How I do it - The "drum skin" duraplasty technique after foramen magnum decompression for Chiari malformations.

BACKGROUND: Chiari malformations are a spectrum of posterior cranial fossa anomalies characterized by herniation of the cerebellar tonsils through the foramen magnum. Surgery is the treatment of choice for selected patients with good postoperative outcomes. METHODS: We describe foramen magnum decompression (FMD) with dural opening and a "drum skin" duraplasty technique. CONCLUSIONS: In our experience, FMD with "drum skin" duraplasty is a safe and effective procedure, reducing the risk of CSF leakage and arachnoidal adhesions and yielding better long-term clinical and radiological outcomes than other traditional techniques.

Low versus High Intracranial Compliance in Adult Patients with Chiari Malformation Type 1-Comparison of Long-Term Outcome After Tailored Treatment.

BACKGROUND: In patients with Chiari malformation type 1 (CMI) presenting with low intracranial compliance (ICC), foramen magnum decompression (FMD) often fails and the complication rate may be higher. We therefore routinely perform a preoperative assessment of ICC from intracranial pressure measurement. Patients with low ICC are treated with ventriculoperitoneal shunt (VPS) before FMD. In this study, we assess the outcome of patients with low ICC, compared with patients with high ICC treated with FMD alone. METHODS: We reviewed the clinical and radiologic data of all consecutive patients with CMI treated between April 2008 and June 2021. ICC was assessed by overnight measurement of the pulsatile intracranial pressure: mean wave amplitude (MWA) above a previously defined threshold for abnormality was considered a surrogate marker for low ICC. The outcome was scored by Chicago Chiari Outcome Scale. RESULTS: Of 73 patients, 23 with low ICC (average MWA 6.8 ± 1.2 mm Hg) received VPS before FMD, whereas 50 with high ICC (average MWA 4.4 ± 1.0 mm Hg) received only FMD. After a mean follow-up of 78.7 ± 41.4 months, 96% of all patients subjectively improved. The mean Chicago Chiari Outcome Scale score was 13.1 ± 2.2. Enlargement of cerebrospinal fluid space in the foramen magnum was achieved in 95% and regression of syringomyelia in 74% of cases. We found no significant difference in outcome between the patients with low and high ICC. CONCLUSIONS: By identifying patients with CMI associated with low ICC and tailoring their treatment by VPS before FMD, we achieved favorable clinical and radiologic outcomes comparable to those with high ICC.

Inferiorly Directed Posterior Cranial Vault Distraction for Treatment of Chiari Malformations.

OBJECTIVE: The authors present a case series of patients with Chiari I malformations treated with distraction osteogenesis of the posterior cranial vault, utilizing a vertical distraction vector for appropriate cranial vault expansion while mitigating the risks of scaphocephaly and cerebellar ptosis. PATIENTS AND METHODS: Patients with syndromic and nonsyndromic Chiari I malformations treated with vertical-vector distraction osteogenesis of the posterior cranial vault were identified from 2008 to 2014. Demographics, preoperative and postoperative clinical symptoms, and perioperative details were assessed. Long-term esthetic outcomes, complications, and symptomatic improvement were evaluated in conjunction with neurosurgery. RESULTS: Nine patients were identified. Five had known syndromes, 2 likely had unidentified syndromes, and 2 were nonsyndromic. Seven had prior Chiari-related surgeries. Most presented with hydrocephalus, motor symptoms, and developmental delay. Operatively, 2 to 3 internal distraction fixators were applied such that the vector of distraction was along a cephalad-caudad axis. Devices were activated on postoperative day 5 and distracted 1 mm per day. Three postoperative complications were found within the first 3 months which included a dislodged distraction arm, a device extrusion, and a local cellulitis. No complications affected the clinical outcome. Radiographic follow-up showed good bone formation, decompression of the posterior fossa, improved cerebrospinal fluid flow, and no cerebellar ptosis. Neurological surveillance showed improvement in intracranial pressure, hydrocephalus, motor symptoms, and behavioral problems. CONCLUSION: The authors have presented 9 patients with Chiari I malformations treated with distraction osteogenesis, along with a novel technique to safely and effectively expand the posterior fossa while minimizing the risk of cerebellar ptosis. LEVEL OF EVIDENCE: Level II (prognostic/risk studies).

Revisiting the Resolution of Chiari Malformation in Nonsyndromic Craniosynostosis: A Case of Posterior Cranial Vault Reconstruction in Secondary Pan-Suture Synostosis.

BACKGROUND: While commonly seen in syndromic craniosynostosis, the incidence of Chiari malformation (CM) in nonsyndromic craniosynostosis has been reported at 5% and there is a lack of understanding of the pathophysiology and management of CM in this patient population. CASE DESCRIPTION: We present a 5-year-old male patient who underwent a sagittal craniosynostosis repair at the age of 5 months and returned at the age of 5 years with daily headaches associated with behavioral changes. He was found to have pan-synostoses and radiographic evidence of increased intracranial pressure, including a Chiari malformation. Neurologic and genetic workup was unremarkable. A cranial vault reconstruction was performed, and subsequent imaging demonstrated resolution of previously noted Chiari malformation. CONCLUSIONS: In our case, we provided a unique window into the underlying pathophysiology for CM in patients with concurrent nonsyndromic craniosynostosis that we hope will add to the current foundation of literature supporting the intricate relation between cranial vault compliance and Chiari malformation or hindbrain herniation. Furthermore, we provide insight into the management of acquired CM and support isolated cranial vault reconstruction in those who do not appear to have symptomatic suboccipital compression.

Chiari malformation type I and basilar invagination originating from atlantoaxial instability: a literature review and critical analysis.

INTRODUCTION: Recently, a novel hypothesis has been proposed concerning the origin of craniovertebral junction (CVJ) abnormalities. Commonly found in patients with these entities, atlantoaxial instability has been suspected to cause both Chiari malformation type I and basilar invagination, which renders the tried and tested surgical decompression strategy ineffective. In turn, C1-2 fusion is proposed as a single solution for all CVJ abnormalities, and a revised definition of atlantoaxial instability sees patients both with and without radiographic evidence of instability undergo fusion, instead relying on the intraoperative assessment of the atlantoaxial joints to confirm instability. METHODS: The authors conducted a comprehensive narrative review of literature and evidence covering this recently emerged hypothesis. The proposed pathomechanisms are discussed and contextualized with published literature. CONCLUSION: The existing evidence is evaluated for supporting or opposing sole posterior C1-2 fusion in patients with CVJ abnormalities and compared with reported outcomes for conventional surgical strategies such as posterior fossa decompression, occipitocervical fusion, and anterior decompression. At present, there is insufficient evidence supporting the hypothesis of atlantoaxial instability being the common progenitor for CVJ abnormalities. Abolishing tried and tested surgical procedures in favor of a single universal approach would thus be unwarranted.

Management of Chiari I Deformity in Children and Adolescents: A Report from the Consensus Taskforce of the Brazilian Society of Pediatric Neurosurgery

Much controversy remains on the current management of Chiari I deformity (CID) in children, with many clinical, surgical and ethic-legal implications. The Brazilian Society of Pediatric Neurosurgery (SBNPed, in the Portuguese acronym) has put together a panel of experts to analyze updated published data on the medical literature about this matter and come up with several recommendations for pediatric neurosurgeons and allied health professionals when dealing with CID. Their conclusions are reported herein, along with the respective scientific background.

Multifocal Gorham-Stout disease associated with Chiari I malformation and recurrent aseptic meningitis: Case report and review of literature.

Gorham-Stout disease is a rare condition of uncertain aetiology characterised by lymphatic proliferation within osseous structures and subsequent massive osteolysis. This report describes the index case of a patient with multifocal Gorham-Stout disease involving the skull base with Chiari I malformation and recurrent aseptic meningitis without fistula. A five-year-old male presented following decompression of a Chiari I malformation with headaches, vomiting, and stiff neck and cerebrospinal fluid pleocytosis without growth of a pathogenic organism. Ongoing symptoms prompted a further three presentations over several months revealing persistent aseptic cerebrospinal fluid monocytic pleocytosis. Further investigation revealed multifocal osseous cystic disease and subsequent bone biopsy suggested Gorham-Stout disease. Suboccipital decompression was not repeated despite craniocervical junction re-stenosis. A literature review demonstrated the extreme rarity of Gorham-Stout disease associated with Chiari I malformation and meningitis. Potential mechanisms of these entities occurring in concert are discussed. Consideration of Gorham-Stout disease as a secondary cause for Chiari I malformation is important amid local bone changes or cerebrospinal fluid leakage prior to pursuing suboccipital decompression considering the poor outcomes reported.

Chiari type 1-a malformation or a syndrome? A critical review.

OBJECTIVE: As the understanding of pathophysiology behind Chiari malformation still is limited, the treatment of Chiari malformation type 1 remains rather empirical. This may result in suboptimal treatment strategy and outcome in many cases. In this review, we critically address whether the condition known today as Chiari malformation type I should rather be denoted Chiari syndrome. METHODS: The current knowledge of Chiari malformation type 1 is summarized from the historical, etymological, genetic, clinical, and in particular pathophysiological perspectives. RESULTS: There are several lines of evidence that Chiari malformation type 1 represents a condition significantly different from types 2 to 4. Unlike the other types, the type 1 should rather be considered a syndrome, thus supporting the reasons to reappraise the traditional classification of Chiari malformations. CONCLUSION: We propose that Chiari malformation type 1 should rather be denoted Chiari syndrome, while the notation malformation is maintained for types 2-4.

Onset and Resolution of Chiari Malformations and Hydrocephalus in Syndromic Craniosynostosis following Posterior Vault Distraction.

BACKGROUND: Patients with syndromic craniosynostosis have an increased incidence of progressive hydrocephalus and Chiari malformations, with few data on the relative benefit of various surgical interventions. The authors compare the incidence and resolution of Chiari malformations and hydrocephalus between patients undergoing posterior vault distraction osteogenesis (PVDO) and patients undergoing conventional cranial vault remodeling. METHODS: Patients with syndromic craniosynostosis who underwent cranial vault surgery from 2004 to 2016 at a single academic hospital, with adequate radiographic assessments, were reviewed. Demographics, interventions, the presence of a Chiari malformation on radiographic studies and hydrocephalus requiring shunt placement were recorded. Mann-Whitney U and Fisher's exact tests were used as appropriate. RESULTS: Forty-nine patients underwent PVDO, and 23 patients underwent cranial vault remodeling during the study period. Median age at surgery (p = 0.880), sex (p = 0.123), and types of syndrome (p = 0.583) were well matched. Patients who underwent PVDO had a decreased incidence of developing Chiari malformations postoperatively compared with the cranial vault remodeling cohort (2.0 percent versus 17.4 percent; p = 0.033). Not surprisingly, no significant difference was found between the groups with regard to the incidence of postoperative hydrocephalus requiring shunt placement (PVDO, 4.1 percent; cranial vault remodeling, 4.3 percent; p = 0.999). CONCLUSIONS: As expected, PVDO did not significantly affect intracranial hydrodynamics to the extent that hydrocephalus shunting rates were different for patients with syndromic craniosynostosis. However, PVDO was associated with a reduced risk of developing a Chiari malformation; however, prospective evaluation is needed to determine causality. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Acquired Chiari malformation following spinal cord injury-a case series.

Introduction: Chiari malformation is characterized by caudal descent of the cerebellar tonsils through the foramen magnum. Acquired Chiari malformations (ACM) have previously been described after a variety of pathologies including lumbar puncture, cerebrospinal fluid (CSF) drainage, lumboperitoneal shunts, and conditions causing craniocephalic disproportion. Case presentation: We present four cases of ACM following spinal cord injury (SCI), which has not previously been described in the literature. Discussion: ACM is rare and typically associated with abnormalities in CSF pressure or space-occupying lesions. This case series describes the potential association of SCI with ACM. We discuss the imaging findings and clinical management of these patients. Early recognition and intervention may be important to prevent progressive neurology in this vulnerable patient group.

Hydrocephalus and Chiari malformation pathophysiology in FGFR2-related faciocraniosynostosis: A review.

BACKGROUND: Patients with syndromic faciocraniosynostosis due to the mutation of the fibroblast growth factor receptor (FGFR) 2 gene present premature fusion of the coronal sutures and of the cranial base synchondrosis. Cerebrospinal fluid (CSF) circulation disorders and cerebellar tonsil prolapse are frequent findings in faciocraniosynostosis. OBJECTIVE: We reviewed the medical literature on the pathophysiological mechanisms of CSF disorders such as hydrocephalus and of cerebellar tonsil prolapse in FGFR2-related faciocraniosynostosis. DISCUSSION: Different pathophysiological theories have been proposed, but none elucidated all the symptoms present in Apert, Crouzon and Pfeiffer syndromes. The first theory that addressed CSF circulation disruption was the constrictive theory (cephalocranial disproportion): cerebellum and brain stem are constricted by the small volume of the posterior fossa. The second theory proposed venous hyperpressure due to jugular foramens stenosis. The most recent theory proposed a pressure differential between CSF in the posterior fossa and in the vertebral canal, due to foramen magnum stenosis.

Can the Etiopathogenesis of Chiari Malformation Be Craniocervical Junction Stabilization Difference? Morphometric Analysis of Craniocervical Junction Ligaments.

OBJECTIVE: The craniocervical junction permits a certain amount of mobility for the cervical spine. The biomechanical properties of occipital bone-atlas joint mainly depend on the bony structure, and atlas-axis joint biomechanical properties mainly depend on ligamentous structure. The underlying etiologic factor of Chiari malformation (CM) is debatable. Nowadays, some researchers argue that stabilization difference is one of the suspicious factors for etiopathogenesis. We aim to analyze the ligamentous morphometric differences of CM. METHODS: Magnetic resonance images of 93 adult healthy subjects (n = 93) without any craniocervical junction development abnormalities and 25 (n = 25) adult patients with craniocervical junction development abnormalities (Arnold CM) were evaluated. Length, width, and length-width ratios of ligaments were evaluated. RESULTS: Length of transverse ligament (mean: 23 ± 3.6 [range: 12.1-31.4]) in the normal population was significantly longer than transverse ligament length in CM patients (mean: 21.3 ± 2.5 [range: 17.2-24.9]). Length of alar ligament (mean: 10.7 ± 2 [range: 5.1-15.4]) in the normal population was significantly longer than alar ligament length in CM patients (mean: 8.8 ± 3.8 [range: 1.1-16.6]) (P = 0.007). CONCLUSIONS: Craniocervical ligaments play an important role in maintaining stability and motion capacity of this region. This study promoted better understanding of craniocervical junction anomalies and provided data that facilitate performing more precise surgical treatment.

Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia.

X-linked hypophosphataemia (XLH) is the most common cause of inherited phosphate wasting and is associated with severe complications such as rickets, lower limb deformities, pain, poor mineralization of the teeth and disproportionate short stature in children as well as hyperparathyroidism, osteomalacia, enthesopathies, osteoarthritis and pseudofractures in adults. The characteristics and severity of XLH vary between patients. Because of its rarity, the diagnosis and specific treatment of XLH are frequently delayed, which has a detrimental effect on patient outcomes. In this Evidence-Based Guideline, we recommend that the diagnosis of XLH is based on signs of rickets and/or osteomalacia in association with hypophosphataemia and renal phosphate wasting in the absence of vitamin D or calcium deficiency. Whenever possible, the diagnosis should be confirmed by molecular genetic analysis or measurement of levels of fibroblast growth factor 23 (FGF23) before treatment. Owing to the multisystemic nature of the disease, patients should be seen regularly by multidisciplinary teams organized by a metabolic bone disease expert. In this article, we summarize the current evidence and provide recommendations on features of the disease, including new treatment modalities, to improve knowledge and provide guidance for diagnosis and multidisciplinary care.

Shunt dependency syndrome and acquired Chiari malformation secondary to cerebrospinal fluid diversion procedures: a 9-year longitudinal observation.

BACKGROUND: Shunt dependency syndrome is a rare long-term complication of cystoperitoneal (CP) shunting for intracranial arachnoid cysts, which is characterized by acute intracranial hypertension with normal-sized or small ventricles. Additionally, acquired Chiari type I malformations (ACIM) could be infrequently secondary to extrathecal shunt drainage of cerebrospinal fluid. CASE REPORT: We described a 12-year-old boy who developed shunt dependency syndrome following a CP shunting for treating a temporal arachnoid cyst. To manage this rare complication, we placed a lumboperitoneal (LP) shunt. During the follow-up period, shunt-induced ACIM and concomitant syringomyelia were noted. CONCLUSION: Shunt dependency syndrome is a rare complication secondary to CP shunting in the treatment of temporal arachnoid cysts, and LP shunting is an effective option to relieve the intracranial hypertension. However, the clinicians should be alert to the ACIM as a rare late complication of cerebrospinal fluid diversion procedures, and the potential protecting effect of the programmable valve should be emphasized.

Rare Hereditary Klippel-Feil Syndrome and Arnold-Chiari Malformation Caused by Cervical Spondylotic Myelopathy.

BACKGROUND: A rare case of familial genetic disorder Klippel-Feil syndrome and Arnold-Chiari malformation caused by cervical spondylotic myelopathy was reported here. CASE DESCRIPTION: The reconstruction of stability and spinal cord decompression was achieved by anterior cervical discectomy, fusion, and internal fixation. CONCLUSIONS: Although the disease genetic characteristics have been studied, operation is necessary when it leads to abnormal neurologic symptoms and the surgery of surgery can have a beneficial outcome.

Myelomeningocele with Associated Anomalies ­ Case Report and Literature Review.

Myelomeningocele is a common defect of the development of the neural tube. It is a complex congenital malformation of the central nervous system (CNS) that can be associated with other concurrent anomalies. We report on a case of lumbar myelomeningocele with concomitant CNS malformations we followed up over a period of 15 years. A concise literature review has also been performed. The current report illustrates that the myelomeningocele is a complex anomaly that is commonly associated with a variety of other CNS malformations such as hydrocephalus and Chiari malformation. It may follow chronic progressive course with exacerbation of clinical symptoms in the long term. Patients that have undergone surgical correction of this spinal defect should be closely monitored over a long period of time because of the possibility of clinical deterioration of the concomitant anomalies such as hydrocephalus, Chiari malformation and siryngomyelia.

Chiari 1 deformity in children: etiopathogenesis and radiologic diagnosis.

The metamerically associated normal hindbrain and normal posterior fossa are programmed to grow together in such a way that the tonsils are located above the foramen magnum and surrounded by the cerebrospinal fluid (CSF) of the cisterna magna. This allows the pulsating CSF to move freely up and down across the craniovertebral junction (CVJ). A developmental mismatch between the rates of growth of the neural tissue and of the bony posterior fossa may result in the cerebellar tonsils being dislocated across the foramen magnum. The cause of this may be, rarely, an overgrowth of the cerebellum. More commonly, it is due to an insufficient development of the posterior fossa, possibly associated with a malformation of the craniocervical joint. When it is not due to a remediable cause, such a herniation is called a Chiari 1 deformity. This definition is anatomic (descent of the tonsils below the plane of the foramen magnum) and not clinical: many patients with the deformity are and will remain asymptomatic. Most authors consider that a descent of 5 mm or more is clinically significant but other factors, such as the diameter of the foramen magnum and the degree of tapering of the upper cervical "funnel," are likely to be as important. Morphologic markers of severity on magnetic resonance imaging are, beside the degree of descent, the peg-like deformity of the tonsils, the obstruction of the surrounding CSF spaces (at the craniocervical junction and in the whole posterior fossa), a compression of the cord, an abnormal signal of the cord, and a syringomyelia, typically cervicothoracic. The syringomyelia is assumed to be explained by the "Venturi effect" that is associated with the increased velocity of the CSF across the restricted CSF spaces. Radiologically, the etiopathogenic assessment should address the size and morphology of the posterior fossa, and the functional status of the craniocervical flexion joint. The posterior fossa is best evaluated on sagittal cuts by the posterior fossa pentagon proportionality associated with the line of Chamberlain, and on coronal cuts, by showing a possible shallowness of the posterior fossa. The functional status of the craniocervical joint is altered in case of a proatlantal hypoplasia, as this condition results in a cranial shift of the joint that brings the tip of the dens and of the flexion axis in front of the medulla, that is, in a situation of osteoneural conflict. Less commonly, similar conflicts may also occur when an abnormal craniocervical segmentation results in an instability of the joint.

"Sandwich Deformity" in Klippel-Feil syndrome: A "Full-Spectrum" presentation of associated craniovertebral junction abnormalities.

Klippel-Feil syndrome (KFS) is defined as congenital fusion of two or more cervical vertebrae resulting from a segmentation failure in the developing spine. According to Samartzis et al., the most commonly fused segments are found at C2/3 (74.1%) and C6/7 (70.4%). In patients with C2/3 fusion, especially when there is additional C1 occipitalization, several secondary anomalies including atlantoaxial dislocation (AAD), basilar invagination (BI), Chiari malformation, and syringomyelia can be identified. In this report, we present a case of a 12-year-old patient with C2/3 and occipitalization and a "Full-Spectrum" presentation of associated CVJ abnormalities including C0/1 fusion, AAD, BI, Chiari malformation, syringomyelia, myelopathy and cranial neuropathy received neurological decompression of the cervico-medullary junction by posterior reduction of the AAD and reconstruction of her CVJ using an unconventional hybrid construct due to a high-riding right vertebral artery in C2. To our knowledge, her "Full-Spectrum" presentation may include the most categories of concomitant abnormalities in the literature. In addition, She received neurological decompression of the cervico-medullary junction using an unconventional hybrid construct due to a high-riding vertebral artery in C2. Three months after the surgery, all of her symptoms recovered significantly. Neither Chiari malformation nor syringomyelia could be identified by MRI two years after the surgery. At the last follow-up (4 years), the patient became completely asymptomatic.