White matter tractography of the neural network for speech-motor control in children who stutter

Stuttering is a neurodevelopmental speech disorder with a phenotype characterized by speech sound repetitions, prolongations and silent blocks during speech production. Developmental stuttering affects 1% of the population and 5% of children. Neuroanatomical abnormalities in the major white matter tracts, including the arcuate fasciculus, corpus callosum, corticospinal, and frontal aslant tracts (FAT), are associated with the disorder in adults who stutter but are less well studied in children who stutter (CWS). We used deterministic tractography to assess the structural connectivity of the neural network for speech production in CWS and controls. CWS had higher fractional anisotropy and axial diffusivity in the right FAT than controls. Our findings support the involvement of the corticostriatal network early in persistent developmental stuttering.

Hippocampal subfield measurement and ILAE hippocampal sclerosis subtype classification with in vivo 4.7 tesla MRI

OBJECTIVE

Neuropathological studies indicate that hippocampal sclerosis (HS) consists of three subtypes (ILAE types 1-3 HS). However, HS subtypes currently can only be diagnosed by pathological analysis of hippocampal tissue resected during epilepsy surgery or at autopsy. In vivo diagnosis of HS subtypes holds potential to improve our understanding of these variants in the ipsilateral as well as contralateral hippocampus. In this study, we aimed to: i) evaluate the reliability of our histology-derived segmentation protocol when applied to in vivo MRI; and ii) characterize variability of HS subtypes along the hippocampal long axis in patients with epilepsy.

METHODS

Eleven subjects with unilateral HS were compared with ten healthy controls. We used 4.7 T MRI to acquire high resolution MR Images of the hippocampus in each subject. In vivo MRI-based diagnoses of HS subtypes were then determined in each patient by two methods: i) hippocampal subfield volumetry of the entire hippocampal body; and ii) subfield area analysis at multiple thin slices throughout the hippocampal body.

RESULTS

Hippocampal body subfield segmentation demonstrated excellent reliability and volumetry of the symptomatic hippocampus revealed abnormalities in all eleven patients. Six subjects demonstrated findings consistent with type 1 HS while five subjects had volumetry-defined atypical HS (two with type 2 HS & three with type 3 HS) in the symptomatic hippocampus, while five subjects were found to have type 3 HS in the contralateral hippocampus. Subfield area analyses demonstrated remarkable variability of HS subtypes along the hippocampal long axis, both ipsilateral and contralateral to the seizure focus.

SIGNIFICANCE

Our results provide preliminary evidence that determining HS Subtype using in vivo MRI may allow preoperative diagnosis of ILAE HS subtypes. Further studies are essential to determine the pathological correlates of these neuroimaging findings. The heterogeneity of abnormalities observed along the long axis of the hippocampus is consistent with previous autopsy studies and highlights the necessity of studying the entire hippocampus both ipsilateral and contralateral to the seizure focus in these future studies.

Curved multiplanar reformatting provides improved visualization of hippocampal anatomy

There is a growing body of literature studying changes in hippocampal subfields in a variety of different neurological conditions, but this work has mainly focused on the hippocampal body given challenges in visualization of hippocampal anatomy in the head and tail when sectioned in the typical coronal image plane. Curved multiplanar reformatting (CMPR) is an image reconstruction method that can improve visualization of complex three‐dimensional structures. The objective of this study was to determine whether CMPR could facilitate visualization of the human hippocampal anatomy along the entire caudal–rostral axis. CMPR was applied to high‐resolution magnetic resonance imaging acquired ex vivo on four cadaveric hippocampal specimens at 4.7 T (T2‐weighted, 0.2 × 0.2 × 0.5 mm³). CMPR provided clear visualization of the classic “interlocking C” appearance of the dentate gyrus and cornu ammonis along the entire caudal–rostral axis including the head and tail, which otherwise show complex anatomy on the standard coronal slices. CMPR facilitated visualization of hippocampal anatomy providing the impetus to develop simplified approaches to delineate subfields along the entire hippocampus including the usually neglected head and tail.

Genetic variants in PIKFYVE: A review of ocular phenotypes

Many studies have identified disease-causing variants of PIKFYVE in ocular tissues; however, a comprehensive review of these variants and their ocular phenotypes is lacking. The phosphoinositide kinase PIKFYVE plays crucial roles in the endolysosomal pathway in autophagy and phagocytosis, both essential for cellular homeostasis. In this review, we evaluate the reported disease-causing PIKFYVE variants and their associated phenotypes in humans to identify potential genotype-phenotype correlations. Variants in PIKFYVE have been associated with corneal fleck dystrophy, congenital cataracts and possibly keratoconus. There are unvalidated associations of variants in PIKFYVE with autism spectrum disorder and congenital heart disease. We show that variants causing corneal fleck dystrophy exist in the chaperonin-like domain of PIKFYVE as well as the region between the chaperonin-like and the kinase domains. Similarly, congenital cataract variants appear to be specific to the kinase domain of the protein. This review consolidates existing knowledge on PIKFYVE variants in ocular disease and bridges fundamental science and clinical manifestations, potentially informing future diagnostic and treatment strategies for PIKFYVE-associated ocular disorders.

Curved multiplanar reformatting allows the accurate histological delineation of hippocampal subfields

BACKGROUND

Hippocampal subfields perform specific roles in normal cognitive functioning and have distinct vulnerabilities in neurological disorders. However, measurement of subfields with MRI is technically difficult in the head and tail of the hippocampus. Recent studies have utilized curved multiplanar reconstruction (CMPR) to improve subfield visualization in the head and tail, but this method has not yet been applied to histological data.

METHODS

We utilized BigBrain data, an open-source database of serially sectioned histological data for our analyses. The left hippocampus was segmented according to histological criteria by two raters in order to evaluate intra- and inter-rater reliability of histology-based segmentation throughout the long axis. Segmentation according to our previous protocol for the hippocampal body was then compared to these histological measurements to evaluate for histological validity. Agreement between segmentations was evaluated using Dice similarity coefficients (DSCs).

RESULTS

Intra-rater reliability (DSCs) of histological segmentation was excellent for all subfields: CA1 (0.8599), CA2 (0.7586), CA3/CA4/DG (0.8907), SLM (0.9123), subiculum (0.8149). Similarly, inter-rater reliability analysis demonstrated excellent agreement (DSCs) for all subfield locations: CA1 (0.8203), CA2 (0.7253), CA3/CA4/DG (0.8439), SLM (0.8700), subiculum (0.7794). Finally, histological accuracy (DSCs) for our previous protocol was excellent for all subfields: CA1 (0.8821), CA2 (0.8810), CA3/CA4/DG (0.9802), SLM (0.9879), subiculum (0.8774). When subfields in the hippocampus head, body, and tail were analyzed independently, DSCs also showed excellent agreement.

CONCLUSIONS

CMPR allows reliable subfield segmentation based on histological criteria throughout the hippocampal head, body, and tail. Our previous protocol for the hippocampal body can be applied to provide histologically valid subfield measurements throughout the entire hippocampal long axis.

Abstract 214: Corticospinal Tract Integrity is Acutely Maintained Within Perihematoma Edema

Background: Perihematoma edema in intracerebral hemorrhage (ICH) is thought to be associated with tissue injury. Fractional Anisotropy (FA), as measured with Diffusion Tensor Imaging (DTI), can be used to assess white matter integrity. We tested the hypotheses that sections of the Corticospinal Tract (CST) passing directly through edema would 1) have low FA relative to the entire tract and 2) predict motor score in ICH patients.

Methods: Patients were prospectively imaged with DTI within 14 days of symptom onset. Hematoma volume was measured on CT using planimetric techniques. Edema volume was assessed on CT using a 5-23 Hounsfield Unit threshold. Mean FA was measured in the edematous region (‘perihematoma edema'), the entire ipsilateral CST, and in the portion of CST passing through the perihematoma edema ('edematous CST'). Motor function was evaluated with a composite of the upper and lower extremity NIHSS motor score (0=normal, 8=hemiplegia).

Results: Patients (n=27, mean age 67±13) were scanned with DTI at a median of 2 (3) days. Hematoma distribution was: lobar 5 (18%), basal ganglia 21 (78%), and brainstem 1 (4%). Median acute ICH volume was 8.2 (22) ml at 2 (2)h. Acute edema volume was 0.9 (1.8) ml and grew to 1.9 (3.9) ml at 26h (26). NIHSS motor score was 3 (6) at 72h and 3 (7) at day 7.

FA in the edema was significantly lower (0.23±0.06) than in contralateral mirror regions (0.37 ±0.07, p<0.0001). Mean FA in the edematous CST was lower (0.34±0.08) than FA in the entire ipsilateral CST (0.44±0.04, p<0.0001), but higher than FA in the perihematoma edema (0.25±0.06, p<0.0001).

There was a weak correlation between FA in the edematous CST and 72h motor score (r= -0.40, p=0.050,) which disappeared at day 7 (r= -0.34, p=0.131). FA in the edematous CST was not related to time to scan (r=-0.027, p=0.892).

Hematoma volume predicted FA in the edematous CST (ß=-0.46, 95% CI:[-0.05- -0.01]; p=0.015). Perihematoma edema volume did not predict FA in the edematous CST independently of the ICH (ß=-0.29, [-0.1-0.04]; p=0.475).

Conclusion: FA is decreased in the CST where it passes through the edema, though not to the extent of the surrounding edema. The transient relationship between decreased FA and motor function suggests that edema temporarily impairs tract function but not integrity.

Training Outcomes and Satisfaction in Canadian MD/PhD and MD/MSc Programs: Findings from a National Survey

PURPOSE

Despite the impact of physician-scientists on scientific discovery and translational medicine, several reports have signalled their declining workforce, reduced funding, and insufficient protected research time. Given the paucity of outcome data on Canadian MD/PhD programs, this study presents a national portrait of the sociodemographic characteristics, training trajectories, productivity, and satisfaction in trainees and alumni from Canadian MD/PhD and MD/MSc programs.

METHODS

Quantitative data were collected in a national survey launched in 2021. Respondents included 74 MD/PhD alumni and 121 trainees across 12 Canadian MD/PhD and MD/MSc programs.

RESULTS

Among MD/PhD alumni, 51% were independent practitioners/researchers while others underwent residency training. Most trainees (88%) were in MD/PhD programs. Significantly more alumni identified as men than did trainees. Significantly more alumni conducted clinical and health services research, while more trainees conducted basic science research. Average time to MD/PhD completion was 8 years, with no correlation to subsequent research outcomes. Self-reported research productivity was highest during MD/PhD training. Concerning training trajectories, most alumni completed residency, pursued additional training, and practised in Canada. Finally, regression models showed that trainees and alumni were satisfied with programs, with significant moderators in trainee models.

CONCLUSION

Survey findings showed Canadian MD/PhD and MD/MSc programs recruit more diverse cohorts of trainees than before, provide productive research years, and graduate alumni who pursue training and academic employment in Canada. Both alumni and trainees are largely satisfied with these training programs. The need to collect in-depth longitudinal data on Canadian MD/PhD graduates to monitor diversity and success metrics is discussed.

Walking while talking: validation in older adults with lower-limb amputation

BACKGROUND

Walking while talking (WWT) is a dual-task (cognitive and motor) performance test that has not yet been validated in older adults with lower-limb amputation (LLA). WWT is composed of two sections: WWT-simple (walking while reciting every letter of the alphabet) and WWT-complex (walking while reciting every other letter of the alphabet).

OBJECTIVE

To determine the validity, and provide normative data and a new scoring system for the WWT test in older adults with LLA.

STUDY DESIGN

Baseline cross-sectional data were collected from 56 community-living older adults (≥50 years old) with LLA at rehabilitation hospitals in Vancouver, BC, London, ON, and Edmonton, AB, Canada.

METHODS

Time and number of recited letters and errors during both sections were recorded. A new score was developed based on all these variables. Correlations of the recorded times with the Activities-specific Balance Confidence (ABC) scale and the 2-Minute Walk Test (2MWT) score were used to evaluate the validity of the WWT test.

RESULTS

As hypothesized, the times for both sections of the WWT were negatively correlated with both the ABC and 2MWT scores. Positive correlations were observed between the scores developed for both WWT sections with the 2MWT score.

CONCLUSION

Times taken to complete each section of the WWT test were correlated with the 2MWT and the ABC scale scores, providing evidence for the validity of the WWT test. We also provided a scoring method that is more objective and in line with the dual-task nature of the test.