Functional cortical deafferentation from the subcortical structures in a patient with early myoclonic encephalopathy: a functional neuroimaging study

Pseudo-sawtooth pattern on amplitude-integrated electroencephalography in neonatal hypoxic-ischemic encephalopathy

OBJECTIVE

The objective of this study was to describe a novel amplitude-integrated electroencephalography (aEEG) pattern in infants with hypoxic-ischemic encephalopathy (HIE) and to assess the clinical significance.

METHODS

The aEEG traces of infants with HIE who were treated with therapeutic hypothermia (TH) from 2012 to 2017 were analyzed. A pseudo-sawtooth (PST) pattern was defined as a periodic increase of the upper and/or lower margin of the trace on aEEG without showing seizure activities on conventional EEG (CEEG).

RESULTS

Of the 46 infants, 6 (13%) had the PST pattern. The PST pattern appeared following a flat trace or a continuous low-voltage pattern and was followed by a burst-suppression pattern. On CEEG, the PST pattern consists of alternating cycles of low-voltage irregular activities and almost flat tracing. The PST pattern was associated with neuroimaging abnormalities and with various degrees of neurodevelopmental outcomes. Positive predictive values of the PST or worse pattern for adverse outcomes were high at 12 h after birth.

CONCLUSION

A novel aEEG background pattern in infants with HIE was reported. The PST pattern likely indicates a suppressed background pattern and may be linked to unfavorable outcomes. Further multicenter validation study is needed to clarify its clinical significance.

Neuronal Networks during Burst Suppression as Revealed by Source Analysis

Introduction

Burst-suppression (BS) is an electroencephalography (EEG) pattern consisting of alternant periods of slow waves of high amplitude (burst) and periods of so called flat EEG (suppression). It is generally associated with coma of various etiologies (hypoxia, drug-related intoxication, hypothermia, and childhood encephalopathies, but also anesthesia). Animal studies suggest that both the cortex and the thalamus are involved in the generation of BS. However, very little is known about mechanisms of BS in humans. The aim of this study was to identify the neuronal network underlying both burst and suppression phases using source reconstruction and analysis of functional and effective connectivity in EEG.

Material/Methods

Dynamic imaging of coherent sources (DICS) was applied to EEG segments of 13 neonates and infants with burst and suppression EEG pattern. The brain area with the strongest power in the analyzed frequency (1–4 Hz) range was defined as the reference region. DICS was used to compute the coherence between this reference region and the entire brain. The renormalized partial directed coherence (RPDC) was used to describe the informational flow between the identified sources.

Results/Conclusion

Delta activity during the burst phases was associated with coherent sources in the thalamus and brainstem as well as bilateral sources in cortical regions mainly frontal and parietal, whereas suppression phases were associated with coherent sources only in cortical regions. Results of the RPDC analyses showed an upwards informational flow from the brainstem towards the thalamus and from the thalamus to cortical regions, which was absent during the suppression phases. These findings may support the theory that a “cortical deafferentiation” between the cortex and sub-cortical structures exists especially in suppression phases compared to burst phases in burst suppression EEGs. Such a deafferentiation may play a role in the poor neurological outcome of children with these encephalopathies.

Clinical management of epileptic encephalopathies of childhood and infancy

Epileptic encephalopathies represent a group of devastating epileptic disorders that appear early in life and are characterized by pharmacoresistant generalized or focal seizures, persistent severe EEG abnormalities, and cognitive dysfunction or decline. The ictal and interictal epileptic discharges are age-specific and are either the main cause or contribute to cognitive deterioration in the idiopathic or symptomatic group respectively. Despite choosing the most appropriate anti-seizure drugs for the seizure-type and syndrome the results are often disappointing and polytherapy and/or alternative therapy becomes unavoidable. In those cases, consideration should be given to the quality of life of the child and carers. In this review we will discuss the clinical and EEG characteristics, evolution and management of age-related epileptic encephalopathies, recognized by the International League Against Epilepsy.

Early-onset epileptic encephalopathies: Ohtahara syndrome and early myoclonic encephalopathy

Ohtahara syndrome and early myoclonic encephalopathy are the earliest presenting of the epileptic encephalopathies. They are typically distinguished from each other according to specific clinical and etiologic criteria. Nonetheless, considerable overlap exists between the two syndromes in terms of clinical presentation, prognosis, and electroencephalographic signature. Newer understandings of underlying etiologies of these conditions may support the previously suggested concept that they represent a single spectrum of disease rather than two distinct disorders. We review both syndromes, with particular focus on the underlying genetics and pathophysiology and implications regarding the classification of these conditions.

Schinzel-Giedion syndrome: a further cause of early myoclonic encephalopathy and vacuolating myelinopathy

Here, we report a male child with Schinzel-Giedion syndrome associated with intramyelinic edema detected on brain magnetic resonance imaging (MRI) and persistent suppression-burst pattern on electroencephalography (EEG) with erratic myoclonus of the extremities and face. Similar to nonketotic hyperglycinemia, Schinzel-Giedion syndrome may be recognized as another causative genetic disease of early myoclonic encephalopathy and vacuolating myelinopathy.