fMRI BOLD and MEG theta power reflect complementary aspects of activity during lexicosemantic decision in adolescents with ASD.

Neuroimaging studies of autism spectrum disorder (ASD) have been predominantly unimodal. While many fMRI studies have reported atypical activity patterns for diverse tasks, the MEG literature in ASD remains comparatively small. Our group recently reported atypically increased event-related theta power in individuals with ASD during lexicosemantic processing. The current multimodal study examined the relationship between fMRI BOLD signal and anatomically-constrained MEG (aMEG) theta power. Thirty-three adolescents with ASD and 23 typically developing (TD) peers took part in both fMRI and MEG scans, during which they distinguished between standard words (SW), animal words (AW), and pseudowords (PW). Regions-of-interest (ROIs) were derived based on task effects detected in BOLD signal and aMEG theta power. BOLD signal and theta power were extracted for each ROI and word condition. Compared to TD participants, increased theta power in the ASD group was found across several time windows and regions including left fusiform and inferior frontal, as well as right angular and anterior cingulate gyri, whereas BOLD signal was significantly increased in the ASD group only in right anterior cingulate gyrus. No significant correlations were observed between BOLD signal and theta power. Findings suggest that the common interpretation of increases in BOLD signal and theta power as 'activation' require careful differentiation, as these reflect largely distinct aspects of regional brain activity. Some group differences in dynamic neural processing detected with aMEG that are likely relevant for lexical processing may be obscured by the hemodynamic signal source and low temporal resolution of fMRI.

Dynamic time warping outperforms Pearson correlation in detecting atypical functional connectivity in autism spectrum disorders.

Resting state fMRI (rsfMRI) is frequently used to study brain function, including in clinical populations. Similarity of blood-oxygen-level-dependent (BOLD) fluctuations during rsfMRI between brain regions is thought to reflect intrinsic functional connectivity (FC), potentially due to history of coactivation. To quantify similarity, studies have almost exclusively relied on Pearson correlation, which assumes linearity and can therefore underestimate FC if the hemodynamic response function differs regionally or there is BOLD signal lag between timeseries. Here we show in three cohorts of children, adolescents and adults, with and without autism spectrum disorders (ASDs), that measuring the similarity of BOLD signal fluctuations using non-linear dynamic time warping (DTW) is more robust to global signal regression (GSR), has higher test-retest reliability and is more sensitive to task-related changes in FC. Additionally, when comparing FC between individuals with ASDs and typical controls, more group differences are detected using DTW. DTW estimates are also more related to ASD symptom severity and executive function, while Pearson correlation estimates of FC are more strongly associated with respiration during rsfMRI. Together these findings suggest that non-linear methods such as DTW improve estimation of resting state FC, particularly when studying clinical populations whose hemodynamics or neurovascular coupling may be altered compared to typical controls.

The osseofasciocutaneous flap: a new method to transfer fibula along with a sufficient amount of skin.

We describe a new technique of bone transfer, using a deep fascial blood supply to transfer bone together with a large area of skin. The viability of this flap and further confirmation by isotope scanning have established that the bone transfer is vascularised. This provides a simple solution to the complex problem of leg trauma with massive skin and bone loss.

Large transverse fasciocutaneous leg flap: whole leg flap.

Large defects of leg and sole often need massive tissue transfer. As an alternative to microvascular transfer, we have developed a fasciocutaneous flap in which almost the whole of the skin of the opposite leg is transferred based just on the septocutaneous perforators of the posterior tibial artery. The flap has been used as a cross-leg fasciocutaneous flap with potential for use as a free flap by taking a segment of the posterior tibial artery. Our experience with 11 cases is presented. Two patients suffered marginal necrosis while donor site problems were seen in another two patients. We have found this flap to be safe, technically easy and with minimal donor-site morbidity.

Choice of surgical procedure in typhoid perforation: experience in 42 cases.

Forty-two patients of typhoid perforation of the gut have been studied. All the patients were subjected to surgery after resuscitation. Simple closure (with or without serosal patch) and temporary ileostomy were the commonly performed surgical procedures. The overall mortality was 14.2%. Postoperative morbidity included wound dehiscence, fistula, encephalopathy, septicaemia, intra-abdominal abscesses and incisional hernia. Faecal fistula formed in 5 out of 42 cases. Ileostomy was found to be the best procedure with regard to morbidity and mortality.