Rictus_grin
Risus sardonicus
Sustained spasm of the facial muscles
Risus sardonicus or rictus grin is a highly characteristic, abnormal, sustained spasm of the facial muscles that appears to produce grinning. It may be caused by tetanus,[1][2] strychnine poisoning, or Wilson's disease, and has been reported after execution by hanging.[medical citation needed]
The condition's name, associated with the Mediterranean island of Sardinia, derives from the appearance of raised eyebrows and an open "grin", which can appear sardonic or malevolent to the lay observer, displayed by those experiencing these muscle spasms.