Presented at the Neonatal Society 2010 Autumn Meeting.
Mitra S1, O’Reilly H1, Cooper R2, Mitchell A3, Everdell N2, Gibson AP2, Hebden JC2, Austin T1
1 Neonatal Unit, Cambridge University Hospitals NHS Foundation Trust, Hills Road, Cambridge, CB2 0QQ, UK
2 Dept. of Medical Physics and Bioengineering, University College London, WC1E 6BT, UK
3 Dept. of Neurophysiology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, CB2 0QQ, UK
Background: Seizures in the newborn are frequently under diagnosed and can be difficult to treat (1). This study aimed to study the relationship between electrical activity and regional blood flow (neurovascular coupling) using a novel integrated optical imaging-EEG system. Ethical approval for the study was received from Cambridgeshire REC.
Methods: Four infants born at term (median 38+5, range 38+1 to 42+1 weeks) and presenting with neonatal seizures due to a variety of pathologies, were studied. A unique dual-modality sensing array, developed at the Biomedical Optics Research Laboratory, UCL was used (2). This consists of two sets of 5 light source and 6 detector fibre bundles, one set arranged over each temporal-parietal region and EEG electrodes forming a standard neonatal montage. Data were collected for between 45 and 100 minutes. Control data was collected from two healthy term infants.
Results: Data were successfully collected from all infants. The four infants presenting with seizures had been treated with anticonvulsant medication. None of the EEG data revealed evidence of electrographic seizure activity or of any definite inter-ictal epileptiform discharges. The optical data however, revealed transient haemodynamic events in three out of four neurologically compromised infants which were absent in the two control infants. The haemodynamic events consisted of a brief rise in HbO2 followed by a significant fall below baseline before slowly returning to normal. Each event lasted 93.2 seconds on average, and the mean inter-event interval was 394 seconds. Images of regional changes in HbO2 were reconstructed using a linear image reconstruction algorithm (3).
Figure 1: Images showing regional changes in HbO2 every 10s over the left (top) and right (bottom)
temporal-parietal region, showing an initial increase and subsequent decrease in HbO2 from baseline.
Conclusion: This study demonstrates the feasibility of simultaneous optical-EEG measurements using an integrated optoelectrode to study neurovascular coupling in the neonatal brain. We have identified consistent, transient haemodynamic events in term infants with perinatal brain injury, in whom the diagnosis of seizure and treatment with phenobarbitone are the only common factors. Whether these features result from disturbances in local autoregulatory control or from continuing seizure-related neuronal activity, not visible to conventional EEG, is uncertain and warrants further investigation.
Corresponding author: topun.austin@addenbrookes.nhs.uk
References
1. Silverstein FS, Jensen FE (2007) Neonatal seizures. Ann Neurol. 62, 112-120.
2. Cooper RJ, Everdell NL, Enfield LC et al. Design and evaluation of a probe for simultaneous EEG and nearinfrared imaging of cortical activation. Phys Med Biol. 2009;54:2093-102.
3. A.P Gibson, T.Austin, N.L Everdell, et al. Whole-head optical tomography of neonatal evoked responses. Neuroimage 2006;30:521-528.