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commissurotomy

n. (context medicine English) The surgical division of a commissure or similar structure.

Wikipedia
Commissurotomy

A commissurotomy is a surgical incision of a commissure in the body, as one made in the heart at the edges of the commissure formed by cardiac valves, or one made in the brain to treat certain psychiatric disorders.

Patients with scleroderma, a disease that thickens and hardens the skin, sometimes require oral commissurotomy to open the corners of the mouth, the commissures, to allow dental treatment. This procedure often leaves characteristic scars.