Functional Imaging and the Cerebellum: Recent Developments and Challenges. Editorial

The Understanding of Pediatric Akinetic Mutism

Pediatric akinetic mutism syndrome is a clinical disease resulting from cerebellar injury and characterized by the absence of speech or reduced speech, emotional lability, there may also be hypotonia, oropharyngeal dysfunction/dysphagia, bladder and intestinal incontinence, or other behavioral disorders and neurological signals. It is described as the most recurrent complication in children, after posterior fossa tumor surgery, mainly related to cerebellar midline injuries. An increasing number of research and prospective reviews have provided valuable information on cerebellar mutism syndrome in recent years. The purpose of this review was to elucidate the pathophysiological basis and the predictive factors for this syndrome. Most cases of mutism are due to injury cerebellar tracts and cerebellar-cerebral circuits, involving particularly distinct points of the dentate-thalamus-cortical and dentato-rubro-thalamus-cortical. Advanced neuroimaging techniques, such as tractography and perfusion studies, have contributed to demonstrating changes in these pathways in patients with pediatric cerebellar mutism.

The role of cerebellum in the child neuropsychological functioning

This chapter proposes a review of neuropsychologic and behavior findings in pediatric pathologies of the cerebellum, including cerebellar malformations, pediatric ataxias, cerebellar tumors, and other acquired cerebellar injuries during childhood. The chapter also contains reviews of the cerebellar mutism/posterior fossa syndrome, reported cognitive associations with the development of the cerebellum in typically developing children and subjects born preterm, and the role of the cerebellum in neurodevelopmental disorders such as autism spectrum disorders and developmental dyslexia. Cognitive findings in pediatric cerebellar disorders are considered in the context of known cerebellocerebral connections, internal cellular organization of the cerebellum, the idea of a universal cerebellar transform and computational internal models, and the role of the cerebellum in specific cognitive and motor functions, such as working memory, language, timing, or control of eye movements. The chapter closes with a discussion of the strengths and weaknesses of the cognitive affective syndrome as it has been described in children and some conclusions and perspectives.

Cerebellar mutism

Mutism of cerebellar origin is a well-described clinical entity that complicates operations for posterior fossa tumors, especially in children. This review focuses on the current understanding of principal pathophysiological aspects and risk factors, epidemiology, clinical characteristics, treatment strategies, and outcome considerations. The PubMed database was searched using the term cerebellar mutism and relevant definitions to identify publications in the English-language literature. Pertinent publications were selected from the reference lists of the previously identified articles. Over the last few years an increasing number of prospective studies and reviews have provided valuable information regarding the cerebellar mutism syndrome. Importantly, the clarification of principal terminology that surrounds the wide clinical spectrum of the syndrome results in more focused research and more effective identification of this entity. In children who undergo surgery for medulloblastoma the incidence of cerebellar mutism syndrome was reported to be 24%, and significant risk factors so far are brainstem involvement and midline location of the tumor. The dentate-thalamo-cortical tracts and lesions that affect their integrity are considered significant pathophysiological issues, especially the tract that originates in the right cerebellar hemisphere. Moderate and severe forms of the cerebellar mutism syndrome are the most frequent types during the initial presentation, and the overall neurocognitive outcome is not as favorable as thought in the earlier publications. Advanced neuroimaging techniques could contribute to identification of high-risk patients preoperatively and allow for more effective surgical planning that should focus on maximal tumor resection with minimal risk to important neural structures. Properly designed multicenter trials are needed to provide stronger evidence regarding effective prevention of cerebellar mutism and the best therapeutic approaches for such patients with a combination of pharmacological agents and multidisciplinary speech and behavior augmentation.

Overlapping and parallel cerebello-cerebral networks contributing to sensorimotor control: an intrinsic functional connectivity study

In concert with sensorimotor control areas of the cerebrum, the cerebellum shows differential activation patterns during a variety of sensorimotor-related tasks. However, the spatial details and extent of the complex and heterogeneous cerebello-cerebral systems involved in action control remain uncertain. In this study, we use intrinsic functional connectivity (iFC) to examine cerebello-cerebral networks of five cerebellar lobules (I-IV, V, VI, and VIIIa/b) that have been empirically identified to form the functional basis of sensorimotor processes. A refined cerebellar seed-region selection allowed us to identify a network of primary sensorimotor and supplementary motor areas (I-V), a network of prefrontal, premotor, occipito-temporal and inferior-parietal regions (VI), and two largely overlapping networks involving premotor and superior parietal regions, the temporo-parietal junction as well as occipito-temporal regions (VIIIa/b). All networks involved the medial prefrontal/cingulate cortex. These cerebral clusters were used in a partial correlation analysis to systematically map cerebral connectivity throughout the entire cerebellum. We discuss these findings in the framework of affective and cognitive control, sensorimotor, multisensory systems, and executive/language systems. Within the cerebellum we found that cerebro-cerebellar systems seem to run in parallel, as indicated by distinct sublobular functional topography of prefrontal, parietal, sensorimotor, cingulate, and occipito-temporal regions. However, all areas showed overlapping connectivity to various degrees in both hemispheres. The results of both analyses demonstrate that different sublobular parts of the cerebellar lobules may dominate in different aspects of primary or higher-order sensorimotor processing. This systems-level cerebellar organization provides a more detailed structure for cerebello-cerebral interaction which contributes to our understanding of complex motor behavior.

Acupuncture regulates the glucose metabolism in cerebral functional regions in chronic stage ischemic stroke patients--a PET-CT cerebral functional imaging study

Background

Acupuncture has been applied to aid in the recovery of post-stroke patients, but its mechanism is unclear. This study aims to analyze the relationship between acupuncture and glucose metabolism in cerebral functional regions in post-stroke patients using ¹⁸ FDG PET-CT techniques. Forty-three ischemic stroke patients were randomly divided into 5 groups: the Waiguan (TE5) needling group, the TE5 sham needling group, the sham point needling group, the sham point sham needling group and the non-needling group. Cerebral functional images of all patients were then acquired using PET-CT scans and processed by SPM2 software.

Results

Compared with the non-needling group, sham needling at TE5 and needling/sham needling at the sham point did not activate cerebral areas. However, needling at TE5 resulted in the activation of Brodmann Area (BA) 30. Needling/sham needling at TE5 and needling at the sham point did not deactivate any cerebral areas, whereas sham needling at the sham point led to deactivation in BA6. Compared with sham needling at TE5, needling at TE5 activated BA13, 19 and 47 and did not deactivate any areas. Compared with needling at the sham point, needling at TE5 had no associated activation but a deactivating effect on BA9.

Conclusion

Needling at TE5 had a regulating effect on cerebral functional areas shown by PET-CT, and this may relate to its impact on the recovery of post-stroke patients.