Alzheimer's Disease Is Associated with Increased Network Assortativity: Evidence from Metabolic Connectivity

Introduction: Unraveling the network pathobiology in neurodegenerative disorders is a popular and promising field in research. We use a relatively newer network measure of assortativity in metabolic connectivity to understand network differences in patients with Alzheimer's Disease (AD), compared with those with mild cognitive impairment (MCI). Methods: Eighty-three demographically matched patients with dementia (56 AD and 27 MCI) who underwent positron emission tomography-magnetic resonance imaging (PET-MRI) study were recruited for this exploratory study. Global and nodal network measures obtained using the BRain Analysis using graPH theory toolbox were used to derive group-level differences (corrected p < 0.05). The methods were validated in age, and gender-matched 23 cognitively normal, 25 MCI, and 53 AD patients from the publicly available Alzheimer's Disease Neuroimaging Initiative (ADNI) data. Regions that revealed significant differences were correlated with the Addenbrooke's Cognitive Examination-III (ACE-III) scores. Results: Patients with AD revealed significantly increased global assortativity compared with the MCI group. In addition, they also revealed increased modularity and decreased participation coefficient. These findings were validated in the ADNI data. We also found that the regional standard uptake values of the right superior parietal and left superior temporal lobes were proportional to the ACE-III memory subdomain scores. Conclusion: Global errors associated with network assortativity are found in patients with AD, making the networks more regular and less resilient. Since the regional measures of these network errors were proportional to memory deficits, these measures could be useful in understanding the network pathobiology in AD.

Altered cerebellar lobular volumes correlate with clinical deficits in siblings and children with ASD: evidence from toddlers

BACKGROUND

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by impaired social and communication skills, narrow interests, and repetitive behavior. It is known that the cerebellum plays a vital role in controlling movement and gait posture. However, recently, researchers have reported that the cerebellum may also be responsible for other functions, such as social cognition, reward, anxiety, language, and executive functions.

METHODS

In this study, we ascertained volumetric differences from cerebellar lobular analysis from children with ASD, ASD siblings, and typically developing healthy controls. In this cross-sectional study, a total of 30 children were recruited, including children with ASD (N = 15; mean age = 27.67 ± 5.1 months), ASD siblings (N = 6; mean age = 17.5 ± 3.79 months), and typically developing children (N = 9; mean age = 17.67 ± 3.21 months). All the MRI data was acquired under natural sleep without using any sedative medication. We performed a correlation analysis with volumetric data and developmental and behavioral measures obtained from these children. Two-way ANOVA and Pearson correlation was performed for statistical data analysis.

RESULTS

We observed intriguing findings from this study, including significantly increased gray matter lobular volumes in multiple cerebellar regions including; vermis, left and right lobule I-V, right CrusII, and right VIIb and VIIIb, respectively, in children with ASD, compared to typically developing healthy controls and ASD siblings. Multiple cerebellar lobular volumes were also significantly correlated with social quotient, cognition, language, and motor scores with children with ASD, ASD siblings, and healthy controls, respectively.

CONCLUSIONS

This research finding helps us understand the neurobiology of ASD and ASD-siblings, and critically advances current knowledge about the cerebellar role in ASD. However, results need to be replicated for a larger cohort from longitudinal research study in future.

Resting-State Functional MRI/PET Profile as a Potential Alternative to Tri-Modality EEG-MR/PET Imaging: An Exploratory Study in Drug-Refractory Epilepsy

Objective The study explores whether the epileptic networks associate with predetermined seizure onset zone (SOZ) identified from other modalities such as electroencephalogram/video electroencephalogram/structural MRI (EEG/VEEG/sMRI) and with the degree of resting-state functional MRI/positron emission tomography (RS-fMRI/PET) coupling. Here, we have analyzed the subgroup of patients who reported having a seizure on the day of scan as postictal cases and compared the findings with interictal cases (seizure-free interval).

Methods We performed independent component analysis (ICA) on RS-fMRI and 20 ICA were hand-labeled as large scale, noise, downstream, and epilepsy networks (Epinets) based on their profile in spatial, time series, and power spectrum domains. We had a total of 43 cases, with 4 cases in the postictal group (100%). Of 39 cases, 14 cases did not yield any Epinet and 25 cases (61%) were analyzed for the final study. The analysis was done patient-wise and correlated with predetermined SOZ.

Results The yield of finding Epinets on RS-fMRI is more during the postictal period than in the interictal period, although PET and RS-fMRI spatial, time series, and power spectral patterns were similar in both these subgroups. Overlaps between large-scale and downstream networks were noted, indicating that epilepsy propagation can involve large-scale cognition networks. Lateralization to SOZ was noted as blood oxygen level–dependent activation and correlated with sMRI/PET findings. Postoperative surgical failure cases showed residual Epinet profile.

Conclusion RS-fMRI may be a viable option for trimodality imaging to obtain simultaneous physiological information at the functional network and metabolic level.

Effect of addition of clonidine to local anaesthetic mixture for peribulbar block

Clonidine added to local anaesthetics prolongs the duration of anaesthesia and analgesia of peripheral, neuraxial and retrobulbar blocks. The present randomized blinded controlled study was conducted to evaluate the effect of the addition of clonidine to local anaesthetic mixture on the quality, onset time, duration of peribulbar block, perioperative analgesia and patients' comfort. The study comprised two groups of 12 patients each. Group A (control) patients received 7 ml of a mixture of 2% lignocaine and hyaluronidase with 1 ml normal saline, while group B (clonidine group) patients had clonidine 1 microg/kg added to the above mixture. Onset and duration of lid akinesia, globe anaesthesia and akinesia, time to first analgesic medication and total analgesic requirement were assessed. Patients were monitored for heart rate, blood pressure, sedation and respiratory depression. Addition of clonidine to local anaesthetic mixture resulted in a significant increase in duration of lid akinesia (85.4+/-25.6 vs 173.3+/-35.3 min, P<0.001), globe anaesthesia (63.2+/-6.9 vs 78.8+/-17.5 min, P=0.012) and globe akinesia (161.3+/-24.3 vs 201.2+/-45.7 min, P=0.016). The onset time and quality of block were similar in both the groups. No significant haemodynamic, respiratory or sedative effects were recorded. The perioperative pain scores and the analgesic requirements were significantly (P<0.01) lower in group B patients. We found that addition of clonidine 1 microg/kg to local anaesthetic mixture significantly increases the duration of anaesthesia and analgesia after peribulbar block.

A dose response study of clonidine with local anesthetic mixture for peribulbar block: a comparison of three doses

Clonidine prolongs anesthesia and analgesia of local anesthetics in various neural blocks as well as the duration of retrobulbar block. We assessed the dose-response relationship of clonidine added to lidocaine in peribulbar block. Sixty patients undergoing cataract surgery were given peribulbar block with 7 mL of 2% lidocaine and hyaluronidase with either saline (Control) or clonidine in 0.5-microg/kg (0.5 Clon), 1.0-microg/kg (1.0 Clon), or 1.5-microg/kg (1.5 Clon) doses. The onset and duration of lid and globe akinesia, globe anesthesia and analgesia, postoperative analgesic requirement, and adverse effects (hypotension, bradycardia, hypoxia, sedation, and dizziness) were recorded. The success rate and onset of block were comparable in all groups. The duration of lid and globe akinesia, globe anesthesia and analgesia was significantly (P < 0.01) prolonged in patients receiving 1.0 and 1.5 microg/kg clonidine as compared with the Control group. Perioperative pain scores and analgesic requirement were significantly less in these groups. 0.5 microg/kg clonidine did not increase the duration of anesthesia and analgesia significantly. Hypotension and dizziness were observed more in patients receiving 1.5 microg/kg clonidine as compared with other groups. We conclude that 1.0 microg/kg clonidine with a mixture of lidocaine (2%) significantly prolonged the duration of anesthesia and analgesia after peribulbar block with limited side effects.

IMPLICATIONS

We studied the effect of the addition of 0.5, 1.0 and 1.5 microg/kg clonidine to a lidocaine-hyaluronidase mixture on the onset and duration of peribulbar block and perioperative analgesia. A dose of 1.0 microg/kg produced a significant increase in duration of anesthesia and analgesia with minimal side effects.