Abstract
Background: Near-infrared spectrophotometry (NIRS) can be used to reliably assess changes in cerebral oxy- and deoxyhaemoglobin (O2Hb and HHb) concentrations associated with normal and pathologic processes. It is well suited for the purpose of functional brain analysis. However, in the term and preterm infant, normal oscillatory fluctuations in cerebral haemodynamics can obscure functional activation changes and complicate data analysis.
Aim: 1. To improve visualization of functional activation changes in the term and preterm infant. 2. To establish a method to detect functional impairments based on NIRS using different functional stimuli.
Methods: The NIRS instrument consists of a measuring system, stimulation unit and sensors. To allow for mapping of different brain regions, 8 locations were analyzed simultaneously. Several different stimulation tasks were performed: tactile (vibration motor), auditory (headphones), and visual (light emitting diodes). Four sensors were placed over either the C3 or C4 area (tactile), T3 or T4 area (auditory), or the occipital O1 area (visual). Left and right sides were alternately stimulated for 20s. Each stimulation period was followed by 10 seconds of rest. Stimulation-rest cycles were repeated for a minimum of 10min.
Results: For tactile stimulation, a total of 29 measurements in 15 neonates were recorded. For auditory stimulation a total of 27 measurements in 14 neonates, and for visual stimulation a total of 30 measurements in 10 neonates were recorded. Without application of specialized data analysis techniques, separated, localized, functional activations were visible in 10% of the measurements. In the remaining 90% haemodynamic changes in O2Hb and HHb, resulting from non-localized, slow vasomotion, obscured the functional signal. The amplitude of this vasomotion in the visual cortex was smaller compared to the other areas, but much larger in neonates than in adults. The latter due to immature autoregulation. Novel data analysis methods, such as an automated movement recognition algorithm and adaptive filter, allowed suppression of the slow vasomotion signal and improved the visualization of functional activation changes.
Conclusions: Suppression of the slow vasomotion signal enables us to more clearly visualize the local changes in cerebral oxygenation due to tactile, auditory and visual stimulation.
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Haensse, D., Szabo, P., Brown, D. et al. 272 Nirs Detects Cerebral Oxygenation Changes Induced by Tactile, Auditory and Visual Stimulation in Term Neonates. Pediatr Res 56, 510 (2004). https://doi.org/10.1203/00006450-200409000-00295
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DOI: https://doi.org/10.1203/00006450-200409000-00295