Regional Differences and Hemispheric Symmetry of Near-Infrared Spectroscopy Readings in Healthy Pediatric Cohort: Implications for Head Injury Assessment

<p><strong>Background.</strong><br />
Portable NIRS devices such as the Infrascanner 2000 have reported &gt; 90 % accuracy for detecting clinically significant, superficial intracranial haematomas in children and adults, offering a radiation-free alternative for early triage.<br />
Current policy statements nevertheless still classify NIRS as investigational, highlighting the lack of paediatric reference data that consider regional and hemispheric variability.<br />
Neonatal datasets provide gestational-age–specific centiles, but comparable data for older infants and children remain scarce.</p><p><strong>Objective.</strong><br />
To characterise regional differences and hemispheric symmetry in NIRS absorbance values across a healthy paediatric cohort and to establish age-agnostic reference ranges and thresholds suitable for clinical use in head-injury assessment.</p><p><strong>Methods.</strong><br />
Fifty-two neurologically-normal participants (age 12–210 months) underwent bilateral frontal, temporal, parietal and occipital measurements with the Infrascanner 2000. Mean regional values, inter-hemispheric deltas (Δ), and age correlations were analysed. Reference intervals were defined as the 2.5th–97.5th percentiles; the 97.5th percentile of |Δ| served as the threshold for abnormal asymmetry.</p><p><strong>Results.</strong><br />
Marked regional variation was observed (ANOVA F &#61; 62.37, p &lt; 0.001), with higher absorbance posteriorly (parietal 6.42 ± 0.47; occipital 6.37 ± 0.41) versus anteriorly (frontal 5.66 ± 0.25; temporal 5.68 ± 0.27). Mean hemispheric differences were minimal (ΔF –0.003 ± 0.087; ΔT –0.037 ± 0.077; ΔP –0.009 ± 0.105; ΔO –0.026 ± 0.090), and age explained &lt; 4 % of variance across regions. The 97.5th percentile of |Δ| (0.193) is proposed as the upper limit for physiological asymmetry.</p><p><strong>Conclusions.</strong><br />
This study furnishes the first comprehensive, age-inclusive normative dataset for the Infrascanner 2000 in healthy children and defines a pragmatic asymmetry cut-off of 0.19 absorbance units. Integration of these reference ranges into emergency protocols may enhance the sensitivity of NIRS-guided triage while reducing avoidable CT utilisation in paediatric head trauma. Findings align with emerging evidence that portable NIRS can complement—but not yet replace—conventional imaging when applied within validated thresholds.</p><br /><p><strong>Clinical impact.</strong><br />
Adopting the proposed centiles and asymmetry threshold could refine decision-rules such as PECARN, thereby mitigating radiation burden without sacrificing diagnostic accuracy.</p>