Alterations in Sphenoid Anatomy in Craniosynostosis: Implications for Fronto-Orbital Advancement.

OBJECTIVE: Fronto-orbital advancement involves removal of the fronto-orbital bandeau. Visualization of the saw blade is lost as it passes through the fronto-orbital-sphenoid junction (FOSJ), placing the temporal lobe at risk of injury. We aim to provide a 3D analysis of the space surrounding this osteotomy to differentiate various types of craniosynostoses. DESIGN: Retrospective cohort. SETTING: Institutional. PATIENTS: Thirty patients with isolated unicoronal synostosis, nonsyndromic bicoronal synostosis, metopic synostosis, Apert syndrome, Crouzon syndrome, and Muenke syndrome. INTERVENTIONS: CT scans conducted between 2 months to 2 years of age were 3D reconstructed to compare craniometrics against normal controls. MAIN OUTCOME MEASURE(S): Craniometrics. RESULTS: The mean bone thickness of the FOSJ at the level of the supraorbital rim was significantly small for the Apert, unicoronal and bicoronal groups. The mean vertical height of the middle cranial fossa from the lesser sphenoid wing was significantly greater in the unicoronal group. The mean vertical height of the tip of the temporal lobe from the lateral sphenoid ridge was greater in the unicoronal, isolated bicoronal, and Apert groups. The mean corneal protrusion beyond the lateral orbital rim was significantly greater in the Apert and unicoronal groups. The mean horizontal depth of the orbit was smallest in the Apert group. The mean vertical distance between the dacryon and the foramen cecum, and the mean volume of temporal lobe beneath the sphenoid shelf were the largest in the Apert group. CONCLUSIONS: Patients with Apert syndrome have the most unfavorable morphology of the anterior and middle cranial fossae.

Long-term sequelae of normocephalic pansynostosis: a rare but insidious entity.

OBJECTIVE: Patients with normocephalic pansynostosis, who have a grossly normal head shape, are often overlooked early in life and present late with elevated intracranial pressure (ICP) requiring timely cranial vault expansion. This study evaluates the long-term clinical outcomes of patients with normocephalic pansynostosis. METHODS: We retrospectively reviewed patients with a clinical and radiographic diagnosis of primary pansynostosis who underwent vault reconstruction between 2000 and 2023. Clinical and treatment course after craniofacial interventions was followed in patients with normocephaly to assess outcomes. RESULTS: Thirty-five patients with primary pansynostosis were identified, of which eight (23.5%) had normocephaly and underwent initial vault expansion at a mean age of 5.0 ± 2.4 years. All eight patients (50.0% male) presented with symptoms of elevated ICP including headaches (50.0%), nausea and vomiting (50.0%), and developmental delay (62.5%) and/or signs of elevated ICP including papilledema (75.0%) and radiologic thumbprinting on head computed tomography scan (87.5%). Three of the four normocephalic patients who had over 7 years of postoperative follow-up developed subjective headaches, vision changes, or learning and behavioral issues in the long-term despite successful vault reconstruction. CONCLUSIONS: Our longitudinal experience with this rare but insidious entity demonstrates the importance of timely intervention and frequent postoperative monitoring, which are critical to limiting long-term neurological sequelae. Multidisciplinary care by craniofacial surgery, neurosurgery, ophthalmology, and neuropsychology with follow-up into adolescence are recommended to assess for possible recurrence of elevated ICP secondary to cranio-cerebral disproportion.

The society for craniofacial genetics and developmental biology 46th annual meeting.

The Society for Craniofacial Genetics and Developmental Biology (SCGDB) held its 46th Annual Meeting at Cincinnati Children's Hospital Medical Center in Cincinnati, Ohio on October 10th-12th, 2023. On the first day of the meeting, Drs. Sally Moody and Justin Cotney were each honored with the SCGDB Distinguished Scientist Awards for their exceptional contributions to the field of craniofacial biology. The following two days of the meeting featured five sessions that highlighted new discoveries in signaling and genomic mechanisms regulating craniofacial development, human genetics, translational and regenerative approaches, and clinical management of craniofacial differences. Interactive workshops on spatial transcriptomics and scientific communication, as well as a poster session facilitated meaningful interactions among the 122 attendees representing diverse career stages and research backgrounds in developmental biology and genetics, strengthened the SCGDB community.

Skeletal changes after midface surgery in patients with craniofacial deformities: a three-dimensional quantification method.

To determine the skeletal changes after midface surgery in patients with syndromic craniosynostosis who underwent Le Fort III (LFIII), monobloc (MB), or facial bipartition (FB). This was a retrospective study including 75 patients: 33 treated by LFIII, 29 by MB, and 13 by FB. Twenty-five had a diagnosis of Apert, 39 Crouzon, and 11 craniofrontonasal syndrome. A three-dimensional mesh was created from the preoperative scan and registered to the postoperative scan to visualise the advancement. LFIII at age 7-12 years effectuated a higher mean advancement in the maxillary (15.5 mm) and zygomatic (7.6 mm) regions when compared to ≥13 years (10.2 mm and 5.5 mm). After MB, mean advancement of the fronto-orbital region was higher at <7 years (16.4 mm), and similarly lower at ages 7-12 (13.8 mm) and ≥13 (12.5 mm). The mean preoperative inter-dacryon distance (34.4 ± 4.4 mm) was reduced by 8.7 ± 4.2 mm after FB without distraction (n = 10). More advancement was seen when midface surgery was performed at a younger age, due to more severe cases and a desire for overcorrection. The highest mean advancement was observed in the fronto-orbital region. Antero-inferior rotational movement was seen after all three techniques.

Whole genome sequencing identifies associations for nonsyndromic sagittal craniosynostosis with the intergenic region of BMP2 and noncoding RNA gene LINC01428.

Craniosynostosis (CS) is a major birth defect resulting from premature fusion of cranial sutures. Nonsyndromic CS occurs more frequently than syndromic CS, with sagittal nonsyndromic craniosynostosis (sNCS) presenting as the most common CS phenotype. Previous genome-wide association and targeted sequencing analyses of sNCS have identified multiple associated loci, with the strongest association on chromosome 20. Herein, we report the first whole-genome sequencing study of sNCS using 63 proband-parent trios. Sequencing data for these trios were analyzed using the transmission disequilibrium test (TDT) and rare variant TDT (rvTDT) to identify high-risk rare gene variants. Sequencing data were also examined for copy number variants (CNVs) and de novo variants. TDT analysis identified a highly significant locus at 20p12.3, localized to the intergenic region between BMP2 and the noncoding RNA gene LINC01428. Three variants (rs6054763, rs6054764, rs932517) were identified as potential causal variants due to their probability of being transcription factor binding sites, deleterious combined annotation dependent depletion scores, and high minor allele enrichment in probands. Morphometric analysis of cranial vault shape in an unaffected cohort validated the effect of these three single nucleotide variants (SNVs) on dolichocephaly. No genome-wide significant rare variants, de novo loci, or CNVs were identified. Future efforts to identify risk variants for sNCS should include sequencing of larger and more diverse population samples and increased omics analyses, such as RNA-seq and ATAC-seq.

Apical expansion of calvarial osteoblasts and suture patency is dependent on fibronectin cues.

The skull roof, or calvaria, is comprised of interlocking plates of bones that encase the brain. Separating these bones are fibrous sutures that permit growth. Currently, we do not understand the instructions for directional growth of the calvaria, a process which is error-prone and can lead to skeletal deficiencies or premature suture fusion (craniosynostosis, CS). Here, we identify graded expression of fibronectin (FN1) in the mouse embryonic cranial mesenchyme (CM) that precedes the apical expansion of calvaria. Conditional deletion of Fn1 or Wasl leads to diminished frontal bone expansion by altering cell shape and focal actin enrichment, respectively, suggesting defective migration of calvarial progenitors. Interestingly, Fn1 mutants have premature fusion of coronal sutures. Consistently, syndromic forms of CS in humans exhibit dysregulated FN1 expression, and we also find FN1 expression altered in a mouse CS model of Apert syndrome. These data support a model of FN1 as a directional substrate for calvarial osteoblast migration that may be a common mechanism underlying many cranial disorders of disparate genetic etiologies.

Visuospatial abilities and 3D-printed based learning.

PURPOSE: The use of 3D-printing in every field of medicine is expanding, notably as an educational tool. The aim of this study was to assess how visuospatial abilities (VSA) of students may impact learning helped with 3D-printed models. METHODS: Participants were undergraduate medical school students during their clinical rotation in oral and maxillofacial surgery in two French Universities. Students were included prospectively and consecutively from September 2021 to June 2023. First, a lecture about craniosynostosis was performed with the help of 3D-printed models of craniosynostotic skulls. Then, a mental rotation test (MRT) followed by a multiple-choice questions (MCQs) form about craniosynostosis presentations were submitted to the students. RESULTS: Forty undergraduate students were finally included. Median MRT score was 15 (10.75;21) and median score to the MCQs was 13 (11.75;14). There was a significantly weak correlation between the MRT-A score and the score to the MCQs (rs = 0.364; p = 0.022). A simple linear regression was calculated to predict the result to the MCQs on MRT-A score [ (F(1,39) = 281.248; p < 0.0001), with a R2 of 0.878 ]. CONCLUSION: This study showed that VSA has an impact on the recognition of complex clinical presentations, i.e. skulls with craniosynostosis. The correlation found between VSA and complex 3D shape recognition after learning aided with 3D-printed model is emphasizing the importance of VSA when using innovative technologies. Thus, VSA training should be envisioned during the curriculum.

Understanding the influence of surgical parameters on craniofacial surgery outcomes: a computational study.

Sagittal craniosynostosis (SC) is a congenital condition whereby the newborn skull develops abnormally owing to the premature ossification of the sagittal suture. Spring-assisted cranioplasty (SAC) is a minimally invasive surgical technique to treat SC, where metallic distractors are used to reshape the newborn's head. Although safe and effective, SAC outcomes remain uncertain owing to the limited understanding of skull-distractor interaction and the limited information provided by the analysis of single surgical cases. In this work, an SC population-averaged skull model was created and used to simulate spring insertion by means of the finite-element analysis using a previously developed modelling framework. Surgical parameters were varied to assess the effect of osteotomy and spring positioning, as well as distractor combinations, on the final skull dimensions. Simulation trends were compared with retrospective measurements from clinical imaging (X-ray and three-dimensional photogrammetry scans). It was found that the on-table post-implantation head shape change is more sensitive to spring stiffness than to the other surgical parameters. However, the overall end-of-treatment head shape is more sensitive to spring positioning and osteotomy size parameters. The results of this work suggest that SAC surgical planning should be performed in view of long-term results, rather than immediate on-table reshaping outcomes.

The effect of Le Fort III procedure in the treatment of obstructive sleep apnea in children with syndromic craniosynostosis.

STUDY OBJECTIVES: Obstructive sleep apnea (OSA) is common in children with Syndromic Craniosynostosis (SC). The efficacy of Fort III procedure in managing OSA in children with SC remains a subject of ongoing debate. This study aimed to explore the efficacy of Le Fort III procedure in the management of OSA in children with SC. METHODS: A retrospective study was performed in children with SC and OSA diagnosed by polysomnography (PSG), which was defined as an apnea and hypopnea index (AHI) ≥ 1. Patients meeting the inclusion criteria were those who underwent Le Fort III surgery and had both baseline PSG and follow-up sleep studies. Relevant clinical and demographic data were collected from all subjects who participated in the study. RESULTS: Overall, forty-five OSA children with SC were identified, with a mean age of 6.8 ± 4.7 years. Twenty-five received the Le Fort III procedure and follow-up sleep studies. The Le Fort III procedure resulted in a significant reduction in AHI (6.0 [2.6, 10.1] versus 37.6 [20.9, 48.0] events/h; P < 0.001). However, normalization of OSA was only achieved in one patient (4%). CONCLUSIONS: The Le Fort III procedure is efficacious in the treatment of OSA in children with SC. However, despite the observed improvement, residual OSA following treatment remains common.

Long-term results of minimally invasive strip craniectomy without helmet therapy for scaphocephaly - a single-centre experience.

Scaphocephaly is the most common type of craniosynostosis and various surgical techniques are used for treatment. Due to late postoperative changes of the head shape, long-term outcome data is important for evaluating any new surgical technique. At our institution, minimally invasive strip craniectomy without regular helmet therapy is the standard treatment in scaphocephalic patients. Between October 2021 and February 2023, we retrospectively examined the skull shape of patients who underwent minimally invasive strip craniectomy for scaphocephaly using a 3D surface scan technique. The cephalic index (CI), the need for helmet therapy and additional cosmetic outcome parameters were investigated. We included 70 patients (72.5% male). The mean follow-up time was 46 (10-125) months and the mean CI was 75.7 (66.7-85.2). In 58 patients, the final cosmetic result was rated as "excellent/good" (mean CI: 76.3; 70.4-85.0), in 11 as "intermediate" (mean CI: 73.3; 66.7-77.6), and in one case as "unsatisfactory" (CI 69.3). The presence of a suboccipital protrusion was associated with a "less than good" outcome. The CI correlated significantly with the overall outcome, the presence of frontal bossing, and the interval between scan and surgery (age at scan). Minimally invasive strip craniectomy is an elegant and safe method to correct scaphocephaly. Our data show good cosmetic results in the long term even without regular postoperative helmet therapy.

Machine learning applications in craniosynostosis diagnosis and treatment prediction: a systematic review.

Craniosynostosis refers to the premature fusion of one or more of the fibrous cranial sutures connecting the bones of the skull. Machine learning (ML) is an emerging technology and its application to craniosynostosis detection and management is underexplored. This systematic review aims to evaluate the application of ML techniques in the diagnosis, severity assessment, and predictive modeling of craniosynostosis. A comprehensive search was conducted on the PubMed and Google Scholar databases using predefined keywords related to craniosynostosis and ML. Inclusion criteria encompassed peer-reviewed studies in English that investigated ML algorithms in craniosynostosis diagnosis, severity assessment, or treatment outcome prediction. Three independent reviewers screened the search results, performed full-text assessments, and extracted data from selected studies using a standardized form. Thirteen studies met the inclusion criteria and were included in the review. Of the thirteen papers examined on the application of ML to the identification and treatment of craniosynostosis, two papers were dedicated to sagittal craniosynostosis, five papers utilized several different types of craniosynostosis in the training and testing of their ML models, and six papers were dedicated to metopic craniosynostosis. ML models demonstrated high accuracy in identifying different types of craniosynostosis and objectively quantifying severity using innovative metrics such as metopic severity score and cranial morphology deviation. The findings highlight the significant strides made in utilizing ML techniques for craniosynostosis diagnosis, severity assessment, and predictive modeling. Predictive modeling of treatment outcomes following surgical interventions showed promising results, aiding in personalized treatment strategies. Despite methodological diversities among studies, the collective evidence underscores ML's transformative potential in revolutionizing craniosynostosis management.

Management of an older Marshall-Smith syndrome patient: a review of literature of MSS and craniosynostosis.

Marshall-Smith Syndrome (MSS) is a rare progressive developmental disorder that severely impairs a patient's intellectual development and physical health. The only known cause for MSS is a mutation in the nuclear factor 1 X (NFIX) gene. This mutation affects neuronal development and protein transcription. Historically, most patients with MSS do not survive beyond 3 years of age. Reports of ocular findings are limited. We report a case of a 9-year-old MSS patient with progressive craniosynostosis, elevated intracranial pressure, and catastrophic ocular complications. A comprehensive PubMed literature search from 2018 to August 2022 updating a previous review of older literature produced 72 articles relating to MSS, which are reviewed.

"When I was Younger, My Story Belonged to Everyone Else": Co-production of Resources for Adults Living with Craniosynostosis.

OBJECTIVE: Despite growing recognition that congenital craniofacial conditions have lifelong implications, psychological support for adults is currently lacking. The aim of this project was to produce a series of short films about living with craniosynostosis in adulthood, alongside a psychoeducational booklet. DESIGN: The resources were developed using multiple focus groups and meetings attended by researchers, patient representatives, a leading charitable organisation, an award-winning film production company, clinicians, and other experts in the field. RESULTS: An online mixed-methods survey was developed based on prior work to request feedback on the acceptability and utility of the resources from the craniosynostosis community. While data collection to evaluate the resources is ongoing, preliminary results (n = 36) highlight an acceptability rating of 100%. CONCLUSIONS: The resources developed represent a step forward in addressing the unmet information and support needs of adults with craniosynostosis and highlight the benefits of co-production in research.

Eyeing Risks: A Critical Analysis of the Use of Periorbital Steroids in Fronto-orbital Advancement.

OBJECTIVE: To evaluate the outcomes associated with two techniques of periorbital steroid administration in bilateral fronto-orbital advancement (FOA). DESIGN: Multi-institutional retrospective chart review. SETTING: Two high volume, tertiary US craniofacial centers. PATIENTS, PARTICIPANTS: Patients who underwent FOA between 2012 and 2021. INTERVENTIONS: Patients were divided into three cohorts based on method of steroid administration. Groups GEL and INJ represent those who received steroids in the form of triamcinolone soaked gelfoam or direct injection of dilute triamcinolone to the frontal/periorbital region, respectively. Group NON did not receive any periorbital steroids. MAIN OUTCOME MEASURE(S): Peri-operative outcomes including hospital length of stay and complications were evaluated based on method of periorbital steroid administration. Variables predictive of infectious complications were assessed using stepwise logistic regression. RESULTS: Four hundred and twelve patients were included in our sample (INJ:249, GEL:87, NON:76). Patients in the INJ group had a higher ASA class (P < .001) while patients in the NON group were significantly more likely to be syndromic (P < .001) and have multisuture craniosynostosis (P < .001). Rate of infectious complications for each cohort were NON: 2.6%, INJ: 4.4%, and GEL: 10.3%. There was no significant difference between groups in hospital length of stay (P = .654) or rate of post-operative infectious complications (P = .061). Increased ASA class (P = .021), increased length of stay (P = .016), and increased intraoperative narcotics (P = .011) were independent predictors of infectious complications. CONCLUSIONS: We identified a dose-dependent relationship between periorbital steroids and rate of postoperative infections, with key contributions from ASA class, hospital length of stay, and dose of intraoperative narcotics.

Neurocognitive outcomes and associated clinical factors 5 years after surgery in children with craniosynostosis.

OBJECTIVE: Craniosynostosis involves early closure of one or more sutures, which is known to limit normal cranium growth and interfere with normal brain development. Various surgical methods are used, ranging from minimally invasive strip craniectomy to more extensive whole-vault cranioplasty. This study aimed to evaluate neurocognitive outcomes 5 years after surgical treatment in children with craniosynostosis and to evaluate relevant clinical factors. METHODS: After exclusion of genetically confirmed syndromic craniosynostosis patients, a retrospective review was conducted on 112 nonsyndromic craniosynostosis patients who underwent surgical treatment and follow-up neurocognitive assessment. Ninety-seven patients underwent strip craniectomy with postoperative orthotic helmet therapy, and 15 received other surgical treatment: 4 with distraction osteotomy and 11 with craniofacial reconstruction. Neurocognitive assessment using the Korean Wechsler Preschool and Primary Scale of Intelligence, Fourth Edition (K-WPPSI-IV), was performed 5 years postoperatively. Clinical factors were assessed regarding neurocognitive outcomes. RESULTS: The mean age at surgery was significantly younger in the strip craniectomy group (strip craniectomy 4.6 months vs other surgical treatment 18.6 months, p < 0.01). Patients with 2 or more sutures involved were more likely to receive more extensive surgical treatment (16.5% in the strip craniectomy group vs 53.8% in the other group, p < 0.01). Four (3.5%) patients who showed evidence of increased intracranial pressure (ICP) also underwent more extensive surgical treatment. Multivariable linear regression revealed a significant correlation of age at neurocognitive testing (-3.18, 95% CI -5.95 to -0.40, p = 0.02), increased ICP (-34.73, 95% CI -51.04 to -18.41, p < 0.01), and the level of maternal education (6.11, 95% CI 1.01-11.20, p = 0.02) with the Full-Scale Intelligence Quotient (FSIQ). Age at surgery, involvement of 2 or more sutures, and type of operation demonstrated no correlation with FSIQ. Among the 97 patients who underwent strip craniectomy, the FSIQ ranged from mean ± SD 100.2 ± 10.2 (bicoronal) to 110.1 ± 12.7 (lambdoid), and there was no significant difference between the suture groups (p = 0.41). The 5 index scores were all within average ranges based on their age norms. CONCLUSIONS: Age at neurocognitive assessment, increased ICP, and maternal education level showed significant correlations with the neurocognitive function of craniosynostosis patients. Although children with craniosynostosis exhibited favorable 5-year postoperative neurocognitive outcomes across various synostosis sutures, longer follow-up is needed to reveal the incidence of neurocognitive dysfunction in these patients.

Health-Related Quality of Life in Mexican Children and Adolescents with Non-Syndromic Craniosynostosis.

OBJECTIVE: Assess the Health-Related Quality of Life in children and adolescents with non-syndromic craniosynostosis and compare it with participants without craniosynostosis. DESIGN: Non-experimental, cross-sectional design. SETTING: The assessment was done remotely and the instrument was sent via chat or email. PATIENTS/ PARTICIPANTS: Participants (ages 8-17) with non-syndromic craniosynostosis (n = 27) and without craniosynostosis (n = 26). MAIN OUTCOME MEASURE(S): We used an adapted version for the Mexican population of the Health-Related Quality of Life Questionnaire for Children and Adolescents -KIDSCREEN-52. RESULTS: All scores were in the average clinical range and both groups scored similarly in all domains except those with craniosynostosis were significantly lower in the Social Support and Peers domain (rpb = 0.48). CONCLUSIONS: Children and adolescents with non-syndromic craniosynostosis reported similar Health-Related Quality of Life as the control group, except for the Social Support domain, which should be investigated in future studies.

Fontanellar bone - A rarity in pediatric cranial abnormalities.

Background: Fontanelles, membranous gaps in the infant skull, are integral for accommodating the expansion of the skull by the growing brain postnatally. The anterior fontanelle, situated at the frontal-parietal bone intersection, typically closes gradually within the first two years. Fontanellar bone, an exceedingly rare ossification anomaly of the anterior fontanelle, clinically mimics craniosynostosis. Case Description: We present the case of a 22-day-old male with an almost closed anterior fontanelle who underwent evaluation. Prenatal and postnatal history were unremarkable. Physical examination revealed a well-nourished infant with a nearly closed fontanelle but no other anomalies. The initial diagnosis was craniosynostosis; however, a head computed tomography scan revealed fontanellar bone. Consequently, a conservative management approach with regular follow-ups was adopted. Conclusion: This case provides valuable insights into fontanellar bone, emphasizing its consideration in differential diagnoses for almost closed anterior fontanelles. The report aims to enhance awareness and understanding of this rare condition, promoting accurate diagnosis and optimal patient outcomes.

Factors associated with late surgical correction of craniosynostosis: A decade-long review of the United States nationwide readmission database.

Late-repair craniosynostosis (LRC), defined as craniosynostosis surgery beyond 1 year of age, is often associated with increased complexity and potential complications. Our study analyzed data from the 2010-2019 Nationwide Readmissions Database to investigate patient factors related to LRC. Of 10 830 craniosynostosis repair cases, 17% were LRC. These patients were predominantly from lower-income families and had more comorbidities, indicating that socioeconomic status could be a significant contributor. LRC patients were typically treated at teaching hospitals and privately owned investment institutions. Our risk-adjusted analysis revealed that LRC patients were more likely to belong to the lowest-income quartile, receive treatment at privately owned investment hospitals, and use self-payment methods. Despite these challenges, the hospital stay duration did not significantly differ between the two groups. Interestingly, LRC patients faced a higher predicted mean total cost compared with those who had surgery before turning 1. This difference in cost did not translate to a longer length of stay, further emphasizing the complexity of managing LRC. These findings highlight the urgent need for earlier intervention in craniosynostosis cases, particularly in lower-income communities. The medical community must strive to improve early diagnosis and treatment strategies in order to mitigate the socioeconomic and health disparities observed in LRC patients.

Severe obstructive sleep apnea in children with syndromic craniosynostosis: analysis of pulse transit time.

STUDY OBJECTIVES: We examined the association between pulse transit time (PTT) and obstructive sleep apnea (OSA) in children with syndromic craniosynostosis (SCS), where OSA is a common problem and may cause cardiorespiratory disturbance. METHODS: Retrospective study of children (age <18 years) with SCS and moderate-to-severe OSA (i.e., obstructive apnea-hypopnea index [oAHI] ≥ 5), or no OSA (oAHI < 1) who underwent overnight polysomnography (PSG). Children without SCS and normal PSG were included as controls. Reference intervals (RIs) for PTT were computed by non-parametric bootstrap analysis. Based on RIs of controls, the sensitivity and specificity of PTT to detect OSA were determined. In a linear mixed-model the explanatory variables assessed were sex, age, sleep stage, and time after obstructive events. RESULTS: In all 68 included children (19 SCS with OSA, 30 SCS without OSA, 19 controls), obstructive events occurred throughout all sleep stages, most prominently during rapid eye movement sleep (REM) and non-REM sleep stages N1 and N2, with evident PTT changes. Greatest reductions were observed 4 - 8 s after an event (p < 0.05). In SCS with OSA, PTT RIs were lower during all sleep stages compared to SCS without OSA. The highest sensitivity was observed during N1 (55.5%), and the highest specificity during REM (76.5%). Lowest PTT values were identified during N1. CONCLUSIONS: Obstructive events occur throughout all sleep stages with transient reductions in PTT. However, PTT as a variable for OSA detection is limited by its sensitivity and specificity.