Posterior Hemisphere Research Articles

Are there cortical somatotopic motor maps outside of the human precentral gyrus?

Human body movements are supported by a somatotopic map - primary motor cortex (M1) - that is found along the precentral gyrus. Recent evidence has suggested two further motor maps that span the lateral occipitotemporal cortex (LOTC) and the precuneus. Confirmation of these maps is important, as they influence our understanding of the organisation of motor behaviour, for example by revealing how visual- and motor-related activity interact. However, evidence for these recently proposed maps is limited. We analysed an open fMRI dataset of 62 participants who moved performed twelve different body part movements. We analysed the magnitude of responses evoked by movements with novel quantitative indices that test for map-like organisation. We found strong evidence for bilateral somatotopic maps in precentral and postcentral gyri. In LOTC, we found much weaker responses to movement, and little evidence of somatotopy. In the precuneus, we found only limited evidence for somatotopy. We also adopted a background connectivity approach to examine correlations between M1, LOTC and the precuneus in the residual time-series data. This revealed a ventral-posterior / dorsal-anterior distinction in the connectivity between precuneus and M1, favouring the head and arms, respectively. Posterior right hemisphere LOTC showed some evidence of preferential connectivity to arm-selective regions of M1. Overall, our results do not support the existence of a somatotopic motor map in LOTC but provide some support for a coarse map in the precuneus, especially as revealed in connectivity patterns. These findings help clarify the organisation of human motor representations beyond the precentral gyrus.

8130 A Case of Cushing’s Disease Presenting with Posterior Reversible Encephalopathy Syndrome

Abstract Disclosure: A.H. Chincholi: None. M.D. Goldberg: None. Introduction: Posterior reversible encephalopathy syndrome (PRES) is characterized by headaches, altered mental status, vision changes, and seizures, along with characteristic imaging findings of bilateral white matteredema in the posterior cerebral hemispheres. The syndrome often occurs in the context of severe hypertension, and has previously been reported in 6 patients with Cushing’s syndrome (CS) - 4 with ectopic sources of ACTH, 1 with micronodular adrenal hyperplasia and 1 pediatric case with Cushing’s disease. Clinical Case: An 18-year-old-man was admitted to our hospital after experiencing a second seizure at home. His presentation was significant for lethargy, hypertension, facial plethora, acne, proximal muscle weakness,central obesity, extensive purple striae, hyperglycemia, and hypokalemia. Two months prior, a diagnosis of ACTH-dependent CS had been made at an outside facility when he presented with a hypertensive emergency and new-onset diabetes. One month prior, he had been hospitalized with pneumonia complicated by acute kidney injury requiring temporary hemodialysis, and his first seizure. Brain MRI had shown extensive T2/FLAIR hyperintensities in the temporal lobes and cerebellum,consistent with PRES. On this admission, morning serum cortisol was 56.1 mcg/dL, and then 57.9 mcg/dL following 10 mg dexamethasone at night; ACTH was 120 pg/mL, and 24-hour UFC was 2,204 mcg. Ketoconazole and spironolactone were added, with no appreciable improvement in his cortisol levels but normalization of blood pressure. He required up to 150 units of insulin per day to manage his hyperglycemia. PituitaryMRI revealed a 0.6 cm adenoma, along with the T2/FLAIR hyperintensities. Chest CT showed no masses. A 10 mcg IV desmopressin stimulation test resulted in a 248% increase in ACTH and 32% increase in cortisol, and a second MRI with a 3T scanner measured the pituitary adenoma to be 1.0 cm. It was concluded that he had Cushing’s disease, and he underwent transsphenoidal resection of the pituitary adenoma. The surgery was curative, as reflected by postoperative central adrenal insufficiency. The patient was discharged on postoperative day 3 with oral hydrocortisone. Two weeks later, he was euglycemic off insulin and his blood pressure had normalized off spironolactone. Three months later, his muscle weakness and his headaches had completely resolved. Brain MRI showed complete resection of the pituitary adenoma and resolution of the white matter changes. Conclusion: To our knowledge, this is the first report of PRES associated with CS due to an ACTH-secreting pituitary adenoma in an adult. We suspect that this patient’s marked secondary hypertension triggered the reversible encephalopathy. Providers should be aware of this potential complication of hypercortisolism. This case also highlights the utility of desmopressin stimulation test in defining the cause of ACTH-dependent CS. Presentation: 6/3/2024

6504 Cerebellar Metastases from Papillary Thyroid Cancer; An Unusual Presentation

Abstract Disclosure: L.E. Chozet: None. A. Gilbert: None. M.A. Escobar Vasco: None. Background: Differentiated papillary thyroid cancer is known to have a very favorable prognosis. Brain metastases arising from papillary thyroid carcinoma are a very rare complication seen in approximately 1% of all cases of differentiated thyroid cancer with cerebellar metastases being even more uncommon. We present a case of a patient presenting with ataxia as the initial and only symptom of papillary thyroid carcinoma, found to have cerebellar metastases. Clinical Case: A 68-year-old man presented with ataxia for 1 week prior to arrival to hospital. CT head revealed hyperdense lesions in the right frontal lobe and left posterior cerebellar hemisphere. The patient underwent resection of left cerebellar mass with final pathology consistent with metastatic papillary thyroid carcinoma. Tumor cells were positive for TTF-1, thyroglobulin, CAM5.2, CK7, and PAX8, and negative for CK5/6, CK20, inhibin, and Napsin A. Ultrasound of the thyroid revealed multinodular goiter with dominant left thyroid lobe nodule 4 cm in size. PET CT showed left Thyroid mass with direct extension to adjacent lymph nodes, right anterior rib mass, left adrenal metastasis and right frontal lobe and left cerebellar metastasis. He received stereotactic radiosurgery with 5 out of 5 treatments completed. He subsequently underwent total thyroidectomy with left modified radical neck dissection, with pathology showing pT3bN1bM1. Next Generation Sequence positive for V600E, RADS1CR193, TERT PROMOTER -124C>T. After multidisciplinary team discussion, it was determined that the best course of action was to refer the patient to MD Anderson for evaluation, candidacy for prospective therapeutic clinical trials. Conclusion: This case demonstrates how differentiated papillary thyroid cancer, despite its favorable prognosis, can still prove to be a dangerous disease especially if undiagnosed for several years. This case also illustrates how papillary thyroid carcinoma can remain clinically silent for years and first present with atypical symptoms consistent with advanced metastases. Presentation: 6/2/2024

Cross subject emotion identification from multichannel EEG sub-bands using Tsallis entropy feature and KNN classifier

Human emotion recognition remains a challenging and prominent issue, situated at the convergence of diverse fields, such as brain–computer interfaces, neuroscience, and psychology. This study utilizes an EEG data set for investigating human emotion, presenting novel findings and a refined approach for EEG-based emotion detection. Tsallis entropy features, computed for q values of 2, 3, and 4, are extracted from signal bands, including theta-θ (4–7 Hz), alpha-α (8–15 Hz), beta-β (16–31 Hz), gamma-γ (32–55 Hz), and the overall frequency range (0–75 Hz). These Tsallis entropy features are employed to train and test a KNN classifier, aiming for accurate identification of two emotional states: positive and negative. In this study, the best average accuracy of 79% and an F-score of 0.81 were achieved in the gamma frequency range for the Tsallis parameter q = 3. In addition, the highest accuracy and F-score of 84% and 0.87 were observed. Notably, superior performance was noted in the anterior and left hemispheres compared to the posterior and right hemispheres in the context of emotion studies. The findings show that the proposed method exhibits enhanced performance, making it a highly competitive alternative to existing techniques. Furthermore, we identify and discuss the shortcomings of the proposed approach, offering valuable insights into potential avenues for improvements.

2 Rethinking the Neuropsychology of g: Structural and Functional Lesion Network Mapping of General Cognitive Ability

Objective:General cognitive ability (g) is central to our understanding of human cognition, as it accounts for nearly half of individual differences in performances on diverse cognitive tests. There is growing interest in the brain networks necessary for g because such knowledge could elucidate neural mechanisms of g. Prior work highlighted the association between g and frontoparietal functional networks. However, the specificity of this relationship has been questioned. Moreover, no studies have compared the relative importance of structural and functional networks for g, and most studies have relied on data from neurologically healthy individuals, which limits causal brain-behavior inference. Lesion network mapping (LNM) can overcome such limitations. LNM integrates lesion location and structural and functional brain network data, and allows for inference upon networks necessary for cognitive functions. Here, we used data from three cohorts of patients with focal brain lesions to perform a large-scale LNM study of g. We also compared the relative value of lesion-behavior mapping, and structural and functional LNM, for predicting g across cohorts.Participants and Methods:Using data from 402 individuals with chronic, focal brain lesions from the Iowa Neurological Patient Registry, we created a bifactor model to estimate g from the shared variance across neuropsychological tests. To create “cognitive comparisons,” we also estimated the unique aspects of domain-specific abilities (visuospatial processing, memory, and processing speed) by removing domain-general variance from each. Next, we used multivariate lesion-behavior mapping to create statistically weighted maps linking deficits in g and domain-specific abilities to regions of focal brain damage. To perform LNM, the local maxima of the lesion-behavior maps were used as seeds for structural and functional connectivity analyses based on normative diffusion-weighted imaging and resting-state functional connectivity data, respectively. The resulting maps were collapsed using principal components analysis (PCA). We quantified the overlap between each map and the lesion volumes of patients from two validation cohorts (n = 101, n = 100). We used these scores to predict observed g in the validation cohorts while controlling for lesion volume. We also compared the relative predictive value of the lesion-behavior maps, and the structural and functional LNMs.Results:Lesion-behavior mapping indicated that lesions of left frontal white matter, bilateral frontal operculum/insula, and a region of white matter in the posterior left hemisphere were associated with impairments in g. Across all lesion-behavior mapping and LNM results, only two of the structural LNM maps linked to g were statistically significantly predictive of g in both validation cohorts: a map corresponding to the anterior thalamic radiation, and another corresponding to left frontal pyramidal projections. Both added value beyond lesion-behavior mapping and functional LNM.Conclusions:The results are notable in several respects: they highlight the importance of structural networks for g, de-emphasize the relevance of functional networks for g, and suggest novel brain circuitry involved in g. Our findings are consistent with animal studies implicating anterior thalamic nuclei in working memory, a cognitive function central to g. Clinically, our study highlights the importance of considering domain-general deficits and the effects of focal lesions on distributed cognitive networks.

Altered intrinsic cerebellar-cerebral functional connectivity is related to negative symptoms in patients with first-episode psychosis

BackgroundNegative symptoms in schizophrenia include cognitive and affective dysfunction, such as diminished expression and amotivation. Although the cerebellar posterior hemisphere and vermis are involved in cognitive and affective functioning, previous studies on the neural mechanism of negative symptoms have mostly been confined to the cerebral cortex. This study aimed to investigate whether resting-state cerebellar-cerebral functional connectivity (FC) is altered in first-episode psychosis (FEP) patients and whether this connectivity is related to negative symptoms. MethodsResting-state functional magnetic resonance images were obtained from 38 FEP patients and 100 healthy controls (HCs). Using the posterior hemisphere and vermis of the cerebellum as seeds, whole-brain FC was compared between FEP patients and HCs. As cerebellar-parietal cortex connectivity is associated with negative symptoms and sociocognitive dysfunctions in schizophrenia patients, its correlation with negative symptoms was explored in FEP patients. ResultsFEP patients showed hyperconnectivity between the cerebellum and bilateral frontal pole (FP), occipital pole, fusiform gyrus, right lingual gyrus, central opercular cortex, anterior middle temporal gyrus, precuneus, and subcallosal cortex. Hypoconnectivity was found between the cerebellum and left FP, right anterior supramarginal gyrus (aSMG), and cerebellum crus I. FC between the left crus II and right aSMG was negatively correlated with the severity of negative symptoms and diminished expression. ConclusionsAltered FC between the cerebellum and cerebral regions related to cognitive, affective, and sensory processing was found in FEP patients and was connected to negative symptoms. These results suggest that the cerebellum plays a role in the pathophysiology of negative symptoms in schizophrenia.

Clinical and histopathological study of a hollow and posteriorly multiperforated polymethylmethacrylate implant in eviscerated rabbit eyes.

The study aimed to evaluate the clinical and tissue response to a hollow polymethylmethacrylate orbital implant with a multiperforated posterior surface in an animal model after evisceration. Sixteen New Zealand rabbits had their right eye eviscerated. All animals received a hollow polymethylmethacrylate implant 12 mm in diameter that is multiperforated in its posterior hemisphere. The animals were divided into four groups, and each one had the eye exenterated at 7, 30, 90, and 180 days post-evisceration. Clinical signs were assessed daily for 14 days post-evisceration and then every 7 days until 180 days. Inflammatory pattern, collagen structure, and degree of neovascularization generated with implant placement were analyzed with hematoxylin-eosin, picrosirius red, and immunohistochemistry staining. There were no signs of infection, conjunctival or scleral thinning, or implant exposure or extrusion in any animal during the study. On day 7, the new tissue migrated into the implant and formed a fibrovascular network through the posterior channels. Inflammatory response reduced over time, and no multinuclea-ted giant cells were found at any time. Hollow polymethylmethacrylate orbital implants with a multiperforated posterior surface enable rapid integration with orbital tissues by fibrovascular ingrowth. We believe that this orbital implant model can be used in research on humans.

496: REVERSIBLE MALIGNANT CEREBRAL EDEMA FOLLOWING CRANIOPLASTY

Introduction: Cranioplasty is a low-risk procedure and is performed for improving hydrocephalus and cerebral protection after decompressive craniectomy. Until recently, a complication that received little attention despite the devastating consequences is malignant cerebral swelling occurring after cranioplasty. There is limited knowledge regarding the pathophysiology or prevention of this condition. We present a novel case wherein a patient developed malignant cerebral swelling and fully recovered from the event. Description: 44-year-old female initially hospitalized in January 2021 for a right MCA occlusion; she received Alteplase and thrombectomy was performed. Hospital course was complicated by post procedure CT head showing midline shift and mass effect for which she was taken for right sided hemicraniectomy and right temporal lobectomy. She underwent tracheostomy, PEG and was discharged. She presented back in August 2021 for an elective right sided cranioplasty. The operative course was uneventful, a hemovac was placed with a subgaleal drain and a postoperative CT head showed cranioplasty in good position. That evening, the patient became increasingly lethargic, and was intubated. She was given hyperosmotic therapy and a repeat CT head showed newly evolving right PCA infarct, cerebellar infarcts with edema, worsening subdural hematoma and left MCA infarcts. While obtaining the repeat CT head, the patient developed seizures with progression to status epilepticus and was started on a midazolam infusion. CEEG showed epileptiform potentials in the right posterior quadrant and left hemisphere, without seizures. Two days later, on a repeat CT head there were no new findings. Patient began to improve clinically, and MRI brain on day 3 didn’t show new infarct or lesion other than encephalomalacia. She was transferred out of the ICU on day 6, a stability CT head three weeks later was stable, and she was discharged to acute rehab. Discussion: Transient malignant swelling followed cranioplasty is a high risk complication and possibly related to severe TBI, SSFS and vacuum suction drainage. Our patient is the first reported survivor from this. Further research and investigation of other cases should be identified to assess for commonalities and interventions to provide the best chance of recovery.

Posterior Reversible Encephalopathy Syndrome in Pregnancy - Relevance in Diagnosis and Management

Posterior reversible encephalopathy syndrome (PRES) is a cliniconeuroradiological syndrome, which may present with headache, encephalopathy, seizures, visual disturbances, and blindness. The lesions in PRES are due to vasogenic oedema in posterior cerebral hemispheres and can be reversible if managed accurately. MRI shows diffuse abnormal signal intensities involving deep white matter of occipital lobes. Reporting 4 cases of PRES diagnosed in our Lady Goschen Hospital, attached to KMC Mangalore in a duration of two years. In all four cases, PRES was suspected when patients presented with eclampsia persistent in spite of administration of Pritchard’s regimen. MRI confirmed diagnosis. Three of them recovered while one of the women succumbed due to status eclampticus, respiratory failure and shock. Clinical improvement with complete resolution of visual disturbances was observed with supportive treatment in the other 3 patients. In order to prevent irreversible brain damage, correct clinical suspicion and timely diagnosis with apt management is essential. If adequate blood pressure-titrated treatment is followed, there may be speedy recovery from eclampsia and hence improvement in maternal condition.

Explicit and Implicit Emotion Processing in the Cerebellum: A Meta-analysis and Systematic Review.

The cerebellum's role in affective processing is increasingly recognized in the literature, but remains poorly understood, despite abundant clinical evidence for affective disruptions following cerebellar damage. To improve the characterization of emotion processing and investigate how attention allocation impacts this processing, we conducted a meta-analysis on task activation foci using GingerALE software. Eighty human neuroimaging studies of emotion including 2761 participants identified through Web of Science and ProQuest databases were analyzed collectively and then divided into two categories based on the focus of attention during the task: explicit or implicit emotion processing. The results examining the explicit emotion tasks identified clusters within the posterior cerebellar hemispheres (bilateral lobule VI/Crus I/II), the vermis, and left lobule V/VI that were likely to be activated across studies, while implicit tasks activated clusters including bilateral lobules VI/Crus I/II, right Crus II/lobule VIII, anterior lobule VI, and lobules I-IV/V. A direct comparison between these categories revealed five overlapping clusters in right lobules VI/Crus I/Crus II and left lobules V/VI/Crus I of the cerebellum common to both the explicit and implicit task contrasts. There were also three clusters activated significantly more for explicit emotion tasks compared to implicit tasks (right lobule VI, left lobule VI/vermis), and one cluster activated more for implicit than explicit tasks (left lobule VI). These findings support previous studies indicating affective processing activates both the lateral hemispheric lobules and the vermis of the cerebellum. The common and distinct activation of posterior cerebellar regions by tasks with explicit and implicit attention demonstrates the supportive role of this structure in recognizing, appraising, and reacting to emotional stimuli.

P 14 Functional activation patterns in patients with essential tremor

Introduction: Despite a significant reduction in the quality of life in patients suffering from an essential tremor (ET), the pathophysiological background of this disease is largely unknown. The cerebellum seems to be involved in the pathological process and the modulation of motor output (Nitschke 2004 (1) , Popa 2013 (2) ). Previous functional imaging studies often did not induce tremor, which is problematic (Sharifi 2014 (3) ). We therefore required a typical tremor-triggering movement in patients in comparison to control-subjects using fMRI. Methods & Patients: We compared the activation patterns in fMRI images of 13 patients with age- and sex-matched controls. Clinical scores were obtained using SARA and Tetras. Subjects performed a visually guided hand movement in a block design in an fMRI setting (Philips, 3 Tesla). Participants were asked to follow the amplitude of a horizontally moving red point using their extended right arm / index finger. The resulting movement overlaid by essential tremor during performance was monitored. Data analysis was done using SPM 8. Results: Group-analysis revealed activation of fronto-parietal areas including the frontal eye field and premotor cortex and parietal areas including the inferior parietal sulcus as well as the basal ganglia. On the cerebellar level lobuli HIV-VI bilaterally, the vermis, and lobuli within the posterior hemispheres extending were activated. Patients showed a decreased activation in various brain areas compared to controls, i.e., the left basal ganglia (Fig. 1) and lobuli HIV, HVIII and IX of the cerebellum on the right side (Fig. 2). On the other hand patients showed a stronger activation of the left parietal cortex. Conclusion: The activation changes in the cerebellum further corroborate an essential role of this structure in ET pathophysiology. Moreover, we propose that some of the changes seen in patients reflect compensatory mechanisms. (1) Nitschke MF, Binkofski F, Buccino G, Posse S, Erdmann C, Kömpf D, Seitz RJ, Heide W. Activation of cerebellar hemispheres in spatial memorization of saccadic eye movements - a fMRI study. Hum Brain Mapp 2004; 22(2): 155-164. (2) Popa, T. u. a. 2013. “Cerebellar RTMS Stimulation May Induce Prolonged Clinical Benefits in Essential Tremor, and Subjacent Changes in Functional Connectivity: An Open Label Trial”. Brain Stimulation 6(2): 175–79. (3) Sharifi S, Nederven A, Booij J, Rootselaar A. Neuroimaging essential in essential tremor: a systematic review. Neuroimage clinical 2014; 5: 217-231.

Cerebellar Grey Matter Volumes in Reactive Aggression and Impulsivity in Healthy Volunteers

Several lines of evidence point towards the involvement of the cerebellum in reactive aggression. In addition to the posterior cerebellar hemisphere, the vermis has been suggested to play a prominent role in impulse regulation. In the present study, we set out to further examine the relationships between cerebellar grey matter volumes, aggression, and impulsivity in 201 healthy volunteers. 3 T structural magnetic resonance imaging scans were acquired to investigate grey matter volumes of the cerebellar vermis and the anterior and posterior lobules. Aggression was assessed with the Buss–Perry Aggression Questionnaire and impulsivity was measured with the Barratt Impulsiveness Scale-11. Results showed that impulsivity was positively associated with grey matter volumes of the cerebellar vermis and inversely correlated with grey matter volumes of the right posterior lobule. In addition, smaller volumes of the right posterior lobules were associated with higher physical aggression. Exploratory analyses indicated that for the right hemisphere, this association was driven by grey matter volumes of lobules VIIb and VIIIa. Our findings provide correlational evidence in healthy volunteers for the involvement of the cerebellar vermis and posterior lobules in a cortico-limbic-cerebellar circuit of aggression.

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.

Visual Diagnosis: Abnormal Behavior in a 2-month-old Boy.

Visual Diagnosis: Abnormal Behavior in a 2-month-old Boy.

Altered gray matter development in pre-reading children with a family history of reading disorder.

Reading disorders are common in children and can impact academic success, mental health, and career prospects. Reading is supported by network of interconnected left hemisphere brain regions, including temporo-parietal, occipito-temporal, and inferior-frontal circuits. Poor readers often show hypoactivation and reduced gray matter volumes in this reading network, with hyperactivation and increased volumes in the posterior right hemisphere. We assessed gray matter development longitudinally in pre-reading children aged 2-5 years using magnetic resonance imaging (MRI) (N=32, 110 MRI scans; mean age: 4.40 ± 0.77 years), half of whom had a family history of reading disorder. The family history group showed slower proportional growth (relative to total brain volume) in the left supramarginal and inferior frontal gyri, and faster proportional growth in the right angular, right fusiform, and bilateral lingual gyri. This suggests delayed development of left hemisphere reading areas in children with a family history of dyslexia, along with faster growth in right homologues. This alternate development pattern may predispose the brain to later reading difficulties and may later manifest as the commonly noted compensatory mechanisms. The results of this study further shows our understanding of structural brain alterations that may form the neurological basis of reading difficulties.

Precision and trueness of maxillary crowded models produced by 2 vat photopolymerization 3-dimensional printing techniques

This cross-sectional study aimed to analyze the precision and trueness of dental models produced using 2 rapid prototyping 3-dimensional printers. A digital crowded maxillary arch with a T-shaped base and 2 hemispheres of 2.5mm radius was printed 10 times with a stereolithography apparatus (SLA) and digital light processing (DLP) in the highest precision and minimum layer thickness (z-resolution) mode. The copies were scanned using the D710 3Shape desktop scanner and assessed for precision and trueness via arch superimpositions and hemisphere measurements. Mann-Whitney U tests were used to compare trueness and precision among printers. Hemisphere radius was compared with the reference measurement and between 3-dimensional printers using 1 sample and independent Student t tests, respectively (α=0.05). The root mean square values of arch superimpositions showed statistically significant differences between the 2 techniques, both for precision (P=0.011): SLA (46.8μm±13.5); DLP (111.1μm±71.9), and trueness (P=0.015): SLA (61.1μm±9.8); DLP (99.8μm±47.2). The color map model analysis indicated greater distortion on premolar and molar surfaces, with a higher range of contraction on the SLA and both contraction and expansion on the DLP. Anterior and posterior hemisphere radius registered increased values with DLP (1.7% and 0.49%) and reduced values with SLA (0.6% and 0.7%); however, only the anterior SLA hemispheres revealed a significant decrease from the reference value (P=0.037). In this study, the SLA printer was significantly different from the DLS printer, with the highest precision and trueness.

Tumor location and reduction in functional MRI estimates of language laterality.

OBJECTIVEBrain tumors located close to the language cortex may distort functional MRI (fMRI)–based estimates of language dominance. The nature of this distortion, and whether this is an artifact of numerous confounders, remains unknown. The authors hypothesized tumor bias based on laterality estimates independent of confounders and that the effects are the greatest for tumors proximal to Broca’s area.METHODSTo answer this question, the authors reviewed more than 1113 patients who underwent preoperative fMRI to match samples on 11 known confounders (tumor location, size, type, and grade; seizure history; prior neurosurgery; aphasia presence and severity; and patient age, sex, and handedness). The samples included 30 patients with left hemisphere tumors (15 anterior and 15 posterior) and 30 with right hemisphere tumors (15 anterior and 15 posterior), thus totaling 60 patients (25 women; 18 left-handed and 4 ambidextrous; mean age 47 [SD 14.1] years). Importantly, the authors matched not only patients with left and right hemisphere tumors but also those with anterior and posterior tumors. Standard fMRI laterality indices (LIs) were calculated using whole-brain and region of interest (ROI) approaches (Broca’s and Wernicke’s areas).RESULTSTumors close to Broca’s area in the left hemisphere decreased LIs independently of known confounders. At the whole-brain level, this appeared to reflect a decrease in LI values in patients with left anterior tumors compared with patients with right anterior tumors. ROI analysis replicated these findings. Broca’s area LIs were significantly lower (p = 0.02) in patients with left anterior tumors (mean LI 0.28) when compared with patients with right anterior tumors (mean LI 0.70). Changes in Wernicke’s area–based LIs did not differ as a function of the tumor hemisphere. Therefore, in patients with left anterior tumors, it is essential to assess language laterality using left posterior ROIs. In all remaining tumor groups (left posterior tumors and right hemisphere tumors), language laterality derived from the anterior language ROI was the most robust measure of language dominance.CONCLUSIONSPatients with tumors close to Broca’s area showed more bilateral fMRI language maps independent of known confounders. The authors caution against the assumption that this reduced language laterality suggests no or little risk to language function following tumor resection in the left inferior frontal gyrus. Their results address how to interpret fMRI data for neurosurgical purposes, along with theoretical questions of contralesional functional compensation and disinhibition.

Cerebellar involvement in olfaction: An fMRI Study.

The role of the cerebellum in olfactory function is not fully understood. In this study, we tried to combine resting state and task functional MRI (fMRI) to improve the understanding of the cerebellum during olfactory processing. A resting state and a block paradigm of olfactory stimulation fMRI were scanned in 50 subjects. The olfactory stimuli, including phenylethyl alcohol and isovaleric acid, were alternately delivered to the subject using a custom-built olfactometer through air flow. The cerebellar activations elicited by isovaleric acid were subsequently used in the seed-based resting-state functional connectivity study. Phenylethyl alcohol did not induce any cerebellum activation, while isovaleric acid with a more unpleasant smell elicited significant cerebellum activations, primarily in the bilateral posterior lateral hemispheres (bilateral lobule crus I and right lobule VI). Seed-based functional connectivity analysis revealed significant within-cerebellum and corticocerebellar connections. The results imply that the cerebellum is probably involved in olfactory-related responses caused by unpleasant odor but does not directly participate in olfactory perception. Our results may further improve the understanding of the cerebellum in olfactory function.

Abstract P762: Hippocampal Plasticity Deficits After Cerebellar Stroke

Cerebellar stroke-induced cognitive and affective symptoms (CCAS) have been observed in patients with infarcts localized to the posterior regions of the cerebellum. Our lab has developed a mouse model of cerebellar stroke in which mice with posterior infarcts display hippocampal-dependent memory deficits. Synaptic plasticity in the hippocampal area CA1 is essential for episodic memory consolidation. There is evidence of functional connectivity of cerebellum with contralateral hippocampus. Therefore, we hypothesize that changes in after cerebellar stroke are the result of synaptic plasticity impairments within the hippocampus. We used a photothrombotic model to induce stroke in the posterior cerebellar hemispheres. Seven days after stroke, we performed extracellular recordings of field excitatory postsynaptic potentials (fEPSP) within the CA1 region of acute brain slices. In shams, theta-burst stimulation (TBS) of Schaffer collateral inputs produced long-term potentiation (LTP). TBS failed to evoke an increase in fEPSP slope in contralateral hippocampus of mice at 7 days post-injury. These data provide strong evidence demonstrating that injury to the cerebellum can produce changes in synaptic function within the hippocampus. The lack of LTP impairment in ipsilateral hippocampus after cerebellar stroke suggests that the observed plasticity deficits are activity dependent. We also observed reduced NMDA receptor, Fos and Arc expression. Brain-derived neurotrophic factor (BDNF) signaling through TrkB receptors is required for LTP and memory formation. We tested whether enhancement of TrkB signaling with the agonist 7, 8 dihydroflavone (DHF) could improve hippocampal plasticity. We observed a full restoration of hippocampal LTP in slices from cerebellar stroke mice that were incubated with DHF (250 nM) prior to TBS. We provide strong evidence for hippocampal dysfunction following cerebellar stroke. Our data have implications for benefit of strategies to enhance neurotrophic signaling not only at the site of injury, but in non-injured regions as well.

Imaging Characteristics and Endovascular Treatment of Brain Arteriovenous Malformations Mainly Fed by the Posterior Cerebral Artery.

Background: A BAVM that is mainly supplied by the posterior cerebral artery (PCA) lies deeply in the middle of the bilateral posterior hemispheres. Few studies have investigated the imaging characteristics and endovascular treatment (EVT) of brain arteriovenous malformations (BAVMs) in this area.Methods: A retrospective study was performed for patients who were diagnosed with PCA-BAVMs from January 2015 to December 2019. The PCA-BAVMs were divided into type I and type II according to their feeding arteries. Type I PCA-BAVMs were supplied by the posterior choroidal artery (PchA) from the PCA. They could be further subdivided into type Ia and type Ib. Type II PCA-BAVMs were supplied by the temporal or occipital branch from the PCA. They could also be further subdivided into type IIa and IIb. Targeted embolization of the risk factors was the main aim of EVT.Results: Forty-two patients were identified, with age ranging from 6 to 63 years. Twenty-four cases belonged to type I (57.1%, 24/42), including 6 Ia cases and 18 Ib cases. Eighteen cases belonged to type II (42.9%, 18/42), including 7 IIa cases and 11 IIb cases. Immediate complete or nearly complete embolization was achieved in 17 (40.5%, 17/42) cases. Partial embolization was achieved in 25 (59.5%, 25/42) cases. Two (4.8%, 2/42) patients experienced intraoperative or postoperative bleeding. The GOS scores at discharge were 3, 4, and 5 in 2 (4.8%, 2/42), 2 (4.8%, 2/42), and 38 (90.4%, 38/42) cases, respectively. There was no statistical difference between patients in type I and type II groups regarding age, BAVM rupture, SM grade, immediate extent of obliteration, and prognosis. Deep venous drainage was more common in patients of the type I group (P < 0.001).Conclusions: Our classification of the PCA-BAVMs was based on the segmentation of the PCA, which is a reasonable approach and could guide the strategy of EVT. EVT is a reasonable option for the PCA-BAVMs. The main aim of EVT is to secure the weak structures. A targeted EVT aimed at the ruptured part of the BAVM can reduce the risk of early rebleeding.