Detailed analysis of inner ear malformations in CHARGE syndrome patients - correlation with audiological results and proposal for computed tomography scans evaluation methodology.

OBJECTIVES: The aim was to describe the spectrum of inner ear malformations in CHARGE syndrome and propose a Computed Tomography (CT) detailed scan evaluation methodology. The secondary aim was to correlate the CT findings with hearing thresholds. METHODS: Twenty ears of ten patients diagnosed with CHARGE syndrome were subjected to CT analysis focusing on the inner ear and internal acoustic canal. The protocol used is presented in detail. ASSR results were analyzed and correlated with inner ear malformations. RESULTS: Cochlear hypoplasia type III was the most common malformation found in 12 ears (60%). Cochlear hypoplasia type II, aplasia with a dilated vestibule, and rudimentary otocyst were also identified. In 20%, no cochlear anomaly was found. The lateral Semicircular Canal (SCC) absence affected 100% of ears, the absence of the posterior SCC 95%, and the superior SCC 65%. Better development of cochlea structures and IAC correlated significantly with the lower hearing thresholds. CONCLUSION: This study demonstrated that rudimentary SCC or a complete absence of these SCCs was universally observed in all patients diagnosed with CHARGE syndrome. This finding supports the idea that inner ear anomalies are a hallmark feature of the CHARGE, contributing to its distinct clinical profile. The presence of inner ear malformations has substantial clinical implications. Audiological assessments are crucial for CHARGE syndrome, as hearing loss is common. Early detection of these malformations can guide appropriate interventions, such as hearing aids or cochlear implants, which may significantly improve developmental outcomes and communication for affected individuals. Recognizing inner ear malformations as a diagnostic criterion presents implications beyond clinical diagnosis. A better understanding of these malformations can advance the knowledge of CHARGE pathophysiology. It may also help guide future research into targeted therapies to mitigate the impact of inner ear anomalies on hearing and balance function.

The spectrum of cochlear malformations in CHARGE syndrome and insights into the role of the CHD7 gene during embryogenesis of the inner ear.

PURPOSE: We reviewed the genotypes and the imaging appearances of cochleae in CHARGE patients from two large tertiary centres and analysed the observed cochlear anomalies, providing detailed anatomical description and a grading system. The goal was to gain insight into the spectrum of cochlear anomalies in CHARGE syndrome, and thus, in the role of the CHD7 gene in otic vesicle development. METHODS: We retrospectively reviewed CT and/or MR imaging of CHARGE patients referred to our institutions between 2005 and 2022. Cochlear morphology was analysed and, when abnormal, divided into 3 groups in order of progressive severity. Other radiological findings in the temporal bone were also recorded. Comparison with the existing classification system of cochlear malformation was also attempted. RESULTS: Cochlear morphology in our CHARGE cohort ranged from normal to extreme hypoplasia. The most common phenotype was cochlear hypoplasia in which the basal turn was relatively preserved, and the upper turns were underdeveloped. All patients in the cohort had absent or markedly hypoplastic semicircular canals and small, misshapen vestibules. Aside from a stenotic cochlear aperture (fossette) being associated with a hypoplastic or absent cochlear nerve, there was no consistent relationship between cochlear nerve status (normal, hypoplasia, or aplasia) and cochlear morphology. CONCLUSION: Cochlear morphology in CHARGE syndrome is variable. Whenever the cochlea was abnormal, it was almost invariably hypoplastic. This may shed light on the role of CHD7 in cochlear development. Accurate morphological description of the cochlea contributes to proper clinical diagnosis and is important for planning surgical treatment options.

Persistent Trigeminal Artery: A Novel Imaging Finding in CHARGE Syndrome.

BACKGROUND AND PURPOSE: Coloboma of the eye, Heart defects, Atresia of the choanae, Retardation of growth and/or development, Genital and/or urinary abnormalities, Ear abnormalities and deafness (CHARGE) syndrome is an autosomal dominant genetic disorder with evolving clinical diagnostic criteria. Recently, a number of additional anomalies have been described in this syndrome, which may aid in early diagnosis, particularly in incomplete phenotypes or atypical cases. The persistent trigeminal artery is an embryonic carotid-vertebral anastomosis, rarely seen in the healthy population, with a reported prevalence of 0.4%. Because we had observed the persistent trigeminal artery in patients with CHARGE syndrome, this study aimed to explore the prevalence of the persistent trigeminal artery in this syndrome. MATERIALS AND METHODS: A retrospective study was performed at our tertiary center. MR imaging studies, clinical records, and genetic results were reviewed for patients diagnosed with CHARGE syndrome between 2006 and 2019. The prevalence of the persistent trigeminal artery in patients with CHARGE syndrome was recorded and compared with other established diagnostic criteria. RESULTS: Twenty-five patients with CHARGE syndrome were included. The persistent trigeminal artery was demonstrated on MR imaging in 14/25 (56%) patients and was seen more frequently than 4 of 9 other established diagnostic criteria in our cohort. When individual major or minor diagnostic criteria were absent, the persistent trigeminal artery was still demonstrated on MR imaging in 52%-67% of these patients with CHARGE syndrome. CONCLUSIONS: The prevalence of the persistent trigeminal artery in CHARGE syndrome of 56% is higher than that of some other established diagnostic criteria and much higher than that in the general population. The persistent trigeminal artery may be a useful addition to the expanding phenotype of CHARGE syndrome, supplementing other diagnostic criteria. Radiologists should be aware of this novel finding demonstrable on MR imaging.

Neuroimaging in Kabuki syndrome and another KMT2D-related disorder.

Recognition of distinct phenotypic features is an important component of genetic diagnosis. Although CHARGE syndrome, Kabuki syndrome, and a recently delineated KMT2D Ex 38/39 allelic disorder exhibit significant overlap, differences on neuroimaging may help distinguish these conditions and guide genetic testing and variant interpretation. We present an infant clinically diagnosed with CHARGE syndrome but subsequently found to have a de novo missense variant in exon 38 of KMT2D, the gene implicated in both Kabuki syndrome and a distinct KMT2D allelic disorder. We compare her brain and inner ear morphology to a retrospective cohort of 21 patients with classic Kabuki syndrome and to typical CHARGE syndrome findings described in the literature. Thirteen of the 21 Kabuki syndrome patients had temporal bone imaging (5/13 CT, 12/13 MRI) and/or brain MRI (12/13) which revealed findings distinct from both CHARGE syndrome and the KMT2D allelic disorder. Our findings further elucidate the spectrum of inner ear dysmorphology distinguishing Kabuki syndrome and the KMT2D allelic disorder from CHARGE syndrome, suggesting that these three disorders may be differentiated at least in part by their inner ear anomalies.

Antenatal diagnosis of CHARGE syndrome: Prenatal ultrasound findings and crucial role of fetal dysmorphic signs. About a series of 10 cases and review of literature.

Although the prognosis of CHARGE syndrome can be highly variable from mild until severe, final diagnosis is difficult to establish in utero. The aim of our study is to compare antenatal and postnatal findings in a retrospective cohort of 10 successive patients with a positive CHD7 gene variant in order to identify the specific prenatal features for CHARGE syndrome diagnosis. Fetal ultrasound, follow-up and supplementary investigations are collected and compared to postnatal findings. Congenital heart defect (7/10), choanal atresia (7/10) and tracheoesophageal atresia (4/10) are the most frequent fetal anomalies found. Inner and external ear anomalies appear as the keystone (constant features) for prenatal diagnosis of CHARGE syndrome in fetuses with multiple anomalies and normal microarray karyotype. External ear malformations are identified in all cases by 3D ultrasound when carefully evaluated. MRI and temporal bone CT-Scan are second line useful tools to assess the diagnosis when looking for semicircular canal agenesis, arhinencephaly and/or choanal atresia. Before availability of prenatal exome sequencing in clinical routine, present findings lead to the recommendation that fetuses, with congenital heart defect (mainly septal and conotruncal), cleft lip/palate or unexplained polyhydramnios should carefully be screened for clues suggesting CHARGE syndrome using 2D and 3D ultrasound, MRI and temporal bone CT-Scan. When CHARGE syndrome is suspected with normal molecular karyotype, CHD7 gene sequencing must be offered.

Biallelic CDK9 variants as a cause of a new multiple-malformation syndrome with retinal dystrophy mimicking the CHARGE syndrome.

CDK9 has been considered a candidate gene involved in the CHARGE-like syndrome in a pair of cousins. We report an 8-year-old boy with a strikingly similar phenotype including facial asymmetry, microtia with preauricular tags and bilateral hearing loss, cleft lip and palate, cardiac dysrhythmia, and undescended testes. Joint contracture, no finger flexion creases, and large halluces were the same as those of a previously reported patient with homozygous CDK9 variants. The ocular phenotype included blepharophimosis, lacrimal duct obstruction, eyelid dermoids, Duane syndrome-like abduction deficit, and congenital cataracts. Optical coherence tomography and electroretinography evaluations revealed severe retinal dystrophy had developed at an early age. Trio-based whole-exome sequencing identified compound heterozygous variants in CDK9 [p.(A288T) of maternal origin and p.(R303C) of paternal origin] in the patient. Variants' kinase activities were reduced compared with wild type. We concluded that CDK9 biallelic variants cause a CHARGE-like malformation syndrome with retinal dystrophy as a distinguishing feature.

Neurocristopathies: Enigmatic Appearances of Neural Crest Cell-derived Abnormalities.

The neural crest is an important transient structure that develops during embryogenesis in vertebrates. Neural crest cells are multipotent progenitor cells that migrate and develop into a diverse range of cells and tissues throughout the body. Although neural crest cells originate from the ectoderm, they can differentiate into mesodermal-type or endodermal-type cells and tissues. Some of these tissues include the peripheral, autonomic, and enteric nervous systems; chromaffin cells of the adrenal medulla; smooth muscles of the intracranial blood vessels; melanocytes of the skin; cartilage and bones of the face; and parafollicular cells of the thyroid gland. Neurocristopathies are a group of diseases caused by the abnormal generation, migration, or differentiation of neural crest cells. They often involve multiple organ systems in a single person, are often familial, and can be associated with the development of neoplasms. As understanding of the neural crest has advanced, many seemingly disparate diseases, such Treacher Collins syndrome, 22q11.2 deletion syndrome, Hirschsprung disease, neuroblastoma, neurocutaneous melanocytosis, and neurofibromatosis, have come to be recognized as neurocristopathies. Neurocristopathies can be divided into three main categories: dysgenetic malformations, neoplasms, and combined dysgenetic and neoplastic syndromes. In this article, neural crest development, as well as several associated dysgenetic, neoplastic, and combined neurocristopathies, are reviewed. Neurocristopathies often have clinical manifestations in multiple organ systems, and radiologists are positioned to have significant roles in the initial diagnosis of these disorders, evaluation of subclinical associated lesions, creation of treatment plans, and patient follow-up. Online supplemental material is available for this article. ©RSNA, 2019.

A novel CHD7 variant disrupting acceptor splice site in a patient with mild features of CHARGE syndrome: a case report.

BACKGROUND: CHARGE syndrome (MIM# 214800)-which is characterised by a number of congenital anomalies including coloboma, ear anomalies, deafness, facial anomalies, heart defects, atresia choanae, genital hypoplasia, growth retardation, and developmental delay-is caused by a heterozygous variant in the CHD7 (MIM# 608892) gene located on chromosome 8q12. We report the identification of a novel c.5535-1G > A variant in CHD7 and provide the evaluation of its effect on pre-mRNA splicing. CASE PRESENTATION: In this study, we report on a female presenting features of CHARGE syndrome. A novel heterozygous CHD7 variant c.5535-1G > A located in the acceptor splice site of intron 26 was identified in the proband's DNA sample after analysis of whole exome sequencing data. In silico predictions indicating that the variant is probably pathogenic by affecting pre-mRNA splicing were verified by genetic analysis based on reverse transcription of the patient's RNA followed by PCR amplifications performed on synthesised cDNA and Sanger sequencing. Sanger sequencing of cDNA revealed that the c.5535-1G > A variant disrupts the original acceptor splice site and activates a cryptic splice site only one nucleotide downstream of the pathogenic variant site. This change causes the omission of the first nucleotide of exon 27, leading to a frameshift in the mRNA of the CHD7 gene. Our results suggest that the alteration induces the premature truncation of the CHD7 protein (UniProtKB: Q9P2D1), thus resulting in CHARGE syndrome. CONCLUSION: Genetic analysis of novel splice site variant underlines its importance for studying the pathogenic splicing mechanism as well as for confirming a diagnosis.

Quantitative brain morphological analysis in CHARGE syndrome.

CHARGE syndrome (CS) is a rare congenital syndrome characterized by coloboma, heart anomaly, choanal atresia, retardation of growth and development, and genital and ear anomalies. While several neuroimaging studies have revealed abnormalities such as hypoplasia of the semicircular canal, olfactory nerve, cerebellum, and brainstem, no quantitative analysis of brain morphology in CS has been reported. We quantitatively investigated brain morphology in CS participants using structural magnetic resonance imaging (MRI) (N = 10, mean age 14.7 years old) and high-angular resolution diffusion MRI (HARDI) tractography (N = 8, mean age 19.4 years old) comparing with gender- and age-matched controls. Voxel-based analyses revealed decreased volume of the bilateral globus pallidus (left and right; p = 0.021 and 0.029), bilateral putamen (p = 0.016 and 0.011), left subthalamic nucleus (p = 0.012), bilateral cerebellum (p = 1.5 × 10-6 and 1.2 × 10-6), and brainstem (p = 0.031), and the enlargement of the lateral ventricles (p = 0.011 and 0.0031) bilaterally in CS. Surface-based analysis revealed asymmetrically increased cortical thickness in the right hemisphere (p = 0.013). The group-wise differences observed in global cortical volume, gyrification index, and left cortical thickness were not statistically significant. HARDI tractography revealed reduced volume, elongation, and higher ADC values in multiple fiber tracts in patients in CS compared to the controls, but FA values were not statistically significantly different between the two groups. Facial features are known to be asymmetric in CS, which has been recognized as an important symptom in CS. Our results revealed that the cortex in CS has an asymmetric appearance similar to the facial features. In addition, the signal pattern of high ADC with statistically unchanged FA values of tractography pathways indicated the presence of other pathogenesis than vasogenic edema or myelination dysfunction in developmental delay in CS.

Fetal MRI findings in a retrospective cohort of 26 cases of prenatally diagnosed CHARGE syndrome individuals.

"CHARGE syndrome" (CS) is a multifaceted syndrome associated with a poor prognosis. The prenatal diagnosis remains challenging especially as the fetal anomalies that may evoke suspicion of CS are not comprehensively described. OBJECTIVE: This study aims to identify the anomalies in MRI with suspected CHARGE syndrome and to propose a possible standardization in the image-based prenatal diagnosis of CS. METHODS: This was a retrospective study of 26 fetuses who underwent MRI and had a confirmed diagnosis of CS, as proven by histopathological and/or neonatal examinations and/or the presence of the CHD7 gene mutation. RESULTS: The three most frequent MRI anomalies confirmed at histopathological and/or neonatal examinations were arhinencephaly in 100% (26 of 26), dysplasia of the semicircular canals agenesis (SCA) in 100% (24 of 24), and posterior fossa anomalies in 100% (22 of 22). Our study also revealed short petrous bones with a particular triangular shape in 24 of 24 cases of SCA. Other relevant findings included external ear anomalies in 36% (9 of 25), cleft lip and palate (9 of 9), ventriculomegaly (VMG) (6 of 6), short corpus callosum (3 of 3), and ocular asymmetry in 36.6% (4 of 11). CONCLUSION: Our study emphasizes the interest of fetal MRI in the diagnosis of CS with an adapted knowledge of semiology.

Relative Preservation of Superior Semicircular Canal Architecture in CHARGE Syndrome.

OBJECTIVES: (1) Describe common patterns of semicircular canal (SCC) anomalies in CHARGE syndrome (CS) and (2) recognize that in CS, the architecture of the superior SCC may be relatively preserved. STUDY DESIGN: This is a retrospective review of temporal bone imaging studies. SETTING: Quaternary care center. SUBJECTS AND METHODS: A sample of 37 patients with CS. All subjects met clinical diagnostic criteria for CS. The presence/absence of anomalies of the middle ear, mastoid, temporal bone venous anatomy, inner ear, and internal auditory canal was recorded. Anomalies of each SCC were considered separately and by severity (normal, dysplasia, aplasia). RESULTS: Thirty-seven subjects (74 temporal bones) were reviewed. Thirty-four (92.0%) patients demonstrated bilateral SCC anomalies. Three (8.0%) had normal SCCs. In patients with SCC anomalies, all canals demonstrated bilateral abnormalities. Thirty-two (86.5%) patients had bilateral horizontal SCC aplasia. These 32 patients also demonstrated posterior SCC aplasia in at least 1 ear. Of 74 temporal bones, 37 (50.0%) had superior SCC dysplasia. All dysplastic superior SCCs showed preservation of the anterior limb. Complete superior SCC aplasia was found in 28 (37.8%) temporal bones. CONCLUSION: SCC anomalies occur with high frequency in CS. Complete absence of the horizontal and posterior canals is typical and usually bilateral. By contrast, the superior SCC often demonstrates relative preservation of the anterior limb.

Imaging of Clival Hypoplasia in CHARGE Syndrome and Hypothesis for Development: A Case-Control Study.

BACKGROUND AND PURPOSE: We present the largest case series to date on basiocciput abnormalities in CHARGE syndrome (Coloboma of the eye, Heart defects, Atresia of the choanae, Retardation of growth and/or development, Genital and/or urinary abnormalities, and Ear abnormalities and/or deafness). We aimed to show that basiocciput abnormalities are common and may aid in diagnosis. We furthermore explored whether clivus size correlates with the type of chromodomain-helicase-DNA binding protein 7 gene (CHD7) mutation, which causes CHARGE syndrome, and with clinical criteria according to Blake et al and Verloes. MATERIALS AND METHODS: We retrospectively analyzed the clivus of 23 patients with CHARGE syndrome with CHD7 mutations on MR imaging or CT. We recorded the size of the clivus, the Welcher angle, basilar invagination, and Chiari I malformations. We compared the clival size and Welcher angle of patients with CHARGE syndrome with those of 72 age-matched controls. Additionally, we tested for correlations between clivus size and mutation type or clinical criteria. RESULTS: Eighty-seven percent of the patients with CHARGE syndrome had an abnormal clivus; 61% had a clivus >2.5 SD smaller than that of age-matched controls. An abnormally large Welcher angle was observed in 35%. Basiocciput hypoplasia was found in 70%, and basilar invagination, in 29%. None of the patients had a Chiari I malformation. At the group level, patients with CHARGE syndrome had a smaller clivus and larger Welcher angle than controls. No significant correlation between clivus size and mutation type or clinical criteria was found. CONCLUSIONS: Most patients with CHARGE syndrome have an abnormal clivus. This suggests that clivus abnormalities may be used as an additional diagnostic tool. Our results provide evidence that CHD7, which is expressed in the presomitic mesoderm during somitogenesis, plays an important role in the formation of the clivus.

Surgical Palliation of Right Aortic Arch With an Isolated Innominate Artery From the Left Ductus Arteriosus.

A right aortic arch with an isolated left innominate artery from the left patent ductus arteriosus is a rare arch anomaly, and establishing continuity between the innominate artery and aorta can be challenging. We describe repair of this lesion in a three-week-old male using an autologous pedicle flap of ascending aorta as well as a homograft patch as the roof to recreate continuity between the aorta and left innominate artery.

Head and Neck MRI Findings in CHARGE Syndrome.

Coloboma of the eye, Heart defects, Atresia of the choanae, Retardation of growth and/or development, Genital and/or urinary abnormalities, and Ear abnormalities and deafness (CHARGE) syndrome is a disorder with multiple congenital anomalies seen on imaging. A retrospective review of 10 patients with CHARGE syndrome who underwent MR imaging of the brain as part of a preoperative evaluation for cochlear implantation was conducted. Structural abnormalities of the entire MR imaging of the head were evaluated, including the auditory system, olfactory system, face, skull base, and central nervous system. The most frequent MR imaging findings included dysplasias of the semicircular canals and hypoplasia of the frontal lobe olfactory sulci. Less frequent findings included cleft lip/palate and coloboma. Our study uncovered new findings of a J-shaped sella, dorsal angulation of the clivus, and absent/atrophic parotid glands, not previously described in patients with CHARGE. Our results emphasize the utility of MR imaging in the diagnosis and management of patients with CHARGE syndrome.

Coronal clival cleft in CHARGE syndrome.

CHARGE syndrome is a genetic disorder with multi-systemic congenital anomalies, most commonly including coloboma, heart malformations, choanal atresia, developmental delay, and genital and ear anomalies. The diagnostic criteria for CHARGE syndrome has been refined over the years. However, there are limited reports describing skullbase and craniocervical junction abnormalities. These osseous malformations are often under recognized, especially on MRI. We report here a case of CHARGE syndrome with colobomas, cleft lip and palate, patent ductus arteriosus, undescended testes, and a coronal clival cleft which has not been previously depicted in CHARGE syndrome. The presence of a coronal clival cleft should alert the radiologist to examine the ears, eyes, palate, choana, and olfactory centers for other signs of CHARGE syndrome.

CT findings of the temporal bone in CHARGE syndrome: aspects of importance in cochlear implant surgery.

To provide an overview of anomalies of the temporal bone in CHARGE syndrome relevant to cochlear implantation (CI), anatomical structures of the temporal bone and the respective genotypes were analysed. In this retrospective study, 42 CTs of the temporal bone of 42 patients with CHARGE syndrome were reviewed in consensus by two head-and-neck radiologists and two otological surgeons. Anatomical structures of the temporal bone were evaluated and correlated with genetic data. Abnormalities that might affect CI surgery were seen, such as a vascular structure, a petrosquamosal sinus (13 %), an underdeveloped mastoid (8 %) and an aberrant course of the facial nerve crossing the round window (9 %) and/or the promontory (18 %). The appearance of the inner ear varied widely: in 77 % of patients all semicircular canals were absent and the cochlea varied from normal to hypoplastic. A stenotic cochlear aperture was observed in 37 %. The middle ear was often affected with a stenotic round (14 %) or oval window (71 %). More anomalies were observed in patients with truncating mutations than with non-truncating mutations. Temporal bone findings in CHARGE syndrome vary widely. Vascular variants, aberrant route of the facial nerve, an underdeveloped mastoid, aplasia of the semicircular canals, and stenotic round window may complicate cochlear implantation.

Prenatal findings in children with early postnatal diagnosis of CHARGE syndrome.

BACKGROUND: CHARGE syndrome is a multiple congenital anomaly syndrome caused by mutations in CHD7. Diagnostic criteria have been proposed to improve diagnosis in fetuses at clinicopathological survey, but no criteria exist for fetal diagnosis during pregnancy. METHOD: We collected prenatal findings of 12 children with CHARGE syndrome diagnosed in the first 3 months and a CHD7 mutation. We retrieved data on prenatal ultrasound (US) follow-up, fetal supplementary investigations, and results of postnatal evaluation. RESULT: Seven pregnancies were complicated by the identification of isolated or multiple congenital anomalies. CHARGE syndrome was suspected in three fetuses but could not be confirmed despite additional examinations. Retrospectively, several postnatal findings could have been seen if they had been specifically searched. Intrauterine growth restriction, previously proposed as an exclusion criterion, complicated two pregnancies and is thus compatible with the diagnosis. CONCLUSION: Diagnosis of CHARGE syndrome remains difficult during pregnancy. If the diagnosis of CHARGE syndrome is raised in utero, we suggest a careful US examination to identify typical external ears, choanal atresia, or microphthalmia. Fetal brain magnetic resonance imaging can be helpful, but a normal result does not exclude the diagnosis. When CHARGE syndrome is highly suspected, CHD7 molecular analysis must be proposed to confirm the diagnosis. © 2016 John Wiley & Sons, Ltd.

Ultrasound evaluation of development of olfactory sulci in normal fetuses: a possible role in diagnosis of CHARGE syndrome.

OBJECTIVES: To describe the timing of the ultrasound appearance of olfactory sulci in normal fetuses, according to gestational age. METHODS: Olfactory sulci were assessed prospectively in the coronal plane on routine brain ultrasound examination in 100 normal fetuses between 22 and 31 + 6 weeks' gestation. Examinations were divided into five groups according to gestational age: Group 1, 22 to 23 + 6 weeks (n = 22); Group 2, 24 to 25 + 6 weeks (n = 9); Group 3, 26 to 27 + 6 weeks (n = 25); Group 4, 28 to 29 + 6 weeks (n = 22) and Group 5, 30 to 31 + 6 weeks (n = 22). For each fetus, olfactory sulci were assessed as absent, developing or formed. RESULTS: Developing sulci appeared as primitive smooth depressions in the frontal lobe, which evolved into deep sharp complete sulci in later pregnancy. It was possible to assess the development of sulci in all cases. Olfactory sulci were consistently absent in Group 1. In Group 2, 44.4% of fetuses had absent olfactory sulci and 55.6% had developing sulci. In Group 3, the olfactory sulci were still developing in 21 (84.0%) fetuses and were completely formed in four (16.0%). Sulci were completely formed in all fetuses in Groups 4 and 5. CONCLUSIONS: Fetal brain ultrasound can visualize developing olfactory sulci from as early as 24 weeks' gestation. After 26 weeks, fetuses have detectable olfactory sulci and, after 28 weeks, they are completely formed. Abnormal development of olfactory sulci is a key feature of CHARGE syndrome. These results may help to improve the prenatal diagnosis of CHARGE syndrome. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.