One commonality between most EEG technologists is that reading neonate EEG is difficult. Baby brains are not yet fully developed and often there isn't even a full array of electrodes to read because of circumference restrictions. In order to help reduce the stress of reading some of these neonates we have created these slides that will help you identify common abnormalities that epileptologists report on.
Mild Abnormalities
• Excessive multifocal sharp transients or immature and dysmature patterns can be seen in stressed premature or term infants.
• Nonspecific and rarely suggest a specific etiologic diagnosis.
• Often transient and usually disappear within a few days.
•Mild and transient focal abnormalities in the EEG are not usually associated with obvious focal pathology.
•Persistent focal EEG abnormalities are often associated with structural lesions such as hemorrhage, porencephaly, infarct, etc.
Significant abnormalities in the EEG are associated with a significant disturbance of brain function and usually indicate a poor prognosis or poor neurologic outcome. The more abnormal the pattern, the more severe the disturbance of brain function.
Abnormalities of Background
•Isoelectric or inactive EEG
•Paroxysmal activity or burst suppression
•Suppression of activity
•Excessive asymmetry and asynchrony
•Positive Rolandic sharp waves
•Slow wave activity
Isoelectric EEG
• A flat record that meets the criteria for electrocerebral inactivity
•Cause: severe encephalopathy
•Counter point: unless an acute toxic metabolic state exists or the patient has received a high dose of drugs such as diazepam or barbiturates.
•Infants with flat EEGs may survive the neonatal period but usually, suffer severe long-term neurologic sequelae.
Low Voltage EEG
•EEG pattern consists of activity below 10 microvolts which is persistent throughout the recording in both the wake and sleep states
• No reactivity and little variability.
•Cause: asphyxia, intracranial hemorrhage, congenital defects, or in association with infectious disease processes such as meningitis or encephalitis.
•Counter Points: hypothermia, high levels of drugs, a postictal state, or severe derangement of blood gas studies.
•Very unfavorable prognosis but does not necessarily predict death
Burst Suppression
•Bursts of abnormal activity superimposed upon an isoelectric or very low amplitude background
•NO change with state or in response to stimuli.
•Associated with severe disturbance of the brain and poor long-term prognosis.
Suppression
Can occur in a generalized fashion with a diffuse disturbance of function, or in a more focal fashion in association with focal lesions, such as porencephaly, a subdural collection of fluid or congenital abnormalities.
Excessive Asymmetry and Asynchrony
•Asymmetry: usually consists of a greater than 50% difference in amplitude over the two sides and is significant if it persists in sequential tracings. Again, this is usually seen in association with other abnormalities and occurs secondary to lateralized lesions such as intracerebral hemorrhage or a subdural collection of fluid
•Asynchrony: consists of excessive intrahemispheric asynchrony which is usually seen in association with other abnormalities.
Positive Rolandic Sharp Waves
•Unilateral or Bilateral and most commonly occur in the Rolandic and midline areas.
•Initially, this was described in infants with intraventricular hemorrhage; however, it has now been shown to also occur in patients who have periventricular leukomalacia and deep white matter lesions.
•Positive sharp waves do not behave like epileptiform discharges or correlate with ictal phenomena.
The source of the positive sharp waves is still to be determined
Slowing
• Diffuse or focal depending on whether the process or lesion is diffuse or focal in nature.
•Older infants
• Diffuse delta slowing which is invariant, with little in the way of superimposed theta activity
•Present both in the wake and sleep states
Little reactivity usually indicates a poor prognosis
Epileptiform Abnormalities
•The interictal discharges are focal or multifocal in nature and may consist of spikes, sharp waves, or broad contoured sharp and slow wave complexes.
•The ictal discharges may take form or shape such as rhythmic slow wave, or rhythmic activity in the alpha, beta, and theta range.
•The ictal and interictal discharges can shift from one area to another.
•A persistent focus in one area usually indicates a focal pathologic process.
•Electrographic seizure discharges can occur without a clinical accompaniment.
•Generalized epileptiform patterns are not usually seen in infants under one year of age.
Hypsarrhythmia
•Characteristic pattern consisting of multifocal spikes and high amplitude slow waves that usually occurs during the first year of life.
•Onset at three to seven months of age
•Infantile spasms
•Cause: prenatal, perinatal, or postnatal insult or acquired conditions that are present early on in life.
Neonatal Seizures
Most common expression of abnormality or an insult to the brain.
Clonic Motor
Focal
•Most frequent type of seizure in neonate
•Most likely due to focal structural lesion of the brain
•EEG: Focal rhythmic time locked spike or sharp wave discharges, usually over the central region, at a rate of 1:3 per second.
•Clinical features: Focal Clonic movement
Multifocal
•EEG: Focal rhythmic time locked spike or sharp wave discharges that migrate to different focal areas of the brain
•Clinical features: clonic movements consistent with EEG changes
Myoclonic Seizure
•EEG: broad sharp waves which may occur unilaterally or bilaterally(asynchronous) over two hemispheres.
•Focal myoclonic seizures consist of focal sharp wave discharges in EEG
Focal Tonic Seizures
•EEG: low voltage fast rhythmic discharges or rhythmic delta waves, typically seen in frontal temporal regions.
•Clinical features: posturing of the body or deviation of eyes.
•Eye deviation may be seen with epileptiform discharges over the occipital region
Seizures w/o EEG Correlate
Motor Automations
•"subtle" seizures, are characterized by: mouthing movements, ocular signs such as blinking, eye opening and eye closure, roving eye movements, nystagmus, locomotion - swimming, pedaling, and rowing movements, and complex purposeless movements such as thrashing and moving from side to side. More likely to be related to a subcortical brain stem release phenomenon secondary to depression of higher cortical functions.
Causes of Neonate Seizures
Day 0-4
•Hypoxia - ischemia
•Intracranial bleeding
•Hypoglycemia, hypocalcemia
•Pyridoxine dependence
Day 5-14
•Infection
•Metabolic abnormalities (hypoglycemia - hypocalcemia)
•Aminoacidurias and inborn errors of metabolism
•Dysgenetic disorders
Day 14-28
•Infection
•Congenital abnormalities
•Cortical malformations
•Trauma
•Subdural hematoma
•Metabolic factors
Conditions with Abnormal Patterns
•Hypoxia - ischemia insult gives rise to severe EEG abnormalities, including multifocal epileptiform activity, asymmetry, or suppression. This is now thought to be the most common cause of neonatal seizures and abnormal EEGs.
•Intracranial hemorrhage is associated with focal seizure discharges, positive Rolandic sharp waves, and/or focal or lateralized suppression of the EEG.
•Metabolic derangements: The most common are hypoglycemia and hypocalcemia, can be associated with focal or multifocal epileptiform abnormalities in the EEG, and the EEG usually improves after treatment.
•Congenital abnormalities: Holoprosencephaly which is associated with a suppression of activity over the posterior or anterior head regions.
•Lissencephaly which is associated with excessive fast activity in the EEG.
•Cortical malformations, cortical dysphasia, and migration disorders can be very epileptogenic with frequent focal epileptiform discharges on the EEG.
•Drugs and drug withdrawal can be associated with irritability, seizures, and focal or multifocal epileptiform abnormalities on the EEG.
Congratulations you made it to the end! Reading brains waves tends to be more of an artform then a science and this is especially true when it comes to neonate brains. But if you know what to look for it will become easier and easier to read neonate EEG.
Resource:
Photo Credit: Mayo Clinic
Yamada.T & Meng. E. (2017).Practical Guide for clinical Neurophysiologic Testing: EEG 2nd Edition.
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