In the world of neonatal medicine, where the fragility of new life demands the utmost precision and care, few figures have left as indelible a mark as Professor Gorm Greisen. As he steps into retirement, the scientific community pauses to reflect on the profound transformation he has brought to our understanding of the newborn brain. His pioneering work over more than four decades has not only expanded fundamental knowledge but has revolutionized clinical approaches to safeguarding the brain health of newborn infants, particularly during the precarious transitional period immediately after birth.
Neonatal brain physiology presents unique challenges due to the rapid changes occurring in the brain’s structure and function. The delicate balance between cerebral blood flow, oxygen delivery, and metabolic demand is critical for preventing brain injury and ensuring long-term neurological outcomes. Professor Greisen’s contributions carved new paths through this complex landscape, particularly through his innovative application of near-infrared spectroscopy (NIRS), a non-invasive technology that measures cerebral oxygenation in real time. This methodological breakthrough has enabled clinicians and researchers to observe the brain’s physiological states and responses dynamically, a feat previously considered unachievable in routine neonatal care.
Historically, monitoring cerebral hemodynamics in newborns was limited to invasive or indirect methods, often lacking continuous real-time data and lacking precise indicators of brain oxygenation and metabolism. Greisen’s foresight and scientific rigor catalyzed the evolution of NIRS from a niche research tool into a robust clinical instrument with profound diagnostic and therapeutic implications. It is this transformation—from experimental physiology to practical bedside monitoring—that underpins many modern neonatal care practices and research protocols today.
One of Greisen’s critical insights was the elucidation of cerebral autoregulation mechanisms in newborns. Autoregulation refers to the brain’s intrinsic ability to maintain stable blood flow despite fluctuating systemic blood pressures. His research illuminated the boundaries and vulnerabilities of this mechanism in both preterm and term infants, demonstrating that autoregulation is not always intact during the early neonatal period. These findings have redefined clinical strategies, underscoring the need for vigilant monitoring of cerebral oxygenation and perfusion to mitigate the risks of ischemic or hemorrhagic injury during this sensitive phase.
Beyond identifying limits, Greisen also advanced understanding of the oxygen–metabolic balance in the newborn brain. He revealed how subtle mismatches in oxygen supply and cerebral metabolic demand could precipitate injury, paving the way for preventative and therapeutic interventions. Through longitudinal studies employing NIRS, his work provided evidence-based frameworks for interventions aimed at optimizing cerebral oxygenation, improving neurodevelopmental outcomes by tailoring respiratory support and hemodynamic management to the individual infant’s physiology.
The breadth of Greisen’s impact extends well beyond the laboratory and neonatal intensive care units. His leadership in international collaborative research initiatives helped standardize methodologies and establish consensus protocols that ensure the comparability and reproducibility of physiological trials worldwide. This harmonization has been vital for advancing neonatal cerebral monitoring as a globally accepted clinical and research standard, benefiting countless infants through improvements in care guidelines and evidence-based practice.
Central to Greisen’s philosophy has been unwavering commitment to methodological rigor. He consistently emphasized the importance of precision in measurement techniques and careful interpretation of data, advocating against over-simplification of complex cerebral physiological phenomena. This intellectual discipline has influenced generations of clinicians and scientists, fostering a culture of critical inquiry and ethical reflection that permeates neonatal research communities today.
Equally noteworthy is Greisen’s role in cultivating a coherent and supportive global research network. He has been a linchpin in nurturing collaborations that transcend geographic and disciplinary boundaries, enabling shared learning and synergistic advances. This network has accelerated progress in neonatal brain monitoring technologies and clinical interventions, promoting cross-pollination among neuroscientists, neonatologists, engineers, and ethicists alike.
The conceptual frameworks developed under Greisen’s stewardship have also shaped how the neonatal brain is perceived – not simply as a fragile and passive organ but as a dynamic, metabolically active structure responsive to both intrinsic developmental signals and extrinsic therapeutic influences. This paradigm shift has underpinned the design of interventions that respect the brain’s unique developmental trajectories and vulnerabilities, optimizing neuroprotection from birth onward.
Crucially, Greisen’s work has underscored the ethical imperatives embedded in neonatal brain research and care. His reflections on the balance between innovation and patient safety, and on the communication of risk and benefit in complex clinical scenarios, have helped safeguard the rights and dignity of some of medicine’s most vulnerable patients. These ethical standards remain central to ongoing efforts to refine and expand cerebral monitoring technologies.
With the advent of advanced imaging and neuromonitoring tools inspired by Greisen’s legacy, neonatal care is now better equipped to detect subtle signs of cerebral compromise earlier, allowing timely and targeted interventions. This early warning capacity is pivotal for preventing long-term neurodevelopmental impairments, which can impose lifelong burdens on affected individuals and families.
Moreover, the infusion of Greisen’s principles into academic culture has elevated neonatal research to new heights, blending technological sophistication with humanistic ethos. The emphasis on collaboration, openness, and reflective practice has created fertile ground for future innovations, ensuring that neonatal brain physiology remains a vibrant and evolving field.
As the field looks to the future, the infrastructural and conceptual foundations laid by Professor Greisen continue to inspire novel explorations in cerebral monitoring, including multimodal approaches integrating NIRS with advanced electrophysiology and imaging techniques. These integrative strategies hold promise for unraveling even deeper complexities of the newborn brain and tailoring individualized neuroprotective therapies.
In summation, the retirement of Professor Gorm Greisen marks not an end but a landmark in the ongoing journey to understand and protect the newborn brain. His exceptional contributions have reshaped neuroscience and neonatology, leaving a legacy that transcends disciplines and borders. The clinical tools, research networks, and ethical frameworks he helped forge continue to illuminate pathways toward safer births and healthier lives, reflecting a lifetime devoted to pioneering research and compassionate care.
As neonatal medicine embraces new frontiers, it is clear that the spirit of inquiry, innovation, and collaboration embodied by Greisen will persist as a beacon for generations of researchers and clinicians. Through this lasting influence, the transformation of newborn brain physiology — from mysterious and vulnerable to measurable and manageable — remains one of the most impressive scientific achievements in recent memory, promising an ever-brighter horizon for the tiniest patients worldwide.
Article References:
Kooi, E.M.W., Pellicer, A., Mitra, S. et al. Gorm Greisen and the transformation of our understanding of newborn brain physiology: a tribute on the occasion of his retirement, on behalf of the ESPR NIRS Special Interest Group. Pediatr Res (2026). https://doi.org/10.1038/s41390-026-05017-0
DOI: https://doi.org/10.1038/s41390-026-05017-0
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