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Huntington's Disease-Like 2 (HDL2), caused by a CTG/CAG expansion in JPH3 on chromosome 16q24, is the most common Huntington's Disease (HD) phenocopy in populations with African ancestry. Qualitatively, brain MRIs of HDL2 patients have been indistinguishable from HD. To determine brain regions most affected in HDL2 a cross-sectional study using MRI brain volumetry was undertaken to compare the brains of nine HDL2, 11 HD and nine age matched control participants. Participants were ascertained from the region in South Africa with the world's highest HDL2 incidence. The HDL2 and HD patient groups showed no significant differences with respect to mean age at MRI, disease duration, abnormal triplet repeat length, or age at disease onset. Overall, intracerebral volumes were smaller in both affected groups compared to the control group. Comparing the HDL2 and HD groups across multiple covariates, cortical and subcortical volumes were similar with the exception that the HDL2 thalamic volumes were smaller. Consistent with other similarities between the two diseases, these results indicate a pattern of neurodegeneration in HDL2 that is remarkably similar to HD. However smaller thalamic volumes in HDL2 raises intriguing questions into the pathogenesis of both disorders, and how these volumetric differences relate to their respective phenotypes., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Objective: Nonfunctional popliteal entrapment is due to embryologic maldevelopment within the popliteal fossa. Functional entrapment occurs in the apparent absence of an anatomic abnormality. Gastrocnemius hypertrophy has been associated with the latter. Both forms of entrapment may cause arterial injury and lower limb ischemia. This study assessed the attachment of the medial head of the gastrocnemius muscle in healthy occluders and healthy nonoccluders., Methods: Provocative tests were used to identify 58 nonoccluders and 16 occluders. Ten subjects from each group underwent magnetic resonance imaging evaluation of the popliteal fossa. The medial head of the gastrocnemius muscle attachment was assessed in the supracondylar, pericondylar, and intercondylar areas., Results: In the occluder group, significantly more muscle was attached towards the femoral midline (supracondylar), around the lateral border of the medial condyle (pericondylar), and within the intercondylar fossa., Conclusion: The more extensive midline position of the medial head of the gastrocnemius in occluders is likely to be a normal embryological variation. Forceful contraction results in compression and occlusion of the adjacent popliteal artery. The clinical significance of these anatomic variations remains unclear. However, these new observations may provide insight for future analysis of the causes and natural history of functional compression and the potential progression to clinical entrapment.