Evaluation and Treatment of Patients with Small Posterior Cranial Fossa and Chiari Malformation, Types 0 and 1.

The diagnosis of Chiari I malformation is straightforward in patients with typical signs and symptoms of Chiari I malformation and magnetic resonance imaging (MRI) confirming ≥5 mm of cerebellar tonsillar ectopia, with or without a syrinx. However, in many cases, Chiari I malformation is discovered incidentally on MRI to evaluate global headache, cervical radiculopathy, or other conditions. In those cases, the clinician must consider if cerebellar tonsillar ectopia is related to the presenting symptoms. Surgical decompression of the cerebellar tonsils and foramen magnum in patients with symptomatic Chiari I malformation effectively relieves suboccipital headache, reduces syrinx distension, and arrests syringomyelia progression. Neurosurgeons must avoid operative treatments decompressing incidental tonsillar ectopia, not causing symptoms. Such procedures unnecessarily place patients at risk of operative complications and tissue injuries related to surgical exploration. This chapter reviews the typical signs and symptoms of Chiari I malformation and its variant, Chiari 0 malformation, which has <5 mm of cerebellar tonsillar ectopia and is often associated with syringomyelia. Chiari I and Chiari 0 malformations are associated with incomplete occipital bone development, reduced volume and height of the posterior fossa, tonsillar ectopia, and compression of the neural elements and cerebrospinal fluid (CSF) pathways at the foramen magnum. Linear, angular, cross-sectional area, and volume measurements of the posterior fossa, craniocervical junction, and upper cervical spine identify morphometric abnormalities in Chiari I and Chiari 0 malformation patients. Chiari 0 patients respond like Chiari I patients to foramen magnum decompression and should not be excluded from surgical treatment because their tonsillar ectopia is <5 mm. The authors recommend the adoption of diagnostic criteria for Chiari 0 malformation without syringomyelia. This chapter provides updated information and guidance to the physicians managing Chiari I and Chiari 0 malformation patients and neuroscientists interested in Chiari malformations.

Intraoperative neuromonitoring in Chiari I malformation surgery: a systematic review and meta-analysis.

Chiari Malformation Type I (CMI) is a prevalent neurosurgical condition characterized by the descent of cerebellar tonsils below the foramen magnum. Surgery, aimed at reducing symptomatology and syrinx size, presents risks, making intraoperative neuromonitoring (IONM) a potentially vital tool. Despite its widespread use in cervical spine surgery, the utility of IONM in CMI surgery remains controversial, with concerns over increased operative time, cost, restricted anesthetic techniques and tongue lacerations. This systematic review and meta-analysis followed the Cochrane Group standards and PRISMA framework. It encompassed an extensive search through PubMed, Embase, and Web of Science up to December 2023, focusing on clinical and surgical outcomes of IONM in CMI surgery. Primary outcomes included the use of various IONM techniques, complication rates, clinical improvement, reoperation, and mortality. The review, registered at PROSPERO (CRD42024498996), included both prospective and retrospective studies, with rigorous selection and data extraction processes. Statistical analysis was conducted using R software. The review included 16 studies, comprising 1358 patients. It revealed that IONM techniques predominantly involved somatosensory evoked potentials (SSEPs), followed by motor evoked potentials (MEPs) and Brainstem auditory evoked potentials (BAEPs). The estimated risk of complications with IONM was 6% (95% CI: 2-11%; I2 = 89%), lower than previously reported rates without IONM. Notably, the clinical improvement rate post-surgery was high at 99% (95% CI: 98-100%; I2 = 56%). The analysis also showed lower reoperation rates in surgeries with IONM compared to those without. Interestingly, no mortality was observed in the included studies. This systematic review and meta-analysis indicate that intraoperative neuromonitoring in Chiari I malformation surgery is associated with favorable clinical outcomes, including lower complication and reoperation rates, and high rates of clinical improvement.

Endoscopic third ventriculostomy (ETV) for Chiari 1 malformation: a systematic review and meta-analysis.

Meta-analysis and systematic review. To understand the role of endoscopic third ventriculostomy (ETV) for the treatment of concurrent Chiari Malformation Type I (CMI) and hydrocephalus in adults. A literature search on PubMed and Medline with MeSH terms relating to ETV and CMI identified 155 articles between 1988 and 2024. After excluding pediatric cases and other CNS pathologies with associated CMI, 11 articles met inclusion criteria. The Newcastle-Ottawa Scale was identified to assess heterogeneity and risk of bias among the 11 studies analyzed in this systematic-review and meta-analyses compared pre- and post-operative outcomes to examine the use of ETV as a treatment modality for CMI with hydrocephalus. From the 11 included studies, 35 cases of concurrent CMI and hydrocephalus treated with ETV were identified. ETV provided a pooled rate of symptom resolution or improvement of 66%. Additionally, meta-analysis discovered the following pooled rates: a reduction of tonsillar descent in 94% of patients, decreased ventriculomegaly in 94%, and ETV patency in 99%. Syringomyelia, nausea, papilledema and cerebellar dysfunction did not have sufficient numbers for meaningful statistical analyses. However, in each of these categories, more than 85% of the symptoms or radiographic findings improved. This review summarizes the safety and efficacy of ETV for the concurrent management of acquired CMI with hydrocephalus. Specifically, ETV improves radiological outcomes of both ventriculomegaly and tonsillar descent as well as the most prevalent neurological symptom, headaches.

Revision Chiari surgery in adults: surgical evaluation algorithm and outcomes in a continuity-of-care practice.

OBJECTIVE: Patients with a prior surgical history for Chiari malformation (CM) as a child or an adult who presents with a recurrence or persistence of symptoms pose a challenging clinical scenario. The authors analyzed preoperative presentations, surgical histories, and outcomes of adult CM revision cases to create an algorithm for the assessment of revision surgery in adult CM patients and contrast this with the care of pediatric CM patients within the context of an integrated continuity-of-care CM practice seeing pediatric and adult patients. METHODS: The authors retrospectively reviewed the records of patients with CM0, -1, and -1.5 who were 21 years of age or older, had a prior history of CM surgery as either children or adults, and underwent revision surgery as adults at the authors' institution from December 2009 to February 2020. The cohort was divided into three groups depending on the type of revision surgery performed: posterior fossa decompression with or without duraplasty (PFD/D group), occipitocervical fusion without ventral decompression (OCF group), and ventral decompression in the form of endoscopic endonasal odontoidectomy (VD group). RESULTS: A total of 50 adult revision cases were divided into 30 PFD/D cases, 13 OCF cases, and 7 VD cases. Forty cases had previously undergone one CM surgery, and 10 had undergone two. Preoperatively, the PFD/D group had significantly fewer cases of diagnosed craniocervical instability (CCI), Ehlers-Danlos syndrome, and dysautonomia than the OCF and VD groups. A retroflexed odontoid was significantly more common in the VD group than in the PFD/D and OCF groups. Postoperatively, rates of improvement were 60.0% with PFD/D, 84.6% with OCF, and 85.7% with VD, but differences in these rates were not statistically significant. CONCLUSIONS: In this challenging group of CM patients, possible etiologies warranting additional surgery included residual dorsal compression, persistent syrinx, CCI, and ventral brainstem compression from a significant retroflexed odontoid. Outcomes after revision were often favorable, but careful evaluation, patient selection, and communication with patients are needed in deciding to reoperate. The suggested algorithm can aid decision-making.

Long-term outcome of operated Chiari I patients between 2005 and 2020 in Eastern Finland.

PURPOSE: The purpose of our study was to examine the long-term outcomes of operated Chiari malformation type 1 (CM1) patients and evaluate whether different duraplasty techniques affected outcome after surgery in Kuopio University Hospital catchment area. METHODS: In this retrospective study, a total of 93 patients were diagnosed with CM1 and underwent posterior fossa decompression surgery with or without duraplasty between 2005 and 2020. All patients' medical records were examined for baseline characteristics, surgical details, and long-term follow-up data after operation. RESULTS: The mean age of CM1 patients was 25.9 years (SD 19.2 years), with female preponderance 69/93 (73.4%). The mean clinical follow-up time was 26.5 months (SD 33.5 months). The most common presenting symptoms were headache, symptoms of extremities, and paresthesia. Posterior fossa decompression with duraplasty was performed in 87 (93.5%) patients and bony decompression in 6 (6.5%) patients. After surgery, preoperative symptoms alleviated in 84.9% (79/93) and the postoperative syringomyelia regression rate was 89.2% (33/37) of all patients. The postoperative complication rate was 34.4% (32/93), with aseptic meningitis being the most common, 25.8% (24/93). Revision surgery was required in 14% (13/93) of patients. No significant correlation between postoperative outcome and extent of dural decompression, or type of duraplasty performed was found. CONCLUSION: This is the largest reported series of surgically treated CM1 patients in Finland. Posterior fossa decompression is an effective procedure for CM1 symptomology. Duraplasty technique had no significant difference in complication rate or long-term outcomes.

Duraplasty using a combination of a pedicled dural flap and collagen matrix in posterior fossa decompression for pediatric Chiari malformation type 1 with syrinx.

PURPOSE: In posterior fossa decompression for pediatric Chiari malformation type 1 (CM-1), duraplasty methods using various dural substitutes have been reported to improve surgical outcomes and minimize postoperative complications. To obtain sufficient posterior fossa decompression without cerebrospinal fluid-related complications, we developed a novel duraplasty technique using a combination of a pedicled dural flap and collagen matrix. The objective of this study was to describe the operative nuances of duraplasty using a combination of a pedicled dural flap and collagen matrix in posterior fossa decompression for pediatric CM-1. METHODS: We reviewed the clinical and radiographic records of 11 consecutive pediatric patients who underwent posterior fossa decompression with duraplasty using a combination of a pedicled dural flap and collagen matrix followed by expansile cranioplasty for CM-1. The largest area of the syrinx and the size of the posterior fossa were calculated. RESULTS: The maximum syrinx area was reduced by a mean of 68.5% ± 27.3% from preoperatively to postoperatively. Four patients (36.4%) had near-complete syrinx resolution (> 90%, grade III reduction), five (45.5%) had 50% to 90% reduction (grade II), and two (18.2%) had < 50% reduction (grade I). The posterior fossa area in the midsagittal section increased by 8.9% from preoperatively to postoperatively. There were no postoperative complications, including cerebrospinal fluid leakage, pseudomeningocele formation, or infection. CONCLUSION: Duraplasty using a combination of a pedicled dural flap and collagen matrix in posterior fossa decompression is a promising safe and effective surgical technique for pediatric CM-1 with syrinx.

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.

Effects of Two Exercise Regimes on Patients with Chiari Malformation Type 1: a Randomized Controlled Trial.

This study aims to measure the effects of two different exercise programs on neck pain, proprioception, balance, coordination, posture, and quality of life in patients with Chiari malformation (CM) type 1. Sixteen patients were randomized to two different exercise programs: a tailored exercise protocol for CM (TEP-CM) and cervical spinal stabilization exercises (CSSE). Both exercise programs were implemented by a physiotherapist 3 days a week for 6 weeks. The primary outcome was Neck Disability Index. Secondary outcomes were visual analogue scale for pain, joint position sense error measurement, Berg Balance Scale, Time Up and Go Test, International Coordination Ataxia Rating Scale, PostureScreen Mobile, and Short Form-36. Assessments were done immediately before and after the intervention programs. Both groups showed significant improvement in Neck Disability Index, and some secondary outcome measures (P < 0.05). However, there were no statistical differences in post-intervention changes between the groups (P > 0.05). This is the first study to examine the effects of different exercise programs on symptoms in patients with CM type 1. Our preliminary findings indicate that exercise programs can improve pain, balance, proprioception, posture, coordination, and quality of life in CM type 1. Therefore, exercise should be considered safe, beneficial, and low-cost treatment option for CM type 1 patients without surgical indications.

[Clinical significance of subthreshold cerebellar tonsil ectopia into foramen magnum and Chiari malformation type 0]. / Klinicheskaya znachimost' podporogovykh ektopii mindalin mozzhechka v bol'shoe zatylochnoe otverstie i mal'formatsiya Kiari nulevogo tipa.

Cerebellar tonsil dislocation into foramen magnum exceeding 5 mm is traditionally considered as Chiari malformation type 1. This disease requires surgical treatment in case of severe clinical manifestations. In patients with hypoplasia of posterior cranial fossa (PCF), subthreshold tonsil dislocations or tonsil position inside the foramen magnum can result clinical signs identical to Chiari malformation type 1. These disorders are presumably referred to phenotypic variant of Chiari malformation type 1 (Chiari malformation type 0). The authors discuss the data on the prevalence and mechanisms of cerebellar tonsil ectopia into foramen magnum, the role of hereditary and environmental factors in development of PCF hypoplasia and its role in Chiari malformation type 1 and 0. Significance of MR-based morphometry of PCF in identifying the primary forms (Chiari malformation type 1 and 0), clinical and radiological signs of malformation type 0, as well as data on surgical treatment of Chiari malformation type 0 combined and non-combined with syringomyelia are analyzed. Literature data confirm validity of the concept of Chiari malformation type 0. We emphasize the need for further analysis of this problem to identify sensitive and specific diagnostic signs of Chiari malformation type 0 and determine optimal treatment strategy.

The management of Chiari malformation type 1 and syringomyelia in children: a review of the literature.

In anticipation of the "Chiari and Syringomyelia Consensus Conference" held in Milan in 2019, we performed a systematic literature review on the management of Chiari malformation type 1 (CM1) and syringomyelia (Syr) in children.We aimed to summarize the available evidence and identify areas where consensus has not been reached and further research is needed.In accordance with PRISMA guidelines, we formulated seven questions in Patients-Interventions-Comparators-Outcomes (PICO) format. Six PICOs concerned CM1 children with/without additional structural anomalies (Syr, craniosynostosis, hydrocephalus, tethered cord, and cranio-vertebral junction anomalies), and one PICO Syr without CM1. We searched Medline, Embase, Cochrane, and NICE databases from January 1, 1999, to May 29, 2019. Cohort studies, controlled and randomized clinical trials (CCTs, RCTs), and systematic reviews were included, all pertinent only to patients ≤ 18 years of age.For CM1, 3787 records were found, 460 full texts were assessed and 49 studies (46 cohort studies, one RCT, and two systematic reviews) were finally included. For Syr, 376 records were found, 59 full texts were assessed, and five studies (one RCT and four cohort studies) were included. Data on each PICO were synthetized narratively due to heterogeneity in the inclusion criteria, outcome measures, and length of follow-up of the included studies.Despite decades of experience on CM1 and Syr management in children, the available evidence remains limited. Specifically, there is an urgent need for collaborative initiatives focusing on the adoption of shared inclusion criteria and outcome measures, as well as rigorous prospective designs, particularly RCTs.

The executive functions, intellectual capacity, and psychiatric disorders in adolescents with Chiari malformation type 1.

PURPOSE: In the last two decades, the non-motor functions of the cerebellum have become the centre of attention for researchers. Anecdotal observations of cognitive and psychiatric manifestations of cerebellar lesions have increased this interest. We aimed to investigate the executive function (EF), intellectual capacity, and comorbid psychiatric disorders in adolescents with Chiari malformation type 1 (CM1), which is a pathological manifestation of posterior cranial fossa structures include the cerebellum. METHODS: The Chiari group consisted of ten adolescents aged 12-18 years old, and the control group consisted of 13 healthy adolescents with similar age and sex with patients. Stroop test (ST), trail making test (TMT), and Behaviour Rating Inventory of Executive Function-Parent form (BRIEF) were used to evaluate EF; Kent EGY and Porteus Maze Test was used to measuring the intelligence quotient (IQ), and a semi-structured interview was used to determine the psychiatric disorders. RESULTS: EF test scores were found comparable between the two groups. IQ scores of the Chiari group were found in the normal range, but significantly lower than controls. No significant difference was revealed in terms of comorbid psychiatric disorders between the two groups. CONCLUSION: In this study, we did not observe an impairing effect of CM1 on EF and intelligence. Also, we found that CM1 did not cause more psychiatric disorders compared to controls. Further studies need to support our findings in adolescents diagnosed with CM1.

Posterior cranial fossa and cervical spine morphometric abnormalities in symptomatic Chiari type 0 and Chiari type 1 malformation patients with and without syringomyelia.

BACKGROUND: To better understand how anatomical features of Chiari malformation type 0 (CM0) result in the manifestation of Chiari malformation type 1 (CM1) signs and symptoms, we conducted a morphometric study of the posterior cranial fossa (PCF) and cervical canal in patients with CM1 and CM0. METHODS: This retrospective study had a STROBE design and included 120 adult patients with MRI evidence of a small PCF (SPCF), typical clinical symptoms of CM1, and a diagnosis of CM1, CM0, or SPCF-TH0-only (SPCF with cerebellar ectopia less than 2 mm and without syringomyelia). Patients were divided by MRI findings into 4 groups: SPCF-TH0-only, SPCF-TH0-syr (CM0 with SPCF and syringomyelia), SPCF-CM1-only (SPCF with cerebellar ectopia 5 mm or more without syringomyelia), and SPCF-CM1-syr (CM1 with syringomyelia). Neurological examination data and MRI parameters were analyzed. RESULTS: All patient cohorts had morphometric evidence of a small, flattened, and overcrowded PCF. The PCF phenotype of the SPCF-TH0-only group differed from that of other CM cohorts in that the length of clivus and supraocciput and the height of the PF were longer, the upper CSF spaces of PCF were taller, and the area of the foramen magnum was smaller. The SPCF-TH0 groups had a more significant narrowing of the superior cervical canal and a smaller decrease in PCF height than the SPCF-CM1 groups. CONCLUSIONS: Patients with SPCF-TH0 with and without syringomyelia developed Chiari 1 symptoms and signs. Patients with SPCF-TH0-syr (Chiari 0) had more constriction of their CSF pathways in and around the foramen magnum than patients with SPCF-TH0-only.

CO2-induced intracranial hypertension and high-amplitude B-waves in a patient with Chiari 1 malformation and sleep apnea syndrome that resolved following CPAP therapy.

Headaches and cognitive impairment in the elderly population have been described as symptoms related to obstructive sleep apnea (OSA). Although papilledema has been observed in some of these patients, suggesting intracranial hypertension (ICH), there are only a few studies in which intracranial pressure (ICP) has been continuously measured in patients with OSA without neurological disease. We present a patient diagnosed with Chiari Type 1 malformation and OSA, who present normal ICP recording during the day and nocturnal ICH associated with high amplitude B-waves and hypercapnia during obstructive apneas, which disappeared following continuous positive airway pressure (CPAP) therapy. The normalization of the cerebral and respiratory parameters with CPAP therapy is important for performing the correct treatment in these patients.

Recrudescence of the syringomyelia after surgery of Chiari malformation type 1 with duraplasty.

Background: Few case reports describe an increase in the size of syringomyelia and the worsening of neurologic symptoms after surgery for foramen magnum decompression. We report three such cases.Material and method: Retrospective review of patients with Chiari malformation (CM) and syringomyelia operated at the Erzurum Regional Hospital, Department of Neurosurgery between 1 January 2008 and 18 June 2018.Results: A total of 118 patients were operated during the study period. Of the 118 patients, 81 were females, 37 were males. Ages range between 4 and 82 years, mean 38 years. Cervical or thoracic syringomyelia was found in 81 patients. Decompressive surgery with duraplasty was performed in all patients, and the patients were followed at least 2 years. The syrinx was the same or smaller in volume in 74 patients postoperatively, however, in three patients (3.7% of all patients with syringomyelia), the syrinx increased in volume.Conclusions: In this study, it was observed that an improvement or resolution of syringomyelia in 74 patients (91.3%) after decompression. There were no changes in the cavity in 4 and increased size in 3.

Quantification of changes in brain morphology following posterior fossa decompression surgery in women treated for Chiari malformation type 1.

PURPOSE: While 84% of patients surgically treated for Chiari malformation type 1 (CM1) demonstrate improved quality of life after posterior fossa decompression surgery, there are many risks associated with this surgery. Surgical planning to identify candidates likely to improve postoperatively may benefit from an improved understanding of morphological changes after decompression surgery. To evaluate these changes, we quantified 59 morphological parameters on 42 CM1 adult female patients before and after CM1 decompression surgery. METHODS: Fifty-nine morphological parameters in the posterior cranial fossa, cranio-cervical, and intracranial regions in the midsagittal plane were evaluated using 42 T1-weighted magnetic resonance images of female CM1 patients before and after surgery, and 42 healthy female controls. Morphological differences before and after surgery were compared through the development of a technique to establish the opisthion location, a key reference point not present after surgery. RESULTS: In addition to the expected reduction of the cranio-caudal dimension of the cerebellum, objective analyses showed a significant increase in the area of the cerebrospinal fluid spaces, posterior (6×) and inferior (2.6×) to the cerebellum (+ 112 ± 102 and + 140 ± 127 mm2, respectively). This increased area was primarily impacted by an average reduction in the occipital bone length of 24.5 ± 7.3 mm following surgery. Based on multiple angles, results demonstrated a 2°-4° anterior rotation of the cerebellum after surgery. CONCLUSION: Our results show that decompression surgery results in significant changes in the cerebellum and cerebrospinal fluid spaces. Further investigation should determine how these morphological changes impact clinical outcomes.

Unexpected Progression of Tonsillar Herniation in Two Pediatric Cases with Chiari Malformation Type I and Review of the Literature.

BACKGROUND: Chiari malformation type 1 (CM-1) is a generally congenital, rarely acquired disease characterized with 5 mm or more displacement of cerebellar tonsils through foramen magnum. METHODS: Here, we report about 2 patients with CM-1 progressed in the degree of tonsillar herniation from our clinic, whereas increasing in prolapse of tonsillar herniation after diagnosis is extremely uncommon. RESULTS: The first patient aged 17 years was diagnosed with CM-1 in 2009 and was operated due to progression of 5 mm radiologically and worsening symptoms in 2014. The second 5-month-old patient initially showed just low-settled tonsillar localization at the borderline, then it descended by 2 cm when the patient reached 3 years of age, yet could not be operated because of parents' objection. CONCLUSION: Due to lack of reports on increasing tonsillar descent in the literature, these case reports will contribute to natural history and management of CM-1.

Cerebrospinal fluid disturbance in overweight women after occipitocervical decompression in Chiari malformation type I.

BACKGROUND: Cerebrospinal fluid disturbance (CSFD) is a well-known complication after occipitocervical decompression (OCD) in patients with Chiari malformation type I (CMI). There is scarce data focusing on preoperative patients' factors predisposing to development of CSF disturbance. The aim of this study is to evaluate a prognostic value of some patients' factors in the prediction of CSFD after OCD in CMI patients. MATERIALS AND METHODS: We undertook a 10-year (2003-2013) retrospective study of all OCD in patients with CMI performed at Sahlgrenska IC, Sahlgrenska University Hospital, Sweden. A total of 52 consecutive patients were obtained from the operation database and we excluded one patient who was previously diagnosed with normal-pressure hydrocephalus. Data regarding preoperative age, body mass index, gender, degree of tonsillar herniation and syrinx were registered. Development of CSFD after OCD was noted. RESULTS: Of the 51 patients reviewed, six had CSFD after OCD and were managed using a form of CSF diversion procedure. All of the patients who developed CSFD were females. They had a mean body mass index of 32.3 compared to a mean of 24.3 in patients without CSFD (p = 0.0011). There was no difference between the two groups with regard to the other examined patient factors. CONCLUSIONS: CSF diversion was needed in six consecutive adult Chiari malformation type I patients who underwent occipitocervical decompression. All patients with postoperative CSFD were female and their mean BMI was significantly higher than patients without this complication.

Demographic confounders in volumetric MRI analysis: is the posterior fossa really small in the adult Chiari 1 malformation?

OBJECTIVE: Measurement of posterior fossa volume has been proposed to have diagnostic utility and physiologic significance in the Chiari malformation type 1. This study evaluated the effects of demographics on posterior fossa volume and total intracranial volume in adult control subjects, adult patients with Chiari malformation type 1, and adult patients with idiopathic intracranial hypertension, who may share some imaging features of patients with Chiari malformation type 1. MATERIALS AND METHODS: Twenty-eight patients with Chiari malformation type 1, 21 patients with idiopathic intracranial hypertension, and 113 control subjects underwent brain MRI including contrast-enhanced 3D gradient-recalled echo (GRE) T1-weighted imaging. Linear measurements of the posterior fossa and intracranial space were obtained. Manual segmentation of the posterior fossa and intracranial space was performed to yield posterior fossa volume and total intracranial volume. Age, sex, race, and body mass index (weight in kilograms divided by the square of height in meters; BMI) were controlled for when comparing cohorts. RESULTS: Three of the 12 linear measurements significantly predicted total intracranial volume (accounting for 74% of variance), and four predicted posterior fossa volume (54% of variance). Age, race, sex, and BMI each statistically significantly influenced posterior fossa volume and total intracranial volume. No statistically significant differences in posterior fossa volume, total intracranial volume, or ratio of posterior fossa volume to total intracranial volume were seen between the Chiari malformation type 1 group and control group after controlling for demographics. Patients with idiopathic intracranial hypertension were more likely than control subjects to have smaller posterior fossa volumes (odds ratio [OR]=1.81; p=0.01) and larger total intracranial volumes (OR=1.24; p=0.06). CONCLUSION: Linear measurements of the posterior fossa are not strong predictors of posterior fossa volume. Age, race, sex, and BMI have statistically significant effects on intracranial measurements that must be considered, particularly with respect to posterior fossa volume in Chiari malformation type 1. Even when these demographic variables are appropriately accounted for, other similarly presenting diseases may show small posterior fossa volumes.

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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Surgical Outcomes in Chiari 1 and Chiari 1.5 Malformation Treated by Posterior Fossa Reconstruction: A Comprehensive Analysis of 110 Pediatric Cases and Literature Review.

Background/Objectives: The management of Chiari malformations (CMs) remains a clinical challenge and a topic of great controversy. Results may vary between children and adults. The purpose of the current single-center study is to critically assess the one-year surgical outcomes of a cohort of 110 children with CM-1 or CM-1.5 who were treated using "posterior fossa reconstruction" (PFR), a surgical technique described in 1994 that has since been used in both adults and children. We also review the literature and discuss the possible causes of the drawbacks and pitfalls in children in whom PFR was ineffective in controlling the disease. Methods: The present cohort was selected from a prospective registry of adults and children with CMs collected since 2006. Patients included in this study were selected from a group of children with CMs who were operated on in our Pediatric Neurosurgical Unit between 1 January 2007 and 31 November 2023. Surgical outcome was defined based on clinical and neuroradiological results as very good, good, or bad. Results: The mean age of our child cohort was 9.9 ± 4.7 years, with 54 girls (49%) and 56 boys (51%). Sixty-six children had CM-1 (60%) while forty-four had CM-1.5 (40%). Following surgery, there was no neurological worsening or death among the children. Most children (70%) had an uneventful recovery and were discharged home on average one week after surgery. However, in 33 children (30%), we recorded at least one postoperative adverse event. Aseptic meningitis syndrome was the most frequent adverse event (n = 25, 22.7%). The final surgical outcome was evaluated one year after PFR by using both clinical and neuroradiological results. The one-year surgical outcome was excellent in 101 children (91.9%), good in 5 (4.5%), and bad in 4 (3.6%). Conclusions: PFR significantly enlarges the volume of the posterior fossa and recreates a CSF environment that generates buoyancy of the cerebellum, with a high percentage of excellent and good clinical results evaluated one year post-surgery.