Supplementary motor area

Last revised by Frank Gaillard on 30 Nov 2022

The supplementary motor area (SMA) is involved in preparing for voluntary movements carried out by the primary motor area (precentral gyrus).

The SMA is located posteriorly on the medial surface of the superior frontal gyrus (sometimes referred to as the medial frontal gyrus) just anterior to the paracentral lobule 1

Its posterior border is the precentral sulcus and its inferior border is the cingulate sulcus 1-3

The anterior and lateral surfaces are less precisely defined without unambiguous anatomical landmarks, even though cytoarchitectonic and histochemical differences have been described 2,3.

Furthermore, the SMA is often divided into SMA proper and pre-SMA again arbitrarily by a line perpendicular to the AC-PC line, running through the anterior commissure 2

Related pathology

Damage to the SMA, for example following tumor resection, leads to supplementary motor area syndrome, which is characterized by 3,4:

  • postoperative contralateral hemiparesis

  • speech impairment (if dominant hemisphere)

These deficits are usually transient with resolution occurring over weeks to months 3,4.

ADVERTISEMENT: Supporters see fewer/no ads

Cases and figures

  • Figure 1
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.