Neuroanatomic Correlates for the Neuropsychological Manifestations of Chiari Malformation Type I

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.

Cognition in Chiari Malformation Type I: an Update of a Systematic Review

Chiari malformation has been classified as a group of posterior cranial fossa disorders characterized by hindbrain herniation. Chiari malformation type I (CM-I) is the most common subtype, ranging from asymptomatic patients to those with severe disorders. Research about clinical manifestations or medical treatments is still growing, but cognitive functioning has been less explored. The aim of this systematic review is to update the literature search about cognitive deficits in CM-I patients. A literature search was performed through the following electronic databases: MEDLINE, PsychINFO, Pubmed, Cochrane Library, Scopus, and Web of Science. The date last searched was February 1, 2023. The inclusion criteria were as follows: (a) include pediatric or adult participants with a CM-I diagnosis, (b) include cognitive or neuropsychological assessment with standardized tests, (c) be published in English or Spanish, and (d) be empirical studies. Articles that did not report empirical data, textbooks and conference abstracts were excluded. After the screening, twenty-eight articles were included in this systematic review. From those, twenty-one articles were focused on adult samples and seven included pediatric patients. There is a great heterogeneity in the recruited samples, followed methodology and administered neurocognitive protocols. Cognitive functioning appears to be affected in CM-I patients, at least some aspects of attention, executive functions, visuospatial abilities, episodic memory, or processing speed. However, these results require careful interpretation due to the methodological limitations of the studies. Although it is difficult to draw a clear profile of cognitive deficits related to CM-I, the literature suggests that cognitive dysfunction may be a symptom of CM-I. This suggest that clinicians should include cognitive assessment in their diagnostic procedures used for CM-I. In summary, further research is needed to determine a well-defined cognitive profile related to CM-I, favoring a multidisciplinary approach of this disorder.

Cognitive and Psychological Functioning in Chiari Malformation Type I Before and After Surgical Decompression - A Prospective Cohort Study

BACKGROUND

Chiari Malformation Type I (CM-I) is defined as cerebellar tonsil displacement more than 5 mm below the foramen magnum. This displacement can alter cerebrospinal fluid flow at the cervicomedullary junction resulting in Valsalva-induced headaches and syringomyelia and compress the brainstem resulting in bulbar symptoms. However, little is known about cognitive and psychological changes in CM-I.

OBJECTIVE

To prospectively assess cognitive and psychological performance in CM-I and determine whether changes occur after surgical decompression.

METHODS

Blinded evaluators assessed symptomatic CM-I patients ages ≥18 with a battery of neuropsychological and psychological tests. Testing was conducted preoperatively and 6 to 18 mo postoperatively. Data were converted to Z-scores based on normative data, and t-tests were used to analyze pre-post changes.

RESULTS

A total of 26 patients were included, with 19 completing both pre- and post-op cognitive assessments. All patients had resolution of Valsalva-induced headaches and there was improvement in swallowing dysfunction (P < .0001), ataxia (P = .008), and sleep apnea (P = .021). Baseline performances in visual perception and construction (z = -1.11, P = .001) and visuospatial memory (z = -0.93, P = .002) were below average. Pre-post comparisons showed that CM-I patients had stable cognitive and psychological functioning after surgery, without significant changes from preoperative levels.

CONCLUSION

CM-I patients had below average performance in visuospatial and visuoconstructional abilities preoperatively. Prospective longitudinal data following surgery demonstrated improved neurologic status without any decline in cognition or psychological functioning. Routine pre- and postoperative formal neuropsychological assessment in CM-I patients help quantify cognitive and behavioral changes associated with surgical decompression.

Ventral Tonsillar Herniation Predicts Headaches in Adults With Chiari Malformation

BACKGROUND

Radiographic characterization of Chiari malformation (CM) has historically focused on caudal tonsillar herniation (CH) below the foramen magnum. Previously, we published evidence linking ventral tonsillar herniation (VH) and medullary symptoms in very young children. We sought to extend that investigation by studying the radiographic and clinical significance of VH in adults diagnosed with CM.

METHODS

We retrospectively reviewed adults with cerebellar ectopia who underwent posterior fossa decompression with or without duraplasty (PFD/D) at our institution. VH was defined as tonsils crossing a line bisecting the caudal medulla at the level of the foramen magnum on axial MRI. Degree of VH was measured as distance between this bisecting line and the ventral tip of the herniated tonsil. Dorsal brainstem compression was qualitatively determined by assessing for obliteration of CSF space between the dorsal brainstem and the tonsils.

RESULTS

Out of 89 cases reviewed, 54 had some degree of VH. Compared with those without VH, the VH group was significantly older in age and more likely to also present with dorsal brainstem compression and headaches. No correlation was observed between degrees of CH and VH in the VH group. The degree of VH significantly decreased 3 months after PFD/D.

CONCLUSIONS

VH is relatively common in CM patients and might be an important independent radiographic metric to evaluate and consider as part of the decision-making process, especially in those presenting with Chiari-like symptomatology referable to the medulla but who do not meet the traditional criteria of cerebellar ectopia greater than 5 mm.

Cerebellar-Subcortical-Cortical Systems as Modulators of Cognitive Functions

Over the past few decades, research has established that the cerebellum is involved in executive functions; however, its specific role remains unclear. There are numerous theories of cerebellar function and numerous cognitive processes falling under the umbrella of executive function, making investigations of the cerebellum's role in executive functioning challenging. In this review, we explored the role of the cerebellum in executive functioning through clinical and cognitive neuroscience frameworks. We reviewed the neuroanatomical systems and theoretical models of cerebellar functions and the multifaceted nature of executive functions. Using attention deficit hyperactivity disorder and cerebellar tumor as clinical developmental models of cerebellar dysfunction, and the functional magnetic resonance imaging literature, we reviewed evidence for cerebellar involvement in specific components of executive function in childhood, adolescence, and adulthood. There is evidence for posterior cerebellar contributions to working memory, planning, inhibition, and flexibility, but the heterogeneous literature that largely was not designed to study the cerebellum makes it difficult to determine specific functions of the cerebellum or cerebellar regions. In addition, while it is clear that cerebellar insult in childhood affects executive function performance later in life, more work is needed to elucidate the mechanisms by which executive dysfunction occurs and its developmental course. The limitations of the current literature are discussed and potential directions for future research are provided.

Revision Chiari Surgery in Young Children: Predictors and Outcomes

INTRODUCTION

Children aged 0-6 years with Chiari malformation (CM) often present with atypical symptoms and require revision surgery more often than older children. We studied characteristics and outcomes of CM patients in this age-group who underwent one or more revision surgeries to assess how often revision surgery is necessary and successful in this age-group.

METHODS

We retrospectively reviewed patients who were diagnosed with CM 1 or CM 1.5 and surgically treated with posterior fossa decompression (PFD) with or without duraplasty before their 7th birthday. Basic demographics, preoperative presentation, operative details, and postoperative outcomes were analyzed.

RESULTS

Forty patients (mean age 3.2 ± 1.7 years, 35% female) were reviewed. The most common presenting symptoms were headache, dysphagia, and respiratory problems. Eight patients required one or more revision surgeries 11.6 ± 7.6 months on average after their initial surgery. Comparing the revision and no revision groups, dysautonomia was significantly more common prior to initial surgery in the children requiring revision (37.5 vs. 3.1%, p = 0.02). The revision group also trended toward more dysphagia (75.0 vs. 46.9%, p = 0.24) and respiratory problems (75.0 vs. 40.6%, p = 0.12). The most frequent reasons for reoperation were symptom recurrence (6/8), residual posterior fossa compression (3/8), significant scar tissue formation (2/8), ventral brainstem compression (1/8), and suspected craniocervical instability (1/8). Of the 8 children undergoing reoperation, surgery achieved symptom resolution or improvement in 5, while 3 had unchanged symptoms. Two patients underwent a third surgery, after which 1 showed improvement and the other did not. This last patient showed short-term improvement after a fourth surgery but had symptom recurrence 12 months later.

DISCUSSION/CONCLUSION

Oropharyngeal and respiratory problems are particularly common in children aged 0-6 years with CM. Presentation with dysautonomia or other signs of brainstem compression will often predict an additional surgery will be needed after an initial PFD. Symptom recurrence is the most frequent reason for reoperation, and revision surgeries lead to improved clinical outcomes in the majority but not all of these young patients. Surgery in very young children is successful, but reoperation should be integrated into an up-front discussion algorithm particularly in children with severe symptoms.