What is the practical utility of Electroencephalogram (EEG) and Optic Nerve Sheath Diameter (ONSD) by Ultrasonography (USG) in hepatic coma in children?

Practical Utility of EEG and ONSD by USG in Hepatic Coma in Children

EEG and optic nerve sheath diameter (ONSD) measurement by ultrasonography are valuable tools in the assessment and management of children with hepatic coma, with EEG abnormalities strongly predicting poor outcomes and need for liver transplantation.

EEG Utility in Hepatic Coma

Diagnostic Value

• EEG provides information on the severity of hepatic encephalopathy (HE) from minimal to severe, independent of patient cooperation 1
• EEG can detect non-convulsive seizures, which occur in approximately 20% of hepatic encephalopathy patients 2
• For diagnostic purposes, the 19 electrodes of the 10-20 International System are recommended, while for monitoring purposes, four electrodes (e.g., P3, P4, F3, F4) may be sufficient 1

Prognostic Value

• Children with moderate or severe abnormalities of EEG background on admission are significantly more likely to require liver transplantation or die 3
• Children with hepatic encephalopathy score ≤2 and normal or only mildly abnormal EEG are significantly more likely to survive without needing liver transplantation 3
• Progressive worsening of HE-EEG grading is associated with the highest mortality rates 2

Grading and Monitoring

• EEG grading based on visual pattern recognition, though informative, lacks reliability; an estimate of the basic background frequency should always be provided 1
• Quantitative EEG analysis may improve the reliability of EEG assessment in hepatic encephalopathy 1
• Hepatic encephalopathy of increasing severity is associated with:
  • Progressive slowing of the EEG 1
  • Initial increase followed by a decrease in EEG amplitude 1
  • Appearance of triphasic waves (common but not specific to HE) 1
  • Discontinuous pattern and eventually isoelectric EEG in severe cases 1

Limitations

• EEG is influenced by drugs, electric noise, and when suppressed in severe coma, cannot reliably provide information on residual cortical or subcortical activity 1
• The EEG classification based on visual pattern recognition, although informative, does not allow reliable grading 1

ONSD by Ultrasonography in Hepatic Coma

Diagnostic Value

• ONSD measured by ultrasonography is significantly increased in patients with hepatic encephalopathy compared to control groups (5.27 mm ± 0.82 vs. 4.73 mm ± 0.57) 4
• Point-of-care ultrasound (POCUS) can detect changes in optic nerve sheath diameter indicative of raised intracranial pressure 5

Prognostic Value

• Current evidence suggests ONSD measurements are not significantly associated with in-hospital mortality in hepatic encephalopathy patients 4
• ONSD measurements do not show significant correlation with West Haven HE grade or Child-Pugh Score in adult patients 4
• In other conditions with raised intracranial pressure, ONSD values >6.62 mm are associated with increased risk of brain death 6

Practical Application in Children

• Cranial ultrasonography, including ONSD measurement, is the preferred initial imaging modality for diagnosing increased intracranial pressure in neonates and children 7, 5
• ONSD measurement provides a non-invasive method to monitor for increased intracranial pressure, which may occur in severe hepatic encephalopathy 7
• Serial measurements may be more valuable than single readings for monitoring disease progression 5

Combined Approach for Management

Initial Assessment

• EEG should be performed in all patients with hepatic coma and unexplained impairment of mental status 1
• Continuous EEG monitoring is preferred over routine EEG whenever feasible in comatose patients with hepatic failure 1
• ONSD measurement by ultrasonography should be included in the initial assessment to evaluate for increased intracranial pressure 7, 5

Ongoing Monitoring

• Serial EEG recordings help monitor treatment response and disease progression 1
• Through the Index of Global Cortical Function (IGCF), sensory evoked potentials can provide information on cortical function in severe hepatic encephalopathy 1
• Repeat ONSD measurements with any change in neurological status to monitor for increasing intracranial pressure 5

Pitfalls to Avoid

• Relying solely on clinical signs of increased intracranial pressure, which may have limited reliability in children 5
• Using EEG-derived indices alone for prognostication without considering the clinical context 8
• Failing to consider medication effects on EEG patterns, which can confound interpretation 8

Conclusion

In children with hepatic coma, EEG provides valuable diagnostic and prognostic information, with abnormal patterns strongly predicting poor outcomes and need for liver transplantation. ONSD measurement by ultrasonography offers a complementary non-invasive method to detect and monitor increased intracranial pressure. Together, these tools enhance the assessment and management of pediatric hepatic coma, potentially improving outcomes through earlier intervention.