Cerebellar lesions at a young age predict poorer long-term functional recovery

Ignoring the cerebellum is hindering progress in neuroscience

Traditionally considered a motor structure, the cerebellum has been shown to play a key role in several cognitive functions. However, for decades, the cerebellum has been largely overlooked and even deliberately excluded from 'whole-brain' neuroimaging studies. Here, we propose that the continued exclusion of the cerebellum has limited our understanding of whole-brain function. We describe reasons - both warranted and unwarranted - behind its historical exclusion from the neuroimaging literature, review literature describing the importance of the cerebellum and its unique role in brain function, and outline the potential unintended negative consequences of exclusion of the cerebellum for our comprehensive understanding of brain function and clinical disorders.

Consistent cerebellar pathway-cognition associations across pre-adolescents & young adults: a diffusion MRI study of 9000+ participants

The cerebellum, long implicated in movement, is now recognized as a contributor to higher-order cognition. The cerebellar pathways provide key structural links between the cerebellum and cerebral regions integral to language, memory, and executive function. Here, we present a large-scale, cross-sectional diffusion MRI (dMRI) analysis investigating the relationships between cerebellar pathway microstructure and cognitive performance in over 9,000 participants spanning pre-adolescence (n>8,000 from the ABCD dataset) and young adulthood (n>900 from the HCP-YA dataset). We assessed the microstructure of five cerebellar pathways-the inferior, middle, and superior cerebellar peduncles; the parallel fibers; and input/Purkinje fibers-using three dMRI measures of fractional anisotropy, mean diffusivity, and number of streamlines. Cognitive performance was evaluated using seven NIH Toolbox assessments of language, executive function, and memory. In both datasets, we found numerous significant associations between cerebellar pathway microstructure and cognitive performance. These associations showed a strong correlation across the two datasets (r = 0.47, p < 0.0001), underscoring the reliability of cerebellar dMRI-cognition relationships in pre-adolescents and young adults. In both datasets, the strongest associations were found between the superior cerebellar peduncle and performance on language assessments, suggesting this pathway plays an important role in language function across age groups. In young adults, but not pre-adolescents, parallel fiber microstructure was linked to inhibitory control, suggesting that contributions to attentional processes may emerge or strengthen with maturation. Overall, our findings highlight the important role of cerebellar pathways in cognition and the utility of large-scale datasets for advancing our understanding of brain-cognition relationships.

Causally Mapping the Cerebellum in Children and Young Adults: from Motor to Cognition

While the cerebellum's role in orchestrating motor execution and routines is well established, its functional role in supporting cognition is less clear. Previous studies claim that motricity and cognition are mapped in different areas of the cerebellar cortex, with an anterior/posterior dichotomy. However, most of the studies supporting this claim either use correlational methods (neuroimaging) or are lesion studies that did not consider central covariates (such as age, gender, treatment presence, and deep nuclei impairment) known to influence motor and cognitive recoveries in patients. Here, we used voxel-based lesion-symptom mapping (VLSM) on children and young adults having undergone cerebellar tumor resection. This approach allows to control for these covariates and evaluate causal relationships between brain anatomy and behavioral performances to disentangle the anatomic substrate of motor and cognitive functions. VLSM analyses showed that both motor and cognitive impairments were greater in children and young adults with lesions of the posterior cerebellum. These results highlight distinct and overlapping structural correlates of motor and cognitive performance in the cerebellum and are consistent with structural and functional hypotheses of integration of the cerebellum in motor and cognitive functions.

Neuroprotective effect of red dragon fruit extract ameliorates oxidative stress and inflammation in D-galactose-induced aging rat model: biochemical, histological and immunohistochemical study

Aging is a worldwide socioeconomic burden. Cerebellar aging is an enigma contributing to many behavioral aging disorders, hence is its hindering by prophylactic measurements is a crucial geriatric research target. Red dragon fruit (RDF) is a tropical fruit with antioxidant, anti-inflammatory and anti-apoptotic properties. This study aimed to determine the protective effect of RDF extract against cerebellar aging. Thirty-two male albino rats were randomly allocated into 4 groups: Control, RDF, aged and RDF-aged groups. Aged group revealed structural distortion affecting cerebellar layers including a significant (P < 0.05) decrease in Purkinje cells number and decrease in granular cell layer thickness by comparison to the control and RDF groups. Additionally, distorted capillary endothelium, and defective myelination were noticed. Interestingly, cerebellar active caspase-3, iNOS, MDA and 3-NT and serum TNF-α levels significantly increased with aging by comparison to the control and RDF groups (all P < 0.05). Biochemical analysis revealed a significant (P < 0.05) decrease in cerebellar SOD and serum GSH levels in aged rats. RDF extract remarkably ameliorated most of the neuronal degenerative changes with a significant (P < 0.05) increase in Purkinje cells numbers, and granular cell layer thickness by comparison to the aged group. Furthermore, it resulted in a significant (P < 0.05) decrease in cerebellum expression of active caspase-3, iNOS, MDA, 3-NT, and serum TNF-α levels associated with a significant (P < 0.05) increase in cerebellar SOD and serum GSH levels by comparison to the aged group. To the best of our knowledge this is the first study showing a neuroprotective effect for RDF against cerebellar aging. RDF might be effective in attenuation of age-induced cerebellar degenerative changes through its anti-apoptotic, antioxidant and anti-inflammatory effects.

Preoperative 11 C-Methionine PET-MRI in Pediatric Infratentorial Tumors

PURPOSE

MRI is the main imaging modality for pediatric brain tumors, but amino acid PET can provide additional information. Simultaneous PET-MRI acquisition allows to fully assess the tumor and lower the radiation exposure. Although symptomatic posterior fossa tumors are typically resected, the patient management is evolving and will benefit from an improved preoperative tumor characterization. We aimed to explore, in children with newly diagnosed posterior fossa tumor, the complementarity of the information provided by amino acid PET and MRI parameters and the correlation to histopathological results.

PATIENTS AND METHODS

Children with a newly diagnosed posterior fossa tumor prospectively underwent a preoperative 11 C-methionine (MET) PET-MRI. Images were assessed visually and semiquantitatively. Using correlation, minimum apparent diffusion coefficient (ADC min ) and contrast enhancement were compared with MET SUV max . The diameter of the enhancing lesions was compared with metabolic tumoral volume. Lesions were classified according to the 2021 World Health Organization (WHO) classification.

RESULTS

Ten children were included 4 pilocytic astrocytomas, 2 medulloblastomas, 1 ganglioglioma, 1 central nervous system embryonal tumor, and 1 schwannoma. All lesions showed visually increased MET uptake. A negative moderate correlation was found between ADC min and SUV max values ( r = -0.39). Mean SUV max was 3.8 (range, 3.3-4.2) in WHO grade 4 versus 2.5 (range, 1.7-3.0) in WHO grade 1 lesions. A positive moderate correlation was found between metabolic tumoral volume and diameter values ( r = 0.34). There was no correlation between SUV max and contrast enhancement intensity ( r = -0.15).

CONCLUSIONS

Preoperative 11 C-MET PET and MRI could provide complementary information to characterize pediatric infratentorial tumors.

Morphological and Functional Principles Governing the Plasticity Reserve in the Cerebellum: The Cortico-Deep Cerebellar Nuclei Loop Model

Cerebellar reserve compensates for and restores functions lost through cerebellar damage. This is a fundamental property of cerebellar circuitry. Clinical studies suggest (1) the involvement of synaptic plasticity in the cerebellar cortex for functional compensation and restoration, and (2) that the integrity of the cerebellar reserve requires the survival and functioning of cerebellar nuclei. On the other hand, recent physiological studies have shown that the internal forward model, embedded within the cerebellum, controls motor accuracy in a predictive fashion, and that maintaining predictive control to achieve accurate motion ultimately promotes learning and compensatory processes. Furthermore, within the proposed framework of the Kalman filter, the current status is transformed into a predictive state in the cerebellar cortex (prediction step), whereas the predictive state and sensory feedback from the periphery are integrated into a filtered state at the cerebellar nuclei (filtering step). Based on the abovementioned clinical and physiological studies, we propose that the cerebellar reserve consists of two elementary mechanisms which are critical for cerebellar functions: the first is involved in updating predictions in the residual or affected cerebellar cortex, while the second acts by adjusting its updated forecasts with the current status in the cerebellar nuclei. Cerebellar cortical lesions would impair predictive behavior, whereas cerebellar nuclear lesions would impact on adjustments of neuronal commands. We postulate that the multiple forms of distributed plasticity at the cerebellar cortex and cerebellar nuclei are the neuronal events which allow the cerebellar reserve to operate in vivo. This cortico-deep cerebellar nuclei loop model attributes two complementary functions as the underpinnings behind cerebellar reserve.

Assessment and recovery of visually guided reaching deficits following cerebellar stroke

The cerebellum is known to play an important role in the coordination and timing of limb movements. The present study focused on how reach kinematics are affected by cerebellar lesions to quantify both the presence of motor impairment, and recovery of motor function over time. In the current study, 12 patients with isolated cerebellar stroke completed clinical measures of cognitive and motor function, as well as a visually guided reaching (VGR) task using the Kinarm exoskeleton at baseline (∼2 weeks), as well as 6, 12, and 24-weeks post-stroke. During the VGR task, patients made unassisted reaches with visual feedback from a central 'start' position to one of eight targets arranged in a circle. At baseline, 6/12 patients were impaired across several parameters of the VGR task compared to a Kinarm normative sample (n = 307), revealing deficits in both feed-forward and feedback control. The only clinical measures that consistently demonstrated impairment were the Purdue Pegboard Task (PPT; 9/12 patients) and the Montreal Cognitive Assessment (6/11 patients). Overall, patients who were impaired at baseline showed significant recovery by the 24-week follow-up for both VGR and the PPT. A lesion overlap analysis indicated that the regions most commonly damaged in 5/12 patients (42% overlap) were lobule IX and Crus II of the right cerebellum. A lesion subtraction analysis comparing patients who were impaired (n = 6) vs. unimpaired (n = 6) on the VGR task at baseline showed that the region most commonly damaged in impaired patients was lobule VIII of the right cerebellum (40% overlap). Our results lend further support to the notion that the cerebellum is involved in both feedforward and feedback control during reaching, and that cerebellar patients tend to recover relatively quickly overall. In addition, we argue that future research should study the effects of cerebellar damage on visuomotor control from a perception-action theoretical framework to better understand how the cerebellum works with the dorsal stream to control visually guided action.

The shifting role of the cerebellum in executive, emotional and social processing across the lifespan

The cerebellum's anatomical and functional organization and network interactions between the cerebellum and the cerebral cortex and subcortical structures are dynamic across the lifespan. Executive, emotional and social (EES) functions have likewise evolved during human development from contributing to primitive behaviors during infancy and childhood to being able to modulate complex actions in adults. In this review, we address how the importance of the cerebellum in the processing of EES functions might change across development. This evolution is driven by the macroscopic and microscopic modifications of the cerebellum that are occurring during development including its increasing connectivity with distant supra-tentorial cortical and sub-cortical regions. As a result of anatomical and functional changes, neuroimaging and clinical data indicate that the importance of the role of the cerebellum in human EES-related networks shifts from being crucial in newborns and young children to being only supportive later in life. In early life, given the immaturity of cortically mediated EES functions, EES functions and motor control and perception are more closely interrelated. At that time, the cerebellum due to its important role in motor control and sequencing makes EES functions more reliant on these computational properties that compute spatial distance, motor intent, and assist in the execution of sequences of behavior related to their developing EES expression. As the cortical brain matures, EES functions and decisions become less dependent upon these aspects of motor behavior and more dependent upon high-order cognitive and social conceptual processes. At that time, the cerebellum assumes a supportive role in these EES-related behaviors by computing their motor and sequential features. We suspect that this evolving role of the cerebellum has complicated the interpretation of its contribution to EES computational demands.

Better detection of reduced motor functioning in brain tumor survivors based on objective motor assessments: an incentive for improved standardized follow-up

Long-term sequelae are well-known in childhood brain tumor survivors, but motor functioning remains poorly described. This cross-sectional study aimed to assess objective motor functioning, patient-specific risk factors, and parental perceptions. Fifty-two childhood brain tumor patients (pilocytic astrocytoma, medulloblastoma, and other types) who were at least 6 months out of treatment were evaluated. Mean age at testing was 11.7 years. Objective motor functioning was assessed with the Movement Assessment Battery for Children (MABC-2-NL) and/or Bruininks-Oseretsky test of motor proficiency (BOT-2). Functional walking capacity was assessed with the 6-min walk test (6MWT). Parent-reported motor functioning was addressed using the ABILHAND-Kids, ABILOCO-Kids questionnaires, and a standardized anamnesis. Patients showed impaired motor functioning in all domains (p < 0.001). Regarding risk factors, younger age at diagnosis (< 5 year) was significantly associated with lower scores on body coordination (p = 0.006). Adjuvant treatment resulted in lower scores for fine manual control of the BOT-2 (p = 0.024) and balance of MABC-2-NL (p = 0.036). Finally, questionnaires revealed an underestimation of motor problems as perceived by the parents. In conclusion, many children who are in follow-up for a brain tumor show impaired motor functioning on multiple aspects, with younger age at diagnosis and adjuvant treatment as specific risk factors. Based on the questionnaires and anamnesis, motor problems appear to be underestimated by the parents.  Conclusion: These findings point to the need for timely prospective screening of motor functioning. Based on a screening assessment, adequate rehabilitation programs can be applied in childhood brain tumor survivors, aiming to reduce the adverse impact on their daily lives, both for functional activities and cardiovascular fitness. What is Known: • A pediatric brain tumor and its treatment are associated with potential long-term motor sequelae. • Test assessments could enable us to objectify motor functioning of these patients. What is New: • Pediatric brain tumors survivors show lower motor performance compared to the norm, which is often underestimated by parents. • Younger age at diagnosis and adjuvant treatment could be specific risk factors.

Surgical management of posterior fossa medulloblastoma in children: The Lyon experience

INTRODUCTION

Modern approach for the treatment of posterior fossa medulloblastomas remains a challenge for pediatric neurosurgeons and pediatric oncologists and requires a multidisciplinary approach to optimize survival and clinical results.

MATERIAL AND METHODS

We report the surgical principles of the treatment of posterior fossa medulloblastomas in children and how to avoid technical mistakes especially in very young patients. We also report our experience in a series of 64 patients operated from a medulloblastoma between 2000 and 2018 in Lyon.

RESULTS

All patients had a craniospinal MRI. Eighty-one percent of the patients (n=50) had strictly midline tumor while 19% (n=14) had lateralized one. Eleven percent (n=7) had metastasis at diagnosis on the initial MRI. Forty-one percent (n=29) had an emergency ETV to treat hydrocephaly and the intracranial hypertension. All patient underwent a direct approach and a complete removal was achieved in 78% (n=58) of the cases on the postoperative MRI realized within 48h postsurgery. Histological findings revealed classical medulloblastoma in 73% (n=46), desmoplastic medulloblastoma in 17% (n=11) and anaplastic/large cell medulloblastoma in 10% (n=7). Patients were classified as low risk in 7 cases, standard risk in 30 cases and high risk in 27 cases. Ninety-six percent (n=61) of the patient received radiotherapy. Seventy-six percent (n=48) received pre-irradiation or adjuvant chemotherapy. At last follow-up in December 2018, 65% (n=41) of the patient were in complete remission, 12% (n=8) were in relapse and 27% (n=15) had died from their disease. The overall survival at five , ten and fifteen years for all the series was of 76%, 73% and 65.7% respectively.

CONCLUSIONS

Medulloblastomas remain a chimiosensible and radiosensible disease and the complete surgical removal represents a favorable prognostic factor. The extension of surgery has also to be weighted in consideration of the new biomolecular and genetic knowledge that have to be integrated by surgeons to improve quality of life of patients.

A New Insight on the Role of the Cerebellum for Executive Functions and Emotion Processing in Adults

Objective: We investigated whether the cerebellum plays a critical or supportive role in in executive and emotion processes in adults. Many investigators now espouse the hypothesis that participants with cerebellar lesions experience executive functions and emotions (EE) disorders. But we hypothesized that these disorders would be milder if the damage is relatively limited to the cerebellum compared to damage involving the cerebellum plus additional cortical areas. Methods: We studied veterans with penetrating Traumatic Brain Injury (pTBI) participating in the Vietnam Head Injury Study (VHIS). We selected veterans with a cerebellar lesion (n = 24), a prefrontal cortex lesion (n = 20), along with healthy controls (HC) (n = 55). Tests of executive functions and emotions were analyzed as well as caregiver burden. We performed between-group null hypothesis significance testing, Bayesian hypothesis tests and correlational analyses. Results: Performance of participants with cerebellar lesions which extended to the cerebral cortex was similar to the HC on the Executive Function tests but they were significantly impaired on the Working Memory Index. No differences were found on the emotional processing tasks with one exception-the Facial Expression of Emotion-Test (FEEST). We then examined a sub-group of participants with large cerebellar lesions (>15%) but minimal lesions in the cerebral cortex (<15%). This sub-group of participants performed similarly to the HC on the Working Memory Index and on the FEEST. Conclusions: We suggest that the cerebellar cortex may not be critical for executive functions or processing emotional stimuli in adults as suggested. Instead, we find that the cerebellum has a supportive role characterized by its computing of the motor requirements when EE processing is required.