The Geometry of the roots of the Brachial Plexus.

Diffusion tensor magnetic resonance imaging (DTI) can be used to reconstruct the brachial plexus in 3D via tracts connecting contiguous diffusion tensors with similar primary eigenvector orientations. When creating DTI tractograms, the turning angle of connecting lines (step angle) must be prescribed by the user; however, the literature is lacking detailed geometry of brachial plexus to inform such decisions. Therefore, the spinal cord and brachial plexus of 10 embalmed adult cadavers were exposed bilaterally by posterior dissection. Photographs were taken under standardised conditions and spatially calibrated in MATLAB. The roots of the brachial plexus were traced from the dorsal root entry zone for 5 cm laterally using a 2.5-mm2 Cartesian grid overlay. The trace was composed of points connected by lines, and the turning angle between line segments (the step angle) was resolved. Our data show that the geometry of the roots increased in tortuosity from C5 to T1, with no significant differences between sides. The 1st thoracic root had the most tortuous course, turning through a maximum angle of 56° per 2.5 mm (99% CI 44° to 70°). Significantly higher step angles and greater variability were observed in the medial 2 cm of the roots of the brachial plexus, where the dorsal and ventral rootlets coalesce to form the spinal root. Throughout the brachial plexus, the majority of step angles (>50%) were smaller than 20° and <1% of step angles exceeded 70°. The geometry of the brachial plexus increases in tortuosity from C5 to T1. To reconstruct 99% of tracts representing the roots of the brachial plexus by DTI tractography, users can either customise the step angle per root based on our findings or select a universal threshold of 70°.

Prevalence of obstructive sleep disturbance in children with failure to thrive.

OBJECTIVES: Failure to thrive (FTT) is a serious condition of childhood, with failure to grow as expected for age and gender. Numerous potential etiologies have been suggested, including occult obstructive sleep disturbance (OSD). We determined the prevalence of OSD in an FTT population, examined correlation to tonsil size, and assessed correlation with a parental questionnaire regarding symptoms. PATIENTS AND METHODS: A cross-sectional prevalence study was conducted. Thirty-six FTT children in Boston Medical Center's FTT Clinic aged 12 to 60 months were evaluated by formal polysomnography, parental questionnaire, and physical examination. The prevalence and nature of sleep disorders in this population are compared with published age-appropriate norms. RESULTS: The prevalence of OSD in an FTT population in these 36 children is 5.5%. This is compared with the prevalence in the general pediatric population, which is between 0.7 and 4.3%. CONCLUSIONS: The prevalence of OSD in FTT tends toward higher than published values for the general pediatric population but does not reach statistical significance. Tonsillectomy and adenoidectomy have been suggested in the literature to be of benefit to improve the growth of children with FTT. Sleep disturbance has been suggested as the underlying pathology. However, using current guidelines, we could not identify an increased prevalence of sleep disturbance in children with FTT. Nonetheless, a continued high level of clinical suspicion is necessary in appropriate diagnosis and treatment of OSD, found in some children with FTT. That growth in children with FTT often improves following management of sleep disturbance (eg, tonsillectomy) is not explained by a significantly higher incidence of OSD in this population.