Journal of Pediatric Neurology 2024; 22(01): 001-007
DOI: 10.1055/s-0042-1758471
Review Article

Embryology and Clinical Development of the Human Olfactory System

1   Department of Paediatrics, University of Calgary Cumming School of Medicine and Alberta Children's Hospital Research Institute (Owerko Centre), Calgary, Alberta, Canada
2   Department of Pathology and Laboratory Medicine (Neuropathology), University of Calgary Cumming School of Medicine and Alberta Children's Hospital Research Institute (Owerko Centre), Calgary, Alberta, Canada
3   Department of Clinical Neurosciences, University of Calgary Cumming School of Medicine and Alberta Children's Hospital Research Institute (Owerko Centre), Calgary, Alberta, Canada
,
Laura Flores-Sarnat
1   Department of Paediatrics, University of Calgary Cumming School of Medicine and Alberta Children's Hospital Research Institute (Owerko Centre), Calgary, Alberta, Canada
3   Department of Clinical Neurosciences, University of Calgary Cumming School of Medicine and Alberta Children's Hospital Research Institute (Owerko Centre), Calgary, Alberta, Canada
› Author Affiliations
Funding This research received funding from Alberta Children's Hospital Research Institute, Grant #60–28450, Project 10027949.

Abstract

The olfactory system is unique as a special sensory system in its developmental neuroanatomy and function. Neonatal olfactory reflexes can be detected in the fetus from 30 weeks gestation and can be tested in term and preterm neonates and older children. Most efferent axons from the olfactory bulb terminate in the anterior olfactory nucleus within the olfactory tract, with secondary projections to the amygdala, hypothalamus, hippocampus, and entorhinal cortex (parahippocampal gyrus), with tertiary projections also to the insula and other cortical regions. The olfactory bulb and tract incorporate an intrinsic thalamic equivalent. The olfactory bulb may be primary in generating olfactory auras in some cases of temporal lobe epilepsy. Developmental malformations may involve the olfactory bulb and tract, isolated or as part of complex cerebral malformations and genetic syndromes. Primary neural tumors may arise in the olfactory bulb or nerve. Impaired olfaction occurs in neonatal hypoxic/ischemic and some metabolic encephalopathies. Loss of sense of smell are early symptoms in some neurodegenerative diseases and in some viral respiratory diseases including coronavirus disease 2019. Testing cranial nerve I is easy and reliable at all ages, and is recommended in selected neonates with suspected brain malformations or encephalopathy.

Ethics Committee Approval

This study was approved by the Conjoint Health Research Ethics Committee of the University of Calgary and Alberta Health Services.




Publication History

Received: 24 July 2022

Accepted: 29 September 2022

Article published online:
30 March 2023

© 2023. Thieme. All rights reserved.

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany

 
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