What is the role of EEG in the workup of hypoxic-ischemic encephalopathy (HIE)?

Updated: Jul 18, 2018
  • Author: Santina A Zanelli, MD; Chief Editor: Dharmendra J Nimavat, MD, FAAP  more...
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Answer

Traditional multichannel EEG is an integral part of the evaluation of infants diagnosed with HIE. It is a valuable tool to assess the severity of the injury and evaluate for electrographic-only seizures (which are very common in neonates with HIE). [60, 61] This is particularly important for infants on assisted ventilation requiring sedation or paralysis. EEG can be very useful to help a clinician decide treatment options based on the report's findings.

Changes in EEG wave patterns evolve over time and are a reliable early indicator of the brain injury. [62]  

Generalized depression of the background rhythm and voltage, with varying degrees of superimposed seizures, are early findings. EEG characteristics associated with abnormal outcomes include (1) background amplitude of less than 30 mV, (2) interburst interval of more than 30 seconds, (3) electrographic seizures, and (4) absence of sleep-wake cycle at 48 hours.

Caution in interpreting early severe background abnormalities needs to be applied because reverting to normal background pattern in few days of life can be associated with normal outcomes. Note that large doses of anticonvulsant therapy may alter the EEG findings.

Serial EEGs should be obtained to assess seizure control and evolution of background abnormalities. Early EEGs are important not only to evaluate the degree of encephalopathy and the presence of seizures but may also help establish early prognosis. [63] Serial EEGs are also helpful in establishing prognosis. Improvement in the EEG findings over the first week, in conjunction with improvement in the clinical condition, may help predict a better long-term outcome. [64]


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