Resting State Functional Connectivity Signatures of MRgFUS Vim Thalamotomy in Parkinson's Disease: A Preliminary Study

Magnetic Resonance-guided high-intensity Focused Ultrasound (MRgFUS) of the thalamic ventral intermediate nucleus (Vim) for tremor has increasingly gained interest as a new non-invasive alternative to standard neurosurgery. Resting state functional connectivity (rs-FC) correlates of MRgFUS have not been extensively investigated yet. A region of interest (ROI)-to-ROI rs-FC MRI “connectomic” analysis focusing on brain regions relevant for tremor was conducted on 15 tremor-dominant patients with Parkinson's disease who underwent MRgFUS. We tested whether rs-FC between tremor-related areas was modulated by MRgFUS at 1 and 3 months post-operatively, and whether such changes correlated with individual clinical outcomes assessed by the MDS-UPDRS-III sub items for tremor. Significant increase in FC was detected within bilateral primary motor (M1) cortices, as well as between bilateral M1 and crossed primary somatosensory cortices, and also between pallidum and the dentate nucleus of the untreated hemisphere. Correlation between disease duration and FC increase at 3 months was found between the putamen of both cerebral hemispheres and the Lobe VI of both cerebellar hemispheres, as well as between the Lobe VI of untreated cerebellar hemisphere with bilateral supplementary motor area (SMA). Drop-points value of MDS-UPDRS at 3 months correlated with post-treatment decrease in FC, between the anterior cingulate cortex and bilateral SMA, as well as between the Lobe VI of treated cerebellar hemisphere and the interpositus nucleus of untreated cerebellum. Tremor improvement at 3 months, expressed as percentage of intra-subject MDS-UPDRS changes, correlated with FC decrease between bilateral occipital fusiform gyrus and crossed Lobe VI and Vermis VI. Good responders (≥50% of baseline tremor improvement) showed reduced FC between bilateral SMA, between the interpositus nucleus of untreated cerebellum and the Lobe VI of treated cerebellum, as well as between the untreated SMA and the contralateral putamen. Good responders were characterized at baseline by crossed hypoconnectivity between bilateral putamen and M1, as well as between the putamen of the treated hemisphere and the contralateral SMA. We conclude that MRgFUS can effectively modulate brain FC within the tremor network. Such changes are associated with clinical outcome. The shifting mode of integration among the constituents of this network is, therefore, susceptible to external redirection despite the chronic nature of PD.

Imaging of Dentate Nucleus Pathologies: A Case Series

The dentate nucleus is the largest cerebellar nucleus, and it controls cognition and voluntary movement. It is found in each cerebellar hemisphere medially and posterolateral to the lateral ventricle. Pathologies of the dentate nucleus can be detected using computed tomography and magnetic resonance imaging of the brain. Here, we present a case series of seven different dentate nucleus diseases and their neuroimaging findings recovered from archives of our institution.

Epstein-Barr Virus Encephalitis in a Patient with Rheumatoid Arthritis

A 53-year-old woman with a 6-year history of rheumatoid arthritis (RA) presented with pharyngeal pain, fever, and altered mental status. The patient had been treated with methotrexate (MTX) 12 mg/week, baricitinib 4 mg/day, and tacrolimus 2 mg/day. Magnetic resonance imaging of the brain revealed diffuse high-intensity lesions in the cerebral white matter, basal ganglia, brainstem, and right cerebellar hemisphere. She was diagnosed with Epstein-Barr virus (EBV) encephalitis due to elevated levels of EBV-DNA in the cerebrospinal fluid and serum. Although MTX-associated lymphoproliferative disorders are well-known complications in patients with RA, EBV encephalitis requires careful attention for such patients undergoing treatment with multiple potent immunosuppressants.

Cerebellar Functional Lateralization From the Perspective of Clinical Neuropsychology

Objective: The cerebellar functional laterality, with its right hemisphere predominantly involved in verbal performance and the left one engaged in visuospatial processes, has strong empirical support. However, the clinical observation and single research results show that the damage to the right cerebellar hemisphere may cause extralinguistic and more global cognitive decline. The aim of our research was to assess the pattern of cognitive functioning, depending on the cerebellar lesion side, with particular emphasis on the damage to the right cerebellar hemisphere.Method: The study sample consisted of 31 patients with focal cerebellar lesions and 31 controls, free of organic brain damage. The Addenbrooke’s Cognitive Examination ACE III and the Trail Making Test TMT were used to assess patients’ cognitive functioning.Results: Left-sided cerebellar lesion patients scored lower than controls in attention and visuospatial domain, but not in language, fluency, and memory functions. Participants with right-sided cerebellar lesion demonstrated a general deficit of cognitive functioning, with impairments not only in language and verbal fluency subscales but also in all ACE III domains, including memory, attention, and visuospatial functions. The TMT results proved that cerebellar damage is associated with executive function impairment, regardless of the lesion side.Conclusion: The cognitive profiles of patients with cerebellum lesions differ with regard to the lesion side. Left-sided cerebellar lesions are associated with selective visuospatial and attention impairments, whereas the right-sided ones may result in a more global cognitive decline, which is likely secondary to language deficiencies, associated with this lateral cerebellar injury.

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.

Electrode montage-dependent intracranial variability in electric fields induced by cerebellar transcranial direct current stimulation

Transcranial direct current stimulation (tDCS) is an increasingly popular tool to investigate the involvement of the cerebellum in a variety of brain functions and pathologies. However, heterogeneity and small effect sizes remain a common issue. One potential cause may be interindividual variability of the electric fields induced by tDCS. Here, we compared electric field distributions and directions between two conventionally used electrode montages (i.e., one placing the return electrode over the ipsilateral buccinator muscle and one placing the return electrode [25 and 35 cm2 surface area, respectively] over the contralateral supraorbital area; Experiment 1) and six alternative montages (electrode size: 9 cm2; Experiment 2) targeting the right posterior cerebellar hemisphere at 2 mA. Interindividual and montage differences in the achieved maximum field strength, focality, and direction of current flow were evaluated in 20 head models and the effects of individual differences in scalp–cortex distance were examined. Results showed that while maximum field strength was comparable for all montages, focality was substantially improved for the alternative montages over inferior occipital positions. Our findings suggest that compared to several conventional montages extracerebellar electric fields are significantly reduced by placing smaller electrodes in closer vicinity of the targeted area.

Case Report: Prominent Brainstem Involvement in Two Patients With Anti-CASPR2 Antibody-Associated Autoimmune Encephalitis

Anti-contactin-associated protein-like 2 (CASPR2) antibody-associated autoimmune encephalitis is commonly characterized by limbic encephalitis with clinical symptoms of mental and behavior disorders, cognitive impairment, deterioration of memory, and epilepsy. The classical lesions reported are located at the medial temporal lobe or hippocampus, whereas prominent brainstem lesions have not been addressed to date. Herein, we reported two patients mimicking progressive brainstem infarction with severe neurological manifestations. On brain magnetic resonance imaging (MRI), prominent brainstem lesions were noted, although multifocal lesions were also shown in the juxtacortical and subcortical white matters, basal ganglia, hippocampus, and cerebellar hemisphere. Unexpectedly and interestingly, both cases had detectable CASPR2 antibodies in sera, and an exclusive IgG1 subclass was documented in the further analysis. They were treated effectively with aggressive immunosuppressive therapies including corticosteroids, intravenous immunoglobulin G, and rituximab, with the first case achieving a rapid remission and the other undergoing a slow but gradual improvement. To the best of our knowledge, this is the first report on prominent brainstem involvement with definite MRI lesions in anti-CASPR2 antibody-associated autoimmune encephalitis, which helps to expand the clinical spectrum of this rare autoimmune disease and update the lesion patterns in the CNS.

Rosette-forming glioneuronal tumours: two case reports and a review of the literature

Rosette-forming glioneuronal tumour (RGNT) is a rare central nervous system (CNS) neoplasm that typically arises in the fourth ventricle. It is even more uncommon to arise outside the midline. In this paper, we report 2 cases of RGNT: one located in the fourth ventricle (a typical site), and the other in the right cerebellar hemisphere (a rare site). Both cases were misdiagnosed on imaging, and the results were inconsistent with the pathological diagnosis. The aim of the article is to deepen medical practitioners’ understanding of RGNT by learning from these 2 cases, summarizing cases located in the cerebellar hemispheres and systematically reviewing RGNT.

Primary Yolk Sac Tumor in the Cerebellar Hemisphere: A Case Report and Literature Review of the Rare Tumor

Yolk sac tumor (YST) is one of rare malignant germ cell tumors (GCTs). Primary intracranial YST, also endodermal sinus tumor (EST), is a quite rare type of brain tumor. Here, we report a case of YST, review the relevant literature, and propose a treatment strategy for this rare tumor. A 6-year-old boy initially manifested symptoms of dizziness and vomiting. Computed tomography (CT) and magnetic resonance imaging (MRI) showed a large irregular oval tumor in the cerebellar hemisphere. We subtotally removed the tumor by microsurgery through the left suboccipital approach. Immunohistochemical staining showed that alpha fetoprotein (AFP) was positive and the Ki-67 proliferation index was high (60%), suggesting a germ cell tumor. After 3 months of follow-up, neither recurrence of tumor nor complications were found in the patient. The diagnosis of YST should be confirmed on the basis of clinical manifestations, neuroimaging and pathological findings. Gross total resection (GTR) is an ideal treatment for YST. However, due to the location of the tumor, GTR is usually difficult, and the rate of postoperative complications is high. This reported case shows that subtotal resection can be a good treatment strategy for YST.

P.158 Feeling Green

Background: Myeloid sarcoma (MS) is a rare solid tumour made of myeloblasts or immature myeloid cells in an extramedullary site or in bone, associated with systemic hematologic neoplasms. When they occur in the brain parenchyma, they can often be misdiagnosed. Methods: The authors report a case of a 4-year old boy 6 months out of remission from AML, presenting with a short history of headaches and vomiting, and found to have a heterogenous contrast-enhancing lesion in the right cerebellar hemisphere, with differential diagnosis of myeloid sarcoma, astrocytoma, medulloblastoma and ATRT. Preliminary diagnosis was made flow cytometry from an intraoperative biopsy. The patient had a long course of chemotherapy and radiation, but eventually died from the systemic burden of his AML. Results: The authors present a literature review on 178 published cases of CNS myeloid sarcomas, and their radiological presentation and the basis of immunohistochemical and pathological diagnosis is discussed. Conclusions: Diagnosis rests on a combination of immunohistochemistry and histopathology of biopsied tissue. Surgical resection is controversial, especially given the efficacy of chemotherapy and radiation, and prognosis remains unclear. As with all uncommon and rare clinical entities, further investigation is warranted to determine prognosis and optimal management of CNS myeloid sarcomas.