EEG

EEG interpretation in pediatrics requires understanding of age-specific features:

1. Neonates:
   • Importance of conceptional age in interpretation
   • Recognition of transient rhythmic discharges
   • Evaluation of background continuity and symmetry
2. Infants:
   • Assessment of developmental milestones in EEG maturation
   • Recognition of normal sharp transients (e.g., benign sleep transients)
   • Evaluation of awake-sleep differentiation
3. Toddlers and Preschoolers:
   • Identification of benign focal epileptiform discharges of childhood
   • Assessment of posterior dominant rhythm development
   • Recognition of normal variants (e.g., wicket spikes, 14 and 6 Hz positive bursts)
4. School-Age Children and Adolescents:
   • Evaluation of fully developed sleep architecture
   • Recognition of activation of certain epileptiform patterns (e.g., during hyperventilation)
   • Assessment of cognitive-related potentials

Challenges and Limitations of Pediatric EEG

Several challenges are unique to pediatric EEG:

1. Patient Cooperation:
   • Difficulty in keeping young children still during recording
   • Challenges in performing activation procedures in young or non-cooperative patients
2. Physiological Artifacts:
   • Increased muscle and movement artifacts
   • Sweating artifacts in infants
3. Interpretation Challenges:
   • Wide range of normal variants that can mimic pathological patterns
   • Rapid evolution of EEG patterns with age
   • Need for age-specific interpretation skills
4. Technical Considerations:
   • Need for specialized equipment (e.g., smaller electrodes, video EEG setups)
   • Importance of high sampling rates to capture fast activity in infants
5. Clinical Correlation:
   • Difficulty in correlating EEG findings with subtle clinical events in young children
   • Importance of detailed history and clinical examination

Emerging Technologies in Pediatric EEG

Recent advancements are enhancing the utility of EEG in pediatric practice:

1. High-Density EEG:
   • Improved spatial resolution for source localization
   • Better detection of focal abnormalities
2. Ambulatory EEG:
   • Long-term monitoring in home environment
   • Improved capture of infrequent events
3. Quantitative EEG (qEEG):
   • Automated analysis of EEG data
   • Potential for early detection of neurological disorders
4. Functional Connectivity Analysis:
   • Assessment of brain network dynamics
   • Insights into developmental disorders and epilepsy
5. Artificial Intelligence in EEG Interpretation:
   • Machine learning algorithms for automated seizure detection
   • Potential for reducing interpretation time and improving accuracy

These technologies offer promising avenues for enhancing diagnostic accuracy and understanding of pediatric neurological disorders.

EEG Findings in Specific Pediatric Conditions

1. Epilepsy Syndromes

• Childhood Absence Epilepsy:
  • 3 Hz generalized spike-and-wave discharges
  • Normal background activity
• Juvenile Myoclonic Epilepsy:
  • 4-6 Hz generalized polyspike-and-wave discharges
  • Photoparoxysmal response in some cases
• Benign Epilepsy with Centrotemporal Spikes (BECTS):
  • Centrotemporal spikes, often bilateral but asynchronous
  • Activation during drowsiness and sleep
• West Syndrome:
  • Hypsarrhythmia: high-amplitude, chaotic background with multifocal spikes
  • Electrodecremental response during spasms
• Lennox-Gastaut Syndrome:
  • Slow spike-and-wave complexes (<2.5 Hz)
  • Paroxysmal fast activity during sleep
  • Multiple seizure types on ictal recordings

2. Neurodevelopmental Disorders

• Autism Spectrum Disorder:
  • Increased epileptiform discharges (up to 60% of cases)
  • Altered power spectra, particularly in gamma frequency
• Attention Deficit Hyperactivity Disorder (ADHD):
  • Increased theta activity, decreased beta activity
  • Altered theta/beta ratio
• Rett Syndrome:
  • Loss of normal sleep architecture
  • Multifocal epileptiform discharges
  • Characteristic "notched delta squeak" pattern

3. Neonatal and Infant Conditions

• Hypoxic-Ischemic Encephalopathy:
  • Suppressed background activity
  • Burst-suppression pattern in severe cases
  • Seizures (focal or multifocal)
• Neonatal Seizures:
  • Focal or multifocal sharp waves or spikes
  • Rhythmic delta activity
  • Subtle electrographic seizures without clinical correlate
• Pyridoxine-Dependent Epilepsy:
  • Burst-suppression pattern
  • Multifocal epileptiform discharges
  • Normalization with pyridoxine administration

4. Metabolic and Genetic Disorders

• GLUT1 Deficiency Syndrome:
  • 2.5-4 Hz spike-wave discharges
  • Focal or multifocal epileptiform discharges
  • Background slowing that improves with ketogenic diet
• Angelman Syndrome:
  • High-amplitude 2-3 Hz delta activity, predominantly frontal
  • Spike and slow-wave discharges
  • Characteristic pattern of notched delta waves intermixed with spikes
• Mitochondrial Disorders:
  • Multifocal epileptiform discharges
  • Background slowing
  • Burst-suppression pattern in severe cases

5. Infectious and Inflammatory Conditions

• Herpes Simplex Encephalitis:
  • Periodic lateralized epileptiform discharges (PLEDs)
  • Focal slowing over affected regions (typically temporal)
  • Multifocal or generalized seizures
• Autoimmune Encephalitis:
  • Extreme delta brush pattern in anti-NMDA receptor encephalitis
  • Multifocal epileptiform discharges
  • Diffuse background slowing
• Subacute Sclerosing Panencephalitis (SSPE):
  • Periodic high-amplitude slow wave complexes
  • Progressive background disorganization

6. Other Neurological Conditions

• Childhood Stroke:
  • Focal slowing over affected region
  • Epileptiform discharges in post-stroke epilepsy
• Traumatic Brain Injury:
  • Diffuse or focal slowing
  • Epileptiform discharges in post-traumatic epilepsy
  • Burst-suppression or suppressed background in severe cases
• Brain Tumors:
  • Focal slowing over tumor location
  • Focal epileptiform discharges
  • Breach rhythm over skull defects post-surgery

Note: EEG findings should always be interpreted in the context of the patient's clinical presentation, age, and overall health status. Some conditions may have overlapping EEG features, and not all patients with a specific condition will demonstrate all the listed EEG abnormalities.