Acquired Chiari Malformation and Syringomyelia Secondary to Space-Occupying Lesions: A Systematic Review

The Benefits of Cognitive Therapeutic Exercise in Symptomatic Arnold-Chiari Syndrome Type I: A Case Report on Gait, Balance, and Pain Management

BACKGROUND

Chiari malformation is a rare congenital condition in which the cerebellar tonsils herniate through the foramen magnum, causing symptoms related to compression of the surrounding structures. Rehabilitation plays a key role in the pre- and post-operative management of the syndrome, as it can improve strength, range of motion, motor coordination, pain management, and performance of activities of daily living.

METHODS

This article presents the case of a 43-year-old woman with Chiari malformation 1B who underwent resection of the filum terminale. She presented as an outpatient at the University Hospital "G. Martino" in Messina, complaining of difficulty walking, balance problems, lumbar pain, and heaviness in the lower limbs. Following a multidisciplinary assessment, she underwent an 11-month rehabilitation protocol based on cognitive therapeutic exercise.

RESULTS

The patient achieved significant improvements in pain, mental confusion, and quality of life after treatment and at the 12-month follow-up.

CONCLUSIONS

The results of this study highlight the significant benefits of cognitive therapeutic exercises in Chiari malformation, with improvements in several key areas, including quality of life, pain management, and ability to perform activities of daily living.

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.

Spontaneous Unilateral Chiari I Secondary to Acquired Tonsillar Hypertrophy/Pseudomass With Syringomyelia in a Juvenile With Progressive Scoliosis

Chiari type 1 malformation (CM-1) is a structural defect of the central nervous system in which part of the cerebellar tonsils descend below the level of the foramen magnum, sometimes with associated syringomyelia. Although Chiari malformations were traditionally believed to be congenital, several cases of acquired CM-1 with syringomyelia have been reported. Usually associated with repeat lumbar puncture, increased intracranial pressure, and craniocephalic disproportion, CM-1 in the absence of an underlying etiology is rare. We report a rare case of spontaneous idiopathic tonsillar hypertrophy causing unilateral CM-1 with syringomyelia associated with progressive scoliosis in a juvenile with a previously normal neonatal MRI brain and no known underlying pathology. A 9-year-old boy was found to have scoliosis at a routine well-child visit with progression indicated on radiographs 4 months later. Whole spine MRI was performed and showed a new CM-1 with globular, mass-like configuration of the descended right tonsil with otherwise normal tonsillar characteristics. Surgical decompression via suboccipital craniectomy and C1 laminectomy with duraplasty was performed with improvement illustrated on repeat MRI 3 months postoperatively. This rare case emphasizes the importance of routine MRI spine early in select patients with idiopathic scoliosis and illustrates the favorable outcomes noted after decompressive craniectomy.

Brain and eye involvement in McCune-Albright Syndrome: clinical and translational insights

McCune-Albright Syndrome (MAS) is a rare mosaic (post-zygotic) genetic disorder presenting with a broad continuum clinical spectrum. MAS arises from somatic, activating mutations in the GNAS gene, which induces a dysregulated Gsα-protein signaling in several tissues and an increased production of intracellular cyclic adenosine monophosphate (cAMP). Overall, MAS is a rare disorder affecting less than 1/100,000 children and, for this reason, data establishing genotype-phenotype correlations remain limited. Affected individuals clinically present with a variable combination of fibrous dysplasia of bone (FD), extra-skeletal manifestations (including cafeí-au-lait spots) and precocious puberty which might also be associated to broad hyperfunctioning endocrinopathies, and also gastrointestinal and cardiological involvement. Central nervous system (CNS) and eye involvement in MAS are among the less frequently described complications and remain largely uncharacterized. These rare complications mainly include neurodevelopmental abnormalities (e.g., delayed motor development, cognitive and language impairment), CNS anomalies (e.g., Chiari malformation type I) and a wide array of ophthalmological abnormalities often associated with vision loss. The pathophysiological mechanisms underlying abnormal neurological development have not been yet fully elucidated. The proposed mechanisms include a deleterious impact of chronically dysregulated Gsα-protein signaling on neurological function, or a secondary (damaging) effect of (antenatal and/or early postnatal) hypercortisolism on early pre- and post-natal CNS development. In this Review, we summarize the main neurological and ophthalmological features eventually associated with the MAS spectrum, also providing a detailed overview of the potential pathophysiological mechanisms underlying these clinical complications.

Cerebellar Tonsillar Descent Mimicking Chiari Malformation

Chiari I malformation has been defined as cerebellar tonsillar descent greater than 5 mm below the foramen magnum. Suboccipital decompression remains the mainstay of treatment for symptomatic patients. Other conditions sometimes have imaging features that mimic Chiari I malformation. These patients are at risk of misdiagnosis and mismanagement, including surgery that may be unnecessary or may even worsen the underlying condition. The aim of this study was to analyse a series of Chiari I malformation mimics and identify differentiating imaging features. The mimics are categorised as post-traumatic cranio-cervical junction arachnoiditis, dural band, spontaneous intracranial hypotension, idiopathic intracranial hypertension, and cysts. Better understanding of these conditions will assist with diagnosis and optimal management, including avoiding unnecessary surgery.

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.

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

PURPOSE

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 .

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Assessment of neuromonitoring use and postoperative readmission rates in pediatric Chiari I malformation with syrinx

INTRODUCTION

While operative intervention for Chiari malformation type I (CMI) with syringomyelia is well established, there is limited data on outcomes of intraoperative neuromonitoring (IONM). This study sought to explore differences in procedural characteristics and their effects on postoperative readmission rates.

METHODS

The Nationwide Readmission Database was queried from 2010 to 2014 for patients ≤ 18 years of age with CMI and syringomyelia who underwent cranial decompression or spinal decompression. Demographics, hospital characteristics, and outcomes were analyzed.

RESULTS

Over the 5-year period, 2789 patients were identified that underwent operative treatment for CMI with syringomyelia. Mean age was 10 ± 4 years with 55% female. During their index hospitalization 14% of the patients had IONM. Patients receiving IONM had no significant difference in Charleston Comorbidity Index ≥ 1 (16% vs. 15% without, p = 0.774). IONM was more often used in those with private insurance (63% vs. 58% without, p = 0.0004) and less likely in those with Medicaid (29% vs. 37% without, p = 0.004). Patients receiving IONM were more likely to have a postoperative complication (23% vs 17%, p = 0.004) and were more likely to have hospital lengths of stay > 7 days (9% vs. 5% without, p = 0.005). Readmission rates for CMI were 9% within 30 days and 15% within the year. The majority (89%) of readmissions were unplanned. 25% of readmissions were for infection and 27% of readmissions underwent a CMI reoperation. The 30-day readmission rate was higher for those with IONM (12% vs. 8% without, p = 0.010). Median cost for hospitalization was significantly higher for patients with IONM ($26,663 ($16,933-34,397)) vs. those without ($14,577 ($11,538-18,392)), p < 0.001.

CONCLUSION

The use of intraoperative neuromonitoring for operative repair of CMI is associated with higher postoperative complications and readmissions. In addition, there are disparities in its use and increased cost to the healthcare system. Further studies are needed to elucidate the factors underlying this association.

Posterior Cranial Fossa Meningioma Causing Tonsillar Herniation and Giant Cervicothoracic Syringomyelia: Case Report and Review of Literature

Syringomyelia is a fluid-filled cyst within the spinal cord and is usually associated with conditions that obstruct the cerebrospinal fluid (CSF) (flow at the foramen magnum or spinal levels such as Chiari malformations, arachnoiditis, and basilar invaginations). Very rarely, posterior cranial fossa tumors can lead to tonsillar herniation and secondary syringomyelia. There are only nine reported cases in the literature. We report a rare case of a 56-year-old female with posterior cranial meningioma and secondary syringomyelia, admitted with headache, nausea, vomiting, and ataxic gait. Magnetic resonance imaging (MRI) demonstrated a large posterior fossa lesion causing early ventriculomegaly and a giant cervicothoracic syrinx within the upper spinal cord extending from the hindbrain inferiorly to the level of T8. She underwent a posterior fossa craniectomy with left C1 hemilaminectomy and complete excision of the tumor. In 6 months following her procedure, an MRI scan showed a significant reduction in the caliber of the syringomyelia throughout its length, and there was a significant improvement in symptoms. Although the pathophysiology of syrinx formation is still poorly understood, the alteration of CSF dynamic flow has been implicated. A common unifying cause appears to be increased transcranial difference in intracranial pressure across the foramen magnum causing tonsillar herniation, irrespective of location in the posterior fossa. With high syrinx pressure, mechanical stress-induced structural change of the spinal cord occurs, allowing the persistence and progression of the syrinx in the spinal cord. Syringomyelia appears to be resolved partially or completely after craniotomy and excision of the posterior fossa lesion.

Clinical and imaging features of spinal extradural arachnoid cysts: a retrospective study of 50 cases

PURPOSE

Spinal extradural arachnoid cysts (SEDACs) are thought to arise from leakage of CSF through a spinal dural defect. This study investigates the demographics and imaging spectrum of SEDACs at our academic institution and compares them with those reported in the literature.

METHODS

Fifty cases with documented MRI diagnosis of SEDAC, Nabors criteria type I meningeal cyst (MC), were identified from retrospective review of imaging records between 1999 and 2020. Patient demographics, presenting symptoms, cyst characteristics, and management outcomes were studied. Statistical analysis was performed to determine associations between maximum cyst size and presenting symptoms along with other imaging findings.

RESULTS

In all 50 subjects, SEDACs were solitary (single) and sporadic (non-familial). The majority were incidental (62%), located posteriorly (92%) and laterally (80%) in the thoracic and thoracolumbar regions (34%, 30%). They were associated with mild mass effect upon the thecal sac (50%) and bone remodeling (92%). Among symptomatic SEDACs, back pain and radiculopathy were the most reported (68%). Larger cysts were located caudally in the spinal canal, and were associated with greater thecal mass effect, bone remodeling, and septations. Four out of six subjects who underwent surgical management had complete or partial remission. One had cyst recurrence.

CONCLUSION

In this largest series of SEDACs, most were discovered incidentally, stable over time, and located in the thoracic spine dorsal to the thecal sac. When symptomatic, back pain and radiculopathy were the most common presenting symptoms. Treatment with complete surgical excision may yield the best results for symptomatic lesions.

Acquired Chiari malformation Type I and holocord syringomyelia associated with a high-flow supratentorial fistulous arteriovenous malformations: A case report and literature review

Background:

Chiari malformation Type I (CMI) is generally considered a congenital lesion and typically associated with syringomyelia. Acquired CMI or adult Chiari malformation caused by intracranial mass is extremely rare. Brain arteriovenous malformations (AVMs) are characteristically symptomatic due to seizure, intracranial hemorrhage, or neurological deficit. We report an extremely rare case of an acquired CMI and extensive syringomyelia associated with a large supratentorial AVM.

Case Description:

A 35-year-old woman was referred to our institute after a diagnosis of CMI and extensive syringomyelia from whole-spine magnetic resonance imaging (MRI) due to complaining of low back pain radiating to the right leg for the past 1 month. She had intermittent headache for 2 years. The patient underwent suboccipital decompression and C1 laminectomy followed by duraplasty. Two months later, she developed severe right-sided sciatic pain and complete right foot drop. Follow-up MRI revealed progressive enlargement of a syrinx cavity at the lower spinal cord and a large right parieto-occipital AVM with markedly dilated cortical draining veins and diffuse engorgement of dural venous sinuses was detected. This AVM supplied mainly by enlarged cortical branches of the right middle cerebral artery and posterior cerebral artery with multiple dural supplies. Endovascular treatment of a high-flow fistulous AVM was successfully performed with N-butyl cyanoacrylate (NBCA) through the hypertrophic branches of the right middle cerebral artery. Four months after embolization, the patient had recovered completely from the right foot drop. Further staged embolization was planned to reduce the size and flow of the AVM before stereotactic radiosurgery. However, the patient was lost to follow-up due to financial reason. One year later, she developed sudden severe headache followed by alteration of conscious due to intraventricular hemorrhage from the AVM, leading to obstructive hydrocephalus requiring cerebrospinal fluid diversion. During a period of 2 years, the patient underwent several staged embolization with NBCA and Onyx. Final cerebral angiography after embolization demonstrated a significant reduction in size and flow of the brain AVM. A control whole-spine MRI revealed a significant reduction in syrinx size. At the end of embolization, the patient had no neurological deficit. However, she had suffered from persistent central neuropathic pain at the right lower extremity. The AVM remnant was further treated by stereotactic radiosurgery.

Conclusion:

Increased cerebral venous hypertension secondary to a high-flow supratentorial AVM leading to posterior fossa venous hypertension may play a major role in the pathogenesis of CMI, induced the formation of syringomyelia. Endovascular treatment of brain AVM, the underlying cause of CMI, resulted in a significant reduction of the size of the syrinx. The need for cranial imaging in initial evaluation of cases with adult Chiari malformation is important.

Diagnosis and treatment of Chiari malformation and syringomyelia in adults: international consensus document

BACKGROUND

Syringomyelia and Chiari malformation are classified as rare diseases on Orphanet, but international guidelines on diagnostic criteria and case definition are missing.

AIM OF THE STUDY

to reach a consensus among international experts on controversial issues in diagnosis and treatment of Chiari 1 malformation and syringomyelia in adults.

METHODS

A multidisciplinary panel of the Chiari and Syringomyelia Consortium (4 neurosurgeons, 2 neurologists, 1 neuroradiologist, 1 pediatric neurologist) appointed an international Jury of experts to elaborate a consensus document. After an evidence-based review and further discussions, 63 draft statements grouped in 4 domains (definition and classification/planning/surgery/isolated syringomyelia) were formulated. A Jury of 32 experts in the field of diagnosis and treatment of Chiari and syringomyelia and patient representatives were invited to take part in a three-round Delphi process. The Jury received a structured questionnaire containing the 63 statements, each to be voted on a 4-point Likert-type scale and commented. Statements with agreement <75% were revised and entered round 2. Round 3 was face-to-face, during the Chiari Consensus Conference (Milan, November 2019).

RESULTS

Thirty-one out of 32 Jury members (6 neurologists, 4 neuroradiologists, 19 neurosurgeons, and 2 patient association representatives) participated in the consensus. After round 2, a consensus was reached on 57/63 statements (90.5%). The six difficult statements were revised and voted in round 3, and the whole set of statements was further discussed and approved.

CONCLUSIONS

The consensus document consists of 63 statements which benefited from expert discussion and fine-tuning, serving clinicians and researchers following adults with Chiari and syringomyelia.

Endoscopic Endonasal Resection of Cranio-Cervical Junction Chordoma and Ventral Chiari Decompression: A Case Report

BACKGROUND

Chiari I malformations secondary to other causes represent a small subset of presenting symptomatic cases. Typically, the primary cause of the malformation is addressed first and results in resolution of the malformation and symptoms. However, in some cases, a patient may present with both a primary Chiari I malformation and another unrelated neurosurgical lesions.

OBJECTIVE

To present a unique case in which resection of a ventral tumor allowed for spontaneous resolution of a simultaneously noted dorsal Chiari I malformation.

METHODS

Pertinent data, including presenting symptoms, hospital course, surgical notes, preoperative images, and postoperative images, were collected using the electronic medical record.

RESULTS

We present a case of a 46-yr-old man with a Chiari I malformation in conjunction with a ventral cranio-cervical junction chordoma. Endoscopic endonasal resection of the chordoma and ventral foramen magnum decompression resulted in radiographic resolution of the Chiari malformation and resolution of his symptoms. Our report represents a rare case of ventral foramen magnum decompression as a treatment for Chiari I malformation.

CONCLUSION

It is felt that the chordoma mass effect was not the source of the Chiari I malformation. Thus, both ventral and dorsal decompressions of the posterior fossa may be considered for Chiari I decompression in select circumstances.

T11/T12 ossification of the yellow ligament contributing to thoracic myelopathy in patient with posterior fossa arachnoid cyst and acquired incidental Chiari I malformation/syrinx

Background:

Thoracic ossification of the yellow ligament (OYL) may contribute to myelopathy. In the case presented, the patient additionally had a chronic posterior fossa arachnoid cyst with an acquired Chiari I malformation and cervicothoracic syrinx.

Case Description:

A 40-year-old female with a posterior fossa arachnoid cyst found 17 years ago, and newly acquired Chiari I malformation (tonsils down 5 mm) with a C7-T5 syrnix, presented with the new onset of lower extremity myelopathy. The MR documented marked dorsolateral cord compression due to T11/T12 OYL. Six months following a laminectomy for resection of OYL, the patient was asymptomatic.

Conclusion:

In patients presenting with the new onset of lower extremity myelopathy, evaluation of the complete neuraxis may be warranted. Here, the patient has an unchanged posterior fossa arachnoid cyst with an acquired Chiari I malformation/C7-T5 syrinx. However, the patient’s symptoms were fully attributed to the MR-documented T11/T12 OYL that was successfully resected.

Coexisting Retrocerebellar Arachnoid Cyst and Chiari Type 1 Malformation: 3 Pediatric Cases of Surgical Management Tailored to the Pathogenic Mechanism and Systematic Review of the Literature

INTRODUCTION

Arachnoid cysts are benign cerebrospinal fluid collection within a duplication of arachnoid membrane and, when found in the retrocerebellar site, they may be associated with tonsils herniation. This rare situation of coexisting retrocerebellar arachnoid cyst (AC) and Chiari malformation type 1 (CM-1) have been previously reported in few cases (10 patients) with syringomyelia and hydrocephalus described to be the most relevant issues. The aim of this paper is to describe 3 pediatric cases of this condition with a systematic review of the literature, underlining the importance of surgical management tailored to the pathogenic mechanism.

METHODS

A restrospective analysis of patients treated for coexisting CM-1 and ACs at the authors' institution has been carried out.

RESULTS

A case of a 10-month-old baby with coexisting AC and CM-1 with tri-ventricular hydrocephalus treated with endoscopic third ventriculostomy, a case of a 1-year-old child with a huge retrocerebellar AC and CM-1 treated with a cysto-peritoneal shunt, and a case of a 15-year-old child with retrocerebellar AC causing symptomatic CM-1 treated with C0-C2 decompression, AC fenestration and duraplasty are described. A long-term follow-up is reported.

CONCLUSIONS

Surgical management of coexisting ACs and CM-1 should not aim at the complete resolution of the cyst or of tonsil herniation, especially when pediatric patients are treated. Rather, the purpose of the neurosurgeon should be to understand the underlying pathogenic mechanism, and then restoring both the cerebrospinal fluid flow in the posterior fossa and the dynamic equilibrium between ventricles, cyst, and subarachnoid space.

Orthostatic Enlargement of a Supracerebellar Arachnoid Cyst With Cerebellar Descent Visualized by Upright Computed Tomography

BACKGROUND

Posterior fossa arachnoid cysts are often asymptomatic, but can rarely cause postural headache, the mechanism of which remains unknown.

CASE DESCRIPTION

We present a 40-year-old woman with an asymptomatic supracerebellar arachnoid cyst. Upright computed tomography (CT) showed enlargement of the arachnoid cyst and caudal descent of the cerebellum compared with supine CT with narrowing of the craniocervical junction cerebrospinal fluid space.

CONCLUSIONS

This finding aids in understanding the association of posterior fossa arachnoid cysts with orthostatic headache. Clinicians should be aware of possible posture-related changes in intracranial structures.

Prevalence and Impact of Underlying Diagnosis and Comorbidities on Chiari 1 Malformation

BACKGROUND

Chiari malformation type 1 affects approximately one in 1,000 people symptomatically, although one in 100 meet radiological criteria, making it a common neurological disorder. The diagnosis of underlying conditions has become more sophisticated, and new radiological markers of disease have been described. We sought to determine the prevalence and impact of additional comorbidities and underlying diagnoses in patients with Chiari malformation type 1 on symptomatology and surgical treatment.

METHODS

A retrospective review of 612 pediatric patients with a Chiari malformation type 1 diagnosis and imaging data evaluated between 2008 and 2018 was performed. Because of extensive clinical heterogeneity, patients were separated into four categories based on their primary comorbidities (nonsyndromic, central nervous system, skeletal, and multiple congenital anomalies) to identify associations with age of onset, radiographic measurements, syringomyelia, and surgical treatment.

RESULTS

The largest group had nonsyndromic Chiari malformation type 1 (70%) and the latest age at diagnosis of any group. In the syndromic group, 6% were diagnosed with a known genetic abnormality, with overgrowth syndromes being the most common. Patients with multiple congenital anomalies had the earliest Chiari malformation type 1 onset, the most severe tonsillar ectopia and obex position, and were overrepresented among surgical cases. Although there were no statistically significant differences between groups and rates of syrinx, we observed differences in individual diagnoses.

CONCLUSION

The underlying diagnoses and presence of comorbidities in patients with Chiari malformation type 1 impacts rates of syringomyelia and surgery. Although most Chiari malformation type 1 cases are nonsyndromic, clinical evaluation of growth parameters, scoliosis, and joint hypermobility should be routine for all patients as they are useful to determine syringomyelia risk and may impact treatment.

Resolution of Tonsillar Herniation and Syringomyelia Following Resection of a Large Anterior Frontal Parasagittal Meningioma

Chiari I malformation is the herniation of cerebellar tonsils below the level of the foramen magnum due to congenital or acquired pathologies. Acquired Chiari I malformation (ACM) may occur secondary to space-occupying lesions (SOLs), such as intracranial tumors due to elevated intracranial pressure (ICP), and can be accompanied by syringomyelia. ACM and syringomyelia have been shown to resolve after resection of the SOL, without the need for adjuvant posterior fossa decompression. The vast majority of SOLs leading to ACM have been reported in the posterior fossa, thus exerting a direct mass effect on the cerebellum. Supratentorial SOLs leading to ACM are much less frequent but, when present, are most commonly parieto-occipital. We report a rare case of a large anterior left frontal, parasagittal meningioma causing ACM and syringomyelia. These findings resolved following the resection of the meningioma, with no further surgical intervention. Our case demonstrates that ACM can occur secondary to an anterior supratentorial mass and further supports the idea that decompression of the posterior fossa is not required for the resolution of intracranial tumor-associated ACM and syringomyelia.

Chiari I malformation in defined genetic syndromes in children: are there common pathways?

PURPOSE

Chiari malformation type I (CMI) is a common pediatric neurologic anomaly that can be associated with a variety of genetic disorders; however, it is not always clear whether the observed associations are real or random. The knowledge of the real associations could provide useful guidance to clinicians. Furthermore, it could be of help to better understand the still unknown genetic etiology of CMI.

METHODS

With the aim of implementing such insights, we retrospectively reviewed clinical, neuroradiological, and genetic data of patients harboring CMI evaluated at the Child Neurology Unit of our institution between January 2008 and December 2018.

RESULTS

The cohort consists of 205 patients (111 males and 94 females), with a mean age at diagnosis of 6.3 years (range 0-18 years). 188 patients completed an average follow-up period of 5.2 years (range one month-18 years). Mean age at last assessment was 11.4 years (range nine months-23 years). 127 (62%) children have been classified as syndromic due to the presence of neurodevelopmental disorders, phenotypic anomalies, or malformations. Among syndromic CMI children, a molecular diagnosis was identified in 35/127 (27.6%) (20 males and 15 females). The most common diagnoses were syndromic craniosynostosis in 8/35 children (22.9%), among which sevenare FGFR-related and one ERF-related craniosynostosis; disorders of the RAS/MAPK pathway, termed RASopathies or RAS/MAPK syndromes in 9/35 (25.7%); disorders of the PTEN-PI3K/AKT signal transduction cascade, termed PTENopathies in 3/35 children (8.6%); and chromosomal rearrangements in 6/35 patients (17.1%), two of whom with del16p11.2.

CONCLUSIONS

We polarized our attention on the defined genetic diagnoses focusing not only on the phenotypic hallmarks but also on the phenotypic overlapping features. In addition, we discussed the pathophysiological mechanisms leading to progressive cerebellar ectopia and the involved molecular pathways. Along with the recent literature evidence, we suppose that interactions between FGFR and RAS/MAPK pathway and between RAS/MAPK and PTEN-PI3K/AKT pathways could explain some phenotypic overlapping features and could have a significant role in the pathogenesis of CMI.

Chiari 1 malformation and raised intracranial pressure

BACKGROUND

The pathophysiology of Chiari 1 malformation (CM1) is inextricably related to intracranial pressure (ICP). The characteristic cerebellar tonsil herniation at the foramen magnum may either cause raised ICP by disturbing CSF flow (as observed in idiopathic CM1) or may itself be the effect of raised ICP (as observed in acquired CM1). Distinguishing between these two phenomena, therefore, is of paramount importance in successfully alleviating the symptoms of the condition and preventing serious complications.

OBJECTIVES

In this article, we discuss the pathophysiology of raised ICP in CM1 and review the current evidence for its investigation and treatment. We also share our own clinical experience which investigates the utility of ICP monitoring in a series of 26 children with CM1.

Chiari I Malformation and Basilar Invagination in Fibrous Dysplasia: Prevalence, Mechanisms, and Clinical Implications

Fibrous dysplasia (FD) is a mosaic disorder of benign fibro-osseous lesions, which may be associated with extraskeletal features as part of McCune-Albright syndrome (MAS). Cranial base abnormalities, including Chiari I malformation (CM1), in which the cerebellum extends below the foramen magnum, and secondary basilar invagination (BI), in which the odontoid prolapses into the posterior cranial fossa, are potentially serious complications of metabolic bone disorders. The purpose of this study was to determine the prevalence, natural history, and risk factors for CM1 and BI in patients with FD/MAS, and to determine mechanisms of cranial base deformities. Clinical and radiographic data from subjects in an FD/MAS natural history study were evaluated and compared to normal controls. In 158 patients with craniofacial FD, 10 (6.3%) cases of CM1 and 12 (7.6%) cases of BI were diagnosed. No cranial base abnormalities were identified in 10 control subjects. Craniomorphometric and volumetric analyses identified cranial constriction and cranial settling as the primary mechanisms of cranial base abnormalities, whereas intracranial hypertension was a contributing factor in a minority of subjects. Longitudinal analyses found progression of odontoid position with age, but no progression of tonsillar position. No endocrinopathies were associated with CM1. MAS endocrinopathies associated with BI included hyperthyroidism (odds ratio [OR] 12.0; 95% confidence interval [CI], 2.9 to 55.6; p < 0.01), precocious puberty (OR 5.6; 95% CI, 1.2 to 26.0; p < 0.05), and hypophosphatemia (OR 7.7; 95% CI, 1.9 to 27.0; p < 0.01). Scoliosis was associated with both CM1 (OR 4.8; 95% CI, 1.1 to 22.8; p < 0.05) and BI (OR = infinity; 95% CI, 4.7 to infinity; p < 0.01). This study successfully characterized cranial base abnormalities in FD/MAS and the pathophysiological connection between them. These findings support routine screening for cranial base abnormalities in patients with craniofacial FD, as well as aggressive management of contributory risk factors. © 2018 American Society for Bone and Mineral Research.

Duraplasty Type as a Predictor of Meningitis and Shunting After Chiari I Decompression

BACKGROUND

Expansile duraplasty is frequently performed during Chiari I decompression. Aseptic and bacterial meningitis are possible complications of this procedure. We sought to compare the rates of meningitis and subsequent need for cerebrospinal fluid (CSF) diversion with duraplasty using bovine pericardial (BPC) xenograft and allograft.

METHODS

We conducted a retrospective review of 112 patients who underwent Chiari I decompression. All patients underwent duraplasty with either allograft or BPC. Occurrence of postoperative lumbar punctures and associated data were recorded to determine rates of meningitis. Rates of subsequent shunting were also recorded.

RESULTS

Overall, 112 patients were included in the study: 30 underwent duraplasty with allograft (27%) and 82 received BPC (73%). A total of 26 patients developed postoperative meningitis (23 cases of chemical meningitis and 3 of bacterial meningitis). Rates of meningitis were higher in patients who received BPC than patients who received allograft (28% vs. 10%, respectively; P = 0.047). The rate of shunting was greater in patients with meningitis compared with patients without meningitis (56.5% vs. 5.75%, respectively; P < 0.0001). Moreover, 13 of the 15 patients (87%) in the BPC cohort who were shunted were found to have meningitis compared with 0 of the 3 shunted patients (0%) in the allograft cohort (P = 0.044).

CONCLUSIONS

We found that rates of total meningitis were greater in patients who underwent Chiari I decompression and duraplasty with BPC compared with an allograft. The rate of shunting was significantly higher for patients who developed meningitis after decompression compared with patients without meningitis.

Acquired Chiari I Malformation with Syringomyelia Secondary to Colloid Cyst with Hydrocephalus-Case Report and Review of Literature

INTRODUCTION

Acquired Chiari malformation and associated syringomyelia have been previously described following lumbar puncture/drainage, lumboperitoneal shunts, and spontaneous cerebrospinal fluid leakage. In addition to these etiologies, space-occupying lesions such as meningiomas, epidermoid cysts, medulloblastomas, and arachnoid cysts are rare causes of acquired Chiari malformation and syringomyelia. We report a rare case of colloid cyst with hydrocephalus causing secondary Chiari malformation with syringomyelia.

CASE REPORT

A 58-year-old lady presented with neck pain and difficulty in walking and numbness of all 4 limbs of 1-year duration. Diagnostics with magnetic resonance imaging of the head and the cervical spine were done in the referring hospital. The patients was then referred with the diagnosis of colloid cyst with hydrocephalus and Chiari malformation 1 with cervicodorsal syringomyelia. She underwent colloid cyst excision through the transcallosal approach. Postoperatively the patient showed improvement in her symptomatology. Magnetic resonance imaging of the brain and cervical spine at 6 months' follow-up showed resolved Chiari malformation and resolving syrinx.

CONCLUSIONS

Colloid cyst with hydrocephalus is a rare cause of secondary Chiari malformation with syringomyelia. Surgical management of the underlying lesion improves acquired Chiari malformation and associated syringomyelia.