Posterior Fossa Volume Research Articles

Chiari malformation type I and craniosynostosis in adults: Retrospective analysis over a 10 year period in a tertiary care Centre

Background Chiari malformation type 1 (CM1) pathophysiology remains uncertain. One theory involves small posterior fossa volumes leading to tonsillar herniation. Craniosynostosis causes suture fusion, which can limit skull growth, and has been investigated in paediatric CM1 cohorts. We aimed to identify the prevalence of concurrent craniosynostosis in adult CM1 patients. Methods Surgically managed CM1 patients were identified from a pre-existing Edinburgh neurosurgical centres database spanning 10 years. Patients aged 16 years of age or older had their case notes reviewed retrospectively. Cross sectional imaging identified and classified craniosynostosis, tonsillar herniation and the presence of hydrocephalus or syrinxes. Results 35 cases met inclusion criteria. Seven cases (20%) had craniosynostosis, all of which were sagittal synostosis. There was no significant association between the presence of craniosynostosis and the degree of tonsillar herniation, presence of hydrocephalus or syrinx formation. Conclusion This is the first study to evaluate the prevalence of craniosynostosis in a cohort of surgically managed adult CM1 patients. Future studies should potentially investigate whether conservatively managed adult CM1 patients have similar rates of craniosynostosis and also lack significant associations to known CM1-related complications.

Volumetry as a Criterion for Suboccipital Craniectomy after Cerebellar Infarction

Objective: The aim of this study was to investigate the use of image-guided volumetry in cerebellar infarction during the decision-making process for surgery. Particular emphasis was placed on the ratio of the infarction volume to the cerebellar volume or cranial posterior fossa volume. Methods: A retrospective, multicenter, multidisciplinary study design was selected. Statistical methods such as regression analysis and ROC analysis included the volumetric data of the infarction, the posterior fossa and the cerebellum itself as new factors. Results: Thirty-eight patients (mean age 75 (SD: 13.93) years, 16 (42%) female patients) were included. The mean infarction volume was 37.79 (SD: 25.24) cm3. Patients treated surgically had a 2.05-fold larger infarction than those managed without surgery (p ≤ 0.001). Medical and surgical treatment revealed a significant difference in the ratio of the cranial posterior fossa volume to the infarction volume (medical 12.05, SD:9.09; surgical 5.14, SD: 5,65; p ≤ 0.001) and the ratio of the cerebellar volume to the infarction volume (medical 8.55, SD: 5.97; surgical 3.82, SD: 3.39; p ≤ 0.001). Subsequent multivariate regression analysis for surgical therapy showed significant results only for the posterior fossa volume to infarction volume ratio ≤/> 4:1 (OR: 1.162, CI: 1.007–1.341, p = 0.04). Younger (≤60 years) patients also had a significantly better outcome at discharge (p ≤ 0.017). A cut-off value for the infarction volume of 31.35 cm3 (sensitivity = 0.875, specificity = 0.2) was determined for the necessity of surgery. Conclusions: Volumetric data on the infarction, the posterior fossa and the cerebellum itself could be meaningful in decision-making towards surgery.

Perioperative Segmentation of the Posterior Fossa and the Keel of Goodrich in Surgical Outcomes of Chiari Malformations

BackgroundChiari I malformation (CM- I) is defined as the extension of brain tissue into the spinal cord. This study aimed to refine the methodology for the acquisition of 3-dimensional measurements of the posterior fossa and introduce occipital keel size as a new marker and its impact in patients with CM. Materials and MethodsIn this retrospective study, all patients who underwent Chiari decompression surgery at Montefiore Medical Center from April 2012 to April 2022 were included. Perioperative clinical information was obtained in addition to maximal keel thickness (KT), foramen magnum area, and pre-and postoperative posterior fossa volumes for each patient and age-matched controls. Volumetric measurements were obtained using AI-based semiautomated segmentation. ResultsA total of 107 patients with CM including 37 males, and 70 females were studied with a mean age of 26.56±17.31 compared with 103 controls without CM. The comparison between the CM and the general population groups demonstrated a significantly increased keel size in Chiari patients. Keel size had a significant relationship with dysphagia, paresthesia, and intraoperative blood loss, while posterior volume change had a significant relationship with sex and early symptomatic improvement. The Foramen magnum area was related to tonsillar descent and more prominent in patients with spina bifida. ConclusionThe Keel of Goodrich is a new anatomical factor that should be taken into consideration when evaluating preoperative symptoms, and intraoperative complications in patients with CM-1. Volumetric analyses demonstrated that posterior fossa volume change had a significant impact on early symptom improvement in patients with Chiari, as did the choice of operative approach. The routine use of semi-automated segmentation of the posterior fossa may help stratify Chiari patients in the future and should be implemented in routine clinical care.

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.

Enhancing Hierarchical Transformers for Whole Brain Segmentation with Intracranial Measurements Integration.

Whole brain segmentation with magnetic resonance imaging (MRI) enables the non-invasive measurement of brain regions, including total intracranial volume (TICV) and posterior fossa volume (PFV). Enhancing the existing whole brain segmentation methodology to incorporate intracranial measurements offers a heightened level of comprehensiveness in the analysis of brain structures. Despite its potential, the task of generalizing deep learning techniques for intracranial measurements faces data availability constraints due to limited manually annotated atlases encompassing whole brain and TICV/PFV labels. In this paper, we enhancing the hierarchical transformer UNesT for whole brain segmentation to achieve segmenting whole brain with 133 classes and TICV/PFV simultaneously. To address the problem of data scarcity, the model is first pretrained on 4859 T1-weighted (T1w) 3D volumes sourced from 8 different sites. These volumes are processed through a multi-atlas segmentation pipeline for label generation, while TICV/PFV labels are unavailable. Subsequently, the model is finetuned with 45 T1w 3D volumes from Open Access Series Imaging Studies (OASIS) where both 133 whole brain classes and TICV/PFV labels are available. We evaluate our method with Dice similarity coefficients(DSC). We show that our model is able to conduct precise TICV/PFV estimation while maintaining the 132 brain regions performance at a comparable level. Code and trained model are available at: https://github.com/MASILab/UNesT/wholebrainSeg.

872 Natural History of Conservatively Managed Patients With Chiari Malformation Type I and Syringomyelia

INTRODUCTION: Chiari malformation type 1 (CM1) describes caudal ectopia of the cerebellar tonsils. Though often asymptomatic earlier in life and found incidentally on imaging, CM1 can disturb cerebrospinal fluid (CSF) flow and generate an array of symptoms. Surgical treatment for CM1 centers around procedures to increase the posterior fossa volume and improve CSF circulation. Many surgeons elect to operate on CM1 patients in the setting of a syrinx, making it difficult to understand the natural history of these patients. METHODS: Retrospective study of 37 CM1 patients with syrinx who were managed conservatively at our institution. All patients had initial and follow-up clinic visits with a neurologist or neurosurgeon. Of the 37 patients, 27 had initial and follow-up MRI images at least six months apart. Student t-tests were used to compare radiological parameters. RESULTS: A total of three patients saw complete resolution of their syrinxes. Regarding clinical symptomatology, 19 out of 32 patients who were initially symptomatic saw clinical improvement by follow up, while 13 remained stable, and five declined. Of the five patients that declined, three had worsening neurological conditions not attributed to the syrinx or CM1 while the remaining two patients were the only patients that declined surgery despite recommendation. A total of 16 patients saw decreases in both syrinx size and tonsillar descent. There were no statistically significant differences between tonsillar descent, syrinx size, and number of vertebral bodies spanned by syrinx between the initial and latest follow up. The presence of tonsillar pegging was predictive of decrease in syrinx size. Tonsillar descent and syrinx size were not predictive of clinical outcomes. CONCLUSIONS: Although the surgical treatment of the CM1 patient successfully resolves the syrinx, the natural history of the syrinx can be benign.

Volumetric assessment of Posterior cranial fossa in a West African population

Background and Objectives: Posterior fossa pathologies can have potentially devastating outcomes. The volumetric capacity of this fossa, known to have ethnoregional variations, can thus be critical in determining outcomes and intervention measures and approaches to pathologies involving this region. This study aimed to evaluate the normal posterior fossa volumes within the West-African subpopulation. Methods: This was a descriptive study of all patients presenting for a cranial imaging study at the study location within a two-year period using a 1.5T MRI of this cranial region. Obtained data included the transverse and anteroposterior diameters, and the height of this fossa and the obtained data was analyzed. P values < 0.05 was statistically significant. Results: A total of 315 patients were recruited (165 males and 150 females). The average posterior fossa transverse diameter, anteroposterior diameter and height were 108.19 mm, 71.58 mm and 35.53 mm respectively for males, and 105.7 mm, 66.48 mm, and 34.24 mm for females respectively. The average posterior fossa volume for males (292.36 cm3) was significantly higher than for females (252.90 cm3) (p= 0.0038). The highest average posterior fossa volume was between 16-30 years for males and above 75 years for females. Conclusion: Posterior cranial fossa volumes for the West African population is significantly higher than those obtained for other regions. In addition to being beneficial in some posterior fossa space occupying lesions, this larger volume can explain the relative rarity and sexual preferences of some posterior fossa congenital abnormalities like Chiari-1 malformation amongst the West African population

A novel classification and management scheme for craniocervical junction disorders with ventral neural element compression.

Craniocervical junction (CCJ) pathologies with ventral neural element compression are poorly understood, and appropriate management requires accurate understanding, description, and a more uniform nomenclature. The aim of this study was to evaluate patients to identify anatomical clusters and better classify CCJ disorders with ventral compression and guide treatment. A retrospective review of adult and pediatric patients with ventral CCJ compression from 2008 to 2022 at a single center was performed. The incidence of anatomical abnormalities and compressive etiologies was assessed. Surgical approach, radiographic data, and outcomes were recorded. Association rules analysis (ARA) was used to assess variable clustering. Among 51 patients, the main causes of compression were either purely bony (retroflexed dens [n = 18]; basilar invagination [BI; n = 13]) or soft tissue (degenerative pannus [n = 16]; inflammatory pannus [n = 2]). The primary cluster in ARA was a retroflexed dens, platybasia, and Chiari malformation (CM), and the secondary cluster was BI, C1-2 subluxation, and reducibility. These, along with degenerative pannus, formed the three major classes. In assessing the optimal treatment strategy, reducibility was evaluated. Of the BI cases, 12 of the 13 patients had anterolisthesis of C1 that was potentially reducible, compared with 2 of the 18 patients with a retroflexed dens (both with concomitant BI), and no pannus cases. The mean C1-2 facet angle was significantly higher in BI at 32.4°, compared with -2.3° in retroflexed dens and 8.1° in degenerative pannus (p < 0.05). Endonasal decompression with posterior fixation was performed in 48 (94.0%) of the 51 patients, whereas posterior reduction/fixation alone was performed in 3 patients (6.0%). Of 16 reducible cases, open posterior reduction alone was successful in 3 (60.0%) of 5 cases, with all successes containing isolated BI. Reduction was not attempted if vertebral anatomy was unfavorable (n = 9) or the C1 lateral mass was absent (n = 5). The mean follow-up was 28 months. Symptoms improved in 88.9% of patients and were stable in the remaining 11.1%. Tracheostomy and percutaneous G-tube placement occurred in 7.8% and 11.8% of patients, respectively. Reoperation for an endonasal CSF leak repair or posterior cervical wound revision both occurred in 3.9% of patients. In classifying, one cluster caused decreased posterior fossa volume due to an anatomical triad of retroflexed dens, platybasia, and CM. The second cluster caused pannus formation due to degenerative hypertrophy. For both, endonasal decompression with posterior fixation was ideal. The third group contained C1 anterolisthesis characterized by a steep C1-2 facet angle causing reducible BI. Posterior reduction/fixation is the first-line treatment when anatomically feasible or endonasal decompression with in situ posterior fixation when anatomical constraints exist.

Morphological and ultrastructural investigation of the posterior atlanto-occipital membrane: Comparing children with Chiari malformation type I and controls.

The fibrous posterior atlanto-occipital membrane (PAOM) at the craniocervical junction is typically removed during decompression surgery for Chiari malformation type I (CM-I); however, its importance and ultrastructural architecture have not been investigated in children. We hypothesized that there are structural differences in the PAOM of patients with CM-I and those without. In this prospective study, blinded pathological analysis was performed on PAOM specimens from children who had surgery for CM-I and children who had surgery for posterior fossa tumors (controls). Clinical and radiographic data were collected. Statistical analysis included comparisons between the CM-I and control cohorts and correlations with imaging measures. A total of 35 children (mean age at surgery 10.7 years; 94.3% white) with viable specimens for evaluation were enrolled: 24 with CM-I and 11 controls. There were no statistical demographic differences between the two cohorts. Four children had a family history of CM-I and five had a syndromic condition. The cohorts had similar measurements of tonsillar descent, syringomyelia, basion to C2, and condylar-to-C2 vertical axis (all p>0.05). The clival-axial angle was lower in patients with CM-I (138.1 vs. 149.3 degrees, p = 0.016). Morphologically, the PAOM demonstrated statistically higher proportions of disorganized architecture in patients with CM-I (75.0% vs. 36.4%, p = 0.012). There were no differences in PAOM fat, elastin, or collagen percentages overall and no differences in imaging or ultrastructural findings between male and female patients. Posterior fossa volume was lower in children with CM-I (163,234 mm3 vs. 218,305 mm3, p<0.001), a difference that persisted after normalizing for patient height (129.9 vs. 160.9, p = 0.028). In patients with CM-I, the PAOM demonstrates disorganized architecture compared with that of control patients. This likely represents an anatomic adaptation in the presence of CM-I rather than a pathologic contribution.

Letter to the Editor Regarding “Posterior Fossa Volume and Dimensions: Relation to Pathophysiology and Surgical Outcomes in Classic Trigeminal Neuralgia”

Letter to the Editor Regarding “Posterior Fossa Volume and Dimensions: Relation to Pathophysiology and Surgical Outcomes in Classic Trigeminal Neuralgia”

In Reply to the Letter to the Editor Regarding “Posterior Fossa Volume and Dimensions: Relation to Pathophysiology and Surgical Outcomes in Classical Trigeminal Neuralgia”

In Reply to the Letter to the Editor Regarding “Posterior Fossa Volume and Dimensions: Relation to Pathophysiology and Surgical Outcomes in Classical Trigeminal Neuralgia”

Management of Persistent Syringomyelia in Patients Operated for Chiari Malformation Type 1

The treatment of persistent syringomyelia associated with Chiari malformation type 1 (CM1) is unclear. This study aims to evaluate the clinical and radiologic outcomes of syringo-subarachnoid shunt (SSS) as a treatment for persistent syringomyelia following posterior fossa decompression (PFD) for CM1. Forty-nine cases treated for CM1 associated syringomyelia at a single center were analyzed, 17 of them undergoing reoperation due to persistent syrinx formation. The patients' demographic data, neurologic presentations, and radiologic results were analyzed, including cerebellar herniation, posterior fossa volume, the level at which the syrinx started and finished, the size and diameter of the syrinx. Seventeen patients underwent SSS placement, with 1 minor surgical complication (a cerebrospinal fluid leak) occurring and requiring revision. No morbidity or mortality was observed. Among these 17 reoperated patients, partial or complete resorption of the syrinx was observed in all cases. The results suggest that if the syrinx diameter is >10 mm at its thickest point, extends for more than 10 vertebrae, and starts from the upper cervical region and extends to the upper thoracic region, the syrinx may not regress after the first surgery and potentially predicting the need for a second operation before PFD. SSS placement for persistent syrinx following PFD for CM1 is a safe and effective surgical treatment method. These criteria may also help predict the need for a second surgery and the overall disease outcome for both the surgeon and patient.

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.

Posterior Fossa Volume and Dimensions: Relation to Pathophysiology and Surgical Outcomes in Classic Trigeminal Neuralgia

A small posterior fossa (PF) has been hypothesized to explain the increased incidence of trigeminal neuralgia (TN) in females and could make microvascular decompression (MVD) more challenging. The aim of this study was to investigate the association between the PF volume and dimensions in relation to biological sex, type of neurovascular conflict (NVC), and outcome after MVD in classic TN. In this observational study, 84 patients with TN operated on with MVD with a preoperative head computed tomography(CT) scan were included. Eighty-two adults without TN who had undergone head CT for other reasons were included as controls. PF volume and dimensions (x-axis, y-axis, and z-axis) were evaluated on the CT scans. For the patients with TN, Barrow Neurological Institute (BNI) grade was evaluated 6 months after MVD. There was no difference in PF volume or dimensions between the patients with TN and controls. Women showed a smaller volume and narrower (x-axis) PF than men, but these differences did not manifest when comparing patients with TN and controls within each sex. Patients with an NVC involving the superior cerebellar artery had a narrower (x-axis) and shorter (y-axis) PF than did patients with an NVC resulting from other arteries. PF volume or dimensions were not associated with BNI grade after MVD. PF anatomy was related to the NVC type but did not differ between patients with TN and controls and was not related to the surgical outcome after MVD.

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.

Syringomyelia Associated with Chiari 1 Malformation in Adults: Positive Outcome Predictors after Posterior Fossa Decompression with Duraplasty.

Syringomyelia (Syr) in patients with Chiari 1 malformation (CM1) may be attributable to abnormal dynamics of cerebrospinal fluid (CSF) in the upper cervical segment; fourth ventricle enlargement has been reported in association with a worse clinical and radiological presentation, independently of the posterior fossa volume. In this study, we analyzed presurgery hydrodynamic markers to evaluate if their changes could be associated with clinical and radiological improvement after posterior fossa decompression and duraplasty (PFDD). As a primary endpoint, we aimed to correlate improvement in the fourth ventricle area with positive clinical outcomes. In total, in this study, we enrolled 36 consecutive adults with Syr and CM1 who were followed by a multidisciplinary team. All the patients were prospectively evaluated with clinical scales and neuroimaging, including CSF flow, the fourth ventricle area, and the Vaquero Index by using a phase-contrast MRI before (T0) and after surgical treatment (T1-Tlast, with a range of 12-108 months). The CSF flow at the craniocervical junction (CCJ), the fourth ventricle area, and the Vaquero Index changes were statistically analyzed and compared to the clinical and quality of life improvement after surgery. The good outcome prediction ability of presurgical radiological variables was tested. Surgery was associated with positive clinical and radiological outcomes in more than 90% of cases. The fourth ventricle area significantly reduced after surgery (T0-Tlast, p = 0.0093), but no significant associations with clinical improvement were found. The presurgical presence of CSF flow at the CCJ was able to predict a good outcome (AUC = 0.68, 95% CI 0.50-0.87 and LH+ = 2.1, IC 95% 1.16-3.07) and was also significantly associated with post-surgical pain relief (rho = 0.61 and p = 0.0144). Presurgery CSF flow at the CCJ is proposed as a radiological marker with the ability to predict a positive outcome after PFDD in adults with syringomyelia and CM1. Measurements of the fourth ventricle area could be useful additional information for evaluating surgical long-term follow-up; further experience on larger cohorts is required to better define the prognostic yield of this radiological parameter.

Potential association among posterior fossa bony volume and crowdedness, tonsillar hernia, syringomyelia, and CSF dynamics at the craniocervical junction in Chiari malformation type I.

The characteristic morphological parameters (bony posterior fossa volume (bony-PFV), posterior fossa crowdness, cerebellar tonsillar hernia, and syringomyelia) and CSF dynamics parameters at the craniocervical junction (CVJ) in Chiari malformation type I (CMI) were measured. The potential association between these characteristic morphologies and CSF dynamics at CVJ was analyzed. A total of 46 cases of control subjects and 48 patients with CMI underwent computed tomography and phase-contrast magnetic resonance imaging. Seven morphovolumetric measures and four CSF dynamics at CVJ measures were performed. The CMI cohort was further divided into "syringomyelia" and "non-syringomyelia" subgroups. All the measured parameters were analyzed by the Pearson correlation. Compared with the control, the posterior cranial fossa (PCF) area, bony-PFV, and CSF net flow were significantly smaller (P < 0.001) in the CMI group. Otherwise, the PCF crowdedness index (PCF CI, P < 0.001) and the peak velocity of CSF (P < 0.05) were significantly larger in the CMI cohort. The mean velocity (MV) was faster in patients with CMI with syringomyelia (P < 0.05). In the correlation analysis, the degree of cerebellar tonsillar hernia was correlated with PCF CI (R = 0.319, P < 0.05), MV (R = -0.303, P < 0.05), and the net flow of CSF (R = -0.300, P < 0.05). The Vaquero index was well correlated with the bony-PFV (R= -0.384, P < 0.05), MV (R = 0.326, P < 0.05), and the net flow of CSF (R = 0.505, P < 0.05). The bony-PFV in patients with CMI was smaller, and the MV was faster in CMI with syringomyelia. Cerebellar subtonsillar hernia and syringomyelia are independent indicators for evaluating CMI. Subcerebellar tonsillar hernia was associated with PCF crowdedness, MV, and the net flow of CSF at CVJ, while syringomyelia was associated with bony-PFV, MV, and the net flow of CSF at the CVJ. Thus, the bony-PFV, PCF crowdedness, and the degree of CSF patency should also be one of the indicators of CMI evaluation.

Transient meningism in children after non-autologous duraplasty for Chiari Malformation surgery: A case series

BackgroundIncreasing the posterior fossa volume is the mainstay of treatment for Chiari type 1 Malformation (C1M) and type 1.5 (C1.5M). Different options to restore CSF flow have been described but no consensus has been reached yet. Bony decompression of posterior cranial fossa with dural opening provides good results but at the price of complications such as pseudomeningocele and aseptic meningitis. A single center retrospective analysis was conducted to find any relationships between outcome and perioperative factors. As a second goal a specific analysis was conducted on the complications and their hypothetical causes. MethodsAll the pediatric patients who underwent to posterior fossa bony decompression and dural opening for C1M or C1.5M in the period 2008-2020 were included in the study. A minimum period of three-months follow-up was considered among the inclusion criteria. ResultsA population of fifty-three consecutive patients was collected. Pseudomeningocele and a mild meningeal irritation resulted the most frequent complications. Considering preoperative and intraoperative factors, the type of dural graft showed a relatively strong correlation (P<.01) with pseudomeningocele appearance and the development of meningism. In the latter case, a short course of steroids was the only treatment required to control symptoms. ConclusionsDifferent factors could influence the outcome in Chiari Malformation surgery and eventually the development of complications. An adequate dural graft selection is of paramount importance when a dural opening for posterior fossa augmentation is planned. In case of mild meningeal irritation, a trial with short course steroids could avoid revision surgery.

Effectiveness of C1 Laminectomy for Chiari Malformation Type 1: Posterior Fossa Volume Expansion and Syrinx-Volume Decrease Rate.

This study aimed to analyze the effect of foramen magnum decompression with C1 laminectomy (C1L) for Chiari malformation type 1 (CM-1) in terms of improving clinical symptoms, expanding posterior fossa volume, and decreasing syrinx volume. Between January 2007 and June 2019, 107 patients with CM-1 were included. The median patient age was 13±13 years (range: 9 months-60 years), female-to-male ratio was 1:1, and average length of tonsil herniation was 13±5 mm (range: 5-24 mm). Surgical techniques were divided into four groups based on duraplasty or C1L usage. Among the study subjects, 38 patients underwent duraplasty and had their syrinx volumes measured separately on serial magnetic resonance imaging. A three-dimensional visualization software was used to evaluate the syrinx-volume decrease rate. Bony decompression exhibited a mere 20% volume expansion of the lower-half posterior fossa. C1L offered a 3% additional volume expansion, which rose to 5% when duraplasty was added (p=0.029). There were no significant differences in complication rate when C1L was combined with duraplasty (p=0.526). Syrinx volumes were analyzed in 38 patients who had undergone duraplasty. Among them, 28 patients who had undergone duraplasty without C1L demonstrated a 5.9% monthly decrease in syrinx volume, which was 7.5% in the remaining 10 patients with C1L (p=0.040). C1L was effective in increasing posterior fossa volume expansion, both with and without duraplasty. A more rapid decrease in syrinx volume occurred when C1L was combined with duraplasty.