Objectives: The objective of this study was to compare gold cup and hydrogel electrodes for frequency of electrode replacement, longevity of the original electrodes after initial placement, recording quality, and skin safety issues in long-term EEG studies in preterm neonates. Methods: We performed a prospective trial with newborns born at ≥۲۳ weeks and ≤۳۰ weeks of gestational age (GA). Two mirror image EEG electrode arrays were utilized on consecutive subjects, where gold cup electrodes alternated with hydrogel electrodes. Results: Our sample included 50 neonates with mean GA of 27 (±۱) weeks. The mean recording time was 84 (±۱۵) hours. No difference was present in the frequency of replacement of either type across the total recording time (p=0.8). We collected the time at which electrodes were first replaced, and found that hydrogel electrodes showed a longer uninterrupted recording time of 28(±۲) hours vs. 20(±۲) hours for gold cup electrodes (p=0.01). Recording quality was similar in either type (p=0.2). None of the patients experienced significant skin irritation from a discrete electrode. Conclusion: Long-term EEG studies can be performed with either gold cup or hydrogel electrodes, validating the safety and quality of both electrode types. Significance: Hydrogel electrodes are a reasonable alternative for use in long-term EEG studies in preterm neonates.

Introduction

Seizures in preterm neonates have been reported with an incidence ranging between 3.9%-48% (Hellstrom-Westas et al. , 1985, Scher et al. , 1993, Vesoulis et al. , 2014, Lloyd et al. , 2017). Seizure incidence varies with the EEG modality utilized- amplitude-integrated EEG (aEEG) versus conventional EEG. Early life seizures in sick premature neonates portend both poor short and long term outcomes. Seizures in extremely low birth weight neonates were associated with short term morbidities such as severe intraventricular hemorrhage, sepsis, meningitis and cystic periventricular leukomalacia (Davis et al. , 2010). Long-term adverse outcomes (cerebral palsy, developmental delay and epilepsy) were reported in preterm neonates with confirmed neonatal status epilepticus (Scher et al. , 1993, Pisani et al. , 2016), and decreased language performance at 2 years of age was noted in patients with seizures detected in the first three days of life (Vesoulis et al. , 2014). To better define the prevalence and significance of seizures in this population, long-term conventional EEG recording in preterm neonates is gaining widespread interest and increasingly being clinically utilized. Full montage EEG (full scalp coverage) has significant advantages over amplitude-integrated EEG. aEEG is a bedside neuromonitoring tool that records EEG signal using one or two channels placed in the centroparietal areas of the newborn’s head (Toet et al. , 2009). aEEG was found to have lower sensitivity and specificity in seizure detection, in newborns (Hellstrom-Westas, 1992, Toet et al. , 2002, Rennie et al. , 2004, Shah et al. , 2008). The time-compressed nature of aEEG tracings and the centro-parietal location of the electrodes, may lead to reduced detection of seizures with low amplitude, brief duration (Hellstrom-Westas, 1992) and focal seizures distant from the aEEG electrodes (Rakshasbhuvankar et al. , 2015). The use of full montage EEG electrode array on a preterm neonate can be challenging due to the small head size and the vulnerability of the premature skin. Additionally, for long term EEG studies, the integrity of the skin must be balanced against EEG recording quality. At our institution, we currently utilize gold cup electrodes for all clinical studies. With application of gold cup electrodes, first a gentle cleansing gel is used to remove debris from the skin, and conductive paste and paper tape are used to fix the electrodes in place. Collodion, used to glue down the gold cup electrodes in most long-term EEG studies, is not used in the preterm population due to the fragility of the preterm scalp, which limits the stability of the gold cup electrodes, especially in a humidified and warm environment such as in an incubator.