This a fixed grin due to mild but sustained contraction of the facial muscle. It is almost invariably due to a wound infection with tetanus but may also give the appearance of a fixed grin.
Approach to the Diagnosis
Careful examination of the trunk and extremities for a wound infection is extremely important. If the patient is not stripped down, the clinician can miss a tetanus infection caused by dirty needles in drug addicts. A history of mental illness should alert one to attempted suicide with strychnine. A urine drug screen is useful in ruling out narcotic addiction. Scleroderma can usually be excluded by an ANA and anticentromere antibody titer, but a skin biopsy may be necessary.