Proximal dentatothalamocortical tract involvement in posterior fossa syndrome

The evaluation of the posterior fossa has gained significant pace and importance in the last 20 years based on the successful progress in neuroimaging. Nowadays, conventional and advanced neuroimaging techniques allow a detailed evaluation of the complex anatomical structures within the compact posterior fossa. A wide spectrum of congenital abnormalities including malformations and disruptions has been shown. Neuroimaging is mandatory for the diagnosis of congenital abnormalities of the posterior fossa. Welldefined diagnostic criteria based on neuroimaging findings are available for the different disorders. Familiarity with the spectrum of congenital posterior fossa anomalies and their diagnostic criteria is mandatory for an accurate evaluation. An accurate and up-to-date classification is important for therapy, prognosis, and genetic counseling of the affected children and their families. In addition, neuroimaging provides useful information in elucidating the pathogenesis, establishing a phenotype (neuroimaging-) genotype correlation, and predicting the neurological outcome.

Cancer, 2009

BACKGROUND: Children treated for a malignant posterior fossa tumor (PFT) are at risk of intellectual impairment. Its severity is not explained by age and radiotherapy alone. The current study was designed to define the correlations between the anatomical damage and the neurological/neuropsychological deficits in children with a malignant PFT. METHODS: Sixty-one consecutive children (mean age, 6.0 years) treated for a malignant PFT with surgery, chemotherapy, and radiotherapy underwent a detailed neuropsychological evaluation, including a full-scale intelligence quotient (FSIQ), on average 5.6 years after the diagnosis. The neurological examination was recorded 1 month after surgery and at the time of the neuropsychological evaluation. Cerebellar and brain injuries were scored based on the magnetic resonance imaging (MRI). Correlation of these injuries with neurological and cognitive outcome were performed after adjustment for other potential risk factors (radiotherapy schedule, age, hydrocephalus, duration of symptoms, socioeconomic status, and surgical complications). RESULTS: Neurological deficits were strong predictors of low cognitive performances irrespective of the other risk factors. The extent of cerebellar deficits and fine motor dexterity impairment were correlated with the degree of damage to the dentate nuclei and inferior vermis. The IQ scores were inversely correlated with the severity of the damage to the dentate nuclei; mean FSIQ was 83 if they were both intact and 65 in the case of bilateral damage (P ¼ .009). CONCLU-SIONS: Damage to the dentate nuclei and to the inferior vermis, observed on MRI, predict the degree of impairment of neurological and neuropsychological functions in children treated for a malignant PFT.

NeuroImage: Clinical, 2019

Introduction: In posterior fossa tumor survivors, lower white matter integrity (WMI) in the right cerebellar-left frontal pathway has been well documented and appears to be related to proximity to the cerebellum, radiation treatment, as well as time since treatment in both cranial radiation and surgery-only treatment groups. The current study investigated theories of transneural degeneration following cerebellar tumor resection that may underlie or relate to reductions in WMI and regional brain volumes using correlations. We hypothesized a positive relationship between the volume of the right cerebellum and known white matter output pathways, as well as with the volume of structures that receive cerebellar projections along the pathway. Methods: Adult survivors of childhood brain tumors were recruited (n = 29; age, M = 22 years, SD = 5; 45% female). Age-and gender-matched controls were also included (n = 29). Participants completed 3 T diffusionweighted and T1 MPRAGE MRI scans. Brain structure volume relative to intracranial vault served as regional volumetric measures. Fractional anisotropy (FA) and radial diffusivity (RD) served as WMI measures. In the survivor group, partial correlations between WMI and regional volume included controlling for disease severity. Results: In posterior fossa tumor survivors, the volumes of the cerebellum, thalamus, and frontal lobe were correlated with WMI of the thalamic-frontal segment of the cerebellar-frontal pathway (r = 0.41-0.49, p < .05). Cerebellar atrophy was correlated with reduced WMI in the cerebellar-rubral segment (FA, r = −0.32 p > .05; RD, r = 0.53, p < .01). In the no-radiation survivor group, the regional volume of each structure along the pathway was associated with WMI in the cerebellar-rubral segment. In the radiation survivor group, significant correlations were found between the regional brain volume of each structure and the thalamic-frontal segment of the pathway. Discussion: The results of this multimodal neuroimaging study provide correlational evidence that the mechanism of injury subsequent to brain tumor treatment may be different depending on type of treatment(s). Without radiation, the primary mechanism of injury is cerebellar tumor growth, resection, and hydrocephalus. Therefore, the most proximal connection to that injury (cerebellar-rubral pathway) was correlated with reductions in volume along the pathway. In contrast, the survivor group treated with radiation may have had possible radiation-induced demyelination of the thalamic-frontal portion of the pathway, based on a strong correlation with volume loss in the cerebellum, red nucleus, thalamus, and frontal lobe. 1. Introduction Cerebellar brain tumors account for about 20% of all childhood tumors, and the majority of children survive (Gurney et al., 1999; Ostrom et al., 2015). However, poor neurocognitive and neuroanatomical outcomes often are associated with survivorship (Ailion et al., 2017; Duffner, 2004). Most cerebellar tumors occur in early childhood during important periods of brain maturation (Mueller and Chang, 2009; Nejat et al., 2008; Ostrom et al., 2015). During this sensitive period for brain development, young children are treated with resection, radiation, chemotherapy, and shunts, all of which are based on age at presentation, location, malignancy, and intracranial pressure. However, many benign tumors require gross total resection followed by no adjuvant treatment at all (Mueller and Chang, 2009).

A & A case reports, 2017

Cerebellar mutism syndrome (CMS) is a common complication of posterior fossa surgery that can confound the postanesthetic examination and have long-lasting impacts. There is confusion surrounding its precise description, diagnostic features, and associated morbidity. Here, we discuss the most up-to-date knowledge of CMS drawing from a clinical case in the context of 3 new reports: (1) an international consensus paper presenting a new proposed working definition by the Iceland Delphi Group, (2) a knowledge update by Gadgil et al, (3) and a review of neuroimaging-based data elucidating the etiology of CMS by Patay.

Pediatric Blood & Cancer, 2011

Pediatric Radiology, 2006

Background: Diffusion tensor imaging and tractography have been used to evaluate a variety of brain malformations. However, these studies have focused mainly on malformations involving the supratentorial compartments. There is a paucity of data on diffusion tensor imaging of posterior fossa malformations. Objective: To describe the color vector maps and modified or abnormal tracts of midline posterior fossa malformations. Materials and Methods: Diffusion tensor imaging was performed in one patient with rhombencephalosynapsis and two with Joubert syndrome. Color vector maps of fractional anisotropy were used to place a region of interest for seed point of fiber tracking. Results: The vermis was severely hypoplastic or absent in rhombencephalosynapsis and Joubert syndrome. In rhombencephalosynapsis, vertically oriented fibers were visualized in the midportion of the cerebellum. The location of the deep cerebellar nuclei could be inferred from the amiculum and were medially located in rhombencephalosynapsis. In the two patients with Joubert syndrome, the horizontally arranged superior cerebellar peduncles were well demonstrated on the color vector maps. Failure of the superior cerebellar peduncles to decussate in the mesencephalon was also well demonstrated on both color vector maps and tractography. The deep cerebellar nuclei were more laterally located in Joubert syndrome. Conclusion: The use of tractography in midline posterior fossa malformations expands our understanding of these malformations.

Turkish neurosurgery, 2008

AIM Cerebellar mutism is a documented complication of posterior fossa surgery in pediatric ages. Risk factors such as the type of tumor, size, and location of tumor, hyrdrocephalus, postoperative cerebellar swelling for cerebellar mutism were investigated in this study. MATERIAL AND METHODS A consecutive series of 32 children with a cerebellar tumor were operated on at the Haseki Educational and Research Hospital, Department of Neurosurgery, between 1990 and 2005. Their speech and neuroradiological studies were systematically analysed both preoperatively and postoperatively RESULTS Cerebellar mutism developed in ten children (32%) in the early postoperative period. The type of tumor, midline localization, and vermian incision were significant single independent risk factors. In addition, an interdependency of possible risk factors (tumor &gt; 5 cm, medulloblastoma) was found. The latency for the development of mutism ranged from 0 to 90 days (mean 15.6 d). The speech returned to nor...

American Journal of Neuroradiology, 2013

BACKGROUND AND PURPOSE: Injury to the dentatothalamic pathway that originates in the cerebellum has been suggested as a mechanism for neurologic complications in children treated for posterior fossa tumors. We hypothesized that time-dependent changes occur in the dentatothalamic pathway. MATERIALS AND METHODS: Diffusion tensor evaluation was performed in 14 children (median age, 4.1 years; age range, 1-20 years) who underwent serial MR imaging at 3T as part of routine follow-up after posterior fossa tumor resection with or without adjuvant therapy. Tensor metrics were obtained in the acute (Յ1 week), subacute (1 to Ͻ6 months), and chronic (Ն6 months) periods after surgery. We evaluated the following dentatothalamic constituents: bilateral dentate nuclei, cerebellar white matter, and superior cerebellar peduncles. Serial dentate nuclei volumes were also obtained and compared with the patient's baseline. RESULTS: The most significant tensor changes to the superior cerebellar peduncles and cerebellar white matter occurred in the subacute period, regardless of the tumor pathology or therapy regimen, with signs of recovery in the chronic period. However, chronic volume loss and reduced mean diffusivity were observed in the dentate nuclei and did not reverse. This atrophy was associated with radiation therapy and symptoms of ataxia. CONCLUSIONS: Longitudinal diffusion MR imaging in children treated for posterior fossa tumors showed time-dependent tensor changes in components of the dentatothalamic pathway that suggest evolution of structural damage with inflammation and recovery of tissue directionality. However, the dentate nuclei did not show tensor or volumetric recovery, suggesting that the injury may be chronic. ABBREVIATIONS: DTT ϭ dentatothalamic; FA ϭ fractional anisotropy; ʈ ϭ perpendicular diffusivity; MD ϭ mean diffusivity; PF ϭ posterior fossa; PFS ϭ posterior fossa syndrome; SCP ϭ superior cerebellar peduncles; ʈ ϭ parallel diffusivity

Seminars in Ultrasound, CT and MRI, 2011

Diffusion tensor imaging (DTI) is an advanced MRI technique that measures the microscopic molecular motion of water to gain information about the brain structure. This modality and its application to fiber tractography have been increasingly used in the last years to study the neuroanatomical background of brain malformations. This article aims to give an overview of the application of DTI and fiber tractography on pediatric posterior fossa including malformations, acquired disorders affecting the white matter, and posterior fossa involvement in phacomatoses. For every disorder, we show the additional information that DTI and fiber tractography are providing compared to conventional MR sequences and discuss their significance. Additionally, we show at the beginning normal DTI and fiber tractography findings of the pediatric posterior fossa. Finally, we briefly discuss potential future uses for DTI and fiber tractography to further understand the pathogenesis of posterior fossa malformations and the neuronal plasticity and connectivity of acquired lesions affecting the posterior fossa. Semin Ultrasound CT MRI 32:539-554

Acta Neurochirurgica, 2002

Summary. Background: Although there are some cases of cerebellar mutism in adults after posterior fossa surgery for cerebellar tumour it generally occurs in children. Reversible pathophsiology and the anatomical substrate of this syndrome still remain unclear. The predominance of cerebellar mutism in children is suggested to be related to the higher incidence of posterior fossa tumours in children. However, the question regarding the reason for the obvious difference in the incidence of this syndrome between the paediatric and adult population still remaing unanswered. The aim of this study was to evaluate and compare children and adult groups separately to understand the incidence and the clinical characteristics better and to elucidate the pathophysiological basis and predictive factors for this syndrome. Method: We reviewed, analysed, and compared the cases of cerebellar mutism individually in children and in adults reported in the English literature. We found 106 reported cases in children and 11 cases in adults which were suitable for analysis. We added two adult cases to these. Findings: The ages of the patients ranged from 2 to 16 (mean, 6.4 year) in children and from 17 to 74 (mean, 38.7 year) in adults. Although vermis was the main location in both groups, the incidence of vermis lesions was considered higher in the paediatric population (%91.5 versus %69.2). The rate of brain stem invasion was prominent in children (%31.1) when compared with adults (%7.6). The latency for the development of mutism and the duration of the mutism were similar in children and adults (mean, 1.4 d versus 2 d and mean, 5.07 wk versus 4.2 wk respectively). Mutism was transient in all the cases of both groups. Interpretation: Recent concepts of cerebellar physiology disclose the importance of the cerebellum in learning, language, and mental and social functions. Pontine nuclei, the thalamus, motor and sensory areas and supplementary motor areas have been proven necessary for the initiation of speech. It can be hypothesized that uncompleted maturation of the reciprocal links in childhood connecting the cerebellum to these structure makes the children more vulnerable to have postoperative cerebellar mutism in comparison to the adult population.