Posterior Cranial Fossa Volume Research Articles

Intracranial volumetric evaluation in postnatally repaired myelomeningocele infants

IntroductionMost myelomeningocele (MMC) cases present with ventriculomegaly or hydrocephalus, yet a comprehensive volumetric assessment of MMC intracranial structures is lacking. This study aimed to provide baseline data on intracranial structural volumes immediately after birth in MMC infants who underwent repair surgeries after birth (postnatal repair).MethodsIn this retrospective single-center study, we analyzed 52 MMC infants undergoing postnatal repair, utilizing head computed tomography scans at birth for volumetric assessment. Intracranial volume (ICV), lateral ventricles volume (LVV), choroid plexus volume (CPV), and posterior cranial fossa volume (PCFV) were measured. Hydrocephalus was classified into no hydrocephalus, progressive hydrocephalus, and hydrocephalus at birth. Comparative analysis employed the Wilcoxon rank-sum test. Receiver operating characteristic (ROC) analysis discriminated cases with and without ventriculoperitoneal shunt (VPS).ResultsThe median values were 407.50 mL for ICV, 33.18 mL for LVV, 0.67 mL for CPV, and 21.35 mL for PCFV. Thirty-seven cases (71.15%) underwent VPS. ROC analysis revealed an LVV cut-off value of 6.74 mL for discriminating cases with and without VPS. Progressive hydrocephalus showed no significant difference in ICV but significantly larger LVV compared to no hydrocephalus. Hydrocephalus at birth demonstrated statistically larger ICV and LVV compared to the other two types.ConclusionBaseline volumetric data were provided, and volumetric analysis exhibited statistical differences among three hydrocephalus types. These findings enhance our understanding of intracranial volumetric changes in MMC, facilitating more objective assessments of MMC cases.

Growth patterns and ratios of posterior cranial fossa structures in the Japanese pediatric population: a study utilizing CT scans.

The changes in the proportion of posterior cranial fossa structures during pediatric development remain unclear. This retrospective study aimed to investigate the growth patterns and ratios of these structures using CT scans. Head CT scans of pediatric patients with minor head trauma from Osaka Women's and Children's Hospital between March 2006 and May 2023 were analyzed. The study segmented the intracranial volume (ICV), posterior cranial fossa volume (PCFV), cerebellum volume (CBMV), and brainstem volume (BSV). Correlation coefficients were calculated among the parameters. Patients aged 0 to 10 years were divided into 15 age-related clusters, and mean and standard deviation values were measured. Growth curves were created by plotting mean values sequentially. Ratios such as PCFV/ICV and (CBMV + BSV)/PCFV were examined. Statistical analyses, including unpaired t tests and logarithmic curve fitting, were performed. A total of 234 CT scans (97 from females, 115 from infants under 1 year of age) were analyzed. Positive correlations were observed among the parameters, with the strongest between PCFV and CBMV. The growth curves for ICV, PCFV, CBMV, and BSV exhibited a two-phase process, with rapid growth until approximately 4 years of age, followed by stabilization. The ratios PCFV/ICV and (CBMV + BSV)/PCFV showed increasing trends from birth onwards, stabilizing by 4 and 1 years of age, respectively. This study provides insights into the growth patterns and ratios of posterior cranial fossa structures in the pediatric population. The findings demonstrate a two-phase growth process and increasing trends in the examined ratios.

Study on the relationship between vertebrobasilar dolichoectasia and posterior cranial fossa space

ObjectiveTo investigate the correlation between vertebrobasilar dolichoectasia (VBD) and posterior cranial fossa (PCF) space. MethodsThe medical records and imaging data of patients with VBD and control group were collected from June 2021 to June 2022 in the Third People's Hospital of Hubei Province. All patients with VBD were graded by head and neck CTA. The grading index was divided into two parts, including vertebral artery bifurcation height and offset degree. Taking the healthy adult subjects of matched age as the control group. The linear volume of posterior cranial fossa was measured by median sagittal CTA images. Middle clivus length, transverse diameter of occipital foramen, supraoccipital length, sagittal diameter of posterior cranial fossa and height diameter of posterior cranial fossa was measured. The volume of the PCF was calculated by 3Dslice software. The relationship between VBD and the volume of PCF was analyzed by SPSS23.0. ResultsThe height diameter of posterior cranial fossa, sagittal diameter of posterior cranial fossa, transverse diameter of occipital foramen, clival length, supraoccipital length and space volume of PCF were 34.78 ± 3.67 mm, 85.49 ± 4.15 mm, 30.89 ± 3.94 mm, 44.53 ± 5.36 mm, 45.21 ± 6.45 mm, 171.08 ± 15.81 cm3 in the case group. The linear volume of PCF and space volume of PCF were significantly lower than those in the control group (P < 0.05). Binary logistic regression analysis showed that the independent risk factors of VBD were height diameter of PCF, sagittal diameter of PCF, transverse diameter of occipital foramen, clival length, supraoccipital length and space volume of posterior cranial fossa. According to the classification, the height and diameter of PCF in grade 1 was significantly smaller than that in grade 2 VBD (P < 0.05). Under the standard of BA bifurcation degree, there were significant differences between different grades of VBD patients and age (P < 0.05). ConclusionThe smaller volume of PCF may leading the greater possibility of VBD. Under the classification of VBD, the older, the longer the course of disease is, the higher degree of VBD classification is.

C1-2 Fusion in Atlantoaxial Dislocation and Basilar Invagination with and without Chiari Malformation: Clinical/Radiological and Craniometric Results

Patients with Chiari malformation (CM) associated with atlantoaxial dislocation (AAD) and basilar invagination (BI) may present with a small posterior cranial fossa, but data on the volumetric analysis are lacking. Additionally, whether additional foramen magnum decompression (FMD) is needed together with atlantoaxial fusion remains controversial. This study evaluated the volumetric alterations of the posterior cranial fossa in these patients and analyzed the radiological and clinical outcomes after posterior C1-C2 reduction and fixation plus C1 posterior arch resection. Thirty-two adult CM patients with AAD and BI (CM-AAD/BI group) and 21 AAD and BI patients without CM (AAD/BI-only group) who received posterior atlantoaxial fusion plus C1 posterior arch resection were retrospectively studied. The clinical and radiological outcomes and volumetric measurements of the posterior cranial fossa were evaluated. The majority of CM-AAD/BI patients (94%) improved clinically and radiologically at 12mo postoperatively, and none required additional FMD. Morphological analysis revealed a significant reduction in the bony posterior cranial fossa volumes of the CM-AAD/BI group (P<0.01) and the AAD/BI-only group (P<0.01) relative to those of the CM group. No significant differences were observed between the CM-AAD/BI and AAD/BI groups. Compared with patients with simple CM, patients with AAD/BI with or without CM demonstrated a considerably and equally reduced bony posterior cranial fossa volume. No additional FMD is needed in the treatment of CM-AAD/BI patients after posterior reduction and fusion plus C1 posterior arch resection.

Acquired Chiari type I malformation: a late and misunderstood supratentorial over-drainage complication.

Acquired Chiari I malformation is an uncommon but possible late complication of supratentorial shunting in children. This condition can be caused by an abnormal thickening of the cranial vault and consequent reduction of the posterior cranial fossa (PCF) volume especially in children with already a small PCF volume. The management of Acquired Chiari I malformation is very challenging, and several options have been proposed for this condition. These are aimed to expand the PCF volume both through decompression and PCF remodeling in order to relieve symptoms of acquired Chiari I malformation. A cranial vault remodeling or a standard Chiari decompression is two proposed techniques aimed to expand the PCF volume thus relieving symptoms . We describe the case of a 16-year-old girl undergone surgical removal of sellar-suprasellar glioneuronal tumor and ventriculo-peritoneal shunting, who developed an acquired symptomatic Chiari type I malformation some years after ventricular-peritoneal shunting. For this condition, she underwent successful standard Chiari decompression with C0-C1 craniectomy and duroplasty. We retrospectively analyzed MRI and CT scan performed during follow-up, in order to evaluate the volume of the posterior cranial fossa and to measure the variation of skull thickness at different periods. MRI and CT scan analysis showed a progressive thickening of the calvaria, in particular of the occipital bone, leading to a progressive reduction of PCF volume with the establishment of acquired Chiari type I malformation. In this case, standard C0-C1 Chiari decompression was effective in restoring PCF volume and relieving symptoms. Acquired Chiari I malformation due to chronic overhunting could be a severe and late complication in patient undergone supratentorial shunting. These patients require careful clinical and radiological follow-up to avoid over-drainage. According to our analysis, a careful selection of pediatric patients for supratentorial shunting should be made according to pre-operative PCF volume in order to foresee higher odds of possible late complications from over-drainage.

Correlation of the inclination of the tentorium cerebellum and the volume of the posterior cranial fossa.

Aim To investigate the influence of the inclination and insertion of the cerebellar tentorium on the posterior cranial fossa (PCF) volume. Methods A retrospective, non-randomized study including 174 patients (117 females and 57 males) who underwent magnetic resonance imaging in the period from 31 December 2020 to 1 June 2021 under the indication (mostly headache) set by a competent ordinary. Acute or chronic intracranial events were not verified in the patients. Results The average value of the PCF volume was 138.93 cm3 and the slope of the tentorium was 44.15°. Comparing the volume of the PCF and the slope of the tentorium in males and females no significant difference was found. A correlation was found in the females age groups 18-24 and 45-54 years. Conclusion Understanding dimensions of the posterior cranial fossa morphometry has clear implications for reducing morbidity and mortality in surgery, especially in the case of applying lateral approaches and their variations.

Morphometric Analysis of Posterior Fossa and Foramen Magnum among Pediatric Age Group 6 to 16 Years

Background Configuration and size of the foramen magnum and posterior cranial fossa plays an important role in the pathophysiology of various disorders like Chiari malformations, basilar invagination etc. Thus, a fundamental knowledge of normal anatomy of this region is important to the clinician for diagnosis and treatment. However, we couldn’t find any anatomical study related to the concerned topic among the pediatric population aged 6 to 16 years in Nepal to the best of our knowledge.&#x0D; Objective To attain the baseline results (volume of bony part of posterior cranial fossa and the surface area of foramen magnum) that will help in the better diagnosis, classification, and treatment of diseases related to posterior fossa and craniovertebral junction and serve as a future reference defining an anatomic range in our region.&#x0D; Method This is a retrospective prospective observational study conducted from 1st February 2021 to 31st January 2022 at Dhulikhel Hospital, Kathmandu University Hospital, Kavrepalanchowk, Nepal. We used convenient sampling technique to fulfil our sample size. We considered 68 patients, who got recruited either from our emergency and OPD departments and were fulfilling our criteria of inclusion. Upon the recruitment, 68 consecutive head CT scan of pediatric patients with normal reports (without any bony or soft-tissue abnormality) were studied. Volume of the posterior fossa was calculated with the help of inbuilt “advanced work station - 3D volume calculator” program in 128 slices - SOMATOM PERSPECTIVE CT Scanner from Siemens, Germany. The area of the foramen magnum was calculated using formula πr2, where r is average radius calculated from obtained antero-posterior and transverse diameter.&#x0D; Result The age of the patients ranged between 6 and 16 years with the mean age of 10.56 ± 3.38 years with male to female distribution of 1: 1.125. The mean volume of the posterior fossa was 165.61 ± 8.52 mm3. The mean AP diameter, transverse diameter, and the surface area of foramen magnum were 3.31 ± 0.12 mm, 2.72 ± 0.12 mm, and 28.60 ± 0.09 mm2 respectively.&#x0D; Conclusion Normal ranges of volume of posterior cranial fossa and various dimensions and surface area of foramen magnum of pediatric population were determined using CT scans, which could serve as future reference in Nepal.

Surgical Management of Chiari Malformation Type I and Instability of the Craniocervical Junction Based on Its Pathogenesis and Classification.

We investigated the mechanism underlying Chiari malformation type I (CM-I) and classified it according to the morphometric analyses of posterior cranial fossa (PCF) and craniocervical junction (CCJ). Three independent subtypes of CM-I were confirmed (CM-I types A, B, and C) for 484 cases and 150 normal volunteers by multiple analyses. CM-I type A had normal volume of PCF (VPCF) and occipital bone size. Type B had normal VPCF and small volume of the area surrounding the foramen magnum (VAFM) and occipital bone size. Type C had small VPCF, VAFM, and occipital bone size. Morphometric analyses during craniocervical traction test demonstrated instability of CCJ. Foramen magnum decompression (FMD) was performed in 302 cases. Expansive suboccipital cranioplasty (ESCP) was performed in 102 cases. Craniocervical posterolateral fixation (CCF) was performed for CCJ instability in 70 cases. Both ESCP and FMD showed a high improvement rate of neurological symptoms and signs (84.4%) and a high recovery rate of the Japanese Orthopaedic Association (JOA) score (58.5%). CCF also showed a high recovery rate of the JOA score (69.7%), with successful joint stabilization (84.3%). CM-I type A was associated with other mechanisms that caused ptosis of the brainstem and cerebellum (CCJ instability and traction and pressure dissociation between the intracranial cavity and spinal canal cavity), whereas CM-I types B and C demonstrated underdevelopment of the occipital bone. For CM-I types B and C, PCF decompression should be performed, whereas for small VPCF, ESCP should be performed. CCF for CCJ instability (including CM-I type A) was safe and effective.

Statistical shape models of the posterior cranial fossa and hindbrain volumes may provide a more robust clinical metric for Chiari malformation

Chiari malformation is characterised by the herniation of the cerebellar tonsils through the foramen magnum. However, tonsillar herniation and other 2D morphometric measurements of the posterior cranial fossa (PCF) have a weak association with patients’ symptoms and clinical outcomes. This study aimed to contrast current 2D metrics with a novel 3D shape analysis of the PCF and the hindbrain, to determine if 3D measurements provides further insight into the pathophysiology of Chiari. The cranium of 12 controls and 21 Chiari malformation patients with (N = 9) and without (N = 12) a syrinx were scanned. The morphology of the PCF was quantified with typical 2D measurements. Additionally, a correspondence-based shape model that normalised the PCF volume, was used to find 3D differences in the shape of the PCF, and the distance of the hindbrain from the inner surfaces of the PCF. Shape analysis showed that, compared to controls, the caudal (p = 0.007; 2.3 mm, IQR: 1.6–3.3 mm) and anterior (p = 0.027; 1.3 mm,IQR: 1.1–1.6 mm) surfaces of the hindbrain were closer to the PCF in patients with and without a syrinx, respectively. However, there were negligible differences in the shape of the PCF between patient groups (p > 0.39). Current morphometric measures should be normalised for variation in PCF volume, so that shape measures are not biased. The reduced CSF space between the hindbrain and PCF will alter CSF dynamics, which may compress cerebellar vasculature and contribute to patient symptomatology.

Morphometric and volumetric analysis of the posterior cranial fossa in adult Chiari malformation type I with and without group B basilar invagination.

The frequent association of basilar invagination (BI) makes the understanding of the pathogenesis of Chiari malformation type I (CMI) difficult. The influence of group B type of BI (the BI without obvious atlantoaxial instability) on the skeletal morphology has not been thoroughly studied. The objective of this study is to evaluate the skeletal alterations in the posterior cranial fossa (PCF) of adult CMI cases with and without group B BI. Fifty-four adult CMI without BI cases (CMI-only group) and 30 adult CMI with group B BI cases (CMI-BI group) were retrospectively studied. Fifty-six adult patients with unruptured intracranial aneurysms were included as the controls. Several linear and angular variables, and the bony volume of the PCF were analyzed based on thin-slice computed tomography data. Morphological analysis revealed a significant difference in several variables from controls compared to CMI-only, and CMI-BI patients. The clivus and occipital bone, shortened and elevated in CMI-only patients, were further flattened in BI-associated CMI patients. Furthermore, although out of the scope for the diagnostic threshold of BI, the CMI-only cases also had a tendency to form BI. The association of BI modified several variables, without further reducing the bony PCF volume. These findings indicate that the variables associated with group B BI tend to be a continuum of the same pathological abnormalities that originate from the same pathological alterations in CMI patients.

A Morphometric Evaluation Together with Computed Tomography Examination of Chiari Type 1 Cases with Craniovertebral Junction Anomaly.

To compare the posterior cranial fossa (PCF) dimensions together with the measurements related to basilar invagination and platybasia of craniovertebral junction anomalies (CVJA) in CVJA (+) and CVJA (-) Chiari malformation Type 1 (CM1) patient groups with each other and with healthy control subjects. The study group was formed of 43 CM1 and 9 tonsillar ectopia (TE) patients. A decrease was determined in the PCF vertical length (clivus and supraocciput line) and PCF volume and an increase in the transverse length (McRae and Twining line) in the CM1 cases compared to the healthy control group. There was no difference between the CVJA (+) and (-) CM1 groups in respect of the vertical and transverse length and PCF volume values. An increase in the classic and modified skull base angles was observed in the CVJA (+) CM1 group compared to the CVJA (-) CM1 group. The Wackenheim clivus angle was determined to be smaller in the CVJA (+) CM1 group compared to the CVJA (-) CM1 group. The PCF is flattened and smaller in CM1 cases compared to normal control subjects. In the planning of CM1 operations, the angle parameters may be more useful than the PCF and CVJA length parameters between CVJA (+) and (-) CM1 groups. The significant decrease in postoperative recovery in the CVJA (+) CM1 group compared to the CVJA (-) CM1 group supports the need for additional operations and/or a different surgical technique in the treatment of CVJA (+) CM1 patients.

Impairment of motor skills in children with achondroplasia-usefulness of brain and cranio-cervical junction evaluation by quantitative magnetic resonance imaging: a case-control study.

Most infants and children with achondroplasia show delayed motor skill development; however, some patients may have clinical consequences related to cranio-cervical junction stenosis and compression. To assess, using brain magnetic resonance imaging (MRI), quantitative variables linked to neuromotor impairment in achondroplasic children. In total, 24 achondroplasic children underwent pediatric neurological assessment and were grouped in two cohorts according to relevant motor skill impairment. Achondroplasic children with (n=12) and without (n=12) motor symptoms were identified, and brain MRI scans were quantitatively evaluated. 3D fast spoiled gradient echo T1-weighted images were used to assess: supratentorial intracranial volumes (SICV); supratentorial intracranial brain volume (SICBV); SICV/SICBV ratio; posterior cranial fossa volume (PCFV); posterior cranial fossa brain volume (PCBFV); PCFV/PCFBV ratio; ventricular and extra-ventricular cerebrospinal fluid (CSF) volumes; foramen magnum (FM) area; and jugular foramina (JF) areas. In both groups, SICV/SICBV ratio, supratentorial ventricular and extra-ventricular space volumes were increased while SICBV was increased only in the asymptomatic group (P < 0.05). PCFV/PCFBV ratio, IV ventricle, infratentorial extra-ventricular spaces volumes were reduced (P < 0.05) in the symptomatic group while PCFBV was increased only in the asymptomatic group (P < 0.05). Foramen magnum (FM) area was more reduced in the symptomatic group than the asymptomatic group (P < 0.05) but no correlation between FM area and ventriculomegaly was found (P > 0.05). Evaluation of the FM area together with infratentorial ventricular and extra-ventricular space volume reduction may be helpful in differentiating patients at risk of developing motor skill impairment. Further investigation is needed to better understand the temporal profile between imaging and motor function in order to propose possible personalized surgical treatment.

Multi-parameter-based radiological diagnosis of Chiari Malformation using Machine Learning Technology.

The known primary radiological diagnosis of Chiari Malformation-I (CM-I) is based on the degree of tonsillar herniation (TH) below the Foramen Magnum (FM). However, recent data also shows the association of such malformation with smaller posterior cranial fossa (PCF) volume and the anatomical issues regarding the Odontoid. This study presents the achieved result regarding some detected potential radiological findings that may aid CM-I diagnosis using several machine learning (ML) algorithms. Midsagittal T1-weighted MR images were collected in 241 adult patients diagnosed with CM, eleven morphometric measures of the posterior cerebral fossa were performed. Patients whose imaging was performed in the same centre and on the same device were included in the study. By matching age and gender, radiological exams of 100 clinically/radiologically proven symptomatic CM-I cases and 100 healthy controls were assessed. Eleven morphometric measures of the posterior cerebral fossa were examined using 5 designed ML algorithms. The mean age of patients was 29.92±15.03years. The primary presenting symptoms were headaches (62%). Syringomyelia and retrocurved-odontoid were detected in 34% and 8% of patients, respectively. All of the morphometric measures were significantly different between the groups, except for the distance from the dens axis to the posterior margin of FM. The Radom Forest model is found to have the best 1.0 (14 of 14) ratio of accuracy in regard to 14 different combinations of morphometric features. Our study indicates the potential usefulness of ML-guided PCF measurements, other than TH, that may be used to predict and diagnose CM-I accurately. Combining two or three preferable osseous structure-based measurements may increase the accuracy of radiological diagnosis of CM-I.

Posterior vault \u201cfree-floating\u201d bone flap: indications, technique, advantages, and drawbacks

BackgroundThe enlargement of the posterior cranial fossa volume is considered one of the main steps of the surgical management of children with multiple sutures craniosynostosis. Different management options have been proposed including fixed expansive craniotomy, free bone flap craniotomy, and distraction osteogenesis.ObjectivesTo review indications to “free bone flap” craniotomy for the posterior fossa expansion, detailing advantages, disadvantages, and complications related to the technique.Results and conclusionsA review of the literature shows that “free bone flap” posterior expansion cranioplasty still has a role, particularly in infants with thin and “honeycomb” structure of the bone, allowing to gain adequate intracranial volume increases and to postpone to a more adequate time surgery aimed at anterior cranial fossa expansion.

Respective Roles of Craniosynostosis and Syndromic Influences on Cranial Fossa Development.

Little is known about the detailed growth of the cranial fossae, even though they provide an important structural connection between the cranial vault and the facial skeleton. This study details the morphologic development of isolated cranial vault synostosis and associated syndromes on cranial fossa development. A total of 125 computed tomographic scans were included (nonsyndromic bicoronal synostosis, n = 36; Apert syndrome associated with bicoronal synostosis, n = 24; Crouzon syndrome associated with bicoronal synostosis, n = 11; and controls, n = 54). Three-dimensional analyses were produced using Materialise software. The regional anterior and middle cranial fossae volumes of nonsyndromic bicoronal synostosis are characterized by significant increases of 43 percent (p < 0.001) and 60 percent (p < 0.001), respectively, and normal posterior cranial fossa volume. The cranial fossae depths of nonsyndromic bicoronal synostosis were increased, by 37, 42, and 21 percent (all p < 0.001) for anterior, middle, and posterior cranial fossae, respectively, accompanying the shortened cranial fossae lengths. The volume and morphology of all cranial fossae in Apert syndrome nearly paralleled nonsyndromic bicoronal synostosis. However, Crouzon syndrome had reduced depths of cranial fossae, and more restricted fossa volumes than both Apert syndrome and nonsyndromic bicoronal synostosis. Cranial vault suture synostosis is likely to be more influential on cranial fossae development than other associated influences (genetic, morphologic) in Apert and Crouzon syndromes. Isolated Apert syndrome pathogenesis is associated with an elongation of the anterior cranial fossa length in infants, whereas in Crouzon syndrome, there is a tendency to reduce cranial fossa depth, suggesting individual adaptability in cranial fossae development related to vault synostosis.

Functional and morphological changes in hypoplasic posterior fossa

BackgroundThe knowledge of the development and the anatomy of the posterior cranial fossa (PCF) is crucial to define the occurrence and the prognosis of diseases where the surface and/or the volume of PCF is reduced, as several forms of craniosynostosis or Chiari type I malformation (CIM). To understand the functional and morphological changes resulting from such a hypoplasia is mandatory for their correct management. The purpose of this article is to review the pertinent literature to provide an update on this topic.MethodsThe related and most recent literature addressing the issue of the changes in hypoplasic PCF has been reviewed with particular interest in the studies focusing on the PCF characteristics in craniosynostosis, CIM, and achondroplasia.Results and conclusionsIn craniosynostoses, namely, the syndromic ones, PCF shows different degrees of hypoplasia, according to the different pattern and timing of early suture fusion. Several factors concur to PCF hypoplasia and contribute to the resulting problems (CIM, hydrocephalus), as the fusion of the major and minor sutures of the lambdoid arch, the involvement of the basal synchondroses, and the occlusion of the jugular foramina. The combination of these factors explains the variety of the clinical and radiological phenotypes. In primary CIM, the matter is complicated by the evidence that, in spite of impaired PCF 2D measurements and theories on the mesodermal defect, the PCF volumetry is often comparable to healthy subjects. CIM is revealed by the overcrowding of the foramen magnum that is the result of a cranio-cerebral disproportion (altered PCF brain volume/PCF total volume). Sometimes, this disproportion is evident and can be demonstrated (basilar invagination, real PCF hypoplasia); sometimes, it is not. Some recent genetic observations would suggest that CIM is the result of an excessive growth of the neural tissue rather than a reduced growth of PCF bones. Finally, in achondroplasia, both macrocephaly and reduced 2D and 3D values of PCF occur. Some aspects of this disease remain partially obscure, as the rare incidence of hydrocephalus and syringomyelia and the common occurrence of asymptomatic upper cervical spinal cord damage. On the other hand, the low rate of CIM could be explained on the basis of the reduced area of the foramen magnum, which would prevent the hindbrain herniation.

Flat-shaped posterior cranial fossa was associated with poor outcomes of microvascular decompression for primary hemifacial spasm

Numerous factors have been investigated on affecting the outcomes of primary hemifacial spasm (HFS) after microvascular decompression (MVD). It is well established that anatomical differences of the posterior cranial fossa (PCF) plays an important role in the occurrence of HFS. However, it is still not clear whether morphological characteristics of PCF affect the surgical outcomes of HFS after MVD. Our study aims to investigate the prognostic factors for surgical outcomes of MVD for primary HFS, with a particular focus on the morphological characteristics of PCF. Between January 2014 and November 2017, a total of 152 HFS patients who underwent MVD treatment in our department were included in this study. The clinical data were retrospectively reviewed. The outcomes of MVD were classified into success and failure groups according to the short- and long-term postoperative responses. Particularly, we established an ellipsoid model for PCF. The related length (Y), width (X) and height (Z) of the PCF were measured and the volume of PCF was calculated employing a formula of [Formula: see text]XYZ. The relationship between PCF volume and surgical outcomes was statistically analysed. The severity of neurovascular compression (NVC) (p = 0.010), type of NVC (p = 0.001) and lateral spread response (LSR) (p < 0.0001) significantly influenced the long-term surgical outcomes of MVD for primary HFS. In particular, for the first time, we demonstrated that a flat-shaped PCF was associated with poor long-term outcome and postoperative recurrence. Our current study suggests that mild NVC, small vessel compression, intraoperative LSR persistence and flat-shaped PCF are independent factors predicting poor prognosis of MVD for primary HFS.

Cranial Fossa Volume in Differing Subtypes of Apert Syndrome.

Based on an established classification system of Apert syndrome subtypes, detailed regional morphology and volume analysis may be useful to provide additional clarification to individual Apert cranial structure characteristics, and treatment planning. Computed tomography scans of 32 unoperated Apert syndrome and 50 controls were included and subgrouped as: type I, bilateral coronal synostosis; type II, pansynostosis; type III, perpendicular combination synostosis. Three-dimensional analysis of craniometric points was used to define structural components using Materialise Mimics and 3-Matics software. Occipitofrontal circumference of all subtypes of Apert syndrome patients is normal. Intracranial volumes of types I and II were normal, but type III was 20% greater than controls. Middle cranial fossa volume was increased in all 3 types, with the greatest increase in type II (86%). Type II developed a 69% increase in anterior cranial fossa volume, whereas type III had 39% greater posterior cranial fossa volume. Increased cranial fossa depth contributed most to above increased volume. The anteroposterior lengths of middle and posterior cranial fossae were reduced in type I (15% and 17%, respectively). However, only the anterior cranial fossa was significantly shortened in type III. Occipitofrontal circumference and overall intracranial volume is not always consistent in individual subunits of Apert syndrome. Detailed and segmental anterior, middle, and posterior cranial fossae volumes and morphology should be analyzed to see what impact this may have related to surgical planning.

What Is the Skull Structure Influence of Squamosal Suture Synostosis in Nonsyndromic and Syndromic Crouzon Craniosynostosis?

The morphologic effect of squamosal synostosis has not been clarified, due to its low occurrence rate, and its inclination to be combined with premature closure of other major sutures, especially in syndromic synostosis. This study's goal is to explore the morphological influence of squamosal synostosis in both syndromic and nonsyndromic craniosynostosis patients. Twenty-five computed tomography (CT) scans from nonsyndromic squamosal synostosis (NSS), Crouzon syndrome with squamosal synostosis (CSS), Crouzon syndrome without squamosal synostosis, and normal controls were included. Three-dimensional (3D) cephalometry, entire cranial volume and cranial fossa volume were measured using Materialise software. The entire cranial volume of all groups was similar. The NSS developed a gradual reduction in the severity of reduced segmental volume from the anterior cranial fossa, to the middle cranial fossa, and to the unaffected volume of posterior cranial fossa. The CSS developed the most severe volume reduction of middle cranial fossa (12608.30 ± 2408.61 mm vs 26077.96 ± 4465.74 mm, 52%), with proportionate volume reduction of the anterior (7312.21 ± 2435.97 mm vs 10520.63 ± 2400.43 mm, 30%) and posterior cranial fossa (33487.29 ± 5598.93 mm vs 48325.04 ± 14700.44 mm, 31%). The NSS developed a narrower anterior cranial fossa, a clockwise rotated Frankfort horizontal plane, and a retracted chin (pogonion). Squamosal synostosis may alter the development of cranial fossa volume, especially the volume of middle cranial fossa. However, the development of cranial base, and related facial features are determined largely by major vault sutures and associated syndromic conditions, rather than the squamosal suture alone. II.

S3-02 SESSION 3: FACIOCRANIOSYNOSTOSIS – PART I CRANIAL FOSSA DEVELOPMENT IN DIFFERING SUBTYPES OF CROUZON SYNDROME

Introduction: Based on an established classification system of Crouzon syndrome subtypes, detailed regional morphology and volume analysis may be useful, in order to add additional clarification to Crouzon cranial structure characteristics, and the interaction between syndrome, suture fusion and gene regulated overall growth of the calvarium and basicranium. Methods: CT scans of 36 unoperated Crouzon syndrome and 56 controls were included and subgrouped as: type I. Bilateral coronal synostosis; type II. Sagittal synostosis; type III. Pansynostosis; type IV. Perpendicular combination synostosis. Results: Type I of Crouzon syndrome patients developed a slightly smaller posterior cranial fossa (22%), and increased superior cranial volume (13%), which is the only subtype that develops a greater superior cranial volume. The effect of competing increases and decreased segmented volume causes a 24% enlargement of overall cranial volume (p=0.321). In class III, the anterior cranial fossa volume was increased by 31% (p=0.007), while the volume of posterior cranial fossa was decreased by 19% (p<0.001). This resulted in a 7% (p=0.046) reduction in the overall intracranial volume. Type II and type IV patients developed a trend toward anterior, middle, posterior fossa and entire cranial volume reduction, although none of these decreases reached statistical significance. Conclusion: Pansynostosis is the most often form of associated craniosynostoses of Crouzon syndrome. Bilateral coronal synostosis may not dominate all forms of Crouzon syndrome. Individualized treatment planning for Crouzon syndrome patient, thoracically, should be taken into account, factors such as the patient’s age, and temporally associated suture involvement, for both anterior and posterior cranial fossae surgery.