• Francesco Vergani, Luis Lacerda, Juan Martino, Johannes Attems, Christopher Morris, Patrick Mitchell, Michel Thiebaut de Schotten, and Flavio Dell'Acqua.
• Department of Neurosurgery, Royal Victoria Infirmary, Newcastle upon Tyne, UK Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.
• J. Neurol. Neurosurg. Psychiatr.. 2014 Dec 1;85(12):1377-85.

IntroductionThe supplementary motor area (SMA) is frequently involved by brain tumours (particularly WHO grade II gliomas). Surgery in this area can be followed by the 'SMA syndrome', characterised by contralateral akinesia and mutism. Knowledge of the connections of the SMA can provide new insights on the genesis of the SMA syndrome, and a better understanding of the challenges related to operating in this region.MethodsWhite matter connections of the SMA were studied with both postmortem dissection and advance diffusion imaging tractography. Postmortem dissections were performed according to the Klingler technique. 12 specimens were fixed in 10% formalin and frozen at -15°C for 2 weeks. After thawing, dissection was performed with blunt dissectors. For diffusion tractography, high-resolution diffusion imaging datasets from 10 adult healthy controls from the Human Connectome Project database were used. Whole brain tractography was performed using a spherical deconvolution approach.ResultsFive main connections were identified in both postmortem dissections and tractography reconstructions: (1) U-fibres running in the precentral sulcus, connecting the precentral gyrus and the SMA; (2) U-fibres running in the cingulate sulcus, connecting the SMA with the cingulate gyrus; (3) frontal 'aslant' fascicle, directly connecting the SMA with the pars opercularis of the inferior frontal gyrus; (4) medial fibres connecting the SMA with the striatum; and (5) SMA callosal fibres. Good concordance was observed between postmortem dissections and diffusion tractography.ConclusionsThe SMA shows a wide range of white matter connections with motor, language and lymbic areas. Features of the SMA syndrome (akinesia and mutism) can be better understood on the basis of these findings.Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

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