Volume Measurement of the Cavum Septi Pellucidi: Normative Values Between 20 and 40 Weeks of Gestation.

BACKGROUND: The cavum septi pellucidi (CSP) is a brain-enclosed cavity located on the midline between the two leaflets of the septum pellucidum that separates the lateral ventricles. This structure develops in the fetus from week 18 and can be seen up to week 37 in almost all cases and then begins to disappear. OBJECTIVES: To measure and determine the normative values of the CSP volume in fetuses between 20 to 40 weeks of gestation. METHODS: The study comprised 161 consecutive pregnant women between 20 to 40 weeks of gestation with single viable fetuses. All patients had normal, disease-free pregnancies. Transvaginal or transabdominal ultrasound was used according to the fetal presentation. The fetal head was assessed in mid-sagittal sections. Once the CSP was visualized, its volume was measured using three-dimensional ultrasound with Virtual Organ Computer-aided Analysis software. The width of the CSP was also measured at the biparietal diameter (BPD) plane. RESULTS: Of the 161 fetuses, the CSP volume was measured in 158. In three patients the CSP was not identified. The CSP volume correlated poorly with gestational age (r=0.229) and with the BPD (r=0.295). The mean CSP volume was 0.508 ± 0.372 ml (range: 0.03-1.78 ml). The simple measurement of the CSP width correlated better with gestational age (r=0.535) and the BPD (r=0.484). CONCLUSIONS: The CSP volume had a poor correlation with gestational age; however, the volume did not exceed 2 ml regardless of gestational age. This information can be used to assess pathologies involving the CSP.

Linking Type and Extent of Head Trauma to Cavum Septum Pellucidum in Older Adults With and Without Alzheimer Disease and Related Dementias.

BACKGROUND AND OBJECTIVES: Cavum septum pellucidum (CSP) is a common but nonspecific MRI finding in individuals with prior head trauma. The type and extent of head trauma related to CSP, CSP features specific to head trauma, and the impact of brain atrophy on CSP are unknown. We evaluated CSP cross-sectionally and longitudinally in healthy and clinically impaired older adults who underwent detailed lifetime head trauma characterization. METHODS: This is an observational cohort study of University of California, San Francisco Memory and Aging Center participants (healthy controls [HCs], those with Alzheimer disease or related dementias [ADRDs], subset with traumatic encephalopathy syndrome [TES]). We characterized traumatic brain injury (TBI) and repetitive head impacts (RHI) through contact/collision sports. Study groups were no RHI/TBI, prior TBI only, prior RHI only, and prior RHI + TBI. We additionally looked within TBI (1, 2, or 3+) and RHI (1-4, 5-10, and 11+ years). All underwent baseline MRI, and 67% completed a second MRI (median follow-up = 5.4 years). CSP measures included grade (0-4) and length (millimeters). Groups were compared on likelihood of CSP (logistic regression, odds ratios [ORs]) and whether CSP length discriminated groups (area under the curve [AUC]). RESULTS: Our sample included 266 participants (N = 160 HCs, N = 106 with ADRD or TES; age 66.8 ± 8.2 years, 45.3% female). Overall, 123 (49.8%) participants had no RHI/TBI, 52 (21.1%) had TBI only, 41 (16.6%) had RHI only, 31 (12.6%) had RHI + TBI, and 20 were classified as those with TES (7.5%). Compared with no RHI/TBI, RHI + TBI (OR 3.11 [1.23-7.88]) and TES (OR 11.6 [2.46-54.8]) had greater odds of CSP. Approximately 5-10 years (OR 2.96 [1.13-7.77]) and 11+ years of RHI (OR 3.14 [1.06-9.31]) had higher odds of CSP. CSP length modestly discriminated participants with 5-10 years (AUC 0.63 [0.51-0.75]) and 11+ years of prior RHI (AUC 0.69 [0.55-0.84]) from no RHI/TBI (cut point = 6 mm). Strongest effects were noted in analyses of American football participation. Longitudinally, CSP grade was unchanged in 165 (91.7%), and length was unchanged in 171 (95.5%) participants. DISCUSSION: Among older adults with and without neurodegenerative disease, risk of CSP is driven more by duration (years) of RHI, especially American football, than number of TBI. CSP length (≥6 mm) is relatively specific to individuals who have had substantial prior RHI. Neurodegenerative disease and progressive atrophy do not clearly influence development or worsening of CSP.

First-trimester cavum veli interpositi: prevalence and natural history.

OBJECTIVE: To confirm the identity and assess the prevalence and evolution of the fluid-filled interhemispheric midline structure, thought to be the cavum veli interpositi (CVI), in fetuses at 11-14 weeks' gestation. METHODS: This was a retrospective study of first-trimester ultrasound scans performed at a single center over 3 months. Inclusion criteria were singleton pregnancies at 11-14 weeks' gestation with known neonatal outcome. Five experts reviewed the images. Mixed-effects logistic regression and generalized estimating equations (GEE) were conducted to analyze the associations between the presence of the structure and variables including ultrasound approach (transabdominal vs transvaginal), maternal body mass index (BMI), gestational age, fetal crown-rump length (CRL) and biparietal diameter (BPD). Second-trimester ultrasound scans of the fetal central nervous system at 18-24 weeks' gestation were evaluated for the persistence of the CVI in fetuses in which the structure was observed in the first trimester. RESULTS: Of the 223 cases reviewed, 104 were included, among which the CVI was observed in 25 (24%) cases. There was no statistically significant difference in CVI visualization between transabdominal and transvaginal ultrasound examinations. GEE showed significant associations between the presence of the fetal structure and CRL (odds ratio (OR) per 10-unit increase, 1.32; P < 0.0001) and BPD (OR per 10-unit increase, 1.88; P = 0.0011). Maternal BMI and gestational age showed no significant effect on the presence of the CVI. At second-trimester follow-up of the 25 fetuses in which the CVI was observed initially, 44% still showed a CVI, 32% exhibited a cavum vergae, 4% had both structures and 20% had neither. CONCLUSIONS: Based on its anatomical location and, in some fetuses, its visualization as a distinct entity from the third ventricle, the identity of the interhemispheric midline structure in the suprathalamic region of the fetal brain between 11-14 weeks' gestation was confirmed as the CVI. The CVI and/or cavum vergae persisted into the second trimester in 80% of fetuses identified initially as having a CVI. Its presence is not linked to pathology, offering reassurance to practitioners and parents. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Resultado a largo plazo de una serie de fetos con agenesia aislada del septum pellucidum / Long-term postnatal outcome of fetuses with isolated agenesis of the septum pellucidum

Objetivo: Reportar el resultado a largo plazo de una serie de fetos con agenesia del septum pellucidum aislada (ASP), con medición de su quiasma óptico mediante neurosonografía fetal (NSG). Método: Se incluyeron todas las pacientes con ASP y NSG evaluadas desde el año 2008 a la fecha y con seguimiento hasta su edad escolar. En todos los casos se consignaron los datos clínicos de NSG y de resonancia magnética (RM), cuando esta se realizó. Se entrevistó telefónicamente a los padres. Resultados: Nueve pacientes cumplieron los criterios: cuatro con displasia septo-óptica (DSO) (rango de seguimiento: 5-14 años) y cinco sin DSO (rango de seguimiento: 7-10 años). Un décimo caso se excluyó por tener solo 6 meses de seguimiento. Ninguna de las ASP tuvo otra anomalía detectada en su seguimiento. Ninguno de los casos con DSO tuvo alteración del tamaño de su quiasma óptico en la NSG ni anormalidad en la vía óptica en la RM. Conclusiones: En nuestra población, el riesgo residual de DSO frente a ASP es del 44,4%. En el seguimiento, nuestra definición de ASP por NSG no tuvo falsos negativos con relación a otras anomalías de aparición posnatal, a excepción de la DSO.

Objective: To report the long-term outcome of a series of fetuses with isolated septum pellucidum agenesis (ASP) with measurement of their optic chiasm by fetal neurosonography (NSG). Method: All patients with ASP and NSG evaluated from 2008 to date and with follow-up until their school age were included. In all cases, clinical, NSG and magnetic resonance imaging (MRI) data were recorded. Parents were interviewed by telephone. Results: Nine patients met the criteria: four with septo-optic dysplasia (SOD) (follow-up range: 5-14 years) and five without SOD (follow-up range: 7-10 years). A tenth case was excluded because only 6 months of follow-up. None of the ASP cases had another anomaly detected in their follow-up. None of the cases with DSO had anomaly of the size of their optic chiasm on NSG or abnormality in the optical pathway in the MRI. Conclusions: In our population, the residual risk of DSO versus ASP is 44.4%. At follow-up, our NSG definition of ASP had no false negatives in relation to other postnatal-onset anomalies, except for SOD.

Lymphoma of the central nervous system originating from the septum pellucidum region: Two case reports with literature review.

RATIONALE: Non-Hodgkin lymphoma affecting the brain, eyes, and cerebrospinal fluid without systemic spread is known as primary central nervous system lymphoma (PCNSL). While intracerebroventricular PCNSL is commonly found in the lateral ventricles and the third and fourth ventricles, the occurrence of PCNSL originating from the septum pellucidum is extremely rare. PATIENT CONCERNS: Two patients presented with recent memory loss and high cranial pressure. DIAGNOSES: Magnetic resonance imaging revealed a clear enhancing lesion in the septum pellucidum region. Pathological examination confirmed that both cases were primary large B-cell lymphoma GCB (germinal center B-cell-like) subtypes located in an "immune-privileged" area. INTERVENTIONS: Both patients underwent total tumor resection, and the procedures were successfully completed without surgical complications. OUTCOMES: Over a 1-year period, treatment included four cycles of high-dose methotrexate combined with temozolomide. During the follow-up period (19-23 months), no recurrence of the lymphoma was observed. LESSONS: In cases of PCNSL in the septum pellucidum, it is crucial to consider it as a potential differential diagnosis for intraventricular tumors. Surgical interventions should focus on maximizing tumor resection while ensuring the protection of critical structures like the fornix and peripheral neural components. The role of surgery compared to biopsy, as well as the long-term complications, necessitates extended follow-up. Additionally, an individualized treatment approach, considering factors such as age, Karnofsky performance score, and organ function assessment, can lead to positive outcomes.

Comparison of Cavum Septum Pellucidum Size in Euploid and Aneuploid Fetuses.

OBJECTIVE: The aim of the present study is to compare the cavum septum pellucidi (CSP) z-score in euploid and aneuploid fetuses and to investigate the performance of the CSP width/length and CSP width/biparietal diameter (BPD) ratios as a diagnostic marker in aneuploidy. METHODS: A total of 54 patients, 20 aneuploid and 35 euploid fetuses, between 18 and 37 weeks of gestation, were included in this retrospective study. The CSP width z-score was compared between the two groups. Receiver operating characteristic (ROC) curves were calculated for the CSP width/length and CSP width/BPD ratios to predict aneuploidy. RESULTS: The median CSP width was 4.8 mm (range, 1.8 to 8.5 mm) in the euploid group, and 5.4 mm (range 3.1 to 8.4 mm) in the aneuploid group. Cavum septum pellucidi width z-score, CSP width/length ratio, and CSP width/BPD ratio were significantly higher in fetuses with aneuploidy than in fetuses with normal karyotype (p = 0.001; p = 0.013; p = 0.028). In the ROC analysis, the CSP width/length ratio had the optimal cutoff value of 0.59, with 72.0% sensitivity and 58.0% specificity, and for the CSP width/BPD ratio, the cutoff value was 0.081 with 83.0% sensitivity and 61.0% specificity for detection of aneuploidy. CONCLUSION: CSP width z-score was found to be increased in aneuploid fetuses. The CSP width /BPD ratio can be used as a new marker for predicting aneuploidy.

OBJETIVO: O objetivo do presente estudo é comparar o escore z do cavum septum pellucidi (CSP) em fetos euploides e aneuploides e investigar o desempenho das relações largura/comprimento do CSP e largura do CSP/diâmetro biparietal (BPD) como marcador diagnóstico de aneuploidia. como marcador de diagnóstico de aneuploidia. MéTODOS:: Um total de 54 pacientes, 20 fetos aneuploides e 35 fetos euploides, entre 18 e 37 semanas de gestação, foram incluídos neste estudo retrospectivo. O escore z da largura da CSP foi comparado entre os dois grupos. As curvas ROC (Receiver Operating Characteristic) foram calculadas para as relações largura/comprimento da PEC e largura da PEC/BPD para prever a aneuploidia. RESULTADOS: A largura mediana da CSP foi de 4,8 mm (variação de 1,8 a 8,5 mm) no grupo euploide e de 5,4 mm (variação de 3,1 a 8,4 mm) no grupo aneuploide. O escore z da largura do cavum septum pellucidi, a relação largura/comprimento do CSP e a relação largura do CSP/BPD foram significativamente maiores em fetos com aneuploidia do que em fetos com cariótipo normal (p < 0,001; p < 0,013; p < 0,028). Na análise ROC, a relação largura/comprimento da CSP teve o valor de corte ideal de 0,59, com 72,0% de sensibilidade e 58,0% de especificidade, e para a relação largura da CSP/BPD, o valor de corte foi de 0,081, com 83,0% de sensibilidade e 61,0% de especificidade para a detecção de aneuploidia. CONCLUSãO:: Verificou-se que o escore z da largura da CSP estava aumentado em fetos aneuploides. A relação A relação largura da CSP /BPD pode ser usada como um novo marcador para prever a aneuploidia.

Modeling fetal cavum septum pellucidi width by quantile regression at 18-34 weeks of gestation: A prospective cross-sectional study.

OBJECTIVE: Develop charts for cavum septum pellucidi (CSP) following a standardized methodology and using quantile regression. The secondary objective was to assess the influence of fetal gender on the generated reference curves. METHODS: In a cross-sectional prospective study 453 low-risk singleton pregnancies were evaluated at a gestational age interval between 18 and 34 weeks. The width of CSP were measured on ultrasound images using a standardized technique and their changes were evaluated by quantile regression as a function of gestational age (GA) interval or head circumference (HC). Differences between sex were evaluated. RESULTS: The measurement of CSP significantly increased with gestation and HC. Linear models better described the changes of CSP with GA and HC. The fits of CSP width with GA and HC were not significantly different. Male fetuses showed significantly higher CSP width when compared to female fetuses (u = 2.973; p = 0.005). CONCLUSIONS: We generated prospective nomograms of fetal CSP development using quantile regression and following a strict standardized methodology. These new charts may be useful to better identify abnormal cases at higher risk of associated anomalies. Further our findings underline the potential effect of gender in developing fetal brain.

Obliterated cavum septi pellucidi: is it always a benign finding? A case report and narrative review of the literature.

OBJECTIVE: The septum pellucidum is a virtual cavity located at the anterior part of the brain midline, which only in fetal life has a certain amount of fluid inside. The presence of an obliterated cavum septi pellucidi (oCSP) in the prenatal period is poorly described in the literature but, nevertheless, it constitutes an important clinical dilemma for the fetal medicine specialist in terms of significance and prognosis. Moreover, its occurrence is increasing maybe because of the widespread of high-resolution ultrasound machine. The aim of this work is to review the available literature regarding the oCSP along with the description of a case-report of oCSP with an unexpected outcome. METHODS: A search of the literature through Pubmed was performed up to December 2022 with the aim to identify all cases of oCSP previously described, using as keywords "cavum septi pellucidi," "abnormal cavum septi pellucidi," "fetus," and "septum pellucidum." Along with the narrative review, we describe a case-report of oCSP. RESULTS: A 39 years old woman was diagnosed with a nuchal translucency between the 95° and 99° centile in the first trimester and an oCSP and "hookshaped" gallbladder at 20 weeks. Left polymicrogyria was found at fetal magnetic resonance imaging (MRI). Standard karyotype and chromosomal microarray analysis (CMA) were normal. After birth, the newborn presented signs of severe acidosis, untreatable seizures and multiorgan failure leading to death. A targeted gene analysis of the epilepsy panel revealed the presence of a de novo pathogenic variant involving the PTEN gene. The literature review identified four articles reporting on the oCSP of which three were case report and one was a case-series. The reported rate of associated cerebral findings is around 20% and the rate of adverse neurological outcome is around 6%, which is higher than the background risk of the general population. CONCLUSIONS: This case-report and review of the literature shows that oCSP is a clinical entity poorly described so far and that, despite the generally good prognosis, it requires caution in counseling. The diagnostic work-up should include neurosonography while fetal MRI may be always indicated for non-isolated cases only, depending on local facilities. Targeted gene analysis or whole exome sequencing may be indicated for non-isolated cases.

Neurosonographic Measurements of the Fetal Anterior Complex in Singleton Pregnancies.

OBJECTIVE: To construct reference ranges of the fetal cerebral anterior complex, including ventricular index (VI), anterior horn of lateral ventricle width (AW), and cavum septi pellucidi (CSP) width, as a function of gestational age (GA), in Thai fetuses. METHODS: Low-risk pregnancies were recruited to measure fetal anterior complex on axial transventricular and coronal transcaudate planes using transabdominal ultrasound. The downside and upside hemisphere were defined as cerebral hemisphere located distal and proximal to the transducer, respectively. The five variables, downside/upside VI, downside/upside AW and CSP width, were measured from each fetus. Best-fit models in predicting mean and standard deviation for each value as a function of GA were constructed, using regression analysis. Distributions of Z-scores of all values based on GA were created to evaluate the fitness of models. Intraclass correlation coefficients were used to assess inter-/intraobserver variability. RESULTS: A total of 395 fetuses were measured for anterior complex. All parameters changed with GA with quadratic function. The models for predicting means and standard deviation of the five parameters as well as percentile charts were created. All models were proven well-fitted. The intra-/interobserver reliability coefficients of all values showed excellent agreement. CONCLUSION: The reference ranges of the fetal anterior complex, including VI, AW, and CSP, in axial transventricular and coronal transcaudate planes have been established and available for clinical use.

A Prolonged Treatment Associated With Absent Septum Pellucidum in Neonatal Abstinence Syndrome: A Case Report.

Neonatal abstinence syndrome (NAS) involves a widely variable treatment course among affected individuals. Prognostic indicators that would help predict length of hospital stay and individualize treatment would be valuable to newborns, parents, and hospital staff, including advanced practice registered nurses. We describe a newborn with a prolonged NAS treatment course necessitating high doses of opioids and phenobarbital, found to have an isolated absent septum pellucidum (ASP). We hypothesize a mechanism for an association between an ASP and a difficult NAS treatment course. Should this be substantiated by other cases, it could provide a valuable prognosticator and indicate alternate treatment pathways.

Algorithmic approach to neuroradiological diagnosis with pre-natal MRI: non-visualization of the fetal cavum septi pellucidi on mid-trimester screening ultrasound.

ADVANCES IN KNOWLEDGE: A systematic approach by the radiologist to analysis of imaging and other clinical data in the fetus with absent septal leaflets suspected on ultrasound will improve diagnostic efficiency, accuracy, and pre-natal counselling.

Fetal agenesis of the septum pellucidum: Ultrasonic diagnosis and clinical significance.

OBJECTIVE: To describe the prenatal ultrasound (US) findings, genetic results, and clinical outcomes of fetuses with suspected agenesis of the septum pellucidum (ASP) in the Chinese population. METHODS: This retrospective, single-center study included a cohort of fetuses with ASP diagnosed by prenatal imaging over a 10-year period. We evaluated US findings, associated anomalies, genetic results, and clinical outcomes. Prenatal and postnatal imaging findings were compared as well as the clinical outcome of delivery. RESULTS: Ninety patients were included, with a median follow-up time of 36 months (1-96 months). Thirty-six fetuses (40%) with isolated ASP were diagnosed by prenatal US or magnetic resonance imaging (MRI); 39 cases (43.3%) had ASP with central nervous system malformations and 15 cases (16.6%) had ASP with non-CNS abnormalities. Additional imaging findings were supplemented with prenatal MRI in 13 cases. Genetic tests were performed on 32 patients, of whom six had abnormalities. Prenatal US results of 40 patients (40/70) diagnosed by referral hospitals did not correspond to our findings. Of the 38 patients with postnatal records, 11 had abnormal neurological development. CONCLUSION(S): The outcome of an isolated ASP is usually favorable; however, neurological developmental delay is commonly observed if it is combined with other malformations.

Visualization of the Third Ventricle, the Future Cavum Septi Pellucidi, and the Cavum Veli Interpositi at 11+3 to 13+6 Gestational Weeks on 3D Transvaginal Ultrasound Including Normative Data.

OBJECTIVES: To show the development of the third ventricle, commissural plate, future cavum septi pellucidi, and cavum veli interpositi in weeks 12-14 by transvaginal 3D ultrasound. METHODS: This is a prospective transvaginal 3D study carried out to define the third ventricle and the diencephalic midline structures surrounding it. 93 of 387 fetuses in which the commissural plate with the future cavum septi pellucidi, cavum veli interpositi, and the roof of the third ventricle could be well visualized, were selected with the choroid plexus of the third ventricle and the pituitary gland serving as leading structures. In a small number of fetuses, the optic chiasm could also be displayed. In addition, the following measurements were performed: third ventricle craniocaudal and anteroposterior, roof of the third ventricle/cavum veli interpositi, and fcsp. RESULTS: The sonomorphologic characteristics of the commissural plate, the future cavum septi pellucidi, and the cavum veli interpositi are described IN 9% OF THE FETUSES examined. Measurements of the third ventricle, cavum veli interpositi, and the roof of the third ventricle show the following results: 3rd V cc = 3.895 + 0.091*CRL mm; 3rd V ap = 4.175 + 0.036*CRL mm; CVI ap = 2.223 + 0.029*CRL mm; CVI cc = 0.139 + 0.02*CRL mm. CONCLUSION: Transvaginal neurosonography enables visualization and measurement of the normal fetal third ventricle at 12-14 weeks of gestation including visualization of the future cavum septi pellucidi and the cavum veli interpositi. BEFORE USE IN PATIENTS CAN BE CONSIDERED, FURTHER SCIENTIFIC WORK IS REQUIRED.

Spontaneous Regression of a Symptomatic Cyst of the Cavum Septi Pellucidi and Vergae.

Spontaneous regression of cysts of the cavum septi pellucidi (CSP) and cavum vergae (CV) is rare and little discussed. The authors present their case report of this phenomenon following a severe headache in a 23-year-old woman, in whom magnetic resonance imaging (MRI) had previously confirmed significant thinning of the left lateral cyst wall. We consider this finding to be a possible predisposing factor to rupture and the spontaneous regression of such cysts. In addition to the mechanism of cyst regression, the interrelated causes of their expansion and formation will be discussed.

It does Exist! Traumatic Hemorrhage in Septum Pellucidum.

Although bleeding into the septum pellucidum often occurs in the presence of a tumour, trauma-induced septal pellucidum hemorrhage has not been reported yet, as far as the current literature is concerned. The absence of hemorrhage on the first post-trauma imaging of the patient but the presence of hemorrhage in the brain tomography taken 12 hours later reveals the existence of trauma-induced septum pellucidum hemorrhage. Key Words: Head trauma, Brain injury, Septum pellucidum, Hemorrhage.

Isolated Absent Septum Pellucidum: A Retrospective Study of Fetal Diagnosis and Postnatal Outcomes.

BACKGROUND: Absent septum pellucidum (ASP) is a brain abnormality often associated with neuroanatomic abnormalities including septo-optic dysplasia (SOD). We aimed to determine how frequently prenatally diagnosed isolated ASP is confirmed by postnatal imaging and to examine clinical outcomes for ASP. METHODS: This was a retrospective study of maternal-fetal dyads referred to Children's National Hospital from January 1, 2012, to June 30, 2019. We included cases with fetal diagnosis of isolated or complex ASP. Diagnosis was based on ASP and the presence or absence of additional neuroanatomic findings. Data included obstetric and birth history, genetic testing, imaging, and neurodevelopmental outcomes. RESULTS: ASP was diagnosed in 35 fetuses. Of 17 fetuses with isolated ASP, 10 had postnatal evaluation. In five (50%) isolated ASP cases, postnatal imaging revealed additional brain abnormalities. The five children with postnatally confirmed isolated ASP had lower rates of hydrocephalus (0% vs 54%) and abnormal feeding (0% vs 20%), hearing (0% vs 14%), and vision (0% vs 14%) than those with complex ASP (n = 17). Children with isolated ASP had lower rates of developmental delay (33% vs 50%) and seizures (11% vs 30%) than children with complex ASP. One child with prenatal isolated ASP was diagnosed with SOD (10%). CONCLUSIONS: Few children with prenatally diagnosed isolated ASP had SOD diagnosed postnatally. Overall, children with isolated ASP demonstrate better outcomes than children with complex ASP. Fetal magnetic resonance imaging is a useful tool to evaluate the septum pellucidum and may reveal additional abnormalities that can impact prognosis and affect prenatal counseling.

Cavum septum pellucidum nomogram during the second trimester of pregnancy.

This study aimed to determine cavum septum pellucidum (CSP) nomogram values between 15-28 weeks of gestation. Routine biometric measurements and CSP width were measured by transabdominal ultrasonography in 6042 structurally normal foetuses between 15-28 weeks of gestation. Distribution of CSP width by the week of pregnancy and percentile values were calculated. The mean week of gestation (GW) was 21 ± 1.7, and the mean biparietal diameter (BPD) was 50.2 ± 5.8 mm. The CSP width range was 1.6-7.7 mm at 15-28 weeks, and the mean CSP width was 4.1 ± 0.8 mm. CSP width was found to have a significant correlation between a gestational week (CSP = GW X 0.2705-1.6121; R = 0.62; p < .01) and BPD (CSP = BPD X 0.0859-0.273; R = 0.651; p 0.01). CSP width was found to differ significantly according to gestational weeks, and percentile distributions were calculated. Between 15 and 28 weeks of gestation, the 95th percentile values of CSP width were found to be 3.7-7 mm. Our study was determined that CSP width increased linearly between 15-28 weeks of gestation. For this reason, we think that it would be more appropriate to use CSP width percentile values in the examination of the foetus. Impact statementWhat is already known on this subject? The cavum septum pellucidum can be easily identified and evaluated by ultrasonography after 18 weeks of pregnancy. CSP can be associated with severe brain anomalies if it is not visualised or deformed. Moreover; large CSP may be associated with chromosomal abnormalities.What do the results of this study add? Our study showed that CSP width increased linearly between 15-28 weeks of gestation. CSP width was found to differ significantly according to gestational weeks, and between 15 and 28 weeks of gestation, the 95th percentile values of CSP width were found to be 3.7-7 mm.What are the implications of these findings for clinical practice and/or further research? We reported that it would be more appropriate to use CSP percentile values according to the gestational week in the definition of abnormal CSP.