trismus
Last reviewed 01/2018
Trismus is a motor disturbance of the trigeminal nerve.
In particular there is spasm of the masticatory muscles, with difficulty in opening the mouth - risus sardonicus or 'lockjaw' to the layperson.
Trismus is a characteristic early symptom of tetanus, but it may also occur secondary to acute infection, after an overdose of phenothiazines, and in disorders of the basal ganglia.