Electroencephalography correlates of spatial working memory deficits in attention-deficit/hyperactivity disorder: vigilance, encoding, and maintenance.

In the current study we sought to dissociate the component processes of working memory (WM) (vigilance, encoding and maintenance) that may be differentially impaired in attention-deficit/ hyperactivity disorder (ADHD). We collected electroencephalographic (EEG) data from 52 children with ADHD and 47 typically developing (TD) children, ages 7-14 years, while they performed a spatial Sternberg working memory task. We used independent component analysis and time-frequency analysis to identify midoccipital alpha (8-12 Hz) to evaluate encoding processes and frontal midline theta (4-7 Hz) to evaluate maintenance processes. We tested for effects of task difficulty and cue processing to evaluate vigilance. Children with ADHD showed attenuated alpha band event-related desynchronization (ERD) during encoding. This effect was more pronounced when task difficulty was low (consistent with impaired vigilance) and was predictive of memory task performance and symptom severity. Correlated with alpha ERD during encoding were alpha power increases during the maintenance period (relative to baseline), suggesting a compensatory effort. Consistent with this interpretation, midfrontal theta power increases during maintenance were stronger in ADHD and in high-load memory conditions. Furthermore, children with ADHD exhibited a maturational lag in development of posterior alpha power whereas age-related changes in frontal theta power deviated from the TD pattern. Last, subjects with ADHD showed age-independent attenuation of evoked responses to warning cues, suggesting low vigilance. Combined, these three EEG measures predicted diagnosis with 70% accuracy. We conclude that the interplay of impaired vigilance and encoding in ADHD may compromise maintenance and lead to impaired WM performance in this group.

Tibial access for supra-inguinal embolization in extremely obese patients.

Extreme obesity is a risk factor for hemorrhagic complications of femoral access (FA). Femoral lines, hematomas, pelvic binders and coagulopathy in the trauma scenario may also add difficulty and/or risk to FA. Radial access (RA) for routine peripheral endovascular procedures has been popularized owing to decreased hemorrhagic complications, increased patient satisfaction, and decreased operator radiation dose. However, though uncommon, cerebrovascular complications from RA approach are a known risk. Relatively recently, tibial access (TA) has been used for lower extremity peripheral vascular disease interventions. The advantages of TA mirror that of RA, with few and mostly minor complications, and the risk of iatrogenic cerebral embolization is nil. We report the feasibility of TA for supra-inguinal embolization in two extremely obese patients {body mass index > 40 kg/m2} following motor vehicle accidents. Commercially available base and microcatheters were used to perform embolization of the affected lower abdominal or pelvic arteries in standard fashion via a novel trans-tibial artery approach.