Diffusion Tensor Imaging Connectomics Reveals Preoperative Neural Connectivity Changes in Children with Postsurgical Posterior Fossa Syndrome

Neuroimaging of postoperative pediatric cerebellar mutism syndrome: a systematic review

Background

Postoperative pediatric cerebellar mutism syndrome (ppCMS) poses serious morbidity after posterior fossa tumor surgery. Neuroimaging studies aim to understand its pathophysiology, yet these vary in methodology and outcome measures. Therefore, we systematically reviewed the current literature to evaluate the evidence for differences in neuroimaging features between children with and without ppCMS.

Methods

Following PRISMA guidelines, a systematic review was conducted by searching for original articles on neuroimaging in children undergoing posterior fossa tumor surgery, comparing patients with and without ppCMS. Articles were selected based on predefined eligibility criteria. Data were systematically extracted, and risk of bias was evaluated.

Results

From the 866 articles identified, 50 studies fulfilled the inclusion criteria. Studies were categorized into 3 imaging domains: structural, diffusion, and functional imaging. Risk of bias assessment revealed a medium risk in most articles, predominantly due to unclear ppCMS definition and qualitative image analysis without blinding for ppCMS diagnosis. Preoperative structural imaging showed the association of ppCMS with midline tumor localization and involvement of the brainstem, superior cerebellar peduncle (SCP), or middle cerebellar peduncle. Postoperative structural and diffusion imaging highlighted SCP injury with reduced white matter integrity, while functional imaging demonstrated hypoperfusion in frontal lobes. Late follow-up showed T2-weighted hyperintensities in the inferior olivary nuclei of ppCMS patients.

Conclusion

Neuroimaging features suggest that ppCMS is associated with efferent cerebellar pathway injury and hypoperfusion in frontal lobes, with level 2 a/b evidence. Large-scale prospective longitudinal neuroimaging studies comparing pre- and postoperative imaging are needed to further elucidate the pathophysiological mechanism of ppCMS.

Advances in Imaging Modalities for Pediatric Brain and Spinal Cord Tumors

BACKGROUND

Neuroimaging has evolved from anatomical imaging toward a multi-modality comprehensive anatomical and functional imaging in the past decades, important functional data like perfusion-weighted imaging, permeability imaging, diffusion-weighted imaging (DWI), and diffusion tensor imaging (DTI), tractography, metabolic imaging, connectomics, event-related functional imaging, resting state functional imaging, and much more is now being offered.

SUMMARY

Precision diagnostics has proven to be essential for precision treatment. Many minimal invasive techniques have been developed, taking advantage of digital subtraction angiography and interventional neuroradiology. Furthermore, intraoperative CT and/or MRI and more recently MR-guided focused ultrasound have complemented the diagnostic and therapeutic armamentarium.

KEY MESSAGES

In the current manuscript, we discuss standard imaging sequences including advanced techniques like DWI, DTI, susceptibility-weighted imaging, and 1H magnetic resonance spectroscopy, various perfusion weighted imaging approaches including arterial spin labeling, dynamic contrast enhanced imaging, and dynamic susceptibility contrast imaging. Pre-, intra, and postoperative surgical imaging including visualize imaging will be discussed. The value of connectomics will be presented for its value in neuro-oncology. Minimal invasive therapeutic possibilities of interventional neuroradiology and image-guided laser ablation and MR-guided high-intensity-focused ultrasound will be presented for treatment of pediatric brain and spinal cord tumors. Finally, a comprehensive review of spinal cord tumors and matching neuropathology has been included.

Cerebellar Mutism Syndrome in Pediatric Neuro-oncology: A Multidisciplinary Perspective and Call for Research Priorities

Cerebellar mutism syndrome (CMS), also known as posterior fossa syndrome, occurs in a subset of children after posterior fossa tumor resection, most commonly medulloblastoma. Patients with this syndrome exhibit often transient, although protracted, symptoms of language impairment, emotional lability, cerebellar, and brainstem dysfunction. However, many patients experience persistent neurological deficits and lasting neurocognitive impairment. Historically, research and clinical care were hindered by inconsistent nomenclature, poorly defined diagnostic criteria, and uncertainty surrounding risk factors and etiology. Proposed diagnostic criteria include two major symptoms, language impairment and emotional lability, as proposed by the international Board of the Posterior Fossa Society in their consensus statement as well as other experts in this field. Risk factors most commonly associated with development of CMS include midline tumor location, diagnosis of medulloblastoma and specific tumor subtype, younger age at diagnosis, and preoperative language impairment. A proposed etiology of CMS includes disruption of the cerebellar outflow tracts, the cerebellar nuclei, and their efferent projections through the superior cerebellar peduncle. Treatment for CMS remains supportive. Herein, we present a comprehensive overview of CMS etiology, diagnosis, risk factors, clinical presentation, and clinical management. In addition, we identify essential multidisciplinary research priorities to advance diagnostics, prevention, and intervention efforts for patients with, or at risk for, development of CMS.

Risk factors for postoperative cerebellar mutism syndrome in pediatric patients: a systematic review and meta-analysis

OBJECTIVE

A review article assessing all the risk factors reported in the literature for postoperative cerebellar mutism syndrome (pCMS) among children remains absent. The authors sought to perform a systematic review and meta-analysis to evaluate this issue.

METHODS

PubMed, Embase, and Web of Science were queried to systematically extract potential references. The articles relating to pCMS were required to be written in the English language, involve pediatric patients (≤ 18 years of age), and provide extractable data, which included a comparison group of patients who did not develop pCMS. The quality of the included studies was evaluated using the Newcastle-Ottawa Scale. Data were pooled using RevMan 5.4, and publication bias was assessed by visual inspection for funnel plot asymmetry. The study protocol was registered through PROSPERO (ID: CRD42021256177).

RESULTS

Overall, 28 studies involving 2276 patients were included. Statistically significant risk factors identified from univariate analysis were brainstem invasion (OR 4.28, 95% CI 2.23-8.23; p < 0.0001), fourth ventricle invasion (OR 12.84, 95% CI 4.29-38.44; p < 0.00001), superior cerebellar peduncle invasion (OR 6.77, 95% CI 2.35-19.48; p = 0.0004), diagnosis of medulloblastoma (OR 3.26, 95% CI 1.93-5.52; p < 0.0001), medulloblastoma > 50 mm (OR 8.85, 95% CI 1.30-60.16; p = 0.03), left-handedness (OR 6.57, 95% CI 1.25-34.44; p = 0.03), and a vermis incision (OR 5.44, 95% CI 2.09-14.16; p = 0.0005). On the other hand, a tumor located in the cerebellar hemisphere (OR 0.23, 95% CI 0.06-0.92; p = 0.04), cerebellar hemisphere compression (OR 0.23, 95% CI 0.11-0.45; p < 0.0001), and intraoperative imaging (OR 0.36, 95% CI 0.18-0.72; p = 0.004) reduced the risk of pCMS.

CONCLUSIONS

This study provides the largest and most reliable review of risk factors associated with pCMS. Although some risk factors may be dependent on one another, the data may be used by surgeons to better identify patients at risk for pCMS and for intervention planning.

Networking of the Human Cerebellum: From Anatomo-Functional Development to Neurosurgical Implications

In the past, the cerebellum was considered to be substantially involved in sensory-motor coordination. However, a growing number of neuroanatomical, neuroimaging, clinical and lesion studies have now provided converging evidence on the implication of the cerebellum in a variety of cognitive, affective, social, and behavioral processes as well. These findings suggest a complex anatomo-functional organization of the cerebellum, involving a dense network of cortical territories and reciprocal connections with many supra-tentorial association areas. The final architecture of cerebellar networks results from a complex, highly protracted, and continuous development from childhood to adulthood, leading to integration between short-distance connections and long-range extra-cerebellar circuits. In this review, we summarize the current evidence on the anatomo-functional organization of the cerebellar connectome. We will focus on the maturation process of afferent and efferent neuronal circuitry, and the involvement of these networks in different aspects of neurocognitive processing. The final section will be devoted to identifying possible implications of this knowledge in neurosurgical practice, especially in the case of posterior fossa tumor resection, and to discuss reliable strategies to improve the quality of approaches while reducing postsurgical morbidity.

Pre-operative imaging and post-operative appearance of standard paediatric neurosurgical approaches: a training guide for neuroradiologists

A short-cut narrative review was conducted according to the SANRA guidelines to identify studies describing normal and abnormal postoperative radiological features of the most common paediatric neurosurgical procedures. Rather than focusing on the original pathology addressed by neurosurgical means, this review explored three main areas of operative neurosurgery: ventricular access, supratentorial & infratentorial craniotomies, and posterior fossa/craniocervical junction decompression. A total of twenty-three landmark papers were included for review based on their relevance to address the research question and serve as a practical guide for paediatric neuroradiology trainees and fellows. Accurate in text referencing of the ClinicalTrials.gov identifier, and weblink, has also been provided for all trials discussed in the results section. All the above is complemented by relevant iconography meant to describe a wide range of postoperative changes and early complications. Finally, the review is enriched by a discussion touching upon haemostatic agents, intentionally retained foreign bodies and the future of machine learning for neuroradiology reporting. Overall, the information presented in a systematic fashion will not only help trainees and fellows to deepen these topics and expand their knowledge in preparation for written and oral boards, but will also represent a useful resource for everyone including trained neuroradiologists and neurosurgeons themselves.