The Chiari malformations: a review with emphasis on anatomical traits

Surgical management of Chiari II malformation: a systematic review of literature

PURPOSE

Chiari II malformation (CM-II) is a congenital malformation of the posterior fossa associated with myelomeningocele. Of the symptomatic patients, 10-33% require surgical treatment. To this date, there is not a consensus about the best surgical technique, and whether to do duroplasty.

METHODS

A literature search of the PubMed database and crossed references was performed, per PRISMA guidelines. Data regarding demographic features, extent of cervicomedullary deformity, clinical presentation, surgical techniques, and clinical outcomes were extracted. Pearson's chi-squared test was applied. The p-values under 0.05 were considered statistically significant.

RESULTS

Twenty studies (N = 330) were analyzed. C3 and C4 levels represented 56.4% of the lowest tonsil displacement. The most reported symptom was dysphagia/swallowing dysfunction (53.8%). Suboccipital craniectomy (SOC) and cervical spine expansion (CSE) with duroplasty were the most reported technique. Dural augmentation was performed in 57.4% of the patients. After surgery, 59.6% observed an improvement in symptoms and quality of life, 12.5% were unchanged, and 27.8% had a worsened clinical status. The mortality rate was 2.5% during the first month after surgery, and 17.4% at the last follow-up evaluation. Patients who underwent CSE presented a better clinical outcome (p = 0.002). The SOC procedure could not be correlated with symptom improvement (p = 0.06).

CONCLUSION

CM-II is associated with high morbidity and mortality. An early onset symptomatic CM-II demands intervention, which provided an improvement of outcome in most patients included in this review. The best surgical technique and the exact effect of the surgical management of CM-II on mortality are not yet clear.

A Critical Update of the Classification of Chiari and Chiari-like Malformations

Chiari malformations are a group of craniovertebral junction anomalies characterized by the herniation of cerebellar tonsils below the foramen magnum, often accompanied by brainstem descent. The existing classification systems for Chiari malformations have expanded from the original four categories to nine, leading to debates about the need for a more descriptive and etiopathogenic terminology. This review aims to examine the various classification approaches employed and proposes a simplified scheme to differentiate between different types of tonsillar herniations. Furthermore, it explores the most appropriate terminology for acquired herniation of cerebellar tonsils and other secondary Chiari-like malformations. Recent advances in magnetic resonance imaging (MRI) have revealed a higher prevalence and incidence of Chiari malformation Type 1 (CM1) and identified similar cerebellar herniations in individuals unrelated to the classic phenotypes described by Chiari. As we reassess the existing classifications, it becomes crucial to establish a terminology that accurately reflects the diverse presentations and underlying causes of these conditions. This paper contributes to the ongoing discussion by offering insights into the evolving understanding of Chiari malformations and proposing a simplified classification and terminology system to enhance diagnosis and management.

Abnormal prenatal brain development in Chiari II malformation

Introduction

The Chiari II is a relatively common birth defect that is associated with open spinal abnormalities and is characterized by caudal migration of the posterior fossa contents through the foramen magnum. The pathophysiology of Chiari II is not entirely known, and the neurobiological substrate beyond posterior fossa findings remains unexplored. We aimed to identify brain regions altered in Chiari II fetuses between 17 and 26 GW.

Methods

We used in vivo structural T2-weighted MRIs of 31 fetuses (6 controls and 25 cases with Chiari II).

Results

The results of our study indicated altered development of diencephalon and proliferative zones (ventricular and subventricular zones) in fetuses with a Chiari II malformation compared to controls. Specifically, fetuses with Chiari II showed significantly smaller volumes of the diencephalon and significantly larger volumes of lateral ventricles and proliferative zones.

Discussion

We conclude that regional brain development should be taken into consideration when evaluating prenatal brain development in fetuses with Chiari II.

Treatment of Chiari III Malformation in Infant with 4K 3D ORBEYE Exoscope

Chiari malformation (CM)-III is the rarest anomaly among CMs.1 Treatment of choice is surgical repair,2 although poor outcome and postoperative mortality has been reported.3 Surgical timing is still debated.4,5 We present the case of a male infant with a prenatal diagnosis of encephalocele. Presentation was characterized by hemodynamic instability, horizontal nystagmus, and left shoulder dystocia due to caesarean section, with a 64 mm × 49 mm × 76 mm soft, fluctuant, and translucent suboccipital-cervical sac. Magnetic resonance imaging revealed a median occipital bone defect with the meningoencephalic sac communicating with the vermian cistern and the fourth ventricle, moderate hydrocephalus, reduction of the posterior cranial fossa volume, hypoplasia of cerebellar hemispheric, vermian structures, and corpus callosum hypoplasia. The patient underwent surgery on day 4 with the use of a 4K 3D ORBEYE exoscope (Video 1). Surgery consisted of disengagement of nervous structures and repair of the neurocutaneous defect, followed on day 12 by a ventriculoperitoneal shunt with a programmable valve. The procedures were well tolerated. At the 14-month follow-up visit he was in range with growth charts (weight, height, and cranic circumference) and gained the physiologic stages of growth. He had no motor impairment but still present were convergent strabismus and mild left C5-C6 radiculopathy, secondary to shoulder dystocia. This is the first case reported in the literature of CM-III treated with the 4K 3D ORBEYE exoscope. Advantages of the exoscope were ergonomic positions for operative staff, possibility for the team to assist in the 4K 3D view, especially in cases with a narrow operative field, with a clear and detailed vision, although a learning curve is required6 to become a valid alternative in pediatric neurosurgery.

Incidental findings on brain magnetic resonance imaging (MRI) in adults: a review of imaging spectrum, clinical significance, and management

Utilization of brain MRI has dramatically increased in recent decades due to rapid advancement in imaging technology and improving accessibility. As a result, radiologists increasingly encounter findings incidentally discovered on brain MRIs which are performed for unrelated indications. Some of these findings are clinically significant, necessitating further investigation or treatment and resulting in increased costs to healthcare systems as well as increased patient anxiety. Moreover, management of these incidental findings poses a significant challenge for referring physicians. Therefore, it is important for interpreting radiologists to know the prevalence, clinical consequences, and appropriate management of these findings. There is a wide spectrum of incidental findings on brain MRI such as asymptomatic brain infarct, age-related white matter changes, microhemorrhages, intracranial tumors, intracranial cystic lesions, and anatomic variants. This article provides a narrative review of important incidental findings encountered on brain MRI in adults with a focus on prevalence, clinical implications, and recommendations on management of these findings based on current available data.

Chiari III malformation with defect in Liliequist membrane on MR imaging

The Liliequist membrane is a radiologically neglected structure, with routine evaluation only carried out in pre-operative and post-operative cases of third ventriculostomy. We report two cases of Chiari III malformation in two unrelated females with similar findings on magnetic resonance imaging study including occipital and low cervical encephalocele, hydrocephalus, and segmentation anomalies in cervical spine. Along with these findings, we report a flow void on T2-weighted images observed in both cases across the site of Liliequist membrane between interpeduncular and chiasmatic cistern. Our findings of CSF flow across the Liliequist membrane may represent spontaneous third ventriculostomy or another congenital defect in the myriad of anomalies seen in cases of Chiari III malformation.

Pediatric Chiari I malformation: novel and traditional measurements associated with syrinx and surgery

PURPOSE

Multiple imaging parameters have been examined to estimate the presence of syrinx and the need for surgery in Chiari I patients (CM1); however, no consistent or definitive criteria have been proposed. The objective of this study was to review existing and identify novel radiological and clinical characteristics of CM1 patients that associate syrinx development and surgical intervention.

METHODS

Patients with Chiari I malformation diagnosed on imaging between 0 and 18 years were retrospectively reviewed from January 1, 2007 to February 12, 2020. Participants were included if they had a baseline MRI of the head and spine prior to surgical intervention if required. Forty age-matched controls with cranial imaging were identified for comparison. Imaging parameters and clinical symptoms were recorded.

RESULTS

A total of 122 CM1 patients were included in this study. Of the 122 patients, 28 (23%) had syrinx, and 27 (22%) had surgery. The following imaging parameters associated with syrinx and surgical intervention were identified: midbrain length (P < 0.001; P = 0.032), the obex position (P = 0.002; P < 0.001) and medullary kinking (P = 0.041; P < 0.001). Among the clinical features, the presence of overall pain (P = 0.017; P = 0.042), neck pain (P = 0.005; P = 0.027), and sensory dysfunction (P < 0.001) were found to be strongly associated with syrinx and surgery.

CONCLUSION

While further investigation is needed, these specific radiological and clinical parameters should be considered when evaluating CM1 patients and may be used to guide further management.

Case Report: Downbeat Nystagmus Due to Epidural Puncture during Labor with Undiagnosed Arnold Chiari Malformation

SIGNIFICANCE

Epidural anesthesia is a safe procedure used in pregnant patients during labor. However, caution should be exercised in those patients that have concurrent Arnold Chiari malformation.

PURPOSE

To report a rare and atypical presentation of downbeat nystagmus, in a pregnant patient with Arnold Chiari malformation type 1 (ACM1), secondary to accidental dural puncture.

CASE REPORT

A 31-year-old African American female presented with a chief complaint of decreased vision and oscillopsia that occurred after giving birth, six months earlier. Her medical history prior to presentation was unremarkable. Her delivery was typical; however, the patient did receive epidural anesthesia which resulted in a dural puncture. The patient noted her symptoms a few days after delivery. Upon examination, persistent down beat nystagmus was noted in both eyes. Magnetic resonance imaging revealed a 2.5 cm inferior displacement of the cerebellar tonsils below the foramen magnum consistent with ACM1. The patient was referred to neurosurgery for posterior fossa decompression. However, surgery was deferred until appropriate weight reduction could be achieved. Follow-up examination six months later revealed no change in her clinical findings.

CONCLUSIONS

This case report highlights an atypical presentation of downbeat nystagmus secondary to an accidental dural puncture in a pregnant patient with undiagnosed ACM1. Clinicians should consider the importance of considering ocular complications that can occur in pregnant patients with ACM1. Questioning of women who have recently given birth about epidural anesthesia should be considered with an acute presentation of downbeat-nystagmus.

Multi-parameter-based radiological diagnosis of Chiari Malformation using Machine Learning Technology

BACKGROUND

The known primary radiological diagnosis of Chiari Malformation-I (CM-I) is based on the degree of tonsillar herniation (TH) below the Foramen Magnum (FM). However, recent data also shows the association of such malformation with smaller posterior cranial fossa (PCF) volume and the anatomical issues regarding the Odontoid. This study presents the achieved result regarding some detected potential radiological findings that may aid CM-I diagnosis using several machine learning (ML) algorithms.

MATERIALS AND METHODS

Midsagittal T1-weighted MR images were collected in 241 adult patients diagnosed with CM, eleven morphometric measures of the posterior cerebral fossa were performed. Patients whose imaging was performed in the same centre and on the same device were included in the study. By matching age and gender, radiological exams of 100 clinically/radiologically proven symptomatic CM-I cases and 100 healthy controls were assessed. Eleven morphometric measures of the posterior cerebral fossa were examined using 5 designed ML algorithms.

RESULTS

The mean age of patients was 29.92 ± 15.03 years. The primary presenting symptoms were headaches (62%). Syringomyelia and retrocurved-odontoid were detected in 34% and 8% of patients, respectively. All of the morphometric measures were significantly different between the groups, except for the distance from the dens axis to the posterior margin of FM. The Radom Forest model is found to have the best 1.0 (14 of 14) ratio of accuracy in regard to 14 different combinations of morphometric features.

CONCLUSION

Our study indicates the potential usefulness of ML-guided PCF measurements, other than TH, that may be used to predict and diagnose CM-I accurately. Combining two or three preferable osseous structure-based measurements may increase the accuracy of radiological diagnosis of CM-I.

Arnold-Chiari Malformation: Core Concepts

Arnold-Chiari malformation (ACM), a defect that involves downward displacement of the hindbrain and herniation of the cerebellar vermis, tonsils, pons, medulla, and fourth ventricle through the foramen magnum, is the most complex of the 4 types of Chiari malformations. Unique to the other types of Chiari malformations, approximately 95 percent of infants with ACM also present with an associated myelomeningocele (MMC), the most severe form of spina bifida. Among affected infants, those with symptomatic comorbidities incur a significantly higher morbidity and mortality risk. Prompt identification and diagnosis of ACM, as well as evidence-based postnatal and postsurgical nursing and medical care, is critical. Early surgical intervention can repair an existing MMC and restore proper cerebrospinal fluid circulation, which can dramatically improve patient outcomes and quality of life, and reduce disease and health care burden.

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

PURPOSE

In the last two decades, the non-motor functions of the cerebellum have become the centre of attention for researchers. Anecdotal observations of cognitive and psychiatric manifestations of cerebellar lesions have increased this interest. We aimed to investigate the executive function (EF), intellectual capacity, and comorbid psychiatric disorders in adolescents with Chiari malformation type 1 (CM1), which is a pathological manifestation of posterior cranial fossa structures include the cerebellum.

METHODS

The Chiari group consisted of ten adolescents aged 12-18 years old, and the control group consisted of 13 healthy adolescents with similar age and sex with patients. Stroop test (ST), trail making test (TMT), and Behaviour Rating Inventory of Executive Function-Parent form (BRIEF) were used to evaluate EF; Kent EGY and Porteus Maze Test was used to measuring the intelligence quotient (IQ), and a semi-structured interview was used to determine the psychiatric disorders.

RESULTS

EF test scores were found comparable between the two groups. IQ scores of the Chiari group were found in the normal range, but significantly lower than controls. No significant difference was revealed in terms of comorbid psychiatric disorders between the two groups.

CONCLUSION

In this study, we did not observe an impairing effect of CM1 on EF and intelligence. Also, we found that CM1 did not cause more psychiatric disorders compared to controls. Further studies need to support our findings in adolescents diagnosed with CM1.

One-Year Outcomes of Chiari Type 1 Malformation and Syringomyelia Treated With Posterior Fossa Decompression

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

The objective of this study was to evaluate posterior fossa structural differences between Chiari type 1 malformation with and without syringomyelia, and assess data of the improvement of syringomyelia after different surgical options.

SUMMARY OF BACKGROUND DATA

Syringomyelia is among the most common concomitant complications of Chiari malformation (CM). However, posterior fossa decompression cannot definitely make the syringomyelia disappear even in the long term. Also, there are no universal criteria defining improvement in syrinx.

MATERIALS AND METHODS

All admitted CM patients at our institution from 2013 to 2018 with a 1-year follow-up were analyzed. Patients without syringomyelia were compared with those who had syringomyelia. Patients were divided into 3 groups according to the procedures performed: posterior fossa decompression versus posterior fossa decompression with duralplasty (PFDD) versus PFDD plus obex unblocking. Divergent prognosis of syringomyelia was defined as a 3-category ordinal variable. A multivariable ordinal regression model was used to estimate the relationship between patient variables and increased odds for better resolution of syringomyelia.

RESULTS

No significant linear difference in bony structure was found between syringomyelia and nonsyringomyelia patients. Among syringomyelia patients, the regression analysis demonstrated that patients with shorter posterior fossa height ( P =0.032), lower Pavlov ratio ( P =0.029), and obex unblocking (vs. PFDD, P <0.001; vs. posterior fossa decompression, P =0.037) were more likely to gain a better resolution of syringomyelia.

CONCLUSIONS

Syringomyelia of CM patients may not simply originate from single linear anatomic variation. Patients with shorter posterior fossa height and lower Pavlov ratio received better syringomyelia resolution. Also, unblocking the obex received better syringomyelia resolution compared with duraplasty alone and bony decompression alone with the avoidance of increased postoperative complications and worse clinical outcomes.

UK Chiari 1 Study: protocol for a prospective, observational, multicentre study

INTRODUCTION

Chiari 1 malformation (CM1) is a structural abnormality of the hindbrain characterised by the descent of the cerebellar tonsils through the foramen magnum. The management of patients with CM1 remains contentious since there are currently no UK or international guidelines for clinicians. We therefore propose a collaborative, prospective, multicentre study on the investigation, management and outcome of CM1 in the UK: the UK Chiari 1 Study (UKC1S). Our primary objective is to determine the health-related quality of life (HRQoL) in patients with a new diagnosis of CM1 managed either conservatively or surgically at 12 months of follow-up. We also aim to: (A) determine HRQoL 12 months following surgery; (B) measure complications 12 months following surgery; (C) determine the natural history of patients with CM1 treated conservatively without surgery; (D) determine the radiological correlates of presenting symptoms, signs and outcomes; and (E) determine the scope and variation within UK practice in referral patterns, patient pathways, investigations and surgical decisions.

METHODS AND ANALYSIS

The UKC1S will be a prospective, multicentre and observational study that will follow the British Neurosurgical Trainee Research Collaborative model of collaborative research. Patients will be recruited after attending their first neurosurgical outpatient clinic appointment. Follow-up data will be collected from all patients at 12 months from baseline regardless of whether they are treated surgically or not. A further 12-month postoperative follow-up timepoint will be added for patients treated with decompressive surgery. The study is expected to last three years.

ETHICS AND DISSEMINATION

The UKC1S received a favourable ethical opinion from the East Midlands Leicester South Research Ethics Committee (REC reference: 20/EM/0053; IRAS 269739) and the Health Research Authority. The results of the study will be published in peer-reviewed medical journals, presented at scientific conferences, shared with collaborating sites and shared with participant patients if they so wish.

Chiari 1.5 malformation, accessory odontoid synchondrosis, and ventral compression: case report

The pathogenesis of Chiari 1 malformations has been explained in several different ways, but extensive evidence suggests a relationship between loss of volume within the posterior cranial fossa and Chiari 1 presentations. It is important to be able to differentiate Chiari 1.5 from Chiari 1 malformations as they have similar clinical presentations, but the latter have progressed further and are characterized by caudal herniations of the brain stem through the foramen magnum. Despite the similarities of presentation, Chiari 1.5 malformations have greater rates of complications following posterior decompression surgeries, which are typically performed to relieve ventral compression. An improved understanding of the odontoid synchondroses could lead to better understanding of Chiari malformations and lead to improved treatment of patients with these presentations. Here we present a rare case of an accessory odontoid synchondrosis in a patient with a Chiari 1.5 malformation and ventral compression.

Progressive hydrocephalus despite early complete reversal of hindbrain herniation after prenatal open myelomeningocele repair

OBJECTIVE

Open prenatal myelomeningocele (MMC) repair is typically associated with reversal of in utero hindbrain herniation (HBH) and has been posited to be associated with a reduction in both postoperative prenatal and immediate postnatal hydrocephalus (HCP) risks. However, the long-term postnatal risk of HCP following HBH reversal in these cases has not been well defined. The authors describe the results of a long-term HCP surveillance in a cohort of patients who underwent prenatal MMC repair at their institution.

METHODS

A retrospective review of all prenatal MMC repair operations performed at the Mayo Clinic between 2012 and 2017 was conducted. Pertinent data regarding the clinical courses of these patients before and after MMC repair were summarized. Outcomes of interest were occurrences of HBH and HCP and the need for intervention.

RESULTS

A total of 9 prenatal MMC repair cases were identified. There were 7 cases in which MRI clearly demonstrated prenatal HBH, and of these 86% (6/7) had evidence of HBH reversal after repair and prior to delivery. After a mean postnatal follow-up of 20 months, there were 3 cases of postnatal HCP requiring intervention. One case that failed to show complete HBH reversal after MMC repair required early ventriculoperitoneal shunting. The other 2 cases were of progressive, gradual-onset HCP despite complete prenatal HBH reversal, requiring endoscopic third ventriculostomy with choroid plexus cauterization at ages 5 and 7 months.

CONCLUSIONS

Although prenatal MMC repair can achieve HBH reversal in a majority of well-selected cases, the prevention of postnatal HCP requiring intervention appears not to be predicated on this outcome alone. In fact, it appears that in a subset of cases in which HBH reversal is achieved, patients can experience a progressive, gradual-onset HCP within the 1st year of life. These findings support continued rigorous postnatal surveillance of all prenatal MMC repair patients, irrespective of postoperative HBH outcome.

The Perplexity Surrounding Chiari Malformations - Are We Any Wiser Now?

Chiari malformations are a diverse group of abnormalities of the brain, craniovertebral junction, and the spine. Chiari 0, I, and 1.5 malformations, likely a spectrum of the same malformation with increasing severity, are due to the inadequacy of the para-axial mesoderm, which leads to insufficient development of occipital somites. Chiari II malformation is possibly due to nonclosure of the caudal end of the neuropore, with similar pathogenesis in the rostral end, which causes a Chiari III malformation. There have been significant developments in the understanding of this complex entity owing to insights into the pathogenesis and advancements in imaging modalities and neurosurgical techniques. This article aims to review the different types and pathophysiology of the Chiari malformations, along with a description of the various associated abnormalities. We also highlight the role of ante- and postnatal imaging, with a focus on the newer techniques in the presurgical evaluation, with a brief mention of the surgical procedures and the associated postsurgical complications.

Spinal cord infarction with resultant paraplegia after Chiari I decompression: case report

Paraplegia after posterior fossa surgery is a rare and devastating complication. The authors reviewed a case of paraplegia following Chiari decompression and surveyed the literature to identify strategies to reduce the occurrence of such events.An obese 44-year-old woman had progressive left arm pain, weakness, and numbness and tussive headaches. MRI studies revealed a Chiari I malformation and a cervicothoracic syrinx. Immediately postoperatively after Chiari decompression the patient was paraplegic, with a T6 sensory level bilaterally. MRI studies revealed equivocal findings of epidural hematoma at the site of the Chiari decompression and in the upper thoracic region. Surgical exploration of the Chiari decompression site and upper thoracic laminectomies identified possible venous engorgement, but no hematoma. Subsequent imaging suggested a thoracic spinal cord infarction. Possible explanations for the spinal cord deficit included spinal cord ischemia related to venous engorgement from prolonged prone positioning in an obese patient in the chin-tucked position. At 6.5 years after surgery the patient had unchanged fixed motor and sensory deficits.Spinal cord infarction is rare after Chiari decompression, but the risk for this complication may be increased for obese patients positioned prone for extended periods of time. Standard precautions may be insufficient and intraoperative electrophysiological monitoring may need to be considered in these patients.

Variant sella morphology and pituitary gland height in adult patients with Chiari II malformation: potential pitfall in MRI evaluation

PURPOSE

To systematically evaluate the sella morphology and pituitary gland height on brain MRI of Chiari II malformation (C2M) patients to understand the observed high incidence of apparent enlargement of the pituitary gland.

METHODS

Brain MRIs of C2M patients at a single tertiary care adult institution were retrospectively reviewed. We also evaluated two age and gender-matched control groups-patients with normal brain MRI (C1 group) and chronic ventricular shunts (C2 group). The heights of tuberculum sella, dorsum sella, and pituitary gland were measured and compared. The presence or absence of dural thickening was noted.

RESULTS

21 patients were included in each group. In C2M group, a pituitary adenoma was suggested on 24% of the MRIs. The dorsum sella was significantly smaller in the C2M group (4.8 mm) compared to both the C1 group (7.4 mm, p < 0.001) and the C2 group (7.1 mm, p < 0.001). The pituitary gland was also larger in the cranial-caudal dimension in C2M group (8.6 mm) as compared to both the C1 group (6.6 mm, p < 0.01) and the C2 group (6.0 mm, p < 0.001). One C2M patient with a pituitary gland<10 mm was suggested to have a pituitary adenoma on outside MRI, although a normal pituitary gland was seen on pathology.

CONCLUSION

C2M patients have shallow sella which can accentuate the pituitary gland height. The mean pituitary height was larger in C2M patients, but no functional pituitary pathology was present. It is important to consider sella morphology when evaluating the pituitary gland of C2M patients to avoid unnecessary medical and surgical interventions.

Management of Chiari malformations: opinions from different centers-a review

PURPOSE

Surgical decision-making in Chiari malformation type I (CM-I) patients tends to depend on the presence of neurological signs and symptoms, syringomyelia, and/or scoliosis, but significant variability exists from center to center. Here, we review the symptoms of CM-I in children and provide an overview of the differences in opinion regarding surgical indications, preferred surgical techniques, and measures of outcome.

METHODS

A review of the literature was performed to identify publications relevant to the surgical management of pediatric CM-I patients.

RESULTS

Most surgeons agree that asymptomatic patients without syringomyelia should not undergo prophylactic surgery, while symptoms of brainstem compression and/or lower cranial nerve dysfunction warrant surgery. Patients between these extremes, however, remain controversial, as does selection of the most appropriate surgical technique.

CONCLUSIONS

The optimal surgical procedure for children with CM-I remains a point of contention, and widespread variability exists between and within centers.

Defining, diagnosing, clarifying, and classifying the Chiari I malformations

PURPOSE

Chiari malformations (CM) have been traditionally classified into four categories: I, II, III, and IV. In light of more recent understandings, variations of the CM have required a modification of this classification.

METHODS

This article discusses the presentation, diagnostics, and treatment of the newer forms of hindbrain herniation associated with the CM type I.

RESULTS

The CM 1 is a spectrum that includes some patients who do not fall into the exact category of this entity.

CONCLUSIONS

While CM have been categorically recognized as discrete and individual conditions, newer classifications such as CM 0 and CM 1.5 exhibit some degree of continuity with CM 1; however, they require distinct and separate classification as symptoms and treatments can vary among these clinical subtypes.

Enhancing nodular lesions in Chiari II malformations in the setting of persistent hindbrain herniation: case report and literature review

BACKGROUND

Chiari II malformation includes concomitant cerebellar tonsillar herniation, hydrocephalus, and myelomeningocele. Rarely, pediatric patients with persistent hindbrain herniation develop a new enhancing nodule at the cervicomedullary junction as adults. These new lesions may be suspicious for neoplastic growth, but it remains unclear if neurosurgical intervention is necessary.

CASE REPORT

A 27-year-old female patient with history of Chiari II malformation and persistent hindbrain herniation presented with a 3-month history of headache and upper extremity weakness and numbness. Neuroimaging revealed a new enhancing nodule near the cervicomedullary junction suspicious for neoplasm. Following posterior fossa decompression and excision of the enhancing lesion, pathological analysis demonstrated only benign glioneural heterotopia.

RESULTS

New enhancing nodules at the cervicomedullary junction in Chiari II malformation are exceedingly rare and are likely benign, reactive changes rather than a neoplastic process. Biopsy or surgical excision of these lesions is likely unnecessary for asymptomatic patients.

Occipital Neuralgia: a noninvasive therapeutic approach

Objective:

to evaluate the application of a noninvasive intervention consisting of a postural modification using personalized models and osteopathy in people with occipital neuralgia.

Method:

retrospective study of the intervention performed in adult population with occipital neuralgia, consisting of postural modification using personalized plantar orthoses and osteopathy, in a study period of four years. The observed variables were: persistence of headache, alignment of the axes, plantar support, center of gravity and center of mass; medical interview data, visual analogue scale, Win-Track gait analysis system and Kinovea software for video analysis (clinical assessment instruments used).

Results:

a total of 34 records of people with occipital neuralgia were studied. A fraction of 58.8% of the patients reported improvement after the intervention. The visual analogue scale data were provided for 64.7% of the records and significant differences (p <0.001) between the means before (8.4 ± 1.7) and after the intervention (2.6 ± 2.7) were found.

Conclusion:

postural modification using personalized orthoses and osteopathy substantially improves the symptomatology of patients with occipital neuralgia.

Chiari Headache

PURPOSE OF REVIEW

Chiari malformations (CM) are a group of neuroanatomical pathologies resulting from overcrowding of the hindbrain. The purpose of this review is to characterize Chiari headache (CH) and describe diagnosis and treatment of the condition.

RECENT FINDINGS

Recent research has helped solidify the criteria for diagnosis of CH. Imaging studies have expanded our understanding of the morphological features producing them and helped to better characterize the pathophysiology. Additionally, identifying this unusual headache disorder accurately has helped with specific treatment options. CH is a disabling condition which can effect multiple domains of a patient's life. The diagnostic criteria has improved, and we now have a better understanding of the pathophysiology and imaging findings associated with CH. Future research is warranted to find new treatment options for individuals suffering from this condition.

Predictors of mortality in children with myelomeningocele and symptomatic Chiari type II malformation

OBJECTIVE Chiari malformation type II (CM-II) in myelomeningocele is associated with a significant rate of mortality and poor outcome. Death is frequently heralded by the onset or progression of neurological symptoms. The authors sought to identify predictors of poor outcome and mortality within the myelomeningocele population at Children's Hospital of Pittsburgh. METHODS A retrospective chart and radiology review was performed on all infants who underwent primary closure of a myelomeningocele defect at Children's Hospital of Pittsburgh between the years of 1995 and 2015. Preoperative symptoms and signs leading to CM-II decompression, as well as operative details and postoperative changes in these symptoms and signs, were investigated in detail and correlated to outcome. Poor outcome was defined as death, stridor, or ventilator dependence. Deceased patients were separately assessed within this subgroup. RESULTS Thirty-two (21%) of 153 patients were found to have symptomatic CM-II. Of the 32 patients meeting inclusion criteria, 12 (38%) had poor outcomes. Eight patients (25%) died since initial presentation; 5 of these patients (16% of the overall cohort) died within the 1st year of life and 3 (9%) died during adolescence. Seven (88%) of the 8 patients who died had central apnea on presentation (p = 0.001) and 7 (44%) of the 16 patients who developed symptoms in the first 3 months of life died, compared with 1 (6.3%) of 16 who developed symptoms later in childhood (p = 0.04). The median Apgar score at 1 minute was 4.5 for patients who died and 8 for surviving patients (p = 0.006). The median diameter of the myelomeningocele defect was 5.75 cm for patients who died and 5 for those who survived (p = 0.01). The anatomical level of defect trended toward higher levels in patients who died, with 4 patients in that group having an anatomical level at L-2 or higher compared with 5 of the surviving patients (p = 0.001). The median initial head circumference for the 5 patients dying in the 1st year of life was 41.5 cm, versus 34 cm for all other patients (p = 0.01). CONCLUSIONS CM-II in spina bifida is associated with a significant mortality rate even when surgical intervention is performed. Death is more frequent in symptomatic patients presenting prior to 1 year of age. Late deaths are associated with symptom progression despite aggressive surgical and medical intervention. In this patient cohort, death was more likely in patients with symptomatic presentation during the first 3 months of life, low Apgar scores, large myelomeningocele defects, early central apnea, and large head circumference at birth.

Sleep in Children with Congenital Malformations of the Central Nervous System

PURPOSE OF REVIEW

Congenital malformations of the central nervous system may be seen in isolation or in association with syndromes that have multiorgan involvement. Among the potential health challenges these children may face, sleep concerns are frequent and may include chronic insomnia, sleep-related breathing disorders, and circadian rhythm disorders.

RECENT FINDINGS

In this review, we describe recent research into sleep disorders affecting children with congenital malformations of the CNS including visual impairment, septo-optic dysplasia, agenesis of the corpus callosum, Aicardi syndrome, Chiari malformation, spina bifida, achondroplasia, Joubert syndrome, fetal alcohol spectrum disorders, and congenital Zika syndrome. In many cases, the sleep disturbance can be directly related to observed anatomical differences in the brain (such as in apnea due to Chiari malformation), but in most syndromes, a complete understanding of the underlying pathophysiology connecting the malformation with sleep problem is still being elucidated. Our review provides a synthesis of available evidence for clinicians who treat this patient population, in whom appropriate diagnosis and management of sleep problems may improve the quality of life for both patient and caregiver.

Orofacial clinical features in Arnold Chiari type I malformation: A case series

Background

Arnold Chiari malformation (ACM) is characterized by an anatomical defect at the base of the skull where the cerebellum and the spinal cord herniate through the foramen magnum into the cervical spinal canal. Among the subtypes of the condition, ACM type I (ACM-I) is particularly outstanding because of the severity of symptoms. This study aimed to analyze the orofacial clinical manifestations of patients with ACM-I, and discuss their demographic distribution and clinical features in light of the literature.

Material and Methods

A case series with patients with ACM-I treated between 2012 and 2015 was described. The sample consisted of patients who were referred by the Department of Neurosurgery to the Oral and Maxillofacial Surgery Service of Hospital da Restauração in Brazil for the assessment of facial symptomatology. A questionnaire was applied to evaluate the presence of painful orofacial findings. Data are reported using descriptive statistical methods.

Results

Mean patient age was 39.3 years and the sample consisted mostly of male patients. A high prevalence of headache (50%) and pain in the neck (66.7%) and masticatory muscles (50%) was found. Only one patient reported difficulty in performing mandibular movements and two reported jaw clicking sounds. Mean mouth opening was 40.83 mm.

Conclusions

ACM-I patients may exhibit orofacial symptoms which may mimic temporomandibular joint disorders. This study brings interesting information that could help clinicians and oral and maxillofacial surgeons to understand this uncommon condition and also help with the diagnosis of patients with similar physical characteristics by referring them to a neurosurgeon.

Key words:Arnold-Chiari malformation, facial pain, diagnosis, orofacial.

Embryology of the craniocervical junction and posterior cranial fossa, part I: Development of the upper vertebrae and skull

Although the embryology of the posterior cranial fossa can have life altering effects on a patient, a comprehensive review on this topic is difficult to find in the peer-reviewed medical literature. Therefore, this review article, using standard search engines, seemed timely. The embryology of the posterior cranial fossa is complex and relies on a unique timing of various neurovascular and bony elements. Derailment of these developmental processes can lead to a wide range of malformations such as the Chiari malformations. Therefore, a good working knowledge of this embryology as outlined in this review of its bony architecture is important for those treating patients with involvement of this region of the cranium. Clin. Anat. 31:466-487, 2018. © 2018 Wiley Periodicals, Inc.

The newer classifications of the chiari malformations with clarifications: An anatomical review

In 1891, Hans Chiari described a group of congenital hindbrain anomalies, which were eventually named after him. He classified these malformations into three types (Chiari malformations I, II, and III), and four years later added the Chiari IV malformation. However, numerous reports across the literature do not seem to fit Chiari's original descriptions of these malformations, so researchers have been encouraged to propose new classifications to encompass these variants (e.g., Chiari 0, Chiari1.5, and Chiari 3.5 malformations). Moreover, there is a continued misunderstanding and misuse of the term "Chiari IV malformation." Therefore, the current review intended to describe anatomical, pathophysiological, and clinical aspects of the newer classifications with clarifications of the Chiari malformations. We reviewed available literature about Chiari malformations and their variants using "PubMed" and "Google Scholar." We also looked into the term Chiari IV, clarifying its original description and citing examples where the term has been used erroneously. References in the reviewed articles were searched manually. Variants of the originally described Chiari malformations are termed Chiari 0, Chiari 1.5, and Chiari 3.5. Each has distinct anatomical characteristics and some of these are extremely rare and incompatible with life (e.g. Chiari 3.5). Chiari IV malformation has been further clarified. Some physicians might be unfamiliar with the newer classifications of Chiari malformations because these conditions are rare or even unique. Furthermore, care is needed in using the term "Chiari IV malformation", which must be consistent with Chiari's original description, i.e. an occipital encephalocele containing supratentorial contents. Clin. Anat. 31:314-322, 2018. © 2018 Wiley Periodicals, Inc.

A prospective study on fetal posterior cranial fossa assessment for early detection of open spina bifida at 11-13 weeks

The objective of this study was to test three measurements: brain stem (BS), intracranial translucency (IT) and brain stem to occipital bone distance (BSOB), as well as one landmark: cisterna magna (CM) visibility, for early diagnosis of open spina bifida (OSB) in a low risk population. A prospective observational study was undertaken in a university hospital. A sample of 1479 women consented to participate between 20 September 2013 and 30 June 2015. Measurements were performed from the mid-sagittal view, as is routinely used for nuchal thickness assessment. CM visibility was assessed qualitatively as the third anechoic band in the posterior cranial fossa (PCF). All pregnancies were screened with a combination of maternal serum alpha-fetoprotein and second trimester anomaly scan and followed until delivery. Predictive values were calculated for each marker. We were able to diagnose two OSB cases and highly suspect one Dandy-Walker malformation case at the first trimester scan by the observation of PCF. PCF characteristics of OSB cases were increased BS diameter, increased BS-BSOB ratio and non-visualization of the CM. All the markers demonstrated high sensitivity and specificity but CM visibility reached the highest positive predictive value. Due to relatively high false positive rates, PCF measurements could not reach a satisfactory performance to validate their clinical use as a single marker. CM visibility has the advantage of being a qualitative marker and reduces the need for sophisticated and time-consuming measurements. Intracranial translucency and BS-BSOB ratio measurements should be used when the CM visibility is absent or in doubt.

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.

Chiari 1 Malformation in a Child with Febrile Seizures, Parasomnias, and Sleep Apnea Syndrome

Introduction

The type I is the most common Chiari malformation in children. In this condition, the lower part of the cerebellum, but not the brain stem, extends into the foramen magnum at the base of the skull leading to disturbances in cerebrospinal fluid circulation and to direct compression of nervous tissue.

Case report

We describe a 4-year-old Caucasian female child with febrile seizures, headache, parasomnias, and a delay of speech. The child underwent a magnetic resonance imaging to investigate these neurological signs, disclosing a Chiari malformation type 1. The polysomnography showed a mild-moderate sleep-disordered breathing, increased number of central sleep apneas, and generalized spike waves at sleep onset.

Conclusions

Seizures have been seldom described in CM1 patients. The main reasons for performing MRI in this case were frequent seizures, a delay of speech, and headache, leading to an unexpected diagnosis of CM1. Polysomnography detected a discrete SDB.

Embryology and pathophysiology of the Chiari I and II malformations: A comprehensive review

Although the Chiari malformations are well-studied and described developmental anomalies, there remains some incongruity in regards to their underlying etiologies. A number of theories have been proposed with the purpose of accounting for the embryology and pathogenesis of the Chiari I and II malformations and their associated complications and clinical syndromes. The present review aims to review the pertinent literature for all of the main theories that have been proposed, and outline their validity and relevance to our contemporary understanding of these anomalies. Clin. Anat. 31:202-215, 2018. © 2017 Wiley Periodicals, Inc.

Machine learning applied to neuroimaging for diagnosis of adult classic Chiari malformation: role of the basion as a key morphometric indicator

OBJECTIVE The current diagnostic criterion for Chiari malformation Type I (CM-I), based on tonsillar herniation (TH), includes a diversity of patients with amygdalar descent that may be caused by a variety of factors. In contrast, patients presenting with an overcrowded posterior cranial fossa, a key characteristic of the disease, may remain misdiagnosed if they have little or no TH. The objective of the present study was to use machine-learning classification methods to identify morphometric measures that help discern patients with classic CM-I to improve diagnosis and treatment and provide insight into the etiology of the disease. METHODS Fifteen morphometric measurements of the posterior cranial fossa were performed on midsagittal T1-weighted MR images obtained in 195 adult patients diagnosed with CM. Seven different machine-learning classification methods were applied to images from 117 patients with classic CM-I and 50 controls matched by age and sex to identify the best classifiers discriminating the 2 cohorts with the minimum number of parameters. These classifiers were then tested using independent CM cohorts representing different entities of the disease. RESULTS Machine learning identified combinations of 2 and 3 morphometric measurements that were able to discern not only classic CM-I (with more than 5 mm TH) but also other entities such as classic CM-I with moderate TH and CM Type 1.5 (CM-1.5), with high accuracy (> 87%) and independent of the TH criterion. In contrast, lower accuracy was obtained in patients with CM Type 0. The distances from the lower aspect of the corpus callosum, pons, and fastigium to the foramen magnum and the basal and Wackenheim angles were identified as the most relevant morphometric traits to differentiate these patients. The stronger significance (p < 0.01) of the correlations with the clivus length, compared with the supraoccipital length, suggests that these 5 relevant traits would be affected more by the relative position of the basion than the opisthion. CONCLUSIONS Tonsillar herniation as a unique criterion is insufficient for radiographic diagnosis of CM-I, which can be improved by considering the basion position. The position of the basion was altered in different entities of CM, including classic CM-I, classic CM-I with moderate TH, and CM-1.5. The authors propose a predictive model based on 3 parameters, all related to the basion location, to discern classic CM-I with 90% accuracy and suggest considering the anterior alterations in the evaluation of surgical procedures and outcomes.

Post-mortem magnetic resonance (PMMR) imaging of the brain in fetuses and children with histopathological correlation

Post-mortem magnetic resonance (PMMR) imaging is rapidly emerging as an alternative, "less invasive", and more widely accepted investigative approach for perinatal deaths in the UK. PMMR has a high diagnostic accuracy for congenital and acquired fetal neuropathological anomalies compared to conventional autopsy, and is particularly useful when autopsy is non-diagnostic. The main objectives of this review are to describe and illustrate the range of common normal and abnormal central nervous system (CNS) findings encountered during PMMR investigation. This article covers the standard PMMR sequences used at our institution, normal physiological post-mortem findings, and a range of abnormal developmental and acquired conditions. The abnormal findings include diseases ranging from neural tube defects, posterior fossa malformations, those of forebrain and commissural development as well as neoplastic, haemorrhagic, and infectious aetiologies. Neuropathological findings at conventional autopsy accompany many of the conditions we describe, allowing readers to better understand the underlying disease processes and imaging appearances.

Radiological evolution of peri-odontoid pannus in a patient with Chiari I malformation: a case-based review

INTRODUCTION

The Chiari I malformation (CIM) is commonly encountered by neurosurgeons and can have different etiologies and clinical presentations.

CASE REPORT

We report a CIM patient who presented with symptoms of ventral brain stem compression and was found to have a large peri-odontoid pannus. Posterior fossa decompression was performed with a planned second-stage odontoidectomy. However, at the 6-month follow-up, postoperative images demonstrated a mostly resolved pannus and improvement of the brain stem compression symptoms, and the patient progressed uneventfully without the need for odontoidectomy.

CONCLUSIONS

This case illustrates the resolution of a significant and symptomatic peri-odontoid pannus in a patient with CIM without craniocervical fusion or odontoidectomy. Such a case indicates that not all peri-odontoid pannus formations in CIM patients are due to hypermobility at the craniocervical junction.

Otto Mennicke (1876-) and the first description of skull base anomalies causing cerebellar tonsillar ectopia: one of the first mentions of the Chiari I malformation

INTRODUCTION

Although Hans Chiari made significant and meaningful contributions to our understanding and classification of hindbrain herniations, others have also contributed to this knowledge. One figure who has been lost to history is Otto Mennicke. Herein, we discuss his role in our understanding of tonsillar ectopia and his life and connection to Hans Chiari.

CONCLUSIONS

Our knowledge of what is now known as the Chiari malformations has been shaped by several clinicians including Otto Mennicke.

Evaluation of the central sleep apnea in asymptomatic children with Chiari 1 malformation: an open question

INTRODUCTION

Type I is the most common Chiari malformation in children. In this condition, the lower part of the cerebellum, but not the brain stem, extends into the foramen magnum at the base of the skull leading to intermittent brain hypertension. In symptomatic children, central sleep apneas are shown in polysomnography evaluation. A central apnea index of 1/h or more is considered abnormal, but >5/h is clearly considered pathological. Therefore, central sleep apnea evaluation in pediatric age may show great age-related variability.

METHOD AND SUBJECTS

We present three patients who were assessed by polysomnography with two different scores for central sleep apneas published in the literature: the method by Scholle (2011) and the American Academy of Sleep Medicine scoring system (2012).

CONCLUSIONS

We speculated that the Scholle scoring system can be more helpful in assessing children with asymptomatic Chiari 1 malformation for a closer follow-up. More studies are needed.

Development of profound Chiari I malformation and cerebellar tissue loss and resolution following shunting of posterior fossa extra-axial cyst. Case report

INTRODUCTION

Chiari I malformation can be due to a multitude of etiologies such as craniosynostosis or hydrocephalus. A posterior fossa extra-axial cyst (PFEAC) appears to be an extremely rare cause of this form of hindbrain herniation.

CASE REPORT

Herein, we report a case of PFEAC that presented with no Chiari I malformation and then presented months later with a significant Chiari I malformation. Following shunt placement of a PFEAC, striking reversal of the Chiari malformation as well as reconstitution of the cerebellum was noted.

CONCLUSIONS

Patients with PFEAC might develop a Chiari I malformation and this might be treated with shunting of the PFEAC alone.

Historical Perspective of Split Cord Malformations: A Tale of Two Cords

INTRODUCTION

Our appreciation and understanding of what is now known as the split cord malformation (SCM) have a long history. The oldest known example of SCM is from roughly AD 100. Other isolated examples can be found in the large body of work of the pathologists of the 1800s, where the SCMs were found incidentally during autopsies.

CONCLUSIONS

SCM has a rich history and has intrigued physicians for over 200 years. Many well-known figures from the past such as Chiari and von Recklinghausen, both pathologists, made early postmortem descriptions of SCM. With the advent of MRI, these pathological embryological derailments can now often be detected and appreciated early and during life. Our understanding and ability to treat these congenital malformations as well as the terminology used to describe them have changed over the last several decades.

Comparison of posterior fossa decompression with and without duraplasty for the surgical treatment of Chiari malformation type I in adult patients: A retrospective analysis of 103 patients

Chiari malformation type I (CM-I) is a congenital neurosurgical disease about the herniation of cerebellar tonsil through the foramen magnum. A variety of surgical techniques for CM-I have been used, and there is a controversy whether to use posterior fossa decompression with duraplasty (PFDD) or posterior fossa decompression without duraplasty (PFD) in CM-I patients. Here, we compared the clinical results and effectiveness of PFDD and PFD in adult patients with CM-I. The cases of 103 adult CM-I patients who underwent posterior fossa decompression with or without duraplasty from 2008 to 2014 were reviewed retrospectively. Patients were divided into 2 groups according to the surgical techniques: PFDD group (n = 70) and PFD group (n = 33). We compared the demographics, preoperative symptoms, radiographic characteristics, postoperative complications, and clinical outcomes between the PFD and PFDD patients. No statistically significant differences were found between the PFDD and PFD groups with regard to demographics, preoperative symptoms, radiographic characteristics, and clinical outcomes(P > 0.05); however, the postoperative complication aseptic meningitis occurred more frequently in the PFDD group than in the PFD group (P = 0.027). We also performed a literature review about the PFDD and PFD and made a summary of these preview studies. Our study suggests that both PFDD and PFD could achieve similar clinical outcomes for adult CM-I patients. The choice of surgical procedure should be based on the patient's condition. PFDD may lead to a higher complication rate and autologous grafts seemed to perform better than nonautologous grafts for duraplasty.

The Chiari 3.5 malformation: a review of the only reported case

INTRODUCTION

In 1894, Giuseppe Muscatello described what we believe to be the only case of an occipitocervical encephalocele with a communication to the stomach. This case and its history and context compared to the Chiari 3 malformation as described 3 years earlier by Hans Chiari are presented.

CONCLUSIONS

Based on the uniqueness of this case, we propose the term Chiari 3.5 malformation be used to describe its anatomical derailment.

Thirty-day outcomes for posterior fossa decompression in children with Chiari type 1 malformation from the US NSQIP-Pediatric database

PURPOSE

The multicenter National Surgical Quality Improvement Program-Pediatric (NSQIP-P) database maintained by the American College of Surgeons was used to describe 30-day outcomes following Chiari type 1 decompression in children and to identify risk factors for readmission, reoperation, and perioperative complications.

METHODS

We identified patients aged 0-18 years who underwent posterior cranial fossa decompression for Chiari type 1 malformation in 2012, 2013, and 2014 in the NSQIP-Pediatric database. Multivariate regression analysis was performed using preoperative and perioperative data to determine risk factors for perioperative adverse events within 30 days of the index procedure.

RESULTS

We identified 1459 patients from the NSQIP-P database for the years 2012-2014. Fifty-five percent of the patients were female. Mean age was 9.8 years (median 10 years). Median operative time was 141 min (IQR 107-181 min). Postoperative complications were noted in 5.3 % and unplanned reoperations in 3.4 % of the patients. Postoperative ventriculoperitoneal shunt placement occurred in 0.9 % of the patients. Wound problems were the most common complication (3.8 % of all patients). Univariate analysis showed the following factors were associated with perioperative adverse events: longer operative times, hospital stay ≥5 days, hydrocephalus, and neurological, renal, and congenital comorbidities. On multivariate analysis, female sex (OR 1.46, 95 % CI 1.01-2.11), increased operative time (OR 1.01, 95 % CI 1.00-1.01), and hospital stay ≥5 days (OR 2.62, 95 % CI 1.55-4.43) were independent factors associated with perioperative adverse events.

CONCLUSION

The NSQIP-P database was used to describe surgical outcomes of posterior cranial fossa decompression in a US nationwide sample of 1459 children with Chiari type 1 malformation. The overall recorded adverse rate was low. Longer operative times and length of hospital stay ≥5 days during the index admission were associated with perioperative adverse events.

Sagittal MRI often overestimates the degree of cerebellar tonsillar ectopia: a potential for misdiagnosis of the Chiari I malformation

BACKGROUND

We hypothesized that by using coronal MRI, Chiari I malformation could be more precisely diagnosed, would provide simple anatomic landmarks, would provide information regarding asymmetry of hindbrain herniation, and would be a better method for analyzing the tonsillar herniation postoperatively when the opisthion has been removed.

METHODS

Fifty consecutive pediatric patients diagnosed with Chiari I malformation had comparison between the measurements of their caudally descended cerebellar tonsils on midsagittal and coronal MRI images.

RESULTS

On MRI coronal imaging, tonsillar asymmetry was found in 48 patients. Maximal left tonsillar descent was 20.9 mm, and maximal right tonsillar descent was 17.4 mm. On MRI sagittal imaging, tonsillar descent ranged from 5 to 27.4 mm. Fifty-eight % of patients had syringomyelia. Five patients (10 %) on coronal MRI were found to have both cerebellar tonsils that were less than 3 mm below the foramen magnum. However, all of these patients had greater than 3 mm of tonsillar ectopia on sagittal imaging. Nineteen patients (38 %) on coronal MRI were found to have one of the cerebellar tonsils that were less than 3 mm below the foramen magnum. Similarly, each of these had greater than 3 mm of tonsillar ecotpia as measured on midsagittal MRI. Also, based on these findings, Chiari I malformation is almost always an asymmetrical tonsillar ectopia.

CONCLUSIONS

Sagittal MRI overestimates the degree of tonsillar ectopia in patients with Chiari I malformation. Misdiagnosis may occur if sagittal imaging alone is used. The cerebellar tonsils are paramedian structures, and this should be kept in mind when interpreting midline sagittal MRI.

Arterial variations around the atlas: a comprehensive review for avoiding neurosurgical complications

INTRODUCTION

Neurosurgical approaches often involve the atlas. Therefore, the arterial relationships and anatomical variations are of paramount importance to the neurosurgeon.

METHODS

Using standard search engines, a literature review of arterial variants near the first cervical vertebra was performed.

CONCLUSIONS

Arterial variations around the atlas are surgically significant. Awareness of their existence and course may provide better pre-operative planning and surgical intervention, potentially leading to better clinical outcomes. Three-dimensional computed tomography angiography (3D CTA) is an important tool for identifying and diagnosing such abnormalities and should be used when such vascular anomalies are suspected.

Tonsillar contusion associated with benign tonsillar ectopia following minor head trauma

PURPOSE

The relationship between tonsil position and symptomatic cerebellar contusion is unclear. To date, there are no reports of symptomatic traumatic brain injury associated with benign tonsillar ectopia. Reported cases are limited to prominent cerebellar tonsillar displacement by ≥5 mm (i.e., Chiari malformations).

METHODS

The authors describe a case of symptomatic concussion in a toddler with unusual computerized tomography (CT) presentation and incidental finding of benign tonsillar ectopia, hemorrhagic contusion of the tonsils, blood-brain barrier (BBB) disruption and delayed atrophy shown using magnetic resonance imaging (MRI) studies. The radiological presentation and the clinical challenges are discussed through a review of the literature.

CONCLUSION

This case suggests that damage to cerebellar structures is not limited only to overt tonsillar herniation. Benign tonsillar ectopia may predispose to cerebellar contusion even after minor concussion and thus has a clinical significance. The current paradigm viewing only noticeable tonsillar herniation as a risk factor for hindbrain injury should be revisited.

Do the cerebellar tonsils move during flexion and extension of the neck in patients with Chiari I malformation? A radiological study with clinical implications

BACKGROUND

In the past, diagnosis of the Chiari I malformation has primarily been made on midsagittal MRI. We hypothesized that based on the frequent presentation of opisthotonos in patients with hindbrain hernia (primarily Chiari II malformation but sometimes Chiari I malformation) that the hyperextension might be a compensatory technique used by such patients to bring the cerebellar tonsils up out of the cervical spine.

PATIENTS AND METHODS

This prospective study reviewed imaging of patients with Chiari I malformation who underwent flexion/extension MRI for evaluation of their hindbrain herniation. Age-matched controls were used for comparison.

RESULTS

In general, there was elevation of the cerebellar tonsils with extension and increased descent with flexion of the cervical spine. In 72 % of patients, flexion of the neck resulted in descent of the cerebellar tonsils. In 64 % of patients, extension of the neck resulted in ascent of the cerebellar tonsils. In the 14 patients with an associated syrinx, 71 % were found to have caudal movement of the cerebellar tonsils with neck flexion, and only 43 % were observed to have any movement of the cerebellar tonsils in neck extension compared to patients without a syrinx where ascent of the tonsils was seen in only nine during neck extension. Two patients were observed to have the reverse finding of ascent of the cerebellar tonsils with neck flexion and descent of the cerebellar tonsils with neck extension. Five patients had no movement of the cerebellar tonsils in either flexion or extension of the neck, and one of these had a small syrinx.

CONCLUSIONS

Although minimal and not in all patients, we observed elevation of the herniated cerebellar tonsils with extension of the cervical spine in patients with Chiari I malformation. This finding provides evidence as to why some patients with hindbrain herniation present with opisthotonos and supports earlier findings that CSF flow is reduced at the craniocervical junction in flexion in patients with Chiari I malformation.

Histological study of the occipital bone from patients with Chiari I malformation

BACKGROUND

This study is focused on the histologic characteristics of occipital bone removed during Chiari I decompression in the hope of discovering unique features that may be related to the pathogenesis of this condition.

METHODS

Ten consecutive pediatric patients with Chiari I malformation underwent standard posterior fossa decompression surgery. Bone that was removed from the posterior fossa was sent for histological examination. Bone from age-matched controls also underwent histological analysis.

RESULTS

For all study and control specimens, bony samples were found to be made up of dense lamellar bone without marrow elements. In all aspects, histologically, the bone tissue had a normal appearance compared to control samples.

CONCLUSIONS

Although many authors have mentioned that the occipital bone in patients with Chiari I malformation is abnormal on imaging or at operation (e.g., thinned, thickened), based on our study, there is no histological difference between the occipital bone removed at operation and controls.