Chiari I "malformations"--an acquired disorder?

Acquired Chiari Type I Malformation Associated with Type IV Dural Arteriovenous Fistula: Case Report

BACKGROUND

 Chiari malformations, usually congenital, can rarely be associated with arteriovenous (AV) fistulas. We present the first case involving a type IV dural AV fistula with a Chiari type I malformation.

METHODS

 Retrospective chart review was performed to obtain pertinent details regarding history and examination, pathologic findings, and treatment course.

RESULTS

 A 63-year-old woman with a 2-year history of migraines presented with 5 months of occipital, right-sided headaches and neck pain exacerbated by Valsalva maneuvers. Computed tomography (CT) and magnetic resonance imaging (MRI) of the head showed a possible right occipital AV malformation, bilateral cerebellar subdural hygromas, and tonsillar crowding at the foramen magnum indicating an acquired Chiari type I malformation. Angiography demonstrated a Cognardtype IV right posterior occipital dural AV fistula supplied by bilateral middle meningeal and posterior meningeal arteries.

CONCLUSION

 After treatment of the dural AV fistula, hygroma evacuation, and decompression of the acquired Chiari malformation, the patient's Valsalva-induced headaches abated.

Research process, recap, and prediction of Chiari malformation based on bicentennial history of nomenclature and terms misuse

There is an absent systematic analysis or review that has been conducted to clarify the topic of nomenclature history and terms misuse about Chiari malformations (CMs). We reviewed all reports on terms coined for CMs for rational use and provided their etymology and future development. All literature on the nomenclature of CMs was retrieved and extracted into core terms. Subsequently, keyword analysis, preceding and predicting (2023-2025) compound annual growth rate (CAGR) of each core term, was calculated using a mathematical formula and autoregressive integrated moving average model in Python. Totally 64,527 CM term usage was identified. Of these, 57 original terms were collected and then extracted into 24 core-terms. Seventeen terms have their own featured author keywords, while seven terms are homologous. The preceding CAGR of 24 terms showed significant growth in use for 18 terms, while 13, three, three, and five terms may show sustained growth, remain stable, decline, and rare in usage, respectively, in the future. Previously, owing to intricate nomenclature, Chiari terms were frequently misused, and numerous seemingly novel but worthless even improper terms have emerged. For a very basic neuropathological phenomenon tonsillar herniation by multiple etiology, a mechanism-based nosology seems to be more conducive to future communication than an umbrella eponym. However, a good nomenclature also should encapsulate all characteristics of this condition, but this is lacking in current CM research, as the pathophysiological mechanisms are not elucidated for the majority of CMs.

Tonsillar herniation as a complication of lumboperitoneal shunt: case report and literature review

Tonsillar herniation is a rare and seldom reported complication after lumboperitoneal (LP) shunting. There have been only few reports that have presented possible options for treatment with varying degrees of success. In this report, we describe a rare case of tonsillar herniation after LP shunting and review related literature.A 17-year-old girl with hydrocephalus related to a traumatic brain injury underwent implantation of an adjustable pressure shunt (valve setting2.5) and a small lumen peritoneal catheter via the L4-L5 interspinal space. One month later, she was admitted to the emergency room with a Glasgow Coma Scale score ofE1M1Vt and dilated pupil. Image studies demonstrated new-onset tonsillar herniation and a mild cervical syrinx. Emergent suboccipital decompressive craniectomy, C1 laminectomy, and duraplasty were performed. This was followed with ligation of the LP shunt and implantation of a ventriculoperitoneal (VP) shunt a few days later. The patient's Glasgow Coma Scale score gradually recovered to 6, which was her previous neurologic status.Tonsillar herniation as a complication after LP shunting is best treated with decompression, ligation or removal of the LP shunt, and a shift to a VP shunt. The tonsillar herniation should be rapidly addressed to avoid persistent symptoms or progression of the neurologic deficits.

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.

Intracranial arachnoid cysts: What is the appropriate surgical technique? A retrospective comparative study with 61 pediatric patients

Objective

Symptomatic intracranial arachnoid cysts (ACs) should be treated either through microsurgical (MS) or endoscopic surgical (ES) fenestration. Implantation of cysto-peritoneal shunt (CPS) system is another treatment option with decreasing indication. In our study, we compared the complication and revision rates between the three operative techniques in pediatric patients.

Methods

We included patients below 18 years with symptomatic intracranial ACs operated between 2004 and 2021. Initial symptoms, location, complication rate, clinical and radiological improvement, postoperative events and revision rate were compared retrospectively.

Results

Sixty-one patients; 33 (54.1%) MS operated (mean age 7.6 years), 18 (29.5%) ES operated (mean age 6.2 years) and 10 (16.4%) with CPS (mean age 3.0 years) were collected. The most common initial symptom was headache in 45.9%. 20 (32.8%) postoperative events were documented. The highest revision rate (60%) was seen in the CPS group compared to 33.3% in MS group and 16.7% in ES group. 31 patients harbored perisylvian ACs, 89% remained event-free after ES, 71% after MS and 20% after CPS. Clinical improvement immediately after surgery was observed in 58 patients (96.9% in MS, 88.9% in ES and 100% in CPS). A radiological volume reduction could be proven postoperative in 51 patients (78.8% MS, 88.9% ES and 90% CPS).

Conclusion

Endoscopic fenestration of AC is a safe and efficient technique which is being widely used nowadays with the highest event free survival compared to microsurgical fenestration especially in perisylvian arachnoid cysts. CPS shows on long terms the highest revision rate but carries the least surgical risks.

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.

Treatment of symptomatic Chiari I malformation by "all-factors-surgery": a report of 194 cases

PURPOSE

Inadequate decompressions can lead to poor improvement of symptoms in patients with Chiari I malformation (CMI). In this study, the "all-factors-surgery" that including all levels decompressions was performed on symptomatic CMI patients for the snake of eliminating all possible pathogenic factors and reducing the chance of reoperation.

METHODS

The "all-factors-surgery" combined operations of posterior fossa decompression, enlarged cranioplasty, duraplasty, cerebellar tonsil partial resection and adhesion release. Total 194 patients from January 2010 to December 2015. The outcome measures included improvement rate of symptoms, patients self-evaluation (improved, unchanged, worsened), Visual Analogue Scale (VAS) score, Japanese Orthopaedic Association (JOA) score, Chicago Chiari Outcome Scale (CCOS) score, the diameter of the syrinx and complications.

RESULTS

Postoperative data were collected from the three stages: at discharge, the short-term follow-up (average, 9.39 months), and the long-term follow-up (average, 54.44 months). Patients self-evaluation improvement rate in the three follow-up stages was 92.27%, 90.07% and 85.93%. The VAS scores (mean, 1.49, 1.21, 1.47 vs 3.76) and JOA scores (mean, 15.66, 15.99, 16.10 vs 14.84) were significant difference between the follow-up and pre-operation (P < .05). The CCOS scores of short-term and long-term follow-up were significantly better than that at discharge (mean, 14.75, 14.87 vs 13.68) (P < .05). The diameter of syrinx in each follow-up stage was significantly less than that in pre-operation (mean, 3.39, 1.95, 1.87 vs 5.09) (P < .05). There were no serious complications, and no one asked for reoperation during the follow up.

CONCLUSION

Symptomatic CMI patients undergoing "all-factors-surgery" had persistently high rates of symptom relief and rarely needed reoperation.

Magnetic Resonance Imaging of Chiari Malformation Type I in Adult Patients with Dysphagia

Objective

To explore the magnetic resonance imaging (MRI) characteristics of Chiari malformation type I (CMI) in patients with dysphagia.

Methods

Adult patients diagnosed with CMI were retrospectively and consecutively reviewed from January 2013 to December 2016. Symptoms and medical characteristics were recorded. According to the clinical manifestations, we divided the patients into two groups. The first group had 21 patients with symptoms of dysphagia and the second group had 71 patients with nondysphagia symptoms. Various length or angle measurements of the posterior cranial fossa (PCF), syringomyelia, and degree of cerebellar tonsillar herniation were investigated using magnetic resonance imaging (MRI). Univariate, correlation, and multivariate logistic regression analyses were used to compare and analyze the data of the two groups.

Results

The mean length of the clivus, height of PCF, and slope inclination angle of clivus significantly decreased in the dysphagia group compared to the nondysphagia group. The mean cranial spinal angle (CSA) and degree of cerebellar tonsillar herniation were significantly larger in the dysphagia group. There were no correlations between the age, sex, disease duration, and the length of cerebellar tonsillar herniation or CSA. There was a positive correlation between dysphagia level and CSA (r=-0.50; p=0.021). Among CSA, age, sex, the degree of tonsillar herniation, syringomyelia, and disease duration, CSA was the individual sign that correlated significantly with dysphagia (OR: 1.447; 95% CI: 1.182-1.698; P<0.001). Interactions between CSA and the degree of cerebellar tonsillar herniation, syringomyelia, and dysphagia existed (OR: 1.104; 95% CI: 1.042-1.170; P=0.001 and OR: 1.081; 95% CI: 1.023-1.142; P=0.006, respectively).

Conclusions

The CMI patients with dysphagia were more likely to have a large CSA on MRI compared with CMI patients without dysphagia. An increased probability with syringomyelia or length of cerebellar tonsillar herniation can enhance the contribution of CSA to dysphagia in patients with CMI.

Outcomes in children undergoing posterior fossa decompression and duraplasty with and without tonsillar reduction for Chiari malformation type I and syringomyelia: a pilot prospective multicenter cohort study

OBJECTIVE

Despite significant advances in diagnostic and surgical techniques, the surgical management of Chiari malformation type I (CM-I) with associated syringomyelia remains controversial, and the type of surgery performed is surgeon dependent. This study's goal was to determine the feasibility of a prospective, multicenter, cohort study for CM-I/syringomyelia patients and to provide pilot data that compare posterior fossa decompression and duraplasty (PFDD) with and without tonsillar reduction.

METHODS

Participating centers prospectively enrolled children suffering from both CM-I and syringomyelia who were scheduled to undergo surgical decompression. Clinical data were entered into a database preoperatively and at 1-2 weeks, 3-6 months, and 1 year postoperatively. MR images were evaluated by 3 independent, blinded teams of neurosurgeons and neuroradiologists. The primary endpoint was improvement or resolution of the syrinx.

RESULTS

Eight clinical sites were chosen based on the results of a published questionnaire intended to remove geographic and surgeon bias. Data from 68 patients were analyzed after exclusions, and complete clinical and imaging records were obtained for 55 and 58 individuals, respectively. There was strong agreement among the 3 radiology teams, and there was no difference in patient demographics among sites, surgeons, or surgery types. Tonsillar reduction was not associated with > 50% syrinx improvement (RR = 1.22, p = 0.39) or any syrinx improvement (RR = 1.00, p = 0.99). There were no surgical complications.

CONCLUSIONS

This study demonstrated the feasibility of a prospective, multicenter surgical trial in CM-I/syringomyelia and provides pilot data indicating no discernible difference in 1-year outcomes between PFDD with and without tonsillar reduction, with power calculations for larger future studies. In addition, the study revealed important technical factors to consider when setting up future trials. The long-term sequelae of tonsillar reduction have not been addressed and would be an important consideration in future investigations.

Acquired Chiari I malformation due to lumboperitoneal shunt: A case report and review of literature

BACKGROUND

The Type I malformations are supposed to be the result of mesodermal defects that create a congenitally small posterior fossa. However, Chiari malformation could be also "iatrogenic" and then called "acquired" Chiari I malformation. In this study, the authors report the clinical feature of a patient who developed a Chiari I malformation after lumboperitoneal shunt.

CASE DESCRIPTION

A 35-year-old woman has been suffering from idiopathic intracranial hypertension and rhinorrhea due to an anterior skull base defect. A valveless lumboperitoneal shunt followed by surgical closure of the defect was performed. Six months later, she suffered from major continuous occipital headaches. The neurological examination found a mild cerebellar gait ataxia and cerebellar dysarthria. The cerebral magnetic resonance imaging (MRI) showed a ptosis of the cerebellar tonsils and a disappearance of the cisterna magna; there was no syringomyelia. This herniation was not present before shunt was performed. A replacement of the lumboperitoneal shunt with a pressure-regulated valve chamber was performed. After a 1-year follow-up, the patient reports a marked decrease of the headache as well as the ataxia, and the last cerebral MRI showed resolution of the Chiari I malformation.

CONCLUSIONS

Symptomatic acquired Chiari malformation with or without syringomyelia as a delayed complication after lumbar shunting is a rare complication, particularly reported in the pediatric population, but could also occur to adult patients. Treating these patients by correcting the shunt's valve could be enough, but should be monitored, as it may fail to resolve the Chiari malformation even years after treatment.

Two distinct populations of Chiari I malformation based on presence or absence of posterior fossa crowdedness on magnetic resonance imaging

OBJECTIVE A subset of patients with Chiari I malformation demonstrate patent subarachnoid spaces around the cerebellum, indicating that reduced posterior fossa volume alone does not account for tonsillar descent. The authors distinguish two subsets of Chiari I malformation patients based on the degree of "posterior fossa crowdedness" on MRI. METHODS Two of the coauthors independently reviewed the preoperative MR images of 49 patients with Chiari I malformation and categorized the posterior fossa as "spacious" or "crowded." Volumetric analysis of posterior fossa structures was then performed using open-source DICOM software. The preoperative clinical and imaging features of the two groups were compared. RESULTS The posterior fossae of 25 patients were classified as spacious and 20 as crowded by both readers; 4 were incongruent. The volumes of the posterior fossa compartment, posterior fossa tissue, and hindbrain (posterior fossa tissue including herniated tonsils) were statistically similar between the patients with spacious and crowed subtypes (p = 0.33, p = 0.17, p = 0.20, respectively). However, patients in the spacious and crowded subtypes demonstrated significant differences in the ratios of posterior fossa tissue to compartment volumes as well as hindbrain to compartment volumes (p = 0.001 and p = 0.0004, respectively). The average age at surgery was 29.2 ± 19.3 years (mean ± SD) and 21.9 ± 14.9 years for spacious and crowded subtypes, respectively (p = 0.08). Syringomyelia was more prevalent in the crowded subtype (50% vs 28%, p = 0.11). CONCLUSIONS The authors' study identifies two subtypes of Chiari I malformation, crowded and spacious, that can be distinguished by MRI appearance without volumetric analysis. Earlier age at surgery and presence of syringomyelia are more common in the crowded subtype. The presence of the spacious subtype suggests that crowdedness alone cannot explain the pathogenesis of Chiari I malformation in many patients, supporting the need for further investigation.

Acute Foramen Magnum Syndrome Following Single Diagnostic Lumbar Puncture: Consequence of a Small Posterior Fossa?

BACKGROUND

Type I Chiari malformation (CMI) is a rare complication of lumbar cerebrospinal fluid (CSF) drainage that is usually reported after lumbar drain or lumboperitoneal shunt placement. It usually remains asymptomatic; however, even if it becomes symptomatic, symptoms are usually mild. There are only a few reports of acute foramen magnum syndrome following continuous lumbar CSF drainage, and acute foramen magnum syndrome after a single diagnostic lumbar puncture (LP) has not been previously reported. We encountered this catastrophic complication in one of our patient.

CASE DESCRIPTION

A 30-year-old woman with a large supratentorial meningioma and associated asymptomatic CMI presented with holocranial headache. She underwent successful and uneventful excision of the tumor. However, she developed quadriplegia and respiratory arrest 48 hours following a diagnostic LP performed on postoperative day 9. She underwent urgent posterior fossa decompression after magnetic resonance imaging showed increased tonsillar impaction and swelling along with cervicomedullary compression. Postoperatively, she steadily improved and regained normal power after 3 months. Retrospective quantitative analysis of magnetic resonance imaging (MRI) revealed a small posterior fossa.

CONCLUSIONS

The association of intracranial tumors and lumbar CSF drainage with CMI is uncommon. The documentation of a small posterior fossa signifies the importance of both developmental (small posterior fossa) and acquired (intracranial tumor/lumbar CSF drainage) factors in pathogenesis of CMI. Although the extreme rarity of acute deterioration following a single LP does not warrant LP to be contraindicated in such patients, documentation of resolution of CMI with postoperative MRI before performing lumbar CSF drainage (whether therapeutic or diagnostic), might be helpful in avoiding this rare complication.

A novel technique to treat acquired Chiari I malformation after supratentorial shunting

PURPOSE

The acquired Chiari I malformation with abnormal cranial vault thickening is a rare late complication of supratentorial shunting. It poses a difficult clinical problem, and there is debate about the optimal surgical strategy. Some authors advocate supratentorial skull enlarging procedures while others prefer a normal Chiari decompression consisting of a suboccipital craniectomy, with or without C1 laminectomy and dural patch grafting.

METHODS

We illustrate three cases of symptomatic acquired Chiari I malformation due to inward cranial vault thickening.

RESULTS

We describe a new surgical approach that appears to be effective in these patients. This approach includes the standard Chiari decompression combined with posterior fossa augmentation by thinning the occipital planum.

CONCLUSION

Internal volume re-expansion of the posterior fossa by thinning the occipital planum appears to be an effective novel surgical strategy in conjunction with the standard surgical therapy of Chiari decompression.

A practical clinical classification of spinal neural tube defects

Current commonly used terminology to describe neural tube defects (NTD) is inconsistent, overlapping, contradictory and, at times, inaccurate making it difficult to convey the nature of the malformation and what needs to be done to optimally treat patients with these congenital abnormalities.NTD can be broadly divided into those that are open with exposed neural tissue and leaking cerebrospinal fluid (CSF) and those that are closed with no exposed neural tissue nor loss of CSF. It appears that the loss of CSF during development is the underlying factor that leads to the entire central nervous system involvement with an open NTD and lack thereof with a closed NTD, wherein only the spinal cord is malformed. There are, however, rare transitional cases that bridge the gap between the two forms.Agreeing on a nomenclature that is used in a standard fashion would be of help in addressing this group of congenital anomalies that have a great deal of variability and, at times, can be quite complex.

Pathogenesis and Cerebrospinal Fluid Hydrodynamics of the Chiari I Malformation

This article summarizes the current understanding of the pathophysiology of the Chiari I malformation that is based on observations of the anatomy visualized by modern imaging with MRI and prospective studies of the physiology of patients before and after surgery. The pathogenesis of a Chiari I malformation of the cerebellar tonsils is grouped into 4 general mechanisms.

Relationship between pharyngitis and peri-odontoid pannus: A new etiology for some Chiari I malformations?

The pathophysiology underlying Chiari I malformations (CIMs) provides room for debate with several theories attempting to address this issue. We retrospectively reviewed many of our past patients with pediatric CIMs (specifically, those with peri-odontoid pannus), and present a hypothesis for the development of the malformation in some of said patients. Our experience with the pediatric CIM has shown that almost 1 in 20 patients who present with symptoms is found to have a peri-odontoid pannus. These masses ranged in size from 4 to 11 mm in diameter. Forty percent had a history of clinically significant pharyngitis or pharyngeal abscess. Pannus formation around the dens (odontoid) resulted in ventral compression of the craniocervical junction in each of these patients. Highlighting the hypermobility that causes such lesions, following fusion, the pannus and symptoms in several patients were diminished. Impairment of normal cerebrospinal fluid circulation out of the fourth ventricle and across the craniocervical junction appears to be a plausible endpoint in this discussion and a suitable explanation for some patients with CIM. Still, the mechanisms by which cerebrospinal fluid circulation is compromised may be variable and are not well understood. This is the first study dedicated to the evaluation of pannus formation in the CIM population. We hypothesize that pharyngeal inflammatory conditions contribute to the formation and progression of hindbrain herniation in a small subset of patients with CIMs.

Treatment of Secondary Tonsillar Herniation by Lumboperitoneal Shunt Revision

Background:

Idiopathic intracranial hypertension (IIH) is a condition that usually affects young, obese women. Management is aimed at controlling symptoms of increased intracranial pressure (ICP) and prevention of visual failure due to papilledema. A common surgical treatment for IIH is the insertion of a lumboperitoneal shunt (LP shunt). Secondary symptomatic tonsillar herniation is an uncommon side effect following lumbar cerebrospinal fluid diversion.

Methods:

We present two cases of symptomatic secondary tonsillar herniation, one associated with a syrinx, in patients with IIH following valved LP shunting. Treatment options for this side effect may include transplanting the shunt to the ventricular system or decompression of the foramen magnum.

Results:

In our cases we elected to alter the construct of the LP shunt by inserting a programmable valve which led to clinical and radiological reversal of the tonsillar herniation as well as a dramatic reduction in an associated syrinx.

Conclusions:

When faced with LP shunt induced symptomatic secondary tonsillar herniation, consideration may be given to altering LP shunt dynamics, prior to inserting a ventricular catheter into normal sized ventricles or decompressing the posterior fossa.

Headaches and Arnold-Chiari syndrome: when to suspect and how to investigate

Migraine and tension-type headache are common clinical problems, occurring even at a young age. When patients report headache as a symptom, it is necessary to exclude a secondary headache induced by an organic disease. Proper diagnosis and management of headache depends on a thorough history review and comprehensive clinical examination. A Chiari malformation is one organic cause that should not be overlooked. A thorough clinical screening is always recommended, including a complete neurological, mental status and physical examination. However, when the symptom pattern suggests a Chiari malformation, neuroimaging is warranted to identify correctly the pathologic condition and the most appropriate therapeutic approach. This paper reviews this condition, the signs and symptoms suggestive of its presence and how to arrive a the proper diagnosis.

Treatment of delayed Chiari malformation and syringomyelia after lumboperitoneal shunt placement: Case report and treatment recommendations

Background:

Delayed Chiari malformation with syringomyelia is an uncommon and sparsely reported complication after lumbar cisternal shunting. A number of treatments have been implemented with varying degrees of success. After review of these modalities, a treatment plan was devised and implemented.

Case Description:

A 15-year-old girl was diagnosed with idiopathic intracranial hypertension (pseudotumor cerebri) and had placement of a Medtronic Spetzler lumboperitoneal shunt. She did well for 10 years and then developed a 3-week history of headache, balance problems, and sensory loss. Workup demonstrated a new Chiari malformation and cervical syrinx. She underwent initial placement of a ventriculoperitoneal shunt, followed by ligation of the lumboperitoneal shunt. She then had a suboccipital decompression and duraplasty. Follow-up at 6 months showed relief of her symptoms and MRI demonstrated resolution of the Chiari malformation and syrinx.

Conclusion:

Delayed Chiari malformation and/or syringomyelia after lumbar shunting is best treated with placement of a ventricular device and ligation of the lumbar shunt. The Chiari malformation and/or syrinx should be surgically addressed for persistent symptoms or progression of the structural abnormality.

Acute foramen magnum syndrome from acquired Chiari I malformation relieved by ventriculoperitoneal shunt revision

An adult case of shunt malfunction presenting with acute quadriparesis as a manifestation of foramen magnum syndrome with acquired Chiari type I malformation is described in this study. The corticospinal function was restored after shunt revision. MRI showing considerable ascent of cerebellar tonsils after surgery is shown. Theories regarding the formation of acquired Chiari I malformations, alongside the possible synergistic roles of intracranial pathologies and cerebrospinal fluid drainage in the development of this entity are discussed.

Analysis of therapeutic choices for slit ventricle syndrome after cyst-peritoneal shunting for temporal arachnoid cysts in children

OBJECT

The goal in this study was to investigate early diagnostic evidence, optimal therapeutic strategies, and prophylactic methods for slit ventricle syndrome (SVS) in patients with temporal lobe arachnoid cysts who received cyst-peritoneal (CP) shunts.

METHODS

Six cases of SVS in patients with temporal lobe arachnoid cysts who received CP shunts were treated by the senior authors in 2 institutions between January 2005 and January 2009. The radiological data, treatment process, and therapeutic results were reviewed retrospectively.

RESULTS

There were 4 boys and 2 girls, whose mean age at presentation was 4 years and 1 month. The main clinical symptoms were severe headache, nausea, vomiting, and decreasing eyesight. Radiological studies showed normal or slightly smaller than normal ventricles, and arachnoid cysts that had shrunk dramatically. The most effective treatment for SVS was to replace the original shunts with devices that had a programmable valve, or if this was unsuccessful, to replace the original shunts with ventriculoperitoneal (VP) shunts. All symptoms in these patients disappeared, and the mean follow-up duration was 24 months.

CONCLUSIONS

The SVS presents more often in patients with hydrocephalus who undergo VP shunting. However, it is also a serious complication in patients with arachnoid cysts who receive a CP shunt. The SVS is not a single condition; rather, different pathophysiological conditions can underlie this complicated syndrome. Because there are no striking morphological changes on radiological studies of the SVS in the patients with CP shunts, it is not easy for this syndrome to be diagnosed in time and treated rationally. Misdiagnosis and delayed treatment usually occur. The use of programmable shunts or VP shunts to replace the original shunt is an optimal therapeutic choice. The use of low-pressure shunts to treat arachnoid cysts should be abandoned unless dictated by specific indications.

Scoliosis and syringomyelia with Chiari malformation after lumbar shunting

Unsteady gait was noted in a 2-year-old boy with a lumboperitoneal (LP) shunt that had been inserted 1 year earlier for increased head circumference caused by communicating hydrocephalus. Scoliosis was also noted during postoperative follow-up. Magnetic resonance imaging revealed new hindbrain tonsillar herniation and an extensive syrinx from C3 to L1. The malfunctioning LP shunt was removed and posterior fossa decompression with ventriculoperitoneal shunt insertion was performed. The unsteady gait recovered completely and scoliosis improved. Magnetic resonance imaging demonstrated resolution of the syrinx and tonsillar herniation. Acquired Chiari I malformation after LP shunt is well documented; usually, patients have no symptoms. This is the first report to have all the cause and effect mechanisms among syringomyelia, scoliosis and Chiari I malformation in 1 patient. We review the literature and discuss the possible mechanisms.

Shunt malfunction causing acute neurological deterioration in 2 patients with previously asymptomatic Chiari malformation Type I. Report of two cases

Patients with symptomatic Chiari malformation Type I (CM-I) typically exhibit a chronic, slowly progressive disease course with evolution of symptoms. However, some authors have reported acute neurological deterioration in the setting of CM-I and acquired Chiari malformations. Although brainstem dysfunction has been documented in patients with CM-II and hydrocephalus or shunt malfunction, to the authors' knowledge only 1 report describing ventriculoperitoneal (VP) shunt malfunction causing neurological deterioration in a patient with CM-I exists. The authors report on their experience with the treatment of previously asymptomatic CM-I in 2 children who experienced quite different manifestations of acute neurological deterioration secondary to VP shunt malfunction. Presumably, VP shunt malfunction created a positive rostral pressure gradient across a stenotic foramen magnum, resulting in tetraparesis from foramen magnum syndrome in 1 patient and acute ataxia and cranial nerve deficits from syringobulbia in the other. Although urgent shunt revisions yielded partial recovery of neurological function in both patients, marked improvement occurred only after posterior fossa decompression.

Resolution of Chiari I Malformation Following Acetazolamide Therapy

A 25-year-old obese woman developed headaches and visual blurring. Examination showed papilledema and cranial MRI showed a large Chiari I malformation. Acetazolamide was initiated and a repeat cranial MRI surprisingly showed resolution of the Chiari I malformation. Chiari I malformation associated with papilledema has never been shown to resolve with acetazolamide therapy.

Evolution of tonsillar ectopia associated with frontal encephalocoele

INTRODUCTION

Chiari I malformation has been traditionally considered a congenital malformation. However, there is growing clinical evidence suggesting that it is an acquired phenomenon as also exemplified by this case.

CASE

Fetal magnetic resonance imaging (MRI) at 28th week gestation revealed a frontonasal encephalocoele with no hindbrain abnormalities. Post-natal MRI of brain and cervical spine of the 7-week-old infant showed the presence of tonsillar ectopia in the absence of hydrocephalus. The normally developed cerebellar tonsil has herniated through the foramen magnum during the third trimester and neonatal period.

DISCUSSION

We hypothesise that the presence of the encephalocoele resulted in dampening expansile forces, produced by the growing brain as well as the cerebrospinal fluid pulsation required to stimulate of the skull growth. As a result, cranial growth is diminished producing a small posterior fossa. The subsequent growth spurt of the cerebellum at the end of the third trimester and during the neonatal period has resulted in cerebellar tonsillar ectopia consequent upon the state of cephalocranial disproportion.

Acute symptomatic cerebellar tonsillar herniation following intraoperative lumbar drainage

Complications of tonsillar herniation associated with lumbar drainage have been reported in the literature. However, acutely symptomatic tonsillar herniation after intraoperative lumbar drainage is rare. The following case illustrates the risk associated with cerebrospinal fluid (CSF) drainage in the setting of tonsillar herniation. The use of lumbar drainage during cranial surgery is a common practice for reducing intracranial pressure and enhancing exposure, but is not without complications. In addition to the complications of the insertion procedure itself, the change in pressure gradient between the intracranial and the suboccipital compartments is of key importance.

The authors present the case of a patient who underwent a subtemporal craniotomy for resection of mesial temporal cavernous malformation with intraoperative lumbar drainage. The patient had a preexisting, asymptomatic 4-mm Chiari malformation and progressive neurological deficits resulting from further cerebellar tonsillar herniation in the early postoperative period developed, which required a lumbar blood patch, decompressive suboccipital craniectomy, and C-1 laminectomy with duroplasty. After placement of the lumbar drain and subsequent CSF drainage, the change in CSF pressure gradient above and below the foramen magnum probably led to the herniation. Unfortunately, the patient has lasting neuropathic pain and cervical cord signal changes on MR images.

Thecal shunt placement for treatment of obstructive primary syringomyelia

OBJECT

The most commonly reported treatment of primary syringomyelia has been laminectomy with duraplasty or direct shunting from the syrinx cavity. Diversion of cerebrospinal fluid (CSF) from the spinal subarachnoid space to peritoneal, atrial, or pleural cavities has been described previously in only a few case reports. Shunting of the CSF from the subarachnoid space rostral to the level of myelographic blockage may reduce the filling force of the syrinx cavity and avoids myelotomy and manipulation of the spinal cord parenchyma. The authors report on 7 patients who underwent thecal shunt placement for primary spinal syringomyelia.

METHODS

This study is a retrospective review of a consecutive series. The authors reviewed the medical records and neuroimaging studies of 7 adult patients with posttraumatic, postsurgical, or postinflammatory syringomyelia treated with thecoperitoneal, thecopleural, or thecoatrial shunt placement at the University of California Los Angeles Medical Center. Myelographic evidence of partial or complete CSF flow obstruction was confirmed in the majority of patients. The mean duration of follow-up was 33 months (range 6-104 months).

RESULTS

Six (86%) of 7 patients showed signs of clinical improvement, whereas 1 remained with stable clinical symptoms. Of the 6 patients with available postoperative imaging, each demonstrated a reduction in syrinx size. Three patients (43%) had > or = 1 complication, including shunt-induced cerebellar tonsillar descent in 1 patient and infections in 2.

CONCLUSIONS

If laminectomy with duraplasty is not possible for the treatment of primary syringomyelia, placement of a thecoperitoneal shunt (or thecal shunt to another extrathecal cavity) should be considered. Although complications occurred in 3 of 7 patients, the complication rate was outweighed by a relatively high symptomatic and imaging improvement rate.

Acquired tonsillar herniation and syringomyelia after pleural effusion aspiration: case report

OBJECTIVE

We present a case of brachial plexus avulsion and reconstructive surgery with cerebrospinal fluid leak between the cervical subarachnoid space and the pleural cavity responsible for tonsillar herniation and syringomyelia.

CLINICAL PRESENTATION

A 17-year-old man presented with headaches when he was positioned upright, simultaneously with a persistent right pleural effusion for about 4 months after reconstructive surgery for a right brachial plexus avulsion. In addition, the headaches had worsened considerably after two aspirations of the pleural effusion. Magnetic resonance imaging (MRI) demonstrated signs of chronic intracranial hypotension and tonsillar herniation with a presyrinx cavity from vertebral level C1 to C7. None of those abnormalities were seen on the MRI scan obtained a few days after the initial trauma 7 months previously. Plexus brachial MRI confirmed the presence of a cerebrospinal fluid leak between the avulsed root of C8 and the pulmonary apex.

INTERVENTION

The leak was treated by surgical closure of the dural tear of the C8 root. Postoperatively, the patient's headaches immediately resolved, and MRI 4 months later showed resolution of cerebellar tonsil herniation and regression of the syrinx.

CONCLUSION

Resolution of acquired tonsillar herniation and syringomyelia can be achieved by closure of the dural tear responsible of the cerebrospinal fluid leak.

Acute deterioration in occult Chiari malformation following missile spinal trauma

✓Patients with Chiari malformation (CM) Type I typically experience chronic, slowly progressive symptoms. Rarely, however, do they suffer acute neurological deterioration following an iatrogenic decrease in caudal cerebrospinal fluid pressure due to, for example, a lumbar puncture. To our knowledge, acute neurological deterioration following missile spinal injury in CM has not been previously described.

The authors report on a 16-year-old girl who was shot in the abdomen and lumbar spine. Although neurologically intact on initial workup, she developed precipitous quadriplegia and apnea in a delayed fashion. Tonsillar herniation with medullary compression and cerebellar infarction was diagnosed on magnetic resonance imaging. Suboccipital decompression resulted in significant neurological improvement. Well-formed tonsillar ectopia diagnosed at surgery suggested a preexisting CM.

The authors conclude that missile spinal trauma can precipitate medullary compression and acute neurological decline, especially in patients with preexisting tonsillar ectopia. Immediate operative decompression to relieve impaction at the cervicomedullary junction can result in significant neurological recovery.

The pediatric Chiari I malformation: a review

BACKGROUND

Both the diagnosis and treatment regimens for the Chiari I malformation (CIM) are varied and controversial. The present paper analyzes the literature regarding this form of hindbrain herniation in regard to definition, anatomy, pathobiology, symptoms, findings, treatment, and outcomes.

DISCUSSIONS

Appropriate literature germane to the CIM is reviewed and discussed. There is variation in the reported anatomy, outcome, and treatment for children with CIM. Based on the literature, most patients have preoperative symptoms or findings (e.g., syringomyelia) improve no matter what surgical technique is utilized. However, standardized treatment paradigms based on randomized controlled studies are still necessary to elucidate the optimal selection and treatment criteria.

Supracerebellar arachnoid cyst – A rare cause of acquired Chiari I malformation

Chiari I malformation (CM) associated with a cervico-thoracic syrinx due to supracerebellar arachnoid cyst has not been reported in the literature. We report such a case, managed by fenestration of the arachnoid cyst and foramen magnum decompression (FMD), aiming to reduce the inferiorly directed pressure on the cerebellum and eliminate the craniospinal pressure dissociation respectively. Imaging done post-operatively showed upward displacement of the cerebellar tonsils with a decompressed craniovertebral junction and disappearance of the syrinx.

Acquired chiari malformation type I associated with a fatty terminal filum. Case report

The authors report the case of a 3-year-old girl with a Chiari malformation Type I (CM-I) and concomitant fatty terminal filum. This child was examined prior to the onset of CM-I as well as after, and the authors present magnetic resonance (MR) images documenting that the malformation was acquired as the child grew in height. This case contributes to the literature describing an acquired CM-I associated with a fatty filum and is the first published account to include MR imaging obtained before and after the onset of the malformation.

Chiari-like tonsillar herniation associated with intracranial hypotension in Marfan syndrome

The authors describe the case of a 12-year-old girl with Marfan syndrome, sacral dural ectasia, and tonsillar herniation, who presented with headache. Initially, it was hypothesized that the headaches were secondary to the tonsillar herniation, and the patient consequently underwent surgical decompression of the foramen magnum. Postoperatively, the patient's condition did not improve, and additional magnetic resonance (MR) imaging demonstrated evidence of a cerebrospinal fluid (CSF) leak at the level of the dural ectasia. It was surmised that the girl's symptoms were due to spontaneous intracranial hypotension (SIH) and that the tonsillar herniation was caused by the leakage. The patient responded well to application of a blood patch at the level of the demonstrated leak, and her headache resolved. This appears to be the first reported case of a patient with Marfan syndrome presenting with a symptomatic spontaneous CSF leak complicated by tonsillar herniation. In this rare association of SIH and connective tissue disorders, recognition of the clinical signs and typical MR imaging features of SIH may lead to more appropriate and less invasive treatment, potentially avoiding surgery.

Shunt-related craniocerebral disproportion: treatment with cranial vault expanding procedures

Two patients with intracranial arachnoid cysts, one with myelomeningocele-hydrocephalus and the other with a subdural fluid collection, were given a cerebrospinal (CSF) extracranial shunt. All four patients developed features of CSF overdrainage following shunting and were treated by cranial vault expanding procedures. Before undergoing decompressive craniotomy, the patients were treated by a variety of procedures, including changing of obstructed ventricular catheters (n=4), insertion or upgrading of programmable valves (n=3), and foramen magnum decompression (n=1). Clinical manifestations of these four patients were attributed to craniocerebral disproportion caused by chronic and progressive skull changes due to dampening of the CSF pulse pressure, which is necessary for maintaining normal cranial growth. On the basis of our previous experience with expanding craniotomies in cases of minimal forms of craniosynostosis, we treated these patients with bilateral parietal craniotomies, with satisfactory results. In conclusion, biparietal decompressive craniotomy constitutes a useful and safe procedure for relieving the clinical manifestations of some CSF overdrainage syndromes, especially in cases with slit-ventricle syndrome and craniocerebral disproportion that prove to be refractory to simpler management procedures.

Acquired Chiari malformation Type I associated with a supratentorial arteriovenous malformation. Case report and review of the literature

Chiari malformation Type I (CM-I), a condition defined by caudal descent of the cerebellar tonsils through the foramen magnum, is generally considered a congenital lesion. Several authors, however, have described an acquired form that appears identical to the congenital lesion on neuroimages. The most commonly reported cause of an acquired CM-I is cerebrospinal fluid diversion through a lumboperitoneal shunt. In this paper, the authors report the case of a patient in whom an acquired CM-I developed in association with a supratentorial arteriovenous malformation (AVM) of the brain. Development of the acquired CM was documented on serial magnetic resonance images. Moreover, the CM was seen to originate and worsen in concert with the clinicoradiological progression of the AVM. The underlying mechanism responsible for the acquired CM in this case is thought to be a high-flow venopathy of the transverse and sigmoid sinuses causing occlusion on the right and redirection of venous outflow into posterior fossa veins, with consequent venous congestion and swelling of the posterior fossa structures.

Idiopathic intracranial hypertension

OBJECTIVE

The history, diagnosis, and therapy of idiopathic intracranial hypertension (IIH) (pseudotumor cerebri) are reviewed. Theories of pathogenesis are considered, the clinical presentation is described, and potential diagnostic and therapeutic challenges are explored.

METHODS

An extensive literature review of IIH and related conditions (secondary pseudotumor syndromes) was performed. The history of and rationale for the diagnosis and medical and surgical approaches to treatment are reviewed. Available outcome studies are presented.

RESULTS

Diagnosis of IIH requires that the modified Dandy criteria be satisfied. Multiple potential contributing causes of intracranial hypertension must be identified or excluded. The clinical presentation most often includes headaches and papilledema, but many other findings have been described. The most important goal of therapy is to prevent or arrest progressive visual loss. Medical therapies include alleviation of associated systemic diseases, discontinuation of contributing medications, provision of carbonic anhydrase inhibitors, and weight loss. Surgical therapies include lumboperitoneal shunting, ventriculoperitoneal shunting, and optic nerve sheath fenestration. On the basis of the advantages and disadvantages of these treatment modalities, a suggested treatment paradigm is presented.

CONCLUSION

Idiopathic intracranial hypertension is the term to be adopted instead of pseudotumor cerebri. IIH remains an enigmatic diagnosis of exclusion. However, prompt diagnosis and thorough evaluation and treatment are crucial for preventing visual loss and improving associated symptoms.

Foetal surgery for spina bifida

In utero repair of open spina bifida or myelomeningocele (MMC) is now performed in selected patients and presents an additional alternative to obstetricians and neonatologists counselling expectant mothers carrying a foetus with MMC. Early foetal intervention may improve neurologic outcomes and reduce the hindbrain herniation associated with the Arnold-Chiari II malformation in open spina bifida. These changes may improve long-term neurologic function and limit requirements for shunt placements and other surgical interventions. Further research is needed to better understand the pathophysiology of MMC, the ideal timing and technique of repair, and the long-term impact of in utero intervention. A prospective, randomized clinical trial is planned comparing prenatal MMC repair with postnatal repair.

Chiari Type II malformation: past, present, and future

OBJECT

The Chiari Type II malformation (CM II) is a unique hindbrain herniation found only in patients with myelomeningocele and is the leading cause of death in these individuals younger than 2 years of age. Several theories exist as to its embryological evolution and recently new theories are emerging as to its treatment and possible prevention. A thorough understanding of the embryology, anatomy, symptomatology, and surgical treatment is necessary to care optimally for children with myelomeningocele and prevent significant morbidity and mortality.

METHODS

A review of the literature was used to summarize the clinically pertinent features of the CM II, with particular attention to pitfalls in diagnosis and surgical treatment.

CONCLUSIONS

Any child with CM II can present as a neurosurgical emergency. Expeditious and knowledgeable evaluation and prompt surgical decompression of the hindbrain can prevent serious morbidity and mortality in the patient with myelomeningocele, especially those younger than 2 years old. Symptomatic CM II in the older child often presents with more subtle findings but rarely in acute crisis. Understanding of CM II continues to change as innovative techniques are applied to this challenging patient population.

Myelomeningocele: prenatal diagnosis, pathophysiology and management

Myelomeningocele (MMC) is a common birth defect that is associated with significant lifelong morbidity. Little progress has been made in the postnatal surgical management of the child with spina bifida. Postnatal surgery is aimed at covering the exposed spinal cord, preventing infection, and treating hydrocephalus with a ventricular shunt. In utero repair of open spina bifida is now performed in selected patients and presents an additional therapeutic alternative for expectant mothers carrying a fetus with MMC. Early fetal intervention may improve neurologic outcome and reduce the hindbrain herniation associated with the Arnold-Chiari II malformation. These changes may improve long-term neurologic function and limit requirements for shunt placements and other surgical interventions. Further research is needed to better understand the pathophysiology of MMC, the ideal timing and technique of repair, and the long-term impact of in utero intervention. A prospective, randomized clinical trial is planned comparing prenatal MMC repair with postnatal repair.

Rapid development of Chiari I malformation in an infant with Seckel syndrome and craniosynostosis. Case report and review of the literature

To illustrate the rapidity with which a child can develop a severe, symptomatic Chiari I malformation, the authors present the case of a 3-month-old infant with Seckel syndrome (microcephaly, micrognathia, craniosynostosis, and multiple other abnormalities) and posterior sagittal and bilateral lambdoid synostosis. The infant underwent magnetic resonance (MR) imaging shortly after birth; the initial image demonstrated the cerebellar tonsils in the posterior fossa, with no herniation. He subsequently developed severe apneic episodes and bradycardia; repeated MR imaging at 3 months demonstrated severe tonsillar herniation with compression of the brainstem. The child underwent posterior fossa remodeling surgery, including release of the posterior sagittal and lambdoid sutures and decompression of the Chiari I malformation. The patient's apnea gradually improved; however, he died of complications of pneumonia and sepsis several weeks later. The authors identified from the literature 21 patients in whom there was a documented MR image or other neuroimage that did not reveal evidence of a Chiari I malformation, followed by a subsequent study with clear documentation of the presence of Chiari I malformation. The interval between the initial study and the development of the tonsillar herniation ranged from 11 days to 18.5 years. In most cases, a lumbar cerebrospinal fluid (CSF) diversion had been performed. This patient developed a severely symptomatic Chiari I malformation during a 3-month period. These reports illustrate that the Chiari I malformation can develop rapidly in the face of increased intracranial pressure, craniosynostosis, and spinal CSF diversion.

[Chiari type I malformation in children: presentation in 34 cases]

Incidental diagnoses of Chiari I malformation are more and more frequent in pauci or asymptomatic children. The value of neurophysiological investigations for surgical indications is discussed.

OBJECTIVE

To determine clinical presentations of Chiari I malformation and relative frequencies of severe and incidental forms, and to evaluate the usefulness of neurophysiological investigations for surgical indications.

METHODS

This retrospective study included 34 patients admitted from 1984 to 2000, with Chiari I malformation diagnosis in different pediatric (intensive care, neurology and neurosurgery) units of a university hospital.

RESULTS

The clinical presentation was severe (two children died) in four cases (12%). Signs of brain stem compression were found in 41% of cases, scoliosis in 21%, and incidental diagnosis in 26%. The polysomnography, performed in 12 cases, showed sleep-apneas in six cases. One child with an incidental diagnosis of Chiari I malformation had many sleep-apneas which required a surgical treatment. A surgical decompression was performed in 69% of cases, with clinical improvement in 77%.

CONCLUSION

The high incidence (12%) of severe forms revealing Chiari I malformations justifies systematic neurophysiological investigations for the initial evaluation and the follow-up of Chiari 1 malformations, including the less symptomatic forms.