Neuroembryonic and fetal brain development: Relevance to fetal/neonatal neurological training.

Insight into neuroembryology, developmental neuroanatomy and neurophysiology distinguish the diagnostic approaches of paediatric from adult neurologists and general paediatricians. These fundamental disciplines of basic neuroscience could be more effectively taught during paediatric neurology and most residency programmes, that will strengthen career-long learning. Interdisciplinary training of fetal-neonatal neurology within these programs requires working knowledge of neuroembryology applied to maternal reproductive health influencing the maternal-placental-fetal triad, neonate, and young child. Systematic didactic teaching of development in terms of basic neuroscience with neuropathological context would better address needed clinical skill sets to be incorporated into paediatric neurology and neonatology residencies to address brain health and diseases across childhood. Trainees need to recognize the continuity of development, established by maternal reproductive health before conception with gene -environment influences over the first 1000 days. Considerations of neuroembryology that explain earlier brain development during the first half of pregnancy enhances an understanding of effects throughout gestation through parturition and into neonatal life. Neonatal EEG training enhances these clinical descriptions by applying serial EEG-state analyses of premature neonates through early childhood to recognize evolving patterns associated with neuronal maturation and synaptogenesis. Neuroimaging studies offer comparisons of normal structural images with malformations and destructive lesions to correlate with clinical and neurophysiological findings. This analysis better assesses aberrant developmental processes in the context of neuroembryology. Time-specific developmental events and semantic precision are important for accurate phenotypic descriptions for a better understanding of etiopathogenesis with maturation. Certification of paediatric neurology training programme curricula should apply practical knowledge of basic neuroscience in the context of nervous system development and maturation from conception through postnatal time periods. Interdisciplinary fetal-neonatal neurology training constitutes an important educational component for career-long learning.

Updated clinical recommendations for the management of tuberous sclerosis complex associated epilepsy.

Children with tuberous sclerosis complex (TSC), may experience a variety of seizure types in the first year of life, most often focal seizure sand epileptic spasms. Drug resistance is seen early in many patients, and the management of TSC associated epilepsy remain a major challenge for clinicians. In 2018 clinical recommendations for the management of TSC associated epilepsy were published by a panel of European experts. In the last five years considerable progress has been made in understanding the neurobiology of epileptogenesis and three interventional randomized controlled trials have changed the therapeutic approach for the management of TSC associated epilepsy. Pre-symptomatic treatment with vigabatrin may delay seizure onset, may reduce seizure severity and reduce the risk of epileptic encephalopathy. The efficacy of mTOR inhibition with adjunctive everolimus was documented in patients with TSC associated refractory seizures and cannabidiol could be another therapeutic option. Epilepsy surgery has significantly improved seizure outcome in selected patients and should be considered early in all patients with drug resistant epilepsy. There is a need to identify patients who may have a higher risk of developing epilepsy and autism spectrum disorder (ASD). In the recent years significant progress has been made owing to the early identification of risk factors for the development of drug-resistant epilepsy. Better understanding of the mechanism underlying epileptogenesis may improve the management for TSC-related epilepsy. Developmental neurobiology and neuropathology give opportunities for the implementation of concepts related to clinical findings, and an early genetic diagnosis and use of EEG and MRI biomarkers may improve the development of pre-symptomatic and disease-modifying strategies.

Maturation of metastases in peripheral neuroblastic tumors (neuroblastoma) of children.

Peripheral neuroblastic tumors of childhood exhibit 3 principal neural crest lineages: primitive neuroblastoma, ganglioneuroblastoma, and ganglioneuroma. They are unique in undergoing maturation of neurons (ganglion cells) and Schwann cells, thereby recapitulating normal fetal neuronal development in the brain. Precision in estimating neurogenesis is enhanced by immunoreactivities of markers of neuronal maturation. Whether organ tissue factors in different sites of metastases influence rates of maturation and whether metastases are similar to their primary neuroblastic tumor are incompletely documented. Four young children, 1 with a mixed primary adrenal tumor and 3 with metastases were studied at surgery or autopsy. Immunocytochemical reactivities included microtubule-associated protein-2, synaptophysin, chromogranin-A, somatostatin, keratan sulfate, vimentin, S-100ß protein, and PHOX2B. Primary tumors were non-uniform with regions of either poor or enhanced maturation. Both neuronal and Schwannian lineages were represented in each tumor type but differed in proportions. Bi- or multi-nucleated ganglion cells matured equal to mononuclear forms. Ganglion cell maturation was similar in metastases regardless of the target organ. Metastases resembled primary tumors. Immunocytochemical markers of neuronal and of Schwann cell maturation provide greater diagnostic precision to supplement histological criteria. Interval between diagnosis of primary tumor and metastases, metastatic target tissues, and chemotherapy over an interval of time do not appear to influence neuroblastic or Schwann cell differentiation.

Fetal anomaly diagnosis and termination of pregnancy.

The aim of this review was to discuss bioethics in prenatal diagnosis and health care after recent legislative and judicial changes affecting reproductive rights, such as the repeal of 'Roe v. Wade' in the United States. We recognize that abortion involves particular moralities that are not universal or shared by all cultures, groups, and individuals. We reviewed the historical aspects of embryology and personhood, fetal morbidity and mortality, and parental options for prenatal diagnostic testing. We examined relevant ethical issues including informed consent, the emergence of fetal pain, reproductive autonomy, the fiduciary responsibilities of pregnant mothers, and the obligations of physicians caring for the maternal-fetal dyad. The code of medical ethics includes respect for decisional privacy and the protection of information shared in confidence. When a fetal anomaly is diagnosed, pregnant mothers must be informed about the risks, burdens, and alternatives in either continuing or terminating the pregnancy. Parental choice should include the right to refuse testing, the informed choice not to know about certain genetic test results, and the right to make informed decisions about the best interests of the future child. In the diagnosis and care of fetal anomalies, moral dilemmas arise. Before fetal viability, the mother's autonomy, sense of beneficence, and personal values should be trusted and respected. Perinatal palliative care should be available to pregnant mothers whose anomalous fetus is carried to birth.

Sequences of synaptogenesis in the human fetal and neonatal brain by synaptophysin immunocytochemistry.

Synaptogenesis is the final phase of axonal pathfinding. Its sequences of spatial and temporal development in the immature nervous system are precisely timed and consistent. Synaptophysin, a principal structural glycoprotein of synaptic vesicle membranes regardless of the chemical transmitter substance within, is a reliable means of demonstrating sequences of synaptogenesis in human fetal brain tissue at autopsy and is resistant to postmortem autolysis. Furthermore, synaptophysin molecules are demonstrated during axoplasmic flow before being assembled into membranes in immature axons and also mature axons of neurons with a high metabolic rate. In brain malformations these sequences often are altered both in distribution of synapses and in timing, often delayed but sometimes precocious, with postnatal clinical manifestations such as epilepsy and cognitive development.

The Alberta Congenital Anomalies Surveillance System: a 40-year review with prevalence and trends for selected congenital anomalies, 1997-2019. / Le système de surveillance des anomalies congénitales de l'Alberta : compte rendu des données sur 40 ans avec prévalence et tendances de certaines anomalies congénitales entre 1997 et 2019.

INTRODUCTION: Current published long-term provincial or territorial congenital anomaly data are lacking for Canada. We report on prevalence (per 1000 total births) and trends in 1997-2019, in Alberta, Canada, for selected congenital anomalies. Associated risk factors are also discussed. METHODS: We used data from the Alberta Congenital Anomalies Surveillance System (ACASS) to calculate the prevalence and perform chi-square linear trend analyses. RESULTS: From 1997 to 2019, the overall prevalence of neural tube defects was stable, at 0.74 per 1000 total births. The same was true for spina bifida (0.38), orofacial clefts (1.99), more severe CHDs (transposition of the great arteries, 0.38; tetralogy of Fallot, 0.33; and hypoplastic left heart syndrome, 0.32); and gastroschisis (0.38). Anencephaly, cleft palate and anorectal malformation significantly decreased with a prevalence of 0.23, 0.75 and 0.54 per 1000 total births, respectively. Significantly increasing trends were reported for anotia/microtia (0.24), limb reduction anomalies (0.73), omphalocele (0.36) and Down syndrome (2.21) and for hypospadias and undescended testes (4.68 and 5.29, respectively, per 1000 male births). CONCLUSION: Congenital anomalies are an important public health concern with significant social and societal costs. Surveillance data gathered by ACASS for over 40 years can be used for planning and policy decisions and the evaluation of prevention strategies. Contributing genetic and environmental factors are discussed as is the need for continued surveillance and research.

The Utility of Simulation-Based Training in Teaching Frontline Providers Modified Sarnat Encephalopathy Examination: A Randomized Controlled Pilot Trial.

BACKGROUND: Limited training in targeted neurological examination makes it challenging for frontline providers to identify newborns with perinatal asphyxia eligible for therapeutic hypothermia. This training is important in the era of telemedicine, where the experts can remotely guide further care of these newborns. METHODS: This randomized controlled pilot study was conducted in a South Indian tertiary hospital. Neonatal nurses, who had no previous hands-on experience in MSEE, were trained in modified Sarnat staging by a didactic teaching session using online teaching module. The nurses were then randomized into two groups for hands-on demonstration by the same trainer (low-fidelity mannequin versus a healthy term newly born infant). After the training period, MSEEs of a normal newborn were performed independently by nurses and were video recorded and assessed by three blinded neonatologists with expertise in neonatal neurology. A follow-up examination was performed by the same nurses after three months to assess skill retention. RESULTS: The 10 global ratings of the components of the MSEE were comparable among both groups in both initial and follow-up assessments. The overall diagnostic value was comparable between the simulation and traditional groups (93.75%, 94.11%, respectively). Follow-up examination after three months showed better skill retention in the simulation group (84%) compared with the traditional group (66.7%). CONCLUSIONS: Online-based and low-fidelity mannequin training was equally effective as the traditional method of teaching MSEE in term neonates.

The ILAE consensus classification of focal cortical dysplasia: An update proposed by an ad hoc task force of the ILAE diagnostic methods commission.

Ongoing challenges in diagnosing focal cortical dysplasia (FCD) mandate continuous research and consensus agreement to improve disease definition and classification. An International League Against Epilepsy (ILAE) Task Force (TF) reviewed the FCD classification of 2011 to identify existing gaps and provide a timely update. The following methodology was applied to achieve this goal: a survey of published literature indexed with ((Focal Cortical Dysplasia) AND (epilepsy)) between 01/01/2012 and 06/30/2021 (n = 1349) in PubMed identified the knowledge gained since 2012 and new developments in the field. An online survey consulted the ILAE community about the current use of the FCD classification scheme with 367 people answering. The TF performed an iterative clinico-pathological and genetic agreement study to objectively measure the diagnostic gap in blood/brain samples from 22 patients suspicious for FCD and submitted to epilepsy surgery. The literature confirmed new molecular-genetic characterizations involving the mechanistic Target Of Rapamycin (mTOR) pathway in FCD type II (FCDII), and SLC35A2 in mild malformations of cortical development (mMCDs) with oligodendroglial hyperplasia (MOGHE). The electro-clinical-imaging phenotypes and surgical outcomes were better defined and validated for FCDII. Little new information was acquired on clinical, histopathological, or genetic characteristics of FCD type I (FCDI) and FCD type III (FCDIII). The survey identified mMCDs, FCDI, and genetic characterization as fields for improvement in an updated classification. Our iterative clinico-pathological and genetic agreement study confirmed the importance of immunohistochemical staining, neuroimaging, and genetic tests to improve the diagnostic yield. The TF proposes to include mMCDs, MOGHE, and "no definite FCD on histopathology" as new categories in the updated FCD classification. The histopathological classification can be further augmented by advanced neuroimaging and genetic studies to comprehensively diagnose FCD subtypes; these different levels should then be integrated into a multi-layered diagnostic scheme. This update may help to foster multidisciplinary efforts toward a better understanding of FCD and the development of novel targeted treatment options.

Ganglion cell maturation in peripheral neuroblastic tumours of children.

Peripheral neuroblastic tumours of neural crest origin are the most frequent solid neoplasms outside the CNS in children. Neuroblastoma/ganglioneuroblastoma/ganglioneuroma have a natural evolution of histological differentiation over time. Together with mitosis-karyorrhexis index and patient age (International Neuroblastoma Pathology Classification criteria), ganglion cell maturation determines grading and prognosis. Maturation presently is usually assessed only histologically. Immunocytochemical tissue markers defining neuroblast maturation in fetal CNS were here applied to peripheral neuroblastic tumours arising in the adrenal medulla or sympathetic chain. Paraffin sections of resected tumours of 4 toddlers were examined using antibodies demonstrating neuronal identity and maturation: MAP2; synaptophysin; chromogranin-A; NeuN; keratan sulfate (KS); glutamate receptor antibody (GluR2). Synaptophysin, normally a late marker of neuroblast differentiation, was the earliest expressed in neuroblastoma. Others include: Ki67; S-100ß protein; vimentin; nestin; α-B-crystallin; neuroblastoma marker PHOX2B. Various degrees of ganglion cell maturation were demonstrated by MAP2, chromogranin, synaptophysin, KS, and GluR2; NeuN was uniformly negative, consistent with sympathetic neurons. KS was sparsely distributed within the tumours in interstitial tissue, within processes of some non-neuronal cells, and adherent to somata and proximal neuritic trunks. Neoplastic ganglion cells with multiple nuclei matured similar to mono-nuclear forms. PHOX2B did not distinguish maturational stages. S-100ß protein and α-B-crystallin labeled Schwann cells, especially Schwannian ganglioneuroma. Immunocytochemical markers of neuroblast maturation in fetal brain also are useful in peripheral neuroblastic tumours, providing greater precision than histology alone. The most practical are MAP2, chromogranin-A, and synaptophysin. Prognosis and choice of treatment including chemotherapy might be influenced.

Semaphorin-Plexin Signaling: From Axonal Guidance to a New X-Linked Intellectual Disability Syndrome.

BACKGROUND: Semaphorins and plexins are ligands and cell surface receptors that regulate multiple neurodevelopmental processes such as axonal growth and guidance. PLXNA3 is a plexin gene located on the X chromosome that encodes the most widely expressed plexin receptor in fetal brain, plexin-A3. Plexin-A3 knockout mice demonstrate its role in semaphorin signaling in vivo. The clinical manifestations of semaphorin/plexin neurodevelopmental disorders have been less widely explored. This study describes the neurological and neurodevelopmental phenotypes of boys with maternally inherited hemizygous PLXNA3 variants. METHODS: Data-sharing through GeneDx and GeneMatcher allowed identification of individuals with autism or intellectual disabilities (autism/ID) and hemizygous PLXNA3 variants in collaboration with their physicians and genetic counselors, who completed questionnaires about their patients. In silico analyses predicted pathogenicity for each PLXNA3 variant. RESULTS: We assessed 14 boys (mean age, 10.7 [range 2 to 25] years) with maternally inherited hemizygous PLXNA3 variants and autism/ID ranging from mild to severe. Other findings included fine motor dyspraxia (92%), attention-deficit/hyperactivity traits, and aggressive behaviors (63%). Six patients (43%) had seizures. Thirteen boys (93%) with PLXNA3 variants showed novel or very low allele frequencies and probable damaging/disease-causing pathogenicity in one or more predictors. We found a genotype-phenotype correlation between PLXNA3 cytoplasmic domain variants (exons 22 to 32) and more severe neurodevelopmental disorder phenotypes (P < 0.05). CONCLUSIONS: We report 14 boys with maternally inherited, hemizygous PLXNA3 variants and a range of neurodevelopmental disorders suggesting a novel X-linked intellectual disability syndrome. Greater understanding of PLXNA3 variant pathogenicity in humans will require additional clinical, computational, and experimental validation.

Transitory and Vestigial Structures of the Developing Human Nervous System.

As with many body organs, the human central nervous system contains many structures and cavities that may have had functions in embryonic and fetal life but are vestigial or atrophic at maturity. Examples are the septum pellucidum, remnants of the lamina terminalis, Cajal-Retzius neurons, induseum griseum, habenula, and accessory olfactory bulb. Other structures are transitory in fetal or early postnatal life, disappearing from the mature brain. Examples are the neural crest, subpial granular glial layer of Brun over cerebral cortex, radial glial cells, and subplate zone of cerebral cortex. At times persistent fetal structures that do not regress may cause neurological problems or indicate a pathologic condition, such as Blake pouch cyst. Transitory structures thus can become vestigial. Examples are an excessively wide cavum septi pellucidi, suprapineal recess of the third ventricle, trigeminal artery of the posterior fossa circulation, and hyaloid ocular artery. Arrested maturation might be considered another aspect of vestigial structure. An example is the persistent microcolumnar cortical architecture in focal cortical dysplasia type Ia, in cortical zones of chronic fetal ischemia, and in some metabolic/genetic congenital encephalopathies. Some transitory structures in human brain are normal adult structures in lower vertebrates. Recognition of transitory and vestigial structures by fetal or postnatal neuroimaging and neuropathologically enables better understanding of cerebral ontogenesis and avoids misinterpretations.

Focal cortical dysplasia type 1.

The ILAE classification of Focal Cortical Dysplasia (FCD) from 2011 has quickly gained acceptance in clinical practice and research and is now widely used around the world. This histopathology-based classification scheme proposed three subtypes, that is, FCD Type 1 (with architectural abnormalities of the neocortex), FCD Type 2 (with cytoarchitectural abnormalities of the neocortex) and FCD Type 3 (architectural abnormalities of the neocortex associated with another principle lesion acquired during early life). Valuable knowledge was gathered during the last decade validating the clinical, pathological and genetic classification of FCD Type 2. This is in contrast to FCD subtype 1 and 3 with only few robust or new insights. Herein, we provide an overview about current knowledge about FCD Type 1 and its three subtypes. Available data strengthened, however, FCD Type 1A in particular, whereas a comprehensive clinico-pathological specification for FCD Type 1B and 1C subtypes remain to be shown. The lack of a valid animal model for FCD Type 1 further supports our call and the ongoing need for systematic research studies based on a careful clinico-pathological and genetic stratification of patients and human brain tissues.

Toward a better definition of focal cortical dysplasia: An iterative histopathological and genetic agreement trial.

OBJECTIVE: Focal cortical dysplasia (FCD) is a major cause of difficult-to-treat epilepsy in children and young adults, and the diagnosis is currently based on microscopic review of surgical brain tissue using the International League Against Epilepsy classification scheme of 2011. We developed an iterative histopathological agreement trial with genetic testing to identify areas of diagnostic challenges in this widely used classification scheme. METHODS: Four web-based digital pathology trials were completed by 20 neuropathologists from 15 countries using a consecutive series of 196 surgical tissue blocks obtained from 22 epilepsy patients at a single center. Five independent genetic laboratories performed screening or validation sequencing of FCD-relevant genes in paired brain and blood samples from the same 22 epilepsy patients. RESULTS: Histopathology agreement based solely on hematoxylin and eosin stainings was low in Round 1, and gradually increased by adding a panel of immunostainings in Round 2 and the Delphi consensus method in Round 3. Interobserver agreement was good in Round 4 (kappa = .65), when the results of genetic tests were disclosed, namely, MTOR, AKT3, and SLC35A2 brain somatic mutations in five cases and germline mutations in DEPDC5 and NPRL3 in two cases. SIGNIFICANCE: The diagnoses of FCD 1 and 3 subtypes remained most challenging and were often difficult to differentiate from a normal homotypic or heterotypic cortical architecture. Immunohistochemistry was helpful, however, to confirm the diagnosis of FCD or no lesion. We observed a genotype-phenotype association for brain somatic mutations in SLC35A2 in two cases with mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy. Our results suggest that the current FCD classification should recognize a panel of immunohistochemical stainings for a better histopathological workup and definition of FCD subtypes. We also propose adding the level of genetic findings to obtain a comprehensive, reliable, and integrative genotype-phenotype diagnosis in the near future.

Excitatory/Inhibitory Synaptic Ratios in Polymicrogyria and Down Syndrome Help Explain Epileptogenesis in Malformations.

BACKGROUND: The ratio between excitatory (glutamatergic) and inhibitory (GABAergic) inputs into maturing individual cortical neurons influences their epileptic potential. Structural factors during development that alter synaptic inputs can be demonstrated neuropathologically. Increased mitochondrial activity identifies neurons with excessive discharge rates. METHODS: This study focuses on the neuropathological examinaion of surgical resections for epilepsy and at autopsy, in fetuses, infants, and children, using immunocytochemical markers, and electron microscopy in selected cases. Polymicrogyria and Down syndrome are highlighted. RESULTS: Factors influencing afferent synaptic ratios include the following: (1) synaptic short-circuitry in fused molecular zones of adjacent gyri (polymicrogyria); (2) impaired development of dendritic spines decreasing excitation (Down syndrome); (3) extracellular keratan sulfate proteoglycan binding to somatic membranes but not dendritic spines may be focally diminished (cerebral atrophy, schizencephaly, lissencephaly, polymicrogyria) or augmented, ensheathing individual axons (holoprosencephaly), or acting as a barrier to axonal passage in the U-fiber layer. If keratan is diminished, glutamate receptors on the neuronal soma enable ectopic axosomatic excitatory synapses to form; (4) dysplastic, megalocytic neurons and balloon cells in mammalian target of rapamycin disorders; (5) satellitosis of glial cells displacing axosomatic synapses; (6) peri-neuronal inflammation (tuberous sclerosis) and heat-shock proteins. CONCLUSIONS: Synaptic ratio of excitatory/inhibitory afferents is a major fundamental basis of epileptogenesis at the neuronal level. Neuropathology can demonstrate subcellular changes that help explain either epilepsy or lack of seizures in immature brains. Synaptic ratios in malformations influence postnatal epileptogenesis. Single neurons can be hypermetabolic and potentially epileptogenic.

Keratan sulfate proteoglycan as an axonal insulating barrier in the forebrain of fetuses with alobar/semi-lobar holoprosencephaly.

BACKGROUND: Keratan sulfate (KS) is an abundant proteoglycan in the developing human CNS where it functions as an extracellular axonal guidance molecule, repelling glutamatergic while facilitating GABAergic axons. It ensheaths axonal fascicles. In fetal brain maturation, KS acts as a barrier to axonal penetration. Its possible role in the pathogenesis of fetal holoprosencephaly (HPE) was studied. MATERIALS AND METHODS: Forebrains of 6 human fetuses with HPE identified by prenatal ultrasound were examined at autopsy with KS immunoreactivity and other markers of cellular maturation and synaptogenesis, with age-matched controls. RESULTS: KS was strongly expressed in astrocytes in the thalamus from 13 weeks gestational age (GA) and in globus pallidus but not corpus striatum. Cortical plate reactivity was limited to the molecular zone, where KS was excessive, ensheathing individual transverse molecular zone axons. Axonal envelopment preceding myelination also was seen in the internal capsule and thalamocortical projections, but perifascicular KS was diminished. KS was not expressed in hippocampus in either HPE or controls. Glutamate receptor-2 (GluR2) was evident in hippocampal granular and pyramidal neurons at mid-gestation. KS distribution did not, however, correlate with synaptophysin. CONCLUSION: Excessive ensheathment of axons by KS provides additional protection of GABAergic inhibitory axons and synapses that may help suppress epileptogenesis. Though involved in selection of excitatory and inhibitory synaptogenesis, KS does not follow a developmental sequence corresponding to synaptophysin or GluR2 reactivities in either HPE or in normal fetal brain.

Survey on Olfactory Testing by Pediatric Neurologists: Is the Olfactory a "True" Cranial Nerve?

BACKGROUND: The olfactory nerve was conceptualized in the 4th century BC by Alcmaeon and described anatomically by Winslow in 1733. Cranial nerves (CNs) were named and numbered by Soemmerring in 1791. Notions still prevail that the olfactory (CN1) is not a "true" cranial nerve. METHODS: To confirm our impression that the olfactory nerve is infrequently tested by North American pediatric neurologists, a survey was distributed to members of national pediatric neurology societies in Mexico, Canada, and the United States. A total of 233 responses were received to 6 multiple-choice questions regarding practice patterns examining CN1 in neonates and children and in metabolic, endocrine, and genetic disorders and cerebral malformations. Two of the questions addressed familiarity with neonatal olfactory reflexes and asked whether the olfactory is a "true" cranial nerve. RESULTS: Only 16% to 24% of North American pediatric neurologists examine CN1 in neonates, even in conditions in which olfaction may be impaired. About 40% of respondents were aware of olfactory reflexes. A minority 15% did not consider CN1 as a "true" cranial nerve. CONCLUSIONS: Olfactory evaluation in neonates is simple, rapid, and inexpensive. It tests parts of the brain not otherwise examined. It may assist diagnosis in cerebral malformations; metabolic, endocrine, and hypoxic encephalopathies; and some genetic diseases, including chromosomopathies. CN1 is neuroanatomically unique and fulfills criteria of a true sensory cranial nerve. We recommend that olfaction be routinely or selectively included during neurologic examination of neonates and children.